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venomous and poisonous anim als of the mojave desert compiled by m. hill

ENVENO


book design Š 2009 by m. hill published by m. hill for gr 601 type systems taught online by carolina de bartolo spr ing 2009 academy of art university, san fr ancisco, ca pr inting by m. hill w ith an hp 9500 color pr inter binding by danya w inter m an, the k ey pr inting and binding, oakl and, ca all r ights r eserved


CON T EN T s

93

inde x of im ages

1 bibliogr a ph y

21 ch a pter four r eptile

90

51

73 ch a pter one mojav e v enom

ch a pter t wo a rthropod

4 1 ch a pter thr ee a mphibi a n

63 51 31

81 introduction

11 ix


INTRODUCTION The southwestern United States has a fascinating diversity of vegetation and wildlife, much of which has evolved to survive under very hostile environmental conditions. For the ďŹ rst time visitor from a more temperate climate, the landscape appears completely alien. Cacti, mesquite trees, and creosote bushes are the common trees to be found. Many familiar species like oak trees have adapted to hot dry weather with smaller structures using water conserving systems. The Mojave landscape is host to a variety of dreaded, venomous and poisonous animals that have each evolved certain specialized survival the desert environment.

defense systems for their


ch apter one

MOJAV E V ENO M A bite is a wound received from the mouth, in particular, the teeth, fangs or sometimes the stinger of an animal, including humans. Animals often strike or bite in self-defense, in an attempt to predate food, as well as part of normal interactions. Other bite attacks may be apparently unprovoked. Bites are usually distinguished by the type of creature causing the wound. Many diff erent creatures are known to bite or to strike at humans. The result of this type of injury is typically survived, unless the animal that is striking has an exceptional envenomous delivery system. Just exactly where are these animals to be found? How dangerous are they? How likely are you to encounter them? What should you do if you have a “bad encounter”? Is everything in the Southwest considered venomous or poisonous? How can you know what is and what’s not? Encounters with venomous or poisonous animals should be cherished and enjoyed safely be it in the home, back yard, or when out hiking or camping. All of these animals are an integral part of the Mojave ecosystem which is a desert especially the Mojave.

biome. The desert biome displays considerable variation,


average annual hospitalization for wild mojave animal bites

500

Venomous bites are usually

environment. The solar energy that all green plants convert into food fuels

named by the type of animal

life here. Although in most ecosystems animals, like plants compete for food from sunlight, here many are adapted venom use to survive as they minimize

poisonous bites

The Mojave animals live in what strikes many humans as an oppressive

250

that causes the wound such as a bee sting or snake bite.

the eff ects of too much energy from the constant solar rays. An ecosystem is defi ned as biotic community together within its physical venomous bites

environment, considered as an integrated unit. Implied here is the concept of

The ecosystem of the Mojave is characterized as a distinctly viable unit of desert community

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11

10

09

08

: Insect bites may deliver infection. : Animal bites may transmit disease. : A bite may cause bodily injury.

Awareness of how an animal is likely to behave

: 80% of animal bites are from unknown sources.

can take the fear out of an encounter and help to

: Any animal with claws or teeth may bite.

keep everybody safe. Most importantly, learning

: An animal bite can infl ict life-long illnesses.

by Mojave animals.

processes form interactive subsystems.

07

1-1. This chart shows the average annual hospitalization for animal bite victims

and can be viewed as nested sets of open systems in which physical, chemical, and biological

06

05

04

03

02

delivery systems. These systems are hierarchical

0 01

and interactive habitats with unique venomous

patients

a structural and functional “whole” unified through life processes.

about venomous and poisonous animals can lead en v enom

mojav e v enom

12

deadly situation.

surviving a potential

13


r ange and h abitat

There are few desert variables including intense

Th e abundance of naturally

heat, varying elevation, moisture, sand and soil

occurring caves is one the most

composition, exposure to ultraviolet rays and

the mojave desert

common geologic features of the Mojave. Underground

wind patterns that create specific kinds of living conditions for many plants and animals. Nature

living gives animals a great advantage of energy effi ciency.

and habitats don’t have hard boundaries and often overlap. Different kinds of habitats within n e va da

a short distance of each frequently occur in the Mojave region. The vastness of the Mojave spans the areas of lower Nevada and southern California, Utah and the upper most part of Arizona. The Mojave waters rarely come above ground. Usually, the river and basin f lows can

is prime territory for venomous animals and to

arizona

california

be seen in secluded upper canyon regions. This

protect their rights to live, many have adapted to develop toxins within their body systems to help them stay and thrive in the Mojave. Many of these animals were thought to be small in numbers

1-2. This map shows the overall region and

but their habitats have been revealed as hidden

water runoff. Here many varieties of cactus and border on dry lakebeds. Their water conserving habits resemble those of the animals. Spindly shrubs and threadlike stems in plants often will at an invader.

poke or prick

location of the vast Mojave that spans

several states of the south west United States.

and large underground territories near basin

Ecologists use a diff erent term for each type of symbiotic relationship. In the scenario where both species benefit, the term mutualism applies. When one species benefits and another is unaff ected that is called commensalism. Parasitism is the opposite, one species benefits, the other is harmed. If neither species benefits then ecologists call this competition. And the fourth term, neutralism defi nes a situation where both species are unaff ected. In the Mojave region,

en v enom

mojav e v enom

14

of symbiosis.

there are many examples

15


overall venom use

species. Kelso Dunes, also known as the Kelso Dune Field, is the largest field of eolian sand deposits in the Mojave Desert. Like many south western dune systems, the Kelso dunes have a number of endemic animal species.

Sand Treader (Macrobaenetes kelsoensis, a species of camel cricket), the Kelso Dunes Jerusalem Cricket (Ammopelmatus kelsoensis, a stenopelmatid)

reptiles

amphibians

Katydid (Eremopedes kelsoensis), as well as several rare and venomous native

arthropods

a giant Mydid fly (Rhaphiomidas tarsalis), and the Kelso Dunes Shieldback

defend digest immobilize

The list includes at least ten species of insect, such as the Kelso Dunes Giant

all animals

endemic to the mojave

Some animals survive only in the Mojave Desert, these are called endemic

bees and wasps, and some beetles. Although not strictly endemic, several plant and reptile species are rare outside of these dunes. One example is the Mojave Fringe-toed Lizard (Uma scoparia), which is specialized in its ability

Some animals live throughout all the southwestern desert areas and some are merely passing through on a migratory path. Regardless, whether living permanently in the Mojave, staying only seasonally or flying by on their way somewhere else, adaptations to the extreme climate and lack of water

how venom or poison is used by the animals

who make venom or poison.

to actually move as if “swimming” under sand.

1-3. A comparison of

For over a century, hypotheses regarding the primary functional utility of venoms have been debated throughout literature. Researchers have speculated that the development of venom delivery systems has been a key

species usually have adapted to these conditions to the highest degree. Th at

innovation leading to the evolutionary radiation of venomous animals over

includes sophisticated methods of defense. While defense systems are varied,

the past thirty million years. An evolutionary radiation is an increase in

they can be narrowed to the categories of venomous and poisonous delivery

taxonomic diversity or morphological disparity, due to adaptive change

systems. The term for venom or poison that enters the bloodstream is called

or the opening of ecospace. Familiar radiations include the radiation

a hemotoxin. Hemotoxins, haemotoxins or hematotoxins are toxins that

of land plants after their colonisation of land, the Cretaceous radiation

destroy red blood cells (that is, cause hemolysis), disrupt blood clotting, and

of angiosperms, and the diversification of insects, a radiation that has

cause organ degeneration and generalized tissue damage. Hemotoxins are

continued almost unabated since the Devonian

frequently employed by venomous animals. The term hemotoxin is to some

en v enom

mojav e v enom

other tissues.

degree a misnomer since toxins that damage the blood also damage

400 million years ago.

must be made even if an animal is only staying for a short while. Endemic

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17


routing

The route of administration is the path by which a fluid, poison or other venomous substance is brought into contact with the body. Often the route of administration, or delivery system can help to diff erentiate all the categories of venomous and poisonous substances. A substance must be transported from the site of entry to the part of the body where its action is desired to take place (even if this only means penetration through the into the skin). Normally, the body’s transport mechanisms for this purpose can be far from trivial. Many animals in the Mojave have the great misfortune of being misidentified

envenomation processes of uptake, distribution, duration and even-

as venomous or poisonous because of their evolved teeth, fangs, claws or other

tual elimination are all critically influenced by the systemic route of the

sharply pointed body parts adapted for life in the Mojave Venomous mam-

administrator, or the animal who is envenomating for food. Toxicokinetics

mals may have been more common in the past. Canine teeth dated at sixty

is used to defi ne the systemic exposure of toxic compounds in the animals

million years old from two extinct species, the shrew-like Bisonalveus browni

who are prey;

and another unidentified mammal, show grooves that some palaeontologists have argued are indicative of a venomous bite. Many other scientists have mojave prey

arachnids frogs toads

It has been suggested that there are some Mojave animals that do not need venom because they have become clever and effective enough to kill with their tooth or claw; whereas venom, no matter how sophisticated, takes time to disable prey. Since their venom is manufactured to help digest prey in most toxic animals, the reasons why animals who kill survive or thrive

other

mojav e v enom

lizards

1-4. The arthropod species consumes the most prey.

of feature does not

may be questioned.

snakes

en v enom

nonvenomous mammals (e.g., many primates, coatis and fruit bats) who also

always reflect an adaptation to venom delivery.

insects

amphibians

reptiles

18

questioned this conclusion given that there are quite a few active, thriving

have deep grooves down the length of their canines, suggesting that this type arthropods

myriapods

measuring exposures in toxicology them.

The pharmacokinetic properties of toxins are those related to the

19


common dangerous and non-dangerous mojave animals

arachnids

venomous

non-venomous

tarantula

whip scorpion

black widow

sun spider

brown recluse

scupuglids

bark scorpion

wind scorpion

poisonous

arthropods

hairy scorpion

myriapods

desert centipede

desert millipede

insects

harvestor ants

kissing bug

By defi nition, all venomous animals produce toxins in the specialized and

africanized bees

unique secretory cells in a venom gland. The collective mix of different toxins

buck catepillar

which are produced by an animal is known as venom, which is produced and stored by an animal until it is needed. During a bite or sting, the venom then desert toad

toads

is activated by the delivered by injection through what is called a venomous amphibians

or venom apparatus. Th is apparatus consists of the venom producing cells. It becomes fi rst a simple means for storing the venom, and secondly this frogs

with a grooved or hollow tooth (a fang) or a stinging apparatus. Many times lizards

gila monster

banded gecko

this apparatus is only used for the delivery of toxins, and once injection

horned lizard

is performed the apparatus may not function again, fall off and or need to

mojave rattler

king snake

coral snake

glossy snake

side winder

gopher snake

be regenerated for the

1-5. The common or familiar names of those Mojave animals that may envenomate or deliver toxic substances. This list compares

en v enom

mojav e v enom

to distinguish in nature.

species that are not rare.Many non-venomous creatures closely resemble venomous creatures and are difficult

apparatus to effectively function.

snakes reptiles

becomes a specialized means for the act of injecting the venom, such as

20

21


clincal effects of envenomation 100

Poisonous animals lack a venom apparatus to actively deliver toxins as

Neurotoxins prevent neurons

a defense mechanism. Instead, the survival of these species depends on the

from communicating with

may be acquired by accumulation from the environment, primarily through the food chain. These toxins are often secondary metabolites of ingested compounds. Poisonous animals obviously must have resistance to the toxins to ensure their survival. So they must ingest the substances (usually found in Mojave plants) that they use as precursors to produce their toxins; otherwise they may loose their toxicity. Defi ning what is “venomous” or

respiratory failure

nausea

swelling

pain

death

that regulate body functions.

0

reptiles

The toxins in poisonous animals may be produced by the animal, or they

known as neurotransmitters

amphibians

absorbed through the skin, resulting in toxic delivery.

using chemical messengers

arthropods

and, poisonous secretions from animals such as toads or frogs may be

each other. Neurons function

frequency of effect (percent)

passive, delivery of toxins. Ingesting a poisonous animal results in toxicity

50

1-6. The main side effects of venom from Mohave animals. Envenomation may cause anaphylaxis in certain people, and the saliva and

humans are not usually the intended victim.

fangs of the snake may harbor many dangerous microbial contaminants, including Clostridium tetani. If neglected, any infection may

As they are not the typical food source for the

spread and has the potential to be

animal, so their toxins would be wasted. For example although all spiders produce venom that allows them to immobilize or kill their prey,

a fatal situation .

“poisonous” is often difficult, simply because

en v enom

mojav e v enom

22

would be impossible.

digesting a human

23


fight or flight

Many venomous animals, especially insects are able to lift twenty times their own body weight and quickly move distances that are many times greater than their own length. Th is is not because they are strong but because they are so small. Muscle power is proportional to its cross-sectional area. Because the mass (the insect’s body), that is moved is in proportion to its volume and the fact that they also have a better leverage system than humans do, they may jump remarkable distances especially during an envenomous strike. Flight has allowed the insect to disperse, escape from enemies, environmental harm, and colonise new habitats within the Mojave region. One of the insect’s adaptations, fl ight mechanics, diff er from other flying animals because their wings are not modified appendages. Fully developed and functional wings occur only in adult insects. To fly, gravity and drag (air resistance to movement) has to be overcome. The high daily temperatures in the Mojave make most insect fl ight dependent on cooler night temperatures. Most of the remote water is underground, and Mojave animals can be found near or around these resources. The arthropods of the Mojave are the largest food source for all animals there, including for themselves. Their habitats are typically found near runoff areas of

en v enom

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24

basins or groundwater.

washes found close to

25


Insects are the only group of invertebrates to have developed fl ight. The evolution of insect wings has been the subject of much debate. Some proponents suggest that the wings of these creatures are para-notal in origin while others have suggested they are modified gills. In the Carboniferous age, the area of this specific region in the Mojave desert hosted super sized insects. Finding gigantic insects has been found consistent with high atmospheric oxygen. The amounts of oxygen present in the atmosphere found from the researched ice core samples ranged as high as 37 % compared to the current 21%. Most groundwater in the Mojave region is known to have higher environmental Two dimensional mechanism

instead of one pair. Th is reflects their ancient origin. As such, understand-

of insect fl ight has a natural

ing the coupling between their fore and hind wings might shed light on

three dimensional extension where the pairs of vortices are

the evolution of f light based on four wings to that based on two. The dragonf ly is not venomous or poisonous, but is prey for arthropods and amphibians. Female dragonf ly lay eggs in or near water, often on f loating or emergent plants. Tethered dragonf lies can be measured for 3d wing kinematics and vertical forces. Kinematics and envenomation are both survival diversifications. Damselfl ies or the suborder Zygoptera are often confused with dragonfl ies, but are distinct. Most

replaced by vortex rings.

oxygen than any other water found on the surface, such as ponds, creeks and the rainy season

accumulation of road water run off.

A distinctive feature of desert dragonf lies is their use of two pairs of wings

damselfl ies hold their wings at rest together above the torso or held slightly open above such as in the family Lestidae, whereas most dragonfl ies at rest hold their wings horizontally or occasionally slightly down and forward. Also, the back wing of the dragonfl y broadens near the base, caudal to the connecting point at the body, while the back wing of the damselfl y is similar to the front wing. The eyes on a damselfl y are set apart and in

en v enom

mojav e v enom

26

eyes touch.

most dragonfl ies the

27


Most of the food of a venomous animal is ingested in the form of macromolecules and other complex substances such as proteins, polysaccharides, fats, and nucleic acids which must be broken down by catabolic reactions into smaller molecules of amino acids or simple sugars. All of which depend on the waste cycles of oxygenation. All before being used by cells of the body for energy, growth, or reproduction. Th is breaking down process is known as digestion and is critical to producing venom. Generally speaking, venom of newborn and small juvenile creatures appears to be more potent than that adults of the same species. The bite from a snake that has not fed recently such as one that has just emerged from hibernation is more dangerous than that of one that has recently fed because it has more venom to inject. Venom glands must replace venom lost with each strike or bite, and replacing venom takes time. Th is requires protein. The overall relationships of the venomous and poisonous animals that are thriving in the

waste and en venoation

Mojave desert to all of the other animal groups Organic wastes are the remains of any living or once-living organism. Most of the venomous and poisonous creatures are key players in the waste cycle in the desert. Organic wastes that can enter a body of water include leaves, grass clippings, dead plants or animals, animal droppings, and or other sewage. Organic waste is decomposed by bacteria; these bacteria remove dissolved oxygen

(organic waste) is available for the bacteria, more bacteria will grow and use oxygen, and the dis-

29

the crustaceans. In the Pancrustacea theory, for example, insects, together with Remipedia and Malacostraca, make up a natural clade known as the scientiďŹ c classiďŹ cation of the living and fossil organisms. It is possible that the venomous and poisonous traits may have been ďŹ rst established in early dissolved oxygen

mojav e v enom

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will drop.

solved oxygen concentration

favoring closer evolutionary ties with insects to

rich waters of the early Mojave desert.

from the water when they breathe. If more food

tends to remain unclear. Evidence has emerged

28


ch apter t wo

A RTHROPO D Arthropods are the most diverse group of animals on earth and comprise more than 85 % of all living animal species. Th is fascinating group of animals features external skeletons (or exoskeletons), segmented bodies and several jointed legs and feet. Familiar members of this enormously large phylum include spiders, centipedes, scorpions, crabs, and all of the insects. Arthropods are animals belonging to the Phylum Arthropoda meaning the greek words arthron, “joint,” and podos “foot,” which together they mean jointed feet, and include the insects, arachnids, and crustaceans. The cuticles of crustaceans are also biomineralized with calcium carbonate. The rigid cuticle inhibits growth, so arthropods replace it periodically by molting. The arthropod body plan consists of repeated segments, each with a pair of appendages. Enabling them to become the most species-rich members of all ecological guilds in most environments. In the Mojave, they make up more than 80% of all described living species, and are one of only two groups very sizes have a wide range.

successful in dry environments. In the Mojave, their


h abitats and r el ationships

Arthropods’ main internal cavity is a hemocoel,

Pigment pit ocelli is that

which accommodates their internal organs and

external patch or patches

through which their blood circulates. They have

major areas of venomous arthropod populations in the mojave

of pigment and photoreceptor cells organized in either

open circulatory systems. Like their exteriors the internal organs of arthropods are generally

a fl at disk or a pit near the head of an animal.

built of repeated segments. Their nervous system is “ladder-like”, with paired ventral nerve cords running through all segments and forming paired ganglia in each segment. Their heads are formed by fusion of varying numbers of segments, and their brains are formed by fusion of the ganglia of these segments and encircle the esophagus. The respiratory and excretory systems of arthropods vary depending as much on their environment as on the subphylum to which they belong. Their vision relies on various combinations of compound eyes and pigment pit ocelli. In most species the ocelli can only detect the direction from which light is coming, and the compound eyes are the main source of information, but the main eyes of spiders

arachnids

2-1. This map depicts

myriapods

the larger populations

insects

of venomous arthropod

are ocelli that can form images and, in a few cases Arthropods’ methods of reproduction and development are diverse and is

mostly based on modifications of the many setae

dependent on migration of other arthropod communities. All Mojave ground

(bristles) that project

species use internal fertilization, but this is often by indirect transfer of the

en v enom

species use either internal or external fertilization. Almost all arthropods lay eggs except for

a rthropod

32

sperm via an appendage or the ground, rather by direct injection. Aquatic

the scorpions.

through their cuticles.

a wide range of chemical and mechanical sensors,

the Mojave region.

communities living in

can swivel to track prey. Arthropods also have

33


The most conspicuous specialization of segments is in the head. The major formal groups or orders of the Mojave arthropods are the arachnida, insecta and diplopoda. Working out the evolutionary stages by which all the diff erent combinations of structures of the arthopods could have appeared is so difficult that it has long been known as the “Arthropod head” problem. For those creatures with toxic delivery systems, the function of the venom glands is the major area of study. The head is typically where venom delivery systems need

arthropod structur e

The original arthropod appendages were most likely biramous, or having an upper body that works as a gill while the lower body was probably used for walking. In some segments of all known arthropods the appendages have been modified to perhaps form gills, mouth-parts, antennae for

many varied and unique structures for delivery of venom.

to originate and for the arthropod this region displays

collecting information, or claws for grasping. Arthropods are each equipped with a unique set of specialized tools with a mandible for eating with a claw, two sets of antenna plus four pairs of walking legs and four pairs of swimmerettes. In many arthropods, appendages have vanished from some regions of the body, and it is common for abdominal appendages to have disappeared or

en v enom

a rthropod

34

varied pods.

be highly modified with

35


clinical effects of envenomation from mojave arthropods 100

Typical arthopod heads possesses a pair of antennae; eyes; mandibles,

Th ere are two di erent types

labrum, maxillae and labium. Lying above the oesophagus is the brain

of excretory systems in the arthropod. Th e end product of biochemical reactions that

The position of the arthropod mouth and the

circum-oesophageal

connectives

allows

the distinction to be made between the oral structures and it should be borne in mind that these structures can move around during

0

2-2. The toxic strike effects from the three major categories of Mojave arthropods. The most dangerous group are the arachnids which

en v enom

include the infamous Black Widow spider, otherwise

a rthropod

known as the worlds most deadly spider.

process of envenomation.

development and are critical for the

maxillae and labium, respectively.

pairs of the upper ganglia lead further on to the mandibles,

na usea

any permeable membrane.

swelling

brain to the ventral ganglionated nerve cord: nerves from the first three

p a in

Ammonia is eliminated via

insects

connectives lead from the tritocerebrum around the gut to connect the

myriapods

much as possible with water.

arachnids

that it needs to be diluted as

to the labrum and stomatogastric nervous system. Circum-oesophageal

dea th

metabolise nitrogen is so toxic

back. Nerves from the protocerebrum lead to the large compound eyes, then

frequency of ef f ect ( p er cent)

protocerebrum, deutocerebrum and tritocerebrum lining up from front to

r esp ir a tor y f a ilur e

or supraesophageal ganglion, divided into three pairs of ganglia: then the

50

36

37


below the gut, and in each segment the cords form a paired ganglia from which their sensory and motor nerves run to other parts of the segment. Although the pairs of ganglia in each segment often appear physically

ar achnids

connecting pairs

Living arthropods have paired main nerve cords running along their bodies

All the arachnid bodies are divided into two main parts. These are referred to as the head or the cephalothorax and the abdomen. The head or

sensory organs, and paired limbs. The fi rst pair

arthropod nervous systems a ladder-like appearance. The brain is in the

of limbs, called chelicerae, may form pincers or

head, encircling and mainly above the esophagus. It consists of the fused

fangs. The second pair, called pedipalps, may

ganglia of the acron and one or two of the foremost segments that form

serve as pincers, sensory appendages, or legs. The

the head, for a total of three pairs of ganglia in most arthropods. But there

rest of the cephalothorax usually has four pairs of

are only two in the portion of chelicerates, which do not have antennae

walking legs. The abdomen contains the genital

or the ganglion connected to them. The ganglia of other head segments

opening and book lung, or modified gills, used

are often close to the brain and function as part of it. In insects these

for gas exchange and oxygenation.

behind the esophagus. Spiders take this process a step further, as all the segmental ganglia are incorporated into the subesophageal which occupy most of the space in the cephalothorax or the front portion known as the super segment.

dorsal view

cephalothorax contains simple eyes, mouth parts,

fused and they are connected by relatively large bundlednerves, which give

other head ganglia combine into paired subesophageal ganglia, under and

location of the chelicerae in the arthropod

ventral view

Scorpions are those arachnids that are quickly recognized by their segmented, curved, stinging tails and their large pedipalps, or pincer looking extremities. The body of a scorpion is composed of a short, compact cephalothorax with an very

referred to as the mesosoma. The feeding parts

can be excreted as dry material; Malphigian tubules fi lter the uric acid and

or appendages and the chelicerae, pedipalps, and

other nitrogenous waste out of the blood in the hemocoel, and dump these

segmented legs all attach to the larger cephalot-

materials into the hindgut, from which they are expelled as feces endowed

horax. The chelicera is the most developed and

with precious micronutrients

envenomous section

2-3. The chelicerae is one of the anterior pair of the appendages of an arachnid often specialized as fangs or often referred to as their pincers or

hind pincers.

a diff erent system. The end product of nitrogen metabolism is uric acid which

chelicerae

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featured in the arachnid.

elongated and segmented abdomen area which is

for Mojave plant life.

Various groups of Mojave arthropods have independently developed

a rthropod

38

39


Members of the spider genus Loxosceles Sicariidae are most commonly known as the brown recluse spiders

a venomous spider

Many spiders living on the Mojave are misidentified as Loxosceles. These spiders are rather nondescript with uniformly colored abdomens that can vary from a tawny to dark brown. The legs and body are covered with fi ne hairs and they have small leg spines. On the the fi rst body segment, to which the legs are attached there is a characteristic darkened violin pattern. Brown recluse spiders make a protective silken retreat that occasionally can entangle prey, but they are more often hunters that prowl for prey. Th ey can be found in high numbers in human structures such as shacks or even abandoned mine shafts in the desert. Their nocturnal wanderings place them in contact with humans. Similar to black widow spiders, brown recluse spiders usually bite only when they become trapped next to the victim’s skin. Bites occur Chelicerate head structures diff er considerably from those of the man-

myriapods and insects living in the Mojave. They possess eyes and a single pair of grasping appendages innervated from the brain, plus

er pair of mouthparts, then the pedipalps, and behind them lie the series of walking limbs. In chelicerates the leg bearing segments are fused with the anterior segments to form a prosoma so that in living arthropods a distinct head actually only exists in the mandibulate structure. Toxicologically, there is far more diversity in spider venoms than in the venoms of myriapods, scorpions and most insects so that the correct identification of spider bites has special significance. Spiders are rarely correctly

transported out of their native range. Making diagnosis difficult, and in some

pinprick. However, after only a few hours, there is ensuing severe pain, erythema, and localized tissue necrosis due to the venom’s proteolytic enzymes. These A localized envenomation will have a necrotic ulcerated lesion or open sore. If this occurs near a systemic artery, the bite can be life-threatening. Within ten minutes of venom injection, there is a constriction of capillaries around the site of the bite indicating that the blood has been envenomated. Potential renal failure is a concern especially for

en v enom

by mistreatment.

cases healing is compounded

Sometimes a bite from a brown recluse spider can go unnoticed, or maybe feel as slight as simply a tiny

smaller body masses.

identified by bite victims or sometimes even their physicians and are readily

either when sleeping humans roll onto the spider or put on clothes into which the spider has crawled.

related enzymes are the components of the venom.

a dense fibrous structure known as a labrum. Behind the mouth lies anoth-

2-4. Depicting the violin

pattern on the head or the cephalothorax.

dibulates, or those head structures found in other arthropods like the

a rthropod

40

41


Using powerful jaws located immediately under the head they grasp and kill their prey by injecting venom in to surface areas. The bite of most centipedes is incapable of penetrating human skin. But some can squirt their uids over distances of several inches. The bite of the giant desert centipede is quite painful, but it is not considered particularly dangerous. The venom causes both pain and swelling, and often red streaking called lymphangitis. There may be systemic symptoms including anxiety, fever, dizziness, palpitations, and nausea. Skin breakdown may occur at the site of a bite but it usually heals without the need for skin grafting.

myriapods

Myriapoda is a subphylum of the arthropods that contain the millipedes and those similar creatures centipedes. Th is group contains thousands of the species, all of which are terrestrial. Although their name suggests they have myriad or 10,000 legs, myriapods actually range from having over 750 legs to having fewer than ten legs. They all have

illnesses happen with this venom.

Many other long-termed

a single pair of antennae and simple eyes. Although not generally considered dangerous to humans there are many myriapods that produce secretions, often containing benzoquinones which

en v enom

the skin.

can cause blistering and discolouration of

a rthropod

42

43


insects

The most common stinging animals are in the insect order Hymenoptera meaning “veil wings”, which includes the bees, wasps and ants. The most primitive Hymenoptera possess ovipositors to insert eggs into plant tissue. In some parasitic groups this structure and glands associated with it have been modified to inject venom to paralyze other insects which are used as food by the developing larvae. (These parasitic wasps comprise the largest number of species in the Hymenoptera, and are extremely beneficial to agriculture as biological control agents of agricultural pest insects.) The stings of these parasitic wasps are often not very painful to humans due to low toxicity. The toxicity of the wasp venom is so low that it is not considered an envenomous design for the defensive sting. The insect, like bees, will usually flee rather than sting when disturbed. The sting has become the specialized defensive tool in other groups of insects and the ants and bees which evolved from these insects. Most wasps and bees are solitary, and do not defend their nests though they will sting in defense if caught. It is in the social Hymenoptera that we see active

Bees, wasps, ants, and even caterpillars-sometimes it seems that everything with more than four legs stings. Fortunately, most insects don’t sting, and most insect venoms are not particularly dangerous to people. The greatest risk that we face from insect stings is anaphylaxis. Th is is a severe allergic reaction that can be triggered by even minute amounts of proteins in a venom. Anaphylaxis is most common in people who have been sensitized to the protein that triggers the reaction, usually by previous exposure from a sting. Given the tremendous diversity of insects and relatively low medical risk from most insect stings, this book covers only a few of the more significant and Mojave members of this class. Insects are a class of arthropods that have three main body sections. Begin-

that cause medically injury and significant stings,

ning with the head, thorax, and abdomen. They have three pairs of legs that

although a few large species of stinging bees can

attached to the thorax, and usually two sets of wings. The insect life cycle is

cause painful and potentially serious stinging if

either three-part (egg, nymph, adult) or four-part (egg, larva, pupa, adult).

captured or perhaps

Insects account for most of the biomass on earth and are represented by over

stepped on.

defense of the nest, and it is mostly these groups

a million known species, divided into 32 orders; it is thought that there may be as many as 10 million species. The most recently discovered order of the

en v enom

a rthropod

44

in Africa in 2002.

insects are the Mantophasmatodea, or “gladiators,” that were fi rst described

45


physiology of the sting

The commonly active components of honey bee venom include enzymes, other smaller proteins and peptides, and amines. Among the principle small proteins and peptides are melittin, apamin, and peptide. The melittin is what constitutes about 50% of the venom dry weight; it hydrolyzes the cell membranes causing changes in permeability and is most responsible for the pain associated with the sting. Peptide is also known as mast cell degranulating peptide and causes mast cells to release histamine as they degranulate, and sets up an in ammatory reaction. Enzymes include phospholipase (11% of

Most fatalities from bees and wasps stinging occur in hypersensitive individuals; death is most often induced by a single sting, and occurs most often within one hour after the sting. The victim is typically over 40 years of age and stung on the head or neck. Most of these deaths are caused by a respiratory dysfunction with the second most common being anaphylaxis or immediate respiratory arrest. Also, arteriosclerosis may be a compounding factor. Large numbers of bee stings

The most common and typical dermatologic expression for honey bee venom is seen as a raised white weal with central red spot of which appears a few minutes after the sting, and lasts for about 20 minutes. Honey bee stings can usually be deďŹ nitively diagnosed by the presence of the detached sting, which will remain in the wound until removed. There may be swelling or edema and the initial intense pain will last only minutes and symptoms should resolve in a few days. Patients who have been sensitized by prior stings may display large, local reactions including 10-50 cm edematous swellings forming a hour post-sting and persisting for 3 days. Symptoms, especially edema, are much more pronounced when the sting is delivered to the face and neck. Many victims with edema and pruritis think they are allergic but these are the typical localized symptoms of the africanized honey bee envenomation. Occasionally similar large reactions occur at sites not adjacent to the

en v enom

sting site and these are considered systemic infections

rather than local reactions.

in non-hypersensitive individuals.

can also cause death

with the melittin becomes a major hemolytic factor.

dry weight), which is non-toxic when pure but in concert

a rthropod

46

47


stinging to the de ath

Uniquely in honey bees amongst bees and wasps of the workers’ stings is their ovipositor. They are barbed, and lodge in the f lesh of mammals upon use and tear free from the bee’s body, leading to the bee’s death within a few short minutes. The sting has its own ganglion and with it continues a sawing action into the target’s f lesh and then releases bee venom for several minutes. The question is how such a trait could have evolved, when it is of such an obvious disadvantage to the individual is resolved when one realizes that mammalian predators can easily destroy the entire colony if not repelled; if the colony is destroyed, a worker being sterile, will die without offspring, so only through defense of the colony can she see to it that her genes are passed on. The barbs ensure that a honey bee’s attack is only suicidal if the attacker is a mammal as they can sting other bees (in inter-colony raids) repeatedly. Thus, under natural conditions, the suicidal aspect of the honey bee sting’s barbs only come into play in the event of an attack which threatens to wipe out the entire colony. The stinger of nearly all other bees and wasps is not barbed, and so can be used to sting mammals repeatedly with the only exceptions being yellowjacket wasps and the Mexican honey wasp who have barbs that are so small that they do not cause the stinging

en v enom

a rthropod

48

stinging more than once.

apparatus to pull free;

49


ch apter thr ee

A MPHIBI A N Amphibians are cold-blooded vertebrates with typically smooth skins; they hatch as aquatic larvae with gills, then transform into air-breathing adults with lungs. The class Amphibia includes frogs, toads, salamanders, and newts and most are capable of living on land or in water. There are nearly 5,000 species of amphibians worldwide, and a signiďŹ cant number of these are poisonous, such as the well-known poison arrow frogs of Central and South America. The poisons in amphibians are usually found in the skin or skin secretions. Frogs and toads are subdivided within the class Amphibians into an order called the Anura. Of the amphibians in the Mojave desert, only two poisonous and potentially dangerous.

species of toad Bufo marinus and Bufo alvarius are considered


h abitats and r el ationships

Although nearly everyone knows one when they

“Frog” may be used for any

No reports of human deaths from Desert toad poisoning have occurred in

see one, the term toad has very little taxonomic

anuran, whereas, “toad”

the Mojave, but about 40-50 pets, mostly dogs, die every year from ingesting

usefulness, even though it is still commonly used

is used for members of the genus Bufo as well as for

to describe the anurans that are not frogs. The two

frogs of similar body form.

or even just mouthing this toad, a clear testament to the potency of the this poison. The milky secretions from the glands of the Desert toad contain over

poisonous species of toads in the United States are

26 biologically active compounds, including potent cardiovascular toxins

both members of the large family of “true toads”

known as bufodienolides and another substance called 5-meo-dmt, which

called Bufonidae. The giant toad also called the

produces psychoactive eff ects.

marine toad or cane toad, or Bufo marinus, is a familiar native to Texas but is endangered and rarely seen. The Desert toad, or Bufo alvarius is formerly called the Colorado River toad, has been popularized by songs and stories about “toad-licking.” Th is toad is native to and found only in the southwestern Mojave.

The cardiotoxic bufodienolides, including bufogenin and bufotoxin are structurally similar to the cardiac drug called digitalis that is purified from the foxglove plant. The bufodienolides are well-absorbed in the gut and ingesting crude toad poison (and even topical exposure from carelessly handling toads) may result in severe headache, nausea and violent vomiting, irregular heart rhythms, blurred vision, and seizures. Severe toxic reactions including death,

not in the true toad family of Bufonidae. They get their name from the keratinous bone on their hind feet that forms a metatarsal “spade” used for burrowing backwards in wet soil. They use this to dig rapidly backward, circling as they descend into deep desert tunnels. These burrows are often shared by other desert creatures, and sometimes

en v enom

will take over their spaces.

in the intense dry heat predators

the closely related cane toad Bufo marinus.

have occurred after mouthing and ingesting the nodes of Spadefoot toads are also anurans, but they are

a mphibi a n

52

53


psychoactive poison

Bufo alvarius requires a minimum overall body length of only three inches

of Bufo alvarius has led some people to ingest the skin of the toad in an

for sexual maturity although breeding adults continue to mature to grow

attempt to experience the psychoactive and/or psychedelic effects. Rather

to be seven inches in length. This desert dweller is of stout build with a

than the expected hallucinations, the usual result is a violent, severe type

squat body and a f lat broad head. The skin is smooth and leathery, sparsely

of poisoning intoxication comparable to a digitalis overdose. The cardio-

covered with pale orange warts or nodes. The belly is creamy colored and

toxic bufodienolides in the toad secretions are well-absorbed in the stomach

usually unmarked. There are one to four prominent round white warts at

whereas the hallucinogenic 5-meo-dmt is typically inactivated in the gut

the corner of the mouth. The granular glands are specialized multi-cellular

by monoamine oxidase (unless the person is taking a certain monoamine

concentrations of tissue. The most prominent of these is the pair of large

oxidase inhibitor) and never makes it into the circulation or to the brain.

kidney-shaped parotoid glands located one on each side of the neck, over

Ingestions of the poisonous secretions are therefore dominated by the largely

and behind the tympanum. Enlarged and elongated glands on the outside

profound effects of the cardiotoxic compounds, leading to nausea, violent

of each hind leg, between the knee and thigh, are called femorals. Simi-

vomiting, severe headache, and potentially low blood pressure and death by

larly, the tibeals are long glands, or a line of shorter ones, that run the full

cardiovascular collapse. Because 5-meo-dmt is inactivated in the gut, there

length between the knee and ankle. An additional gland concentration can

is virtually no possibility of having a “psychedelic� experience by taking

be found on each of the stubby forearms where they are usually are orange

in or eating, otherwise ingesting the secretions, which explains why toad

or creamy colored. On the Desert toad all of these glands

licking is not a very clever or popular recreational drug. bufo alvarius

Interestingly, the hallucinogenic compound 5-meo-dmt is heat-stable whereas the cardiotoxic bufodienolides are not. The integrative medicine physician Dr. Andrew Weil has reported that the crude poison from Bufo alvarius can be collected, dried, and smoked. The bufodienolides become parotoid gland

inactivated by the heat, and the 5-meo-dmt still remains pharmacologically active. Along with Weil’s other ethnopharmacological research the fact that

secrete milky-white Bufo poison.

The presence of the potent hallucinogen 5-meo-dmt in the secretions

the tryptamine derivative 5-meo-dmt is found only in Bufo alvarius and not in other toads led to the hypothesis that the preColumbian peoples of the New World may have smoked the dried secretions from this toad as

highlights the area where parotoid gland is in location to other nodes found on the legs and

a mphibi a n

54

3-1. The most identifying characteristic of Bufo alvarius is the presence of large granular glands that look like nodes. This figure

feet of Bufo alvarius.

en v enom

ritual intoxicant.

a certain kind of

55


noctur nal h abits

With their large size and frequent habit of simply

On land, amphibians will

sitting nonchalantly out in the open as they wait

feed on worms and insects like

for something edible to happen by, Desert toads might seem to be an easy target for predators, but

spiders and fl ies. Each of the amphibian species have many diff erent feeding habits. Some

these large, slow toads are very well defended.

toads may feed by protruding

Bufo alvarius is nocturnal and remains hidden

their long tongue. Whereas,

underground throughout the day escaping the

caecilians will kill their prey

extreme temperatures with the strategy of lead-

with the help of their sharp

ing a subterranean life. At dusk, these desert toads

clincal effects of desert toad poisoning 100

saw-like teeth.

leave their hidden recesses and will congregate in

50

those damp wet areas near springs and streams

this Desert toad called Bufo alvarius. Large healthy toads can be gathered after dark using a fl ashlight and collection box or a cloth bag. Often during the summer monsoon or stormy season Desert toads are common nocturnal guest visitors to human habitats near water or natural desert vegetation. They emerge after the short summer rains in order to feed in large temporary rain pools. During the rest of the year Desert toads will hibernate in their underground spaces.

en v enom

a mphibi a n

56

dr ooling

vomiting

seizur e

dea th

3-2. The main side effects of poisoning from the two varieties of toads are typically minor unless left untreated. Deliberate ingestion of the Bufo poison is always more harmful

to any Mojave creature.

night predator.

The Desert toad can be an allusive

0 s pade t oad (b ufo marinus)

the period of time for the greatest activity for

desert toad (bufo alvarius)

storms. The breeding season May through July is

frequency of ef f ect ( p er cent)

even places like temporary pools left after heavy

mouth ir r ita tion

that may be in fields irrigated for agriculture,

57


bio-indicators

All amphibians breathe through their skin as such they are much more

According to recent surveys, many amphibians

directly affected by changes to any chemistry in the air and or the

are said to have disappeared from areas, where

water quality that is associated with pollution (including loss of ozone layer

they were found in abundance. In fact, some

in upper atmosphere). They are also sensitive to fungi and diseases which can

amphibians like the Poison dart frog, California

infect them through their skin. They also require aquatic habitats for their

tiger salamander and Houston toad are listed

reproduction so they are much more directly aff ected by changes in water

among the endangered species while others are

levels in lakes and streams either by climate or weather changes but also from

already extinct. Many biologists share the idea

changes in human uses of water.

or opinion that climate change, global warming

Because of their complex life cycles they often have to move between habitats making them sensitive to changes in not only those specific habitats that they need for food and shelter but also all the places they need to travel through to get to these habitats. The desert amphibian lives in a variety of arid and semi-arid habitats, such as brushy plains desert, semi-arid grasslands and tree

in the abundant rodent burrows. Any changes in roads, trails, traffic, fi res, logging and other kinds of disturbances can all aff ect the ability of these

declining population of amphibians. For example the harmful ultra violet rays of the harsh Mojave sun aff ect the proper hatching of amphibian eggs as they do not have

en v enom

Mojave regions.

species to survive even in the most remote

loss are all playing a detrimental role in all these

protective shells.

Desert amphibians frequently fi nd their habitat

ensure their survival.

lined canyon lands. Their developed envenomous skills actually

and environmental pollution along with habitat

a mphibi a n

58

59


the role of ultr av iolet light and en venom ation

It is important to mention the role of the intense desert sun in the evolution of envenomation. While It has been demonstrated that species of Amphibians that were exposed to controlled ultraviolet rays as eggs had malformed legs, there are some venomous Mojave animals, including reptiles, and insects such as bees, can see into the near ultraviolet for survival. There are many food sources such as fruits, some owers and seeds stand out more strongly from the background in ultraviolet wavelengths when it is compared with human color vision. Some species of Scorpions will glow or take on a yellow to green color under ultraviolet illumination thus assisting the control of these sometimes fatally venomous arachnids. Urine trails of rodents can be detected using ultraviolet light as well. Many creatures use the ultraviolet wavelength emissions from celestial objects as references for navigation. A local ultraviolet emissor can disrupt the navigation process and will eventually attract the ying insect. Di erent designs of ultraviolet light traps are also used by entomologists to study

60

a mphibi a n

en v enom

it plays with sunlight.

envenomation and the role

61


ch apter four

R EP T IL E Reptiles make up a group of about 8,000 species of cold blooded vertebrates that are divided into four orders: the Crocodilia or crocodiles and alligators, the Rhynchocephalia or tuataras of New Zealand, the Squamata or lizards and snakes, and the Chelonia or turtles. Like birds and mammals, but unlike the amphibians, reptiles are amniotes; during development, the embryo is simply enclosed in an amnion, a tough, membranous sac ďŹ lled with uid. Most all reptiles are oviparous and lay eggs, although some are ovoviviparous and still retain the eggs internally until after they hatch. Most reptiles have three-chambered hearts, a pair of lungs, and a pair of kidneys. Medical scientists have become interested in the unique metabolism of many reptiles that allows them to survive, and in some cases thrive, under and overall conditions.

dangerously harsh habitats


liz ar ds

Lizards are classiďŹ ed in a suborder of Squamata called the Sauria or Lacertilia.

major areas of gila monster habitats

Most lizards are four-legged and have both external ear openings and eyelids. Glass lizards have no true legs, but they do have ears and eyelids. Lizards generally have dry skin and tend not to live in or near water. Many lizards can change color at times of stress or to blend in with their environments; many can also regenerate lost limbs or their tails. The largest lizards in the world n e va da

are monitors, such as the komodo dragon of Asia. At 175-310 pounds it is very dangerous, but more often non-venomous. The only venomous lizards in the world are the Gila Monster and the beaded lizard of Mexico. The Mojave is

arizona

the home of the largest populations of Gila Monsters in the world. There is no other lizard besides the Gila Monster in North America that lays eggs that over winter and hatch the following year. The brightly colored california

Long and slender, short and stout, most lizards have well developed legs, but they come in many styles to suit their particular environment. Their toes, too, may have strong claws for climbing or digging, fringes for shimmying through sand or even webbing for guiding and swimming in

4-1. The circles on this

various desert aquifers that

map indicate the known underground areas where large populations of the

Gila Monster dwell.

can be several miles long.

one to three years to reach adult size.

newborns require

Over thousands of years, some lizards have developed reduced limbs or lost their limbs altogether. These lizards usually burrow underground where they have adapted to also closing their nostrils to prevent sand from getting into them. Desert lizards inhabit scrubland, succulent desert, and oak woodland where they seek shelter in burrows, thickets, and under rocks in locations with ready access to moisture. Such as major groundwater resources. In fact

en v enom

r eptile

64

to like water.

Gila Monsters seem

65


the gil a monster

The name Gila refers to the Gila River Basin in Arizona, where they were once

the decline in groundwater levels and lizard populations 20

plentiful. Recently, large populations of Gila Monsters have been discovered hidden in massive underground caves, where groundwater is more plentiful. Th is suggests they are successful at using their venom as survival. Heloderma means “studded skin”, from the Ancient Greek words Helos meaning the head of a nail or stud and derma, or skin. Suspectum comes from the describer paleontologist Edward Drinker Cope, who suspected that the lizard might be venomous due to the appearance of specialized grooves on pairs of their fi nely shaped teeth.

gila monsters

The venom of Gila monsters is complex and similar to that of the elapid

0

Gila monsters have venomous glands in their lower jaws, rather than in the

more than 20 diff erent toxins that can act synergistically with themselves. The primary toxins in Gila monster venom are called gilatoxin, hemorrhagic toxin, and phospholipase a2. There is also a component called hyaluronidase that causes tissue breakdown and aids in the spread of the venom away from the bite. Gila monsters do not have fangs, but instead have grooved teeth that are used to direct the venom into the wound by capillary action. Th ey

all lizards

upper jaws. Th e venom glands are modified salivary glands and they produce

groundwater well test levels ( inches)

group of venomous snakes, such as coral snakes. Unlike venomous snakes

-20

the form of anaphylaxis or respiratory failure due to the proteins contained

4-2. This data compares the decline in recent groundwater levels to the lizard populations of the Mojave. The Gila Monster, a venomous animal, demonstrates a more

en v enom

the venom.

within the toxic mixture of

2005

Fatalities have occurred, but mostly in the case of an allergy developing in

2000

a chain reaction of swelling, nausea, vomiting, and occasionally bleeding.

year

competitive survival rate.

in prey, although it usually causes extreme pain in humans. It also causes

1995

The venom itself primarily contains neurotoxins and causes respiratory failure

1990

a sufficient amount of venom.

19 85

19 80

typically bite or inject for a prolonged time, to allow the penetration of

r eptile

66

67


gila monster envenomation 24

Pain is initially confi ned to the area of the bite. When bitten, it is important to disengage the lizard as soon as possible. Th is may be done by placing 12

a strong stick between the bitten part and the back of the lizard’s mouth and pushing against the rear of the jaw. If this doesn’t work, immersion in water may make it release its hold. The brittle teeth of the Gila monster may

Most lizard bites actually occur on any of the fi ngers, or the hands, and arms when someone is working with or trying to catch a lizard. The

bites usually occur when a person (especially a child or a even a hiker) death

convulsions

delerious

respiratory arrest

blurred vision

headache

necrosis

numbness

vomiting

swelling

pain

0

disturbs a lizard.

time (hours)

legs and feet are also common bite sites. These

by a medical professional.

remain imbedded in the wound and must be removed

4-3. This timetable shows how long a Gila bite victim has to experience the various side effects and

en v enom

r eptile

68

the envenomation.

how long the the victim has to survive

69


h abitats and r el ationships

The Gila monster emerges from hibernation in the

The juveniles typically have larger bands of pink scales than adults, although the

Urban sprawl, the pet trade

months of January or February and mates in May

banded Gila monster, or h. s. cinctum, has a tendency to retain the band pattern.

and habitat destruction has

and June. It is the male who initiates courtship

h. suspectum sexually matures at 3-5 years. After egg-laying, adult Gila monsters

by fl icking his tongue to search around for the

gradually spend less time on the surface to avoid the hottest Mojave summer heat

female’s scent. If the female rejects his advances

(although they may be active in the evening), eventually starting their winter

several states. It is illegal to

she will bite him and crawl away. When successful

hibernation around November. Juvenile Gila monsters are known to eat up to

hunt, trap or capture any

the copulation has been observed to last from 15

50% of their body weight in one feeding, the adults may consume up to 35%

Gila Monster.

minutes to as long as 2.5 hours. The female will lay

of their body weight. When eating such large amounts they may have to only

eggs in July or August, burying them in sand 12.7

consume three of these large meals a year.

directly aff ected the process of Gila reproduction. Th is has

centimetres (5.0 in) below the surface. The clutch consists of two to twelve eggs, with fi ve being the average clutch. The process of incubation lasts nine months as the hatchlings emerge during the months of April through June the following year. The hatchlings are about 6.3 in long, and are able to bite and inject venom upon hatching.

Little is known about the social behavior of h. suspectum, but they have been observed engaging in male-male combat, in which the dominant male lies on top of the subordinate one and pins it with its front and hind limbs. Both lizards arch their bodies, pushing against each other, and twisting around in an eff ort to gain the dominant position. A wrestling match ends when the pressure exerted forces them to separate, although bouts may be repeated over a continuous amount of time. These bouts are typically observed just before

The Gila juveniles typically have larger bands of pink scales than adults,

the mating season. It is thought that those with greater strength and endur-

although the banded Gila monster has a tendency to retain the band pattern.

ance win more often and enjoy greater reproductive success.

The Gila monster will sexually mature at the between the ages of 3-5 years. After the female egg-laying, adult Gila monsters gradually spend less time on the surface to avoid the hottest part of the summer, although they become far when they engage prey.

more active during the evening

resulted in legal action in

Although the Gila monster has a low metabolism and one of the lowest lizard sprint speeds, it has one of the highest aerobic scope values among all lizards, allowing them to engage in intense aerobic activity for a sustained period of time. It has also been observed that males have a higher aerobic scope than females, presumably because of sexual selection for a trait advantageous in prolonged combat. The Gila monster may live up to

en v enom

r eptile

70

30 in captivity.

20 years in the wild, or up to

71


current estimated gila monster population 1 0, 000

Th ough the Gila monster is

exenatide (marketed as Byetta) for the management of human type 2 diabe-

a venomous animal, laggard

monster’s saliva. In a three-year study with people with type 2 diabetes, ex-

movement combined with wild

tes. It is a synthetic version of a protein, exendin-4, derived from the Gila

captive

5, 000

In 2005 the United States Food and Drug Administration approved the drug

slow reaction times means that it poses little threat to humans.

The vast e ectiveness is due to the fact that the lizard hormone is about 50 percent identical to glucagon-like peptide-1 hormone in the human digestive tract that increases the production of insulin when blood sugar levels become

g il a monst e r s

enatide led to healthy sustained glucose levels and progressive weight loss.

0 2009

2008

2007

2006

2005

2004

2003

2002

2001

hormone, helping diabetics keep their blood sugar levels from getting too

1999

high. The lizard hormone remains e ective much longer than the human y ear

and nurture the

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Gila monsters in captivity.

4-4. The estimated Gila Monster population indicates that more are in captivity. The San Diego Zoo the first zoo to successfully breed

in appetite contributing

to weight loss.

high. Exenatide also slows the emptying of the stomach and causes a decrease

r eptile

72

73


snakes

Snakes are long, scale-covered vertebrates with limbless bodies. They also lack

map showing location of the lake mead area

eyelids and external ear openings. Along the underside of the body, snakes have a specialized row of scales. Some families of snake retain vestigial pelvic girdles although none have pectoral girdles. The bones of the upper jaw are not fused at the snout, but can unhinge when eating. 45,000 people are bitten by snakes every year in the us. There are 11 species of rattlesnakes identiďŹ ed

ally occur in the Lake Mead region. Recreation and casual human activities

v i r g i n r i v er

n e va da

in the Mojave. Most of them occur in rocky areas but most snakebites actu-

induce skakebites in general, and this region is surrounded by urban sprawl. Snakes are cold-blooded and take on the temperature of their surroundings. The snake shown in these images was in direct sunlight, however it was still

california

fend itself or make a hasty retreat. The large surface area of a snake’s body allows a snake to warm up and cool down faster. Snakes will often coil their

lake mead

Th is increases the snake’s energy level, making it easier for the snake to de-

c o lo r a d o r i v er

a bit cooler than the person holding it. Snakes warm up by lying in sunlight.

bodies to control the amount of skin exposed to sunlight. Snakes cool down by seeking cooler shaded areas and during very hot weather seek shelter under a r i zo n i a

rocks or underground. During long periods of cold weather, snakes often choose to hibernate. Some of the more common snakes seen include the highly toxic Mojave green rattlesnake, the sidewinder rattlesnake, the California king snake, the red

4-5. Lake Mead hosts large areas of human recreation

The green snake thrives

en v enom

in this region.

communities in the Mojave.

sidewinder rattlesnakes are

dangerous and venomous.

racer and the gopher snake. Of these snakes, only the Mojave green and the

r eptile

74

75


The most notable characteristic of all rattlesnakes

The function of the rattle has been debated for centuries, but it is now clear that

found in the Mojave is the typical presence of the

it serves as a warning to anything that might harm the snake. It is a fact that

rattle or string of rattles at the end of the tail. The

Rattlesnakes in the wild are seldom observed using their rattles but only in the

lightweight, hollow rattle string is composed of

cases where they are disturbed, and they do not use their rattles to distract or

interlocking rattle segments with multiple lobes

attract prey (such as inquisitive birds), or to locate other rattlesnakes.

the rattle.

on each segment of

The size of the rattle and its relationship to the rattlesnake’s age is often a source of controversy. Many myths abound, including the myth that rattlesnakes have no rattle at all for up to three years, or that they “throw off ” their rattles. They don’t, although they can break off. In truth, wild rattlesnakes

venomous snakebites in the mojave

usually have fewer than 16 rattle segments, although snakes that are raised

100

in captivity may have more. Another misconception is that all species of the

rattle snakes

that make little to no noise.

rattlesnake can rattle. Some actually have rattles

50

ve nomous bit es (perc en t)

all others

0 2009

1999

1989

1979

r eptile

76

4-6. More than half of snakebites occur with children

or pets.

en v enom

year

77


A rattlesnake’s fangs function like hypodermic needles to deliver venom.

overall strike range of mojave snakes

These long, thin, hollow specialized front teeth fold up and lie fl at against the

20

roof of the mouth when not in use. Within the gum, the base of each fang is connected to the venom apparatus that lies further back in the mouth. Fangs are frequently broken off or shed, and new fangs replace the lost ones within a few weeks. The fangs are extended to about 90 degrees only to inject venom; otherwise, they are retracted and are not used when swallowing prey. There is often confusion regarding the terms bite and strike. To make a bite a rattlesnake must only open its mouth and embed its fangs. A more restrained rattlesnake can bite (as can a decapitated rattlesnake head), but it can’t

10

strike because that involves coordinated movement of the head, neck, and body of the whole snake. Unrestrained rattlesnakes typically deliver a bite via a strike; defi ned as the rapid movement of the head towards a target, carried out by extension of the head and front part of the snake body, with the middle and tail end

from a fully extended or uncoiled body position, the strike is almost always delivered to 0

4-7. This scatter chart compares the two components of speed and range of the strike that the typical

en v enom

snakes in the Mojave region.

rattlesnake will have. This data compares well with the

25

20

15

10

05

10 range (feet)

the victim from a striking coil.

speed (m/s)

(posterior) of the body remaining stationary. While a rattlesnake can bite

r eptile

78

79


Th e venom of diff erent

Symptoms generally occur immediately, but only about one third of all bites

effects of a venomous snakebite

species also varies what the

manifest symptoms. When no symptoms occur, probably little to no venom

40

overall eff ect of a snakebite

was injected into the victim. In 50 percent of Mojave snake bites, very little

will be. Some venom acts

venom is injected because the snake has to chew the skin for envenomation

directly on the nervous system while others may

to occur. In as many as 25 percent of all venomous pit viper bites, no venom

simply apply toxicity

is injected, possibly because the fangs may be injured, the venom sacs may

solely in local tissues.

be empty at the time of the bite, or the snake may not use the fangs when it strikes. Poisonous snakebite venom contains some of the most complex toxins

The clinical effects of envenomation include

50

pain, swelling, and tenderness at the site, steady increased swelling and bruising away from the bite site. Low blood pressure and dizziness with uncontrollable nausea along with some vomiting and diarrhea. Numbness ocurring especially

breathing, confusion, and ultimately unconsciousness. Frequently, the limb that has been envenomated will swell tremendously and will

of blood vessels. Blood blisters may also form around the

r eptile

en v enom

has to survive the envenomation.

80

coma

death

delerious

c onvulsions

b lurred vision

4-8. This timetable shows how long a snakebite victim has before the bite becomes life threatening and the prey

become purple from blood that has leaked out

area of the bite.

re spiratory arrest

necrosis

h eadache

vomiting

nu mbness

pain

0 swelling

time (hours)

around the mouth, muscle twitching, diffi culty

brain, heart, kidneys, and blood.

known; venoms can affect the central nervous system

81


delivering snake venom

Snake size inf luences venom delivery. Bigger

Rattlesnakes and other crotalids use their venom primarily to fi rst halt the

rattlesnakes really do inject more venom. More

victim, then kill, and digest prey, and as a certain defense against predators

recently, we have begun to examine defensive

and aggressors. Th is becomes the primary mechanism of an envenomous

strikes, which are particularly important to the

toxicity is blood system massive leakage of blood vessels, causing danger-

problem of human snakebite. Rattlesnakes also

ous cardiovascular shock from a loss of fluid directly within the vascular

appear to inject more venom into study models

system into the surrounding cells and tissues. The venom interferes with

of human limbs (warm, human-scented, saline

the typical normal blood clotting mechanism, thereby quickly increasing

fi lled gloves) than into mice. However, roughly

the rate of internal bleeding. The components of some kinds of crotaline

10 percent of the bites are dry, which is much

venoms, especially Mojave toxin also cause neuromuscular paralysis, which

more frequent than that observed for predatory

can result in a speedy death from respiratory arrest.

bites. Large rattlesnakes inject far more venom than small rattlesnakes when biting defensively. The larger rattlesnakes have much more venom available and experimental evidence from predatory strikes suggests that even smaller snakes can

sight is basically poor, sensitive only to movement. Snakes usually fi nd prey with their advanced sense of smell. Snakes have a specialized organ called the Jacobson’s Organ, which consists of two pits lined with a sensory tissue. When snakes fl ick their tongue, tiny particles of scent are transported

en v enom

to the pits behind the venom gland.

according to their sense of prey.

control, or meter, their venom

Lacking external ear openings, hearing in snakes senses vibrations. Their eye-

r eptile

82

83


predatory strikes of rat tlesnakes 20

Several companies around the

Venom is ejected from the fangs, sometimes in multiple pulses which is most

world collect and breed snakes

commonly observed when a snake is physically restrained and sometimes

to be used in producing their venom. Th e practice is vital in protecting snake species while

even from a third or reserve fang. Venom extraction which is commonly called “venom milking,” is a very dangerous practice and conducted with research professionals and only for legitimate reasons. It is actually true that

traditional snake hunter. All

most professionals who extract venom eventually suff er a serious or even

Mojave snakes, however, are

fatal snakebite. Extractions should be performed only to study venom or the

currently protected by law

mechanics of venom expulsion. The flow of venom

against venom procurement.

Milking snakes can be quite important, as venom is the key ingredient in anti-venom.

0

Or “antivenin” as it is often called. The Irula people in Tamil Nadu, India, actually make their living as snake milkers, who catch, milk

anti-venoms can fetch 2,000 dollars per gram. Venom procurement

0

4-9. These data were obtained from the predatory strikes of various-sized Rattlesnakes (Crotalus viridis). Even though baby and juvenile rattlesnakes have more toxic venom larger snakes have

en v enom

venom in the glands and they use it.

substantially more

60

50

40

30

20

10 snout-vent length (cm)

may off er economic opportunities.

venom expended (mg)

and release the wild snakes. There are certain

is controlled by the snake.

providing income for the more

r eptile

84

85


learning behavior

While getting bitten by a snake might strike fear in people, the fangs are not where the venom comes from, they are simply methods of transfer. The place

total snake envenomations in the mojave desert 10,000

where the venom is made is in special glands located on the head of the animal. The venom glands di erentiate into false and true venom glands. False venom glands are made up either from mucus producing supralabial glands that run on either side of the head extending as a continuous strip from near the snout to below and well tucked behind the eye. These then lead Snakes are not slimy but if they get frightened they may defecate on you as a way of showing

thoroughly with soap and hot water, as snakes do carry salmonella bacteria in their feces. It is helpful to remember when you are holding a snake that it likely sees you as a very odd tree, and does not recognize you as a human being. Snakes also react by instinct rather than thought, and as long as you keep this in mind, being around snakes is

2005

2000

1995

1990

1985

year

4-10. Overall snake envenomations in the United States has steadily decreased. In the Mojave much of this decline is largely the result of the overall education about

r eptile

the overall behavior of envenomous animals.

en v enom

0 1980

as being interesting observation experience.

very easy to do as well

86

5,000

fear. If this happens, be sure to wash the area

snake envenoma tions

lead to the bases of the teeth

to several ducts that

87


Animals who do envenomate do so for survival. There are many ways to prevent envenomation. Some bites, such as those bites infl icted when you step on a snake are nearly impossible to prevent. However, there are precautions that can reduce your chances of being bitten by a snake. Th ese include leaving snakes alone. More often people are bitten because they try to kill a snake or get too close to it. Stay out of any tall grass unless you wear thick leather boots and remain on the hiking paths as much as possible. Keep hands and feet out of areas you cannot see. Do not pick up rocks or fi rewood unless you are clearly out of a snake’s striking distance. Be cautious and alert when climbing rocks. If you are bitten, don’t use any tourniquet, as this isolates the venom across only a small area and causes the digestive enzymes in the injected venom to concentrate the damage. Don’t use alcohol orally as it speeds the heart and

en v enom

the body’s counteracting ability.

blood flow and reduces

r eptile

88

89


bibliogr aphy

Ashton, Ray Jr. and Patricia Sawyer Ashton. Reptiles and Amphibians: Part One, Th e Snakes. Miami. Windward. 1988. Bauchot, Roland. Snakes: A Natural History. [translated from the French by Catherine Berthier]. New York: Sterling. 1994. Gotch, A.F. Reptiles, Th eir Latin Names Explained. New York: Blandford Press, 1986. Hayes, 1995, Animal Behavior. 50:33–40; Hayes et. al., 1995. Klauber, L.M. Rattlesnakes: Their Habitats, Life Histories, and Influence on Mankind. Second Edition. First published in 1956, 1972. University of California Press, Berkeley. 1997. Mattison, Chris. Lizards of the World. New York: Facts on File. 1989. McGavin, George. Insects, Spiders, and Other Terrestrial Arthropods. London; New York, N.Y. : Dorling Kindersley, 2002. Mehrtens, John M. Living Snakes of the World. New York. Sterling Publishing Co. 1987. Munro, P. et al. A Mojave Dictionary. Los Angeles: ucla, 1992. Nevada’s Plants and Animals: Banded Gila Monster. (n.d.); Retrieved from http://

en v enom

www.dfg.ca.gov/hcpb/species/jsp/

inde x

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index

chapter one 1-1.

page 13

aver age annual hospitilization for mojave animal bites

1-2.

page 15

the mojave desert

1-3.

page 17

over all venom use in the mojave desert

1-4.

page 18

mojave prey

1-5.

page 20

common dangerous and nondangerus mojave animals

1-6.

page 23

clinical effects of envenomation

chapter two 2-1.

page 33

major areas of venomous arthropod populations

2-2.

page 37

clinical effects of envenomation from mojave arthropods

2-3.

page 39

location of the chelicer ae in the arthropods

2-4.

page 40

dorsal view of the brown recluse spider

chapter three 3-1.

page 55

bufo alvarius

3-2.

page 57

clinical effects of desert toad poisoning

chapter four 4-1.

page 65

major areas of gila monster habitats

4-2.

page 67

the decline in groundwater and lizard populations

4-3.

page 68

untreated gila monster envenomation

4-4.

page 73

current estimated gila monster population

4-5.

page 75

map showing location of lake mead area

4-6.

page 76

annual venomous snakebites in the mojave

4-7.

page 78

over all strike r ange of mojave snakes

4-8.

page 80

effects of a venomous snake bite

4-9.

page 84

predatory strikes of r attlesnakes total snake envenomations in the mojave desert

en v enom

4-10. page 87

inde x

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Envenom; poisonous desert animals  

Documentary of naturally occuring toxic delivery systems.

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