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The Threats on an Endangered Species: Brachyteles Brandi Dean ABSTRACT- The muriqui monkey (Brachyteles) is an endangered species located in Brazil. It has been on the IUCN Redlist since 1982. Deforestation, mining, and hunting have greatly reduced the muriqui’s population and natural habitat. These monkeys have developed extremely adaptable behaviors that have greatly benefitted the re-growth of their population. Those behaviors, along with constant observation and many protections given by the government may be enough to restore the muriqui population. BACKGROUND- Muriquis are monkeys found in the genus Brachyteles. There are two species of muriqui that only differentiate by where they live: B. hypoxanthus (northern) and B. arachnoides (southern). These monkeys are closely related to the Woolley and Spider monkeys, and both species are endangered (Groves, 2005). Muriqui are easily distinguishable by their markings (Strier, 2000). Their bodies are a light tan colored and their faces are a darker brown. They have very long arms, legs and tail. The average life expectancy of B. arachnoides and B. hypoxanthus is still unknown, but it is assumed that they do have a long life spans (Mendes, et al. 2008). Muriquis are confined to specific areas of southeastern Brazil in the Atlantic coastal forest. The estimated population of muriquis consists of about 1,300 individuals (Mendes, et al. 2005 & 2008). Almost 88% of B. arachnoides live in a large, continuous forest and more than 50% of northern muriqui live on fragmented, privately owned forests (Strier 1996 & 1997). There are two forests where muriqui have been observed frequently are the Parque Estadual de Carlos Botelho (PECB) and the EstaJco Biologica de Caratinga (EBC). The EBC has tall trees


and a mostly warm climate. The plants lose their leaves once a year and start growing more as soon as the old leaves fall and have adapted to a not necessarily warm or cold climate. These characteristics make up a tropical semi-deciduous mesophytic broadleaf forest (Fonseca, 1985). Male muriqui remain in the groups that they were born in for their entire lives (Strier, 2002). Relationships among males in the same group are relatively equal. There are rarely any fights or aggressive behavior (Strier, 1900 & 1992). Young males tend to be friendlier towards the mature muriqui while mature males tend to value the prime-aged males more (Strier, 2002). Female muriqui leave the groups that they were born in when they are around 5 to 7 years old, which is around the time they become sexually mature. They spend the rest of their lives in the group where they find their first reproductive mate (Strier, 1996 & 2002). In primates, there is usually increase in aggression between males when the females go in to estrus. This is not seen in muriqui groups. The associations between male muriqui during the mating seasons are more helpful in monitoring more estrus females than interacting with each female individually and fighting the males (Strier, 2002). THREATS- There are three major anthropological threats to the tropical forests of Brazil where the muriqui survive: hunting, deforestation and mining (Mendes, 2008). Today, less than 7% of the Atlantic coastal forest exists and most of it is fragmented (Fonesca, 1983 & 1985). The deterioration of the forest can be attributed to logging and timber plantations, cattle ranching, farming, urban expansion, highway construction and general infrastructure development (Mendes, 2008). Hunting the muriqui by the natives for sport is a cultural trait that dates back to the colonization of the area (Mendes, 2008). The Brazilian mining mainly collects bauxite, sand, clay and granite. Mining takes a big toll on the forest. It is an accelerator of deforestation, erosion, flooding, silting and pollution of rivers and streams (Mendes, 2008).


These threats cause a significant decrease in the muriqui’s habitat and availability of food. The deforestation causes the forest to be fragmented which leads to higher densities of muriqui in certain areas. The density of muriqui populations affects the female’s birth-bias (Strier, 2000). According to the local resource competition hypothesis, there should be a bias in the sex of the infants to disperse sex and avoid stressed food competition (Clark, 1978). If there is a high-density then there is more prominence in female births. This happens because with density comes competition for food, and a female leaves the group after a certain amount of time, reducing the competition. If densities are low, then food competition is more relaxes and the birth-bias shifts to male (Strier, 2000). Males do not leave the group. Muriqui’s are partly frugivores and partly folivores, depending on the seasonal availability of the food (Martins, 2006). Fruit makes up about 20 – 60% of the muriqui’s diet (Milton 1984). Flowers and their nectar are also seasonally included in their diet (Ferrari & Strier, 1992). A muriqui’s diet becomes more leaf prominent when the availability of fruit and flowers becomes scarce (Ferrari & Strier, 1992). If these anthropological threats continue, then there will be more fragmented areas of the forest that will have smaller food patches for the muriqui. The diets of the muriqui that live in these fragmented areas are forced to include more leaves than the diets of the muriqui that still live in the remaining undisturbed forest (Strier, 2000). The muriqui respond to the increase in food competition by separating their large groups into smaller groups and dispersing to find other food sources (Strier 1991 & 1989). This fissioning is only temporary, the groups reunite at larger food patches when the competition for food lowers (Strier, 1989). They rejoin their groups to better defend the larger food source (Wrangham, 1980). During periods of food shortages infants and young muriqui are the most susceptible to stress (Froehlick et al. 1981).


The fragmented forest due to farming, mining and deforestation causes the muriqui groups to be more isolated. This could lead to inbreeding among close relatives which increases the loss of genetic diversity and increases the expression of lethal recessive genes (Strier 2000). These risks are amplified in the muriqui because they have a relatively long life span, meaning adults and their offspring can be sexually active at the same time (Strier 2000). If a population was highly inbred high infant mortalities and low birth rates would be observed in the muriqui groups (Ralls et al. 1986). CURRENT STATE OF THREATS- Currently, there are still some areas in the forest where the muriqui are still hunted, mostly by squatters. The national parks that contain forests with the muriqui do not allow hunting by anyone (Garcia, 2005). There are still large threats of illegal harvesting of plants, like palm trees, and threats of natural damage, such as wild fires that reduce the forest. The state and national parks allow tourists to wander in possible muriqui habitats, but some have certain restrictions around where muriqui are known to live (Garcia, 2005). The forest is slowly growing back; there is secondary growth in places of the forest that were used for farming and logging (Strier, 2000). These areas support a food source with more variation and density than the older, less disturbed regions of forest (Peres, 1996). The secondary growth has been able to support muriqui population growth and an expansion of their home range by allowing their diets to have more variety (Strier, 2000). Having a more diverse diet helps the muriqui survive times when fruit availability it scarce. The small populations of muriqui were expected to experience the negative effects of genetic drifts and inbreeding leading to a vulnerability to extinction. But, over the years of observing the muriqui, it was seen that their population has been continuously growing due to a strongly female-biased infant sex ratio and low mortality rates (Strier 1991 & 1996). The highly


dense groups helped to increase the population but if the groups were to decrease due to any catastrophic even, then there would be a more male-biased infant sex ratio and the muriqui population would become more susceptible to extinction (Strier, 2000). If the muriqui were suffering from inbreeding then there would be a high mortality rate for juveniles (Ralls et al. 1979). The low mortality rate suggests that they are not closely inbred. Muriquis have been expanding into new parts of the forest, which suggests that there are parts of the forest that they have not yet exploited but are capable of sustaining their population (Strier, 1991). This means that muriquis have not reached their population limit. Even if these unoccupied regions of the forest have different vegetation than the currently populated area, observations of the muriquis have shown that they can adapt their diet easily. These adaptations may alter their grouping patterns (de Sa & Strier, 1992). Today, the muriqui population seems to be steadily growing. PROTECTIONS AGAINST THREATS- Most of the forest where the muriqui populations exist are in state and national parks or are protected in some other ways (Mendes, 2008). Some of the largest areas known to have muriqui are: Guaraqueรงaba Environmental Protection Area, Paranรก (283,014 ha), Alto Ribeira State Park (55,0000 ha) and Intervales State Park (45,000 ha) among others. There have been long term research projects enacted to continually observe the state of

the muriqui population (Talebi and Soares, 2005). The projects are essential to construct an efficient and beneficial conservation plan. In 1998, a Population and Habitat Viability Analysis was constructed for the muriqui (Rylands et al. 1998). This analysis led to more surveys in the surrounding areas. In 2002, a Committee for the Conservation and Management of the Muriqui was created by the Brazilian Institute for the Environment. There are captive programs that receive wild muriqui infants yearly because their mothers had been killed by illegal harvesters


(Mendes, 2008). From these efforts, the muriqui has been promoted from “critically endangered” in 2000 to just “endangered” in 2003. HUMAN POPULATIONS/CULTURES AFFECTED- Muriqui help pollinate flowers and disperse the seeds of the fruit they eat. This not only benefits the environment, but also the natives that live off of the environment. They pollinate flowers when they eat the nectar of seasonal flowers. When they reach in the flower to get the nectar pollen gets on their face and hands, which can then be transferred to the next flower they get nectar from (Ferrari & Strier, 1992). They also eat a wide variety of fruit, and don’t fully digest the seeds. Muriquis move fast over large areas of land, digest their food in a matter of eight hours and defecate in high trees (Martins, 2006). These behaviors create a vastly scattered pattern of seed dispersal in the muriquis stool (Martins, 2006). The restrictions of muriqui hunting have affected the natives that hunted them as a cultural tradition. The natives were probably also using them as a food source, meaning that when they couldn’t hunt them anymore they had to find another food source to replace them. The protection of the muriqui’s habitat has made development in that area of Brazil to be slowed. No urban development can be made in any of the parks or protected areas where the muriqui live. The great toll that mining has on the forest and surrounding environment destroys the natural resources that the human population uses to sustain their lives. It pollutes the drinking water and kills the fruit trees (Mendes, 2008). Overall, the threats on the muriqui also negatively affect the human population. CONCLUSION- From the many years that the muriqui have been observed, it can be seen that there has been a slow steady increase in their overall population size. Even though the threats


still persist, there have been many conservation efforts made to protect the muriquis. The muriqui have a way of changing their behavior once their resources or habitat becomes scarce. When resources are low, they separate into smaller groups and the females have mostly female offspring. These behaviors have been the most beneficial in preserving their healthy population. Studies and observations should still be made on the muriqui to make sure the steady population increase remains.


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Strier, K. B. (1992). Causes and consequences of nonaggression in the woolly spider monkey, or muriqui (Brachyteles arachnoides). Aggression and peacefulness in humans and other primates, 100-116. Strier, K. B. (1991). Demography and conservation of an endangered primate, Brachyteles arachnoids. Conservation Biology, 5(2), 214-218. Strier, K. B. (1989). Effects of patch size on feeding associations in muriquis (Brachyteles arachnoides). Folia Primatologica, 52(1-2), 70-77. Talebi, M., & Soares, P. (2005). Conservation research on the southern muriqui (Brachyteles arachnoides) in S達o Paulo State, Brazil. Neotropical Primates,13, 2002-2005. Wrangham, R. W. (1980). An ecological model of female-bonded primate groups. Behaviour, 262-300. Zingeser, M. R. (1973). Dentition of Brachyteles arachnoides with reference to Alouattine and Atelinine affinities. Folia primatologica, 20(5-6), 351-390.

The Threats on an Endangered Species: Brachyteles  

This is a review on multiple articles focusing on the health of the Brachyteles population in multiple locations.

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