THE AQUATIC FROGS OF AFRICA

Keeping and breeding the African dwarf clawed frog.

By Paul Irven

The dwarf clawed frog has long been a popular addition to home aquaria, often being housed with fish in a community tank. However, these diminutive aquatic frogs can be more successfully kept and bred, in their own dedicated aquarium. This article will discuss my personal experiences of keeping and breeding this interesting amphibian.

The African dwarf clawed frog, from the genus Hymenochirus, is a member of the Family Pipidae, and is also related to the much larger Xenopus frogs. There are four recognised species within the genus Hymenochirus; H. boettgeri, H. boulengeri, H. curtipes and H. feae. These species are found from the forests of Equatorial Africa to the tropical rainforests of Nigeria and Cameroon in the north, and south through Gabon to the Congo River basin in the east.

Known as the Zaire or Congo dwarf clawed frog, Hymenochirus boettgeri is found in Nigeria, Zaire and the Cameroons, whilst H. curtipes is found in the lower Congo basin and is known as the Western dwarf clawed frog. The Gabon dwarf clawed frog H. feae is essentially found in the Gabon and Hymenochirus boulengeri is known as the Eastern dwarf clawed frog. All species are very similar visually, so individual identification is not easy, but the two commonest species in captivity have always been H. curtipes the “Western” and H. boettgeri the “Congo”.

In the wild, they inhabit shallow, slow-moving rivers, creeks and still ponds during the dry season and move to flooded forest areas during the rainy season. Their colouration ranges from a dull green to a light brown or grey with dark spots. This provides them with the ideal camouflage against the bottom of their watery environment. Dwarf clawed frogs measure between 1 to 1.5 inches in length and they have three claws on each back foot, a pointed snout and a narrow body and can live up to five years.

The commercial imports of African dwarf clawed frogs into the UK for the aquarium trade began in 1975 and continued throughout the 1980s, as they proved very popular. Since then, imports have tailed off dramatically. Today, they are less commonly available in aquatic outlets and fewer are kept in private aquaria as a result.

I first started keeping African dwarf clawed frogs in 1993 and I first bred them in 1994 but due to work commitments, they left my collection in 1995. I always believed mine to be the “western” variety, going on details of where they were imported from in 1993. Then, some 25 years later in 2020, the species returned to my care once again when I was offered four mature specimens that were being kept in a large mixed-species community fish tank.

These frogs can be kept as part of a community aquarium. However, I chose to keep my first young specimens in their own “species-tank” and for various reasons, I would recommend this method to anyone thinking of keeping them.

The first frogs I obtained in 1993 were a group of five individuals purchased from different aquarium outlets to increase the chances of them being unrelated. All five were mixed in a neutral tank environment. This allowed them to “pair off” naturally, as sexing these frogs is very difficult, especially when very young. So, by letting them choose their partner, it helps to ensure strong opposing sex pairings by natural selection. For many social species, I have always believed that allowing for natural pair selection facilitates stronger and better pair bonds to be established. In many cases, this will directly lead to more productive breeding as a result.

There are no specific aquarium size requirements for this species, but I would suggest that a small-to-mediumsized aquarium is most suitable (no more than about 2ft in length). They are a small species and are quite timid by nature. In my experience, they seem to appear more secure in a smaller environment. This also allows the keeper to control the water parameters better. I have used both plastic and glass tanks for this species, although glass may provide a greater level of temperature control.

Good filtration and water aeration are crucial but this must not be too vigorous. The water movement needs to be subtle, remembering that they are not strong swimmers. In the wild, they inhabit still pools and very gentle streams. A planted aquarium is always best and plenty of hiding places are another important aspect of their captive care. They spend much of the daylight hours resting or hiding, so the provision of small “caves” built from carefully arranged rocks, stones or slate is useful. Care should be taken because these frogs can get their thin legs easily trapped by larger substrate material, hence why using a small gravel substrate is best. I would certainly not recommend using sand, because of their method of eating, which is to launch themselves in a somewhat random fashion at their food and so the potential for ingesting sand particles would be high.

Good water quality is very important, I have always used a commercial water treatment such as “Aquasafe” which is readily obtained in most aquarium outlets. This neutralises any potential chemicals present in the water including chlorine. Water that is soft, but mildly acidic, is preferred. The depth of the water is important and should only be around 12 inches high, remembering that these frogs need to constantly return to the surface for air. The ideal water temperature should be around 24°C but can range up to 27°C as a maximum temperature. That said, some people suggest that low temperatures of 15°C can stimulate spawning behaviour, although I did not try this and personally feel that is too cold. A good aquarium thermometer with a thermostat incorporated should control the temperature, but the position of the tank is also important as excessive sunlight can be detrimental. Standard overhead tubular aquarium lighting is sufficient, but again, this must not be too bright or too hot. Therefore, LED lights may not be suitable for these frogs.

African dwarf clawed frogs will readily eat all manner of small aquatic live-food such as daphnia, tubifex, blood worm and brine shrimps. Although they can be accustomed to eating the freeze-dried equivalents, in my experience, they much prefer live food and are much healthier on it too.

If the frogs have never eaten freeze-dried food before they will probably refuse it and this can be problematic if supplies of live food are not always reliable. I found this to be the case myself when my supplier suddenly let me down and I couldn’t find another source of live food quickly enough. I would say this is one of the biggest issues in keeping the species long-term.

These frogs are said to be nocturnal, but I found them to be fairly crepuscular as they become accustomed to your feeding pattern or routine. They “hang” in the water eagerly waiting for food, and I always fed mine every evening. Feeding times spark greater activity and they can become quite aggressive towards one another whilst feeding. If you try to feed each frog in its own area or corner of the tank it will reduce competition to a degree, which can be quite rough, as the frogs lunge for their food they will tussle and bite each other`s legs in the squabble. They are territorial over food and clumsy. They will not come up to the top to feed but wait until it drops to the bottom of the tank. Some people feed them twice a day, morning and evening, but I would suggest that if you do that use only small amounts at each feed. Over-feeding can be a problem, as they are ravenous feeders, which can cause obesity, which will be detrimental to any breeding attempts. Their body shape is naturally curved downwards which facilitates their hunting, stalking and searching method of feeding amongst the substrate.

Interestingly, when I obtained my second, older, batch of frogs more recently (that had been kept in a large mixed community of fish, alongside a large pair of musk turtles), they were used to swimming up for their food. This is probably because of the competition for food from the fish and turtles and I wondered how they managed to get enough food at all living in this environment. Having kept the species in their own tank in the past, and bearing in mind these frogs were used to the fish, I decided to try this older group in a small mixed community fish tank. But I also created a feeding device to make sure they got enough food and to help prevent the fish from eating it before the frogs did. This device was simply a length of clear aquarium air-line pipe gently cable-tied to an aquarium glass scraper rod, with a syringe at one end so that I could siphon up the food and direct it right in front of the frogs. This worked very well, but it wasn’t long before the fish soon discovered this novel feeding device for themselves too.

It is interesting to note that these frogs occasionally shed a thin layer of skin, presumably as they grow, and I have seen them consume this as it is pulled from their bodies. If you do keep these frogs in a community fish tank, another thing to consider is that any fish species that have a sucker mouth, such as algae-eating species, will try to latch onto these frogs, either by mistake or on purpose, but it is clear that the frogs do not appreciate this extra attention.

As the dwarf clawed frogs become mature, the males develop a prominent post-axillary gland behind the forelegs. In general, the females are about 40% larger than the males and as they start producing eggs their body shape takes on a pear-shaped appearance, compared to the male's narrow body shape. The female's genital region and ovipositor will also become more pronounced.

These frogs are not particularly easy to breed. Whilst it is not too difficult to induce spawning, it can be hard to care for the eggs and tadpoles.

There are several key factors to follow to improve the chances of successful reproduction in this species:

• Obtain several unrelated frogs to allow for natural pair selection.

• Feed them live food, brine shrimp is said to help bring them into breeding condition.

• The water level must be at the right height and of the right temperature.

• The water quality and aeration must be good.

• Control daylight hours.

Once the conditions are right, gradually raise the water temperature to between 23°C – 26°C, but no higher. Then, simultaneously reduce the water level from 12 inches to between 10 – 8 inches in height, but no lower than 8 inches. I believe these two factors are crucial in triggering spawning. It may help to attempt this in the summer months (in the UK).

Courtship will begin with the males calling, usually in the evening and at night, this can be quite loud and persistent. If the females respond this only intensifies the males calling and if you have several frogs in the tank, each frog calling spurs the others on, I believe this competition for mates also encourages more calling but also mating behaviour. The males will relentlessly pursue their chosen mate. If she is responsive he will attempt to clasp onto the female with his forelegs, holding her around the waist, just above the hind legs. This is known as amplexus. A pair in amplexus can remain in this state for many hours. The longer they remain clasped together, the better the chances of successful spawning. Amplexus is a prelude to proper mating/spawning, and it may occur several times a day in a bonded pair. Sometimes the amplexus is quite strong as pairs in this state will often remain together whilst swimming up to take in air from the surface, and despite their primitive lungs, their air capacity seems quite good. Spawning normally occurs either late in the afternoon, early evening or, most commonly, overnight.

I would not attempt to move or disturb the frogs when in amplexus. Leaving them to spawn in their tank, moving the eggs is far easier than trying to move the frogs to an eggrearing tank. The frogs can get easily stressed and they might separate from amplexus if moved.

When mating, the eggs and sperm are released at the same time to maximise fertilisation. Once the frogs spawn the eggs should be removed as soon as possible to another tank set up with the correct water parameters before spawning. If the eggs are left with the adults, they will likely eat or damage the eggs. The eggs are very small measuring about 0. 9mm in diameter and are extremely sticky. If fertile, each egg should have two clearly defined “poles” – a dark-coloured “animal-pole” and a slightly lighter-coloured “vegetative-pole”. If there is one at each end, the eggs will look healthy. With a good pairing you can expect about 70% of the eggs produced to be fertile, this is a good ratio. Infertile eggs will be apparent in comparison, they do not have the “poles” at each end of the egg cell and are usually just very small and dark-coloured, they will fall to the bottom of the tank and quickly start to disintegrate. Any infertile or damaged eggs should be removed as soon as possible to prevent the water from fouling. The frogs' eggs are light-sensitive and strong light can destroy the eggs, equally the ideal water temperature for embryo development is between 20-22°C and it is important not to let the water become stagnant. Some light water movement and aeration are necessary for the rearing tank.

Within only 24 hours the fertile eggs can be seen to internally divide, after two days the embryos will start to move with tiny jerky movements. These movements gradually become stronger until they break free from the egg. Once out the tadpoles do not require any food for the first 24 hours as the embryos will utilise their yolk sac for nourishment at this early stage, but from the second day onwards they will require live baby daphnia and brine shrimps eggs to feed on. They may not start feeding immediately but should feed by the third or fourth day at the latest. Care must be taken not to overfeed the tadpoles at this stage as it can lead to dead tadpoles and foul the water. At about six days old, the tadpoles will be free swimming.