Small, but full of attitude: the narrow-bridged mud turtle – Stephan Ettmar

Juveniles of Claudius angustatus are fast growers. If you look closely, you will see the growth marks on the scutes of the carapax

A studied ecologist with a strong focus on herpetology and limnology (fi sh ecology). After obtaining his diploma, he has worked for 7 years in the pet trade, until in 2017 he started his own company ZooCon. Under this brand name, he works as a zoological consultant for private people and companies, writes expert opinions and publishes texts as a science and animal husbandry communicator. His focus for private pet keeping are aquatic turtles, geckos and predatory freshwater fi sh.

INTRODUCTION In many documentaries, snapping turtles (Chelydra serpentina) and alligator snapping turtles (Macrochelys temminckii) are shown as river monsters and vicious predators. Over the years this practice has created an image of these species that makes them desirable for keepers that are looking for unusual aquatic chelonians. The big problem is their large size though: even small snapping turtles will easily outgrow a standard 150 cm long aquarium and even though the alligator snapping turtle is a slow grower after it reaches approximately 30 cm straight carapace length (SCL), they grow to be among the largest turtles around. Luckily, there exists a turtle species that does not even belong to the family of the true snapping turtles (Chelydridae), but combines all traits a chelonian hobbyist with a knack for the unusual is looking for: the narrow-bridged mud turtle (Claudius angustatus) shows the ferociousness and self-esteem of a snapping turtle, but only reaches the size of a razorback musk turtle (Sternotherus carinatus), making it an ideal aquatic pet. The species was described in 1865 (Tabasco, Mexico) by Edward Drinker Cope, an American naturalist who scientifi cally described many species of fi sh, reptiles and even dinosaurs in the 19th century. Together with the genus Staurotypus, Claudius angustatus are placed within a subfamily of the large chelonian family of mud and musk turtles – Kinosternidae (Reptile Database 2020). In 1888, Duméril & Bocourt published a beautiful drawing of the then previously undepicted chelonian. Narrow bridged mud turtles reach a maximum size of around 18 cm SCL (Schilde 2001), but most specimens will stay considerably smaller – more around 14 cm SCL. Data from literature suggest that males will grow larger than females (Legler & Vogt 2013, Schilde 2001), but in my breeding group of currently 1 male and 2 females, the male is smaller and way lighter than both females. Being typical mud turtles, their shell shape is typically compact and oval with a beaked snout. Their vastly reduced plastron and enlarged head makes them peculiar and easy to recognize. In many specimens, “vampire tooth” – like horn spikes are present on the upper jaw. This led to the sometimes used common name “vampire mud turtle”. Another common name used within their natural range in Mexico is “Chopontil” or “Taiman” (Legler & Vogt 2013). Claudius hatchlings are just over an inch long, but already have the fi erce attitude of adults. Therefore, I placed the fi rst hatchling that I acquired in late 2010 in its own 20 liter tank on my desk, so I could watch it a lot while studying for

Like other mud turtles, Claudius likes to rest under logs or in caves under water

University. I was scared that this small turtle (usually my hatchlings are about double the size of a baby Claudius) could easily die when not fed regularly and that other hatchlings of different species could harm it. This gave me the opportunity to intensely study the behavior of the species. It turned out that Claudius angustatus are hardy, hungry and hostile – I loved every minute of watching it! As the years went by, the turtle became a family favorite and I decided that giving it away, even for breeding purposes was not an option. Instead, I enlarged the group and to make sure that nothing would happen to the individuals, housed each one separately. The baby I raised to be a nice-looking female hadn’t had laid eggs until 2016, but at the age of 7 years she appeared to be adult, because slowly her skin color changed to dark grey and the striking carapacial patterns it showed before started to dilute. NATURAL HISTORY AND GENERAL BIOLOGY Narrow bridged mud turtles naturally occur in the lowlands of Mexico (in the federal states of Oaxaca, Chiapas, Tabasco, Campeche, Quintana Roo), Belize and Guatemala. There, they inhabit temporary ponds and oxbows where they lead a rather cryptic life. During the dry season, starting around March, they bury themselves in the mud and aestivate over the summer. They only emerge after heavy rainfalls, when resources are favorable for feeding and mating. Therefore, scientifi c

data on natural history are scarce. The latest

It helps to have the surface of the water covered with fl oating plants like duckweed to make Claudius angustatus feel more secure

synopsis of knowledge comes from Vogt & Legler (2013), but in 2020, Vásquez-Cruz and Reynoso-Martínez published further natural history notes regarding diet. Claudius angustatus are considered to be strictly carnivorous with a preference for crustaceans, aquatic insects and their larvae, but Vásquez-Cruz and Reynoso-Martínez (2020) even found remnants of another turtle species (Trachemys venusta) in an adult male’s feces. From hobbyist literature (Schilde 2001) we know that narrow bridged mud turtles will also gladly accept live and frozen fi sh, snails and even rodents. In addition, they like dried food as well, like for example Tropical’s REPTILES CARNIVORE, BIOREPT W fl oating sticks or dried gammarus, crickets, etc… As a treat, AROWANA XXL fl oating sticks can be offered. From personal observations, Claudius are not really active hunters, but rather sometimes try to lure in potential prey with their mouths gaping open under water over extended periods. They motionlessly observe their surroundings and when a prey item is within striking distance, they will quickly strike and catch it. Their ability to move their eyes (to a certain degree) independently of each other greatly helps them to monitor their surroundings and to detect food. They also recognize their caretaker and will beg for food or try to gain attention by behavior like frantic paddling or moving tank decorations around. Due to the reduced shell of narrow bridged mud turtles, their defensive behavior is more pronounced than in other turtle species. Schilde (2001) even mentions that Claudius angustatus is the only turtle species capable of jumping. Even fresh hatchlings will defend themselves with fi erce bites when they are taken out of the incubator.

KEEPING CONDITIONS For adult Claudius, I provide glass aquariums of 120 cm length with 200 l and 300 l gross volume. These tanks are not fi lled to the maximum because I have built-in land areas for egg deposition and sunbathing or aestivating. They are situated in my turtle room in my basement, so artifi cial lighting is necessary. Aquarium for female 1 has a conventional 36 W T8 tube for light, the other tanks for the male and female 2 have 35 W metal halide (HID) lamps with UVA/B spectrum. While there are plants in tanks of the females, no plants survive in the enclosure for the male. Water quality is sustained by a direct connection to the sewer system for easy change of water and a mat fi lter that is run by an air lift. This is a popular fi ltration system among fi sh breeders and is called “Hamburg mat fi lter”. I change about 50% of water every 7 to 20 days, but because of the effi cient fi lter mats and their large capacity I can wait for over three weeks before doing a water change and at least optically no detrimental effects take place. The fi lter mats are washed once a year. All aquariums are decorated with a sandy bottom, some driftwood, occasional stones and plants. I co-habitate most of my turtles with other animals. I found out that above a certain size, Claudius won’t chase red cherry shrimp (Neocaridina davidi) anymore. Therefore, the aquarium for the male and the one for female 1 have dense populations of these small crustaceans to take care of organic detritus. Female 2 lives together with a school of Endler’s guppies (Poecilia wingei). This is a more fragile combination, because fi sh seem to attract more attention of the turtles, but so far the guppies are also too small to be recognized as food. A good friend of mine who is raising another Claudius for me reports that all kind of fi sh he introduced disappeared sooner or later (mostly sooner). Careful precautions must be taken when attempting to co-habitate turtles with fi sh (Böhm 2014)! The adults are fed mostly twice a week with a wide array of feeding items: they readily accept fi sh in all forms, crayfi sh and shrimps (mostly frozen/thawed), snails, mussels, rodents (f/t), but will also voraciously devour pellets or gelatin foods containing a certain amount of greens (like Tropical’s GEL FORMULA FOR HERBIVOROUS FISH). Every now and then I offer some sepia bone for additional calcium intake for the female because they produce a lot of eggs for a small turtle. I noticed that narrow-bridged mud turtles are so fast at begging for food and striking at moving things that they sometimes are not very accurate and tend to be hard to feed with tongs because there is a serious threat for injury due to attempts to swallow tongs or biting hard on the metal.

BREEDING The male is introduced to the females at

When Claudius are picked up, they will immediately display their defensive behaviour that includes hissing and biting

For copulation, males will mount females after a short courtship ritual

irregular intervals. Although other keepers told me that continuous communal keeping of pairs can work (Schaffer, Schilde, pers. comm.), I prefer to closely observe matings and let the male stay in the female enclosure over night as a maximum. After a few seconds of orienting himself, the male starts a courtship ritual of head bobbing and waving his front legs towards the female. He also starts to sniff around her anal and bridge region. Quite obviously, information via hormone transfer through the water is exchanged in that way. After a few minutes of courting, the female usually stops in her motions and lets the male get on her back. The actual mating lasts for about half an hour and after copulation is complete, they disconnect and head their ways without any signs of aggression. I then put the male back in his own tank. All of this can happen at different times of the day, so it seems like Claudius are not too shy when it comes to mating attempts. Possibly this is a result of rarely meeting in nature. When the female is not receptive to mating attempts, she will try to force the male away and severe bites can happen. Also, frustrated males will try to force copulation and bite females. To prevent serious injuries from these fi ghts, it is very important to monitor pairs. After some weeks, females will start egg depositions. Usually, clutches will consist of 5 to 8 eggs, but small females will also lay fewer eggs per clutch (Klawonn 2019). Multiple clutches are produced each year and females can be real egg-laying machines, producing up to 63 eggs per season (Klawonn 2019)! However, it is not advised to force your turtles to such high numbers, because this will most certainly harm the female’s health long term. With moderate feeding amounts and a seasonal cycle including a phase of aestivation, Claudius females will produce an average of 3-4 clutches per season, which still can be up to 25 eggs (own observations). Incubation of Claudius eggs is a tricky procedure, as they take 5 to 8 months to hatch if incubation parameters are stable. Some breeders like Klawonn (2019) and Weber (pers. comm.) place eggs in cool conditions (18-20°C) over the fi rst four weeks of incubation to break embryonic diapause and induce development, but I just let the incubation substrate dry off a bit at ambient room temperatures to do so. While Claudius eggs may start to crack way before hatching, increased osmotic pressure seems not to be a primary factor for the start of

hatching. Usually, babies from the same clutch will not hatch all at the same time, instead it is common that several weeks pass between emergence of the fi rst and the last hatchling. Therefore, there is an important rule in Claudius incubation: never dispose eggs unless they hatch or explode!

Plastron view of a hatchling. Even at this small size, they will viciously defend themselves

RAISING HATCHLINGS After leaving the egg, narrow-bridged musk turtle hatchlings are very mobile and are ever ready to defend themselves. Stories of specimens that try to bite while still sitting in the egg are defi nitely trustworthy. I was bitten by one of the hatchlings while lifting it out of the incubator to place it into a transport box. This attitude makes it easy to introduce them to different kinds of food. Their strong feeding response enables the keeper to offer almost everything because they get used to feeding rituals within days. Accepted feeding items include, but are not limited to: chopped fi sh, shrimps, snails, chicken heart, chopped baby mice, dried gammarus, pellets (e.g. Tropical’s PRO DEFENCE size S, CICHLID GRAN or DISCUS GRAN D-50 PLUS) and even fi sh food fl akes. To avoid strong competition for food and to reduce stress, every hatchling is housed individually in a 28 x 19 x 14 cm plastic box fi lled with a bit over a 4 l of water. These grow-out tanks include one or two stones, a piece of tile to hide under and climb out of the water and some cork bark to hide. In some tanks, I have added fl oating live plants like Elodea or Cabomba, which are used to sleep in. But these get destroyed very fast. The water is changed every 5 to 7 days or if it gets messy after offering a certain type of food. There is no further fi ltration. Under these described circumstances, the animals show steady growth (table below). As they grow, they will be placed in larger, individual enclosures.

DISCUSSION Although it is clear that Claudius make great pets because of their personality and their relatively small size, they are not easy to breed. There are reports where males would kill females or vice versa. In other cases, a great

Date 2017-02-16 2017-03-14 2017-04-14 2017-05-17

Juvenile 1 SCL (mm) M (g) 31 5 36 9 37 9 39 12

Juvenile 2 SCL (mm) M (g) 30 5 33 8 36 9 37 10

Juvenile 3 SCL (mm) M (g) 29 6 33 8 36 9 n/a n/a

Juvenile 4 SCL (mm) M (g) 29 6 34 8 37 10 39 13

Date 2016-12-22 Female SCL (mm) 145 M (g) 760 Male 1 SCL (mm) 125 M (g) 463 Male 2 SCL (mm) 118 M (g) 460

number of infertile eggs are produced with only little hatching success even though the pairs get along fi ne (Klawonn 2019). It seems like the size of the animals chosen to breed does matter, since there are proven adult Claudius at the size of about 10 cm SCL and at about 18 cm SCL. In European literature (Schilde 2001) there is a differentiation between a small morph where both sexes hardly pass 12 cm SCL only known from the northern border of their distribution and a large form with a maximum size of males of 18 cm and roughly 14 cm for females. Interestingly, my females are way heavier and a bit taller than the males (see table above), which enables them to escape if they should be bothered too much by the male. Or put in other words: the males are more scared of the females, which causes them to rely on more subtle courtship rituals than the kinosternidae-typical “overpowering”. Another problem is the availability of (captive bred) males in Europe. In many cases, keepers don’t have enough males to swap through in case they can’t bond with the female for mating. Many males are of wild caught origin, because there is a strong trend towards producing more females in captivity among many European keepers. Keeping in mind that it is proven that Claudius show genetic sex determination, the question of infl uencing the sex through incubation despite a genetic fi xation arises. In Pogona vitticeps, sex determination can be infl uenced through extreme conditions during incubation (Quinn et al. 2007). Claudius eggs need to be exposed to extreme temperatures or dryness in order to break embryon-

The webbed feet of Claudius angustatus make them surprisingly good swimmers given that enough space is provided to do so

ic diapause or incubation will take up to 229 days (Schilde, 2001). Here might be a link to a skewed sex ratio among hatchlings. Serious sex ID is possible in specimens above 7 or 8 cm SCL. Another fact that could possibly infl uence breeding success is the body condition of captive Claudius. I noticed that many Claudius live in considerably small enclosures with little water because people assume that since they are mud turtles, they don’t like to move much. In fact, I have noticed that my adults are strong swimmers and enjoy moving around the decoration of their enclosures. Still, I have a feeling that at times my female is a little overweight. Due to their harsh environment in nature, they will devour food whenever there is a possibility. Maybe breaks in activity by forcing captive animals to aestivate by reducing water levels and strict feeding protocols help to get non-producing Claudius into breeding condition.

ACKNOWLEDGEMENTS I’d like to say thanks to Gerhard Dreiszker for providing me with the 2 males to start this breeding project, my wife Manuela Ettmar for encouraging me to pursue the project and Tropical for suggesting to write the article. Ole Klawonn, Gerhard Schaffer and Till Weber provided great insights into keeping and breeding Claudius and helped a lot during the journey.

Böhm, S. (2014): Fische und Wasserschildkröten – geht das überhaupt? Schildkröten im Fokus 11(3): 3-23. Klawonn, O. (2019): Die Großkopfschlammschildkröte (Claudius angustatus) – Pfl ege und Nachzucht einer ausgefallenen Art. Reptilia 139: 50-56. Legler, J. and Vogt, R.C. (2013): The Turtles of Mexico. Land and Freshwater Forms. University of California Press. 416 pp. Reptile Database (2020): Claudius angustatus COPE, 1865 https://reptile-database.reptarium.cz/species?genus=Claudius&species=angustatus. Last accessed: Oct 29th, 2020 Quinn, A. E., Georges, A., Sarre, S. D., Guarino, F., Ezaz, T. & Graves, J.A. (2007): Temperature sex reversal implies sex gene dosage in a reptile. Science 316 (5823): 411. Schilde, M. (2001): Schlammschildkröten. Kinosternon, Sternotherus, Claudius und Staurotypus. NTV Verlag. 136 pp.

Extruded soft sticks with dried crickets and meal worms

For daily feeding of: bearded dragons, Chinese water dragons, frill-necked dragons, leopard geckos, red-footed tortoises, aquatic and semi-aquatic turtles, monitor lizards and other insect-eating reptiles and amphibians.