British Chelonia Group Symposium 1991
The Kinosternidae turtles are a family of small to medium sized animals with pointed snouts and relatively small tails. All species, of which there are about 22 (depending on author accepted), are aquatic, New World turtles with elongated to oval carapaces. Although all toes are webbed, they are poor swimmers. The family are divided into two genera (under review), the genus Kinosternon containing the Mud Turtles, and the genus Sternotherus containing 7 species of Musk Turtle. The Loggerhead Musk Turtle belongs to the latter. The distribution of the family is from Eastern Canada down into South America.
The Loggerhead Musk Turtle is a small species inhabiting rivers, creeks, pools and freshwater streams in northern Florida, the southern half of Georgia and Southeastern Alabama. It is described as being "a characteristic and abundant inhabitant of many of the freshwater streams of north-central Florida" (Pritchard, 1979). The status of the species today in unclear, but it is certainly no longer as abundant.
Adult carapace length is typically about 10cm, but specimens up to 13cm have been recorded. The carapace colour varies from pale to dark brown with varying degrees of radiating streaks and marks, depending on the specimen. the carapace has a noticeable vertebral keel. Juvenile specimens, and some adults also have two dorsolateral keels, but this is usually a juvenile feature disappearing with age. The plastron is small and is a clear pinky-yellow colour.
The head is large with a pointed snout, and cannot be fully retracted as with many other turtle species. The jaws are powerful and sharply hooked. There is a pair of barbels under the lower jaw. The coloration of the head is variable, but best described as greyish to pink, and well marked with dark dots,blotches and oscelli. The limbs and tail have the same coloration and are speckled with dark spots. The skin around the limbs, (on the soft parts) and surrounding the tail is papillose. The remaining skin is very fine and pinkish in coloration: this is caused by the presence of very fine blood capillaries beneath the skin, which can assist in gaseous exchange when the animal is submerged.
Primary sexual characteristics are the long, spine-tipped tail of the male and the associated swelling at the base of the tail to incorporate the sex organ. Females have a distinctly slimmer, shorter tail, with the anus positioned much closer to the plastron. Secondary sexual characteristics are the heavier jaws and head of the mature male, although this is best seen by comparing a number of specimens. The females which I have seen all have had appreciably paler coloured heads than the males. This may just be coincidence, but it appears to hold true for the first generation offspring of a known pair showing the characteristic,and also for all of my adult and subadult specimens.
The Loggerhead Musk Turtle is described as an opportunistic feeder in the wild, eating assorted molluscs and other invertebrates, especially hardshelled species such as crayfish, for which the powerful jaws are well adapted. Some authors report that the species feeds on filamentous algaeand other aquatic plants. There is little doubt that plant matter can be ingested with prey animals, and subsequently found in the gut, but the deliberate inclusion of vegetation in the diet is not, I think, characteristic of the species. It is also possible that the foraging behaviour of individuals amongst aquatic vegetation may mislead the observer. Juveniles take a similar diet to the adults,but maybe more heavily insectivorous until they have attained a large enough size to deal with molluscs etc.
Copulations is reported in the wild in March and April with nesting from July onwards. Normal clutches comprise one to five brittle-shelled eggs, averaging 28xl7mm. Natural incubation periods are not recorded.
The requirements for maintaining and breeding the Loggerhead Musk Turtle are simple. Due to the small adult size, the space required to house a pair or group of these turtles is within most people's capacity. Some authors quote minimum floor spaces for containers from 25x5Ocm to 33x103cm (eg. Ewert, 1985). For specimens the size of my animals, a standard aquarium measuring 3Ox6Ocm appears adequate. Thefurnishings are kept simple and comprise a Rena 225 power filter and a raised haul-out area of slate on which is a plastic container containing 8cnm of damp moss peat/pea gravel mixture for nesting. The slate is raised on blocks in such a way as to allow the animals to swim under it, maximising the space available to them. For specimens of this size, I can recommend a water depth of 8cm as being sufficient to allow proper feeding and mating. The filter is positioned in such a way that the output is not too turbulen tfor the inmates. Access to the haulout is provided by the strategic positioning of a suitable rock. As a rule, the filter sponge is cleaned every fortnight. The water is totally changed every couple of months, with partial changes carried out as necessary.
The pair is kept alone because of possible interference by other turtle species which could jeopardise breeding. I have not found the Loggerhead Musk Turtle to be aggressive to turtles of unrelated species, but I have had problems with intraspecific fighting between males kept in the presence of a female.
The adults are fed twice weekly, on a diet comprising:
- Peeled prawns
- Muscle meat (sheet heart, fowl)
- Pondsnails, mealworms occasionally
- Dog brawn (especially chicken flavoured as it contains bone fragments).
All food is lightly sprinkled with a calcium supplement incorporating vitamin D (usually marketed for lactating bitches and young puppies). A multivitamin powder is used about once a month. A small piece of cuttlefish bone is floated in each aquarium, and this is well chewed. Hatchlings are fed every other day on the same diet, but are also offered assorted small invertebrates such as Daphnia, Tubifex sp., Asellus, etc.
As a result of not being overfed, coprophagy (reingesting of faeces) is practised. I believe that this is natural and beneficial. It also ensures crystal clear water at all times! To date, first year, second year, and fourth year youngsters, as well as the adults appear in good health, are alert and not overweight, and show good growth under these conditions.
Mating is attempted by males at any opportunity, but the receptiveness of the female appears seasonal, peaking in late spring, i.e. April/May. Whilst my turtles are kept indoors, they do experience a very definite seasonality, with winter temperatures falling to as low as 40°F occasionally, although never for prolonged periods. This is because the tanks are kept in an attic room, and the room is heated for the cooler months, in preference to heating a series of tanks individually. I believe this is beneficial to a species whose range extends into temperate zones, and probably assists in stimulating the correct periods for spermatogenesis and oogenesis in male and female respectively. This can be important for a potential breeding project, and may well result in stronger,more vigorous offspring. Average summertemperature is about 75°F. The animals are also aware of the seasonal changes in daylight intensity, as well as daylength, although artificial lighting, controlled by a timeswitch is used to extend their photoperiod.
There appears to be no actual courtship, as in some other turtle species, and mating usually involves the male pursuing the female, scenting around her posterior to establish her gender and reproductive condition using pheromone signals. The female's response is usually to scurry away, with the male in close pursuit, ready to mount. If mating is allowed by the female, and coitus is achieved, the pair may remain in this position for up to thirty minutes. This year(1990)my breeding female layed two clutches of two eggs, nine weeks apart. This clutch size is not surprising, as she is a very small female.
Eggs are excavated carefully after the female has layed, and are half buried in tubs of Vermiculite,which is maintained damp,but never wet. The tub is then incubated in a small heated area, with a temperature set to 80°F. The eggs are examined weekly, and candled in the early stages to follow the development of the embryos. The eggs are never turned, as this is unlikely to happen in nature. The container is checked daily for hatchlings after about sixty days. The incubation period for a typical egg is 102 days which agrees well with 103 days quoted by Ewert (1985).
Typical eggs from my breeding female measure in the region of 30xl7mm with the hatchling measuring 25mm along the carapace and 20mm along the plastron. One aberrant egg measured 23x14mm, and hatched after only 84 days to give a hatchling with a 15mm carapace and a 12mm plastron. It remains to see if this hatchling will reach a full adult size or if it will be affected in any way.
Size/Weight details of my Sternotherus minor minor
|SPECIMEN DETAILS||CARAPACE LENGTH (mm)||PLASTRON LENGTH (mm)||WEIGHT (grams)|
|Breeding Female||85 ||72||135|
|4 year male||83||62||115|
|2 year male||50||36||25|
|2 year female||46||33||25|
The Kinosternidae turtles in general, and the genus Sternotherus in particular are turtles well suited to maintenance and propagation in captivity. The combination of relative hardiness, small size, and ready adjustment to confinement is a combination not apparent in many of the more commonly available species. It would therefore, be of great benefit if any U.K. turtle enthusiasts who hold these species would consciously attempt to breed from pairs, or offer single animals to those with opposite sexes, so as to try to establish a viable gene pool of this attractive species. It is probably true to say that many people overlook this family, and concen trate their attention on the larger, more boldly coloured relatives, sometimes becoming quickly disillusioned with the amount of space required for housing them, and especially with the considerable amount of work involved in keeping large turtles clean. These are problems not associated with small species maintained under the conditions outlined. I hope that this account will encourage other interested turtle keepers to select a single species which captures their attention, and attempt to breed from them. By deliberately focussing attention on a particular species, and observing them carefully, and most importantly, writing these findings up, we all can make a contribution to advancing our knowledge of the various Chelonian species that we have in our care.
Ewert, M.A., Embryology of Turtles. In: Biology of the reptilia, Volume 14,75-268. Wiley, New York.
Pritchard, P.C.H. (1979). Encyclopedia of Turtles;. TFH Publications, New York.
Testudo Volume Three Number Three 1991