Martin HALLMEN
Powered by: Thamnophis.com

Introduction

Besides other "blackish" snakes of the Genus Thamnophis in North America (PETERSON & FABIAN 1982, CATLING & FREEDMAN 1981) most melanistic animals in natural populations are known for the Common Garter Snake Thamnophis sirtalis sirtalis. Most of them are found near Lake Erie (ROSSMAN et al. 1996). As a reason for this local accumulation in natural populations a possible isolation and resulting effects of inbreeding are reported (MUTSCHMANN 1995). In about 1988 3-4 melanistic specimens of the Common Garter Snake Thamnophis sirtalis sirtalis were imported to Europe (BOL 1996). Up to 1998 probably all melanistic animals of this species kept in European terraria are descents of these animals. Possible effects of inbreeding of the European terraria population of black animals of the Common Garter Snake are discussed (BOL 1996, SCHMIDT 1997, CHLEBOWY 1997).

Keeping conditions
The animals on which the following observations were made are 2,2 melanistic garter snakes bought on 20.9.1997 at the age of 2 month (figure 1). These melanistic snakes are the F3-F4 generation of the imported animals mentioned above (VAN HET MEER pers. inform. 1997). For the keeping conditions in the juvenile age and some other observations on these snakes see HALLMEN (1997a, 1997b). During the observation time the snakes were adult. The 2,2 melanistic specimens of Thamnophis sirtalis sirtalis were kept in a wooden terrarium (80 X 50 X 40 cm). The setting consists of a large water bowl (1,5 l), hiding places (1 oak bark and 1 clay tube, 1 wooden root for climbing, chips of beech wood and a lamp (60 W), which gave light and warmth during observation time for 12 hours. The snakes were fed with a diet mostly of smelt (HALLMEN 1998) once per week. Sometimes the pray fish were dusted with the vitamin powder KORVIMIN.

Observation
Starting-point was the information of a snake breeding friend of mine and a Thamnophis-expert (CHLEBOWY pers. inform. 1997), that his melanistic specimens of the Common Garter Snake Thamnophis sirtalis sirtalis bite each other while being fed or after short periods of separation. At that time his observations were of no importance to me, because my melanistic garter snakes behaved in a normal way also during feeding. To initiate copulation I separated my male and female melanistic Common Garter Snakes for several weeks in early 1998. After putting them together after about 4 weeks immediately aggressive attacks and biting could be observed between all individuals. The attacks were so vehement, that I could not leave the snakes alone. Several times I had to part them from each other. Immediately after putting all 4 animals together they showed nervous movements of the tail. That was to be seen over the whole period of aggressiveness even at the end of this abnormal behavior. At the beginning the aggressive behavior was very fast. Tongue flickering was shown to sense the head or other parts of the body of each other. This was followed by short but violent bites at different parts of the anterior half of the body. When 2 snakes met head first, each tried to move to the side of the contrahent by permanent tongue flickering. In those cases I sometimes interrupted and separated the animals but left them in the same terrarium. Bitten snakes reacted with sudden flight behavior into a different corner of the terrarium. The most and severest bites could be seen between the female snakes. The males were not bitten so often by the females. The two males only showed tongue flickering against each other. Even against the females the males did not react in an aggressive way. The period of really violent attacks lasted for about 15 minutes. For another 15-20 minutes the biting could be seen regularly but it was not so intensive. Afterwards aggressions occurred only sporadically. After 2 hours a no longer aggressive behavior could be seen and the snakes behaved in a normal way. The day after these unusual observations all snakes were basking together in the light of the lamp. After these events no more aggressiveness was to be seen again. At the time of observing this unusual behavior a single male of the Western Plains Garter Snake Thamnophis radix haydenii was kept in the same terrarium together with the four melanistic snakes. No melanistic animal showed any aggressiveness against the single Western Plains Garter Snake. They behaved in an indifferent way. After separating the 2,2 melanistic garter snakes in the late summer for 3 weeks the animals showed nearly no aggressive behavior against each other when being put together. Even the females bit each other only once.