by Kai Kolodziej
The garter snakes of the genus Thamnophis are quite often in focus of various scientific research. Even though they are one of the most researched groups of snakes and thousands are kept by private keepers, there is still much to be learned. Thamnophis species are often kept in groups and even in nature these snakes can be found in large groups or one might even say, masses, in certain times of the year. One of the best-known examples is the mass brumation of garter snakes (Thamnophis sirtalis) which is well documented in northern parts of their range.
Furthermore, we know that garter snakes have a highly developed communication mechanism based on pheromones, some males of red-sided garter snakes (Thamnophis sirtalis parietalis) release a pheromone to attract other males. Odd as it may seem, they use these pheromones to distract other males and mate more successfully with the females. In addition to that the males, which release the female-like pheromones also show heat kleptoparasitism. This means that they use the already heated up males to warm up faster than other males emerging at the same time. This form of female-mimicry is unique in nature.
If this weren’t enough, garter snakes are one of the first genera of snakes where scientists believe that they have some sort of sociality, or if you would like to anthropomorphize this behaviour: they have friends. Taken into account that most reptiles, particularly snakes, are believed to be solitary animals this new study shows them in a totally different light.
Let’s take a deeper look into this study: The scientists used 40 snakes, thirty juvenile wild caught females and ten captive bred juveniles of the same age. The snakes were housed in groups of ten individuals, the test enclosures were designed with four hiding places, each one placed in the middle of every wall of the enclosure. Water was available in each corner of the enclosure and the snakes were monitored with a DSLR camera during the daytime. So, the snakes had to form groups to hide with no hiding place offering better conditions in terms of temperature or humidity, even the water bowls were evenly distributed.
The survey was done over the course of eight days and each individual was marked with a coloured dot on the head to allow individual recognition. Two times a day the setup was cleaned and the hiding snake groups were photographed. When the enclosure was cleaned, each hiding place and the whole enclosure was disinfected to eliminate smell and pheromones, in addition to that the hiding places were placed on different sides of the tank than previously. The interesting thing was that the snakes were more likely to enter a hiding place with more snakes in it and they stayed longer in hiding places with more animals already resting in them. Even more is the fact that they formed the same groups most of the time, even when they were shuffled in the process of the study. That meant that these snakes could identify each other and choose with whom they wanted to stay in a hiding place.
This hidden social life of reptiles (and especially snakes) is a topic of ongoing research and within the last few years more and more sides of their social interactions are being discovered. The thing is, reptiles were considered asocial for such a long time that nobody really looked into this topic, especially in snakes. Moreover, most of the social interaction is hidden, due to their secretive lifestyle and most of their communication is mostly invisible to us as they use chemical cues. Along with this study, much research has been done to reveal the mystery about the cryptic social life of snakes. For example, parental care in pit vipers and African pythons (Python natalensis) and social grouping in sea snakes was observed. Timber rattlesnakes (Crotalus horridus) showed familial recognition inside their dens. Arizona black rattlesnakes (Crotalus cerberus) demonstrated more interaction than could be explained just by coincidence and preferred certain individuals. Our perception on the social life of snakes is slowly changing
Literature:
Morgan Skinner and Noam Miller (2020): Aggregation and social interaction in garter snakes (Thamnophis sirtalis sirtalis). Behavioral Ecology and Sociobiology 74(5).
