This article was written by Gordon M. Burghardt, PhD, a member of the ASP Board of Directors.
Sociality in reptiles, particularly snakes, has been long misunderstood and even denied. Today it is well-established that many crocodilians have complex courtship rituals and parental care that is far more extensive than that found in many birds and mammals. Cooperative hunting has even been described. Turtles develop dominance relationships and recently it has been discovered that many have social vocalizations, particularly aquatic species. One South American river turtle is truly amazing. Mothers migrate up the river over a hundred miles to lay their eggs in large communal nesting aggregations and then depart downriver. When the eggs are about to hatch the mothers return to the nesting beaches, the hatchlings and mothers vocalize to each other, the hatchlings move into the river, and then the hatchlings follow the mothers back downstream. Whether this is just a communal response or mothers and hatchlings recognize each other is still not known, but this is one of the major recent discoveries showing how much is still unknown about reptile behavior and the endless opportunities for major discoveries.
Lizards have been known for decades to have territorial systems as well as dominance hierarchies, though there is great variation in sociality, even within closely related groups. Parental care is also present, especially in skinks and many also guard their eggs. And some skinks have long-term monogamy and family ties that span generations. There is even evidence of kin-based altruism in green iguanas. The colorful markings, dewlaps, and crests are used in social communication along with head-bobbing and other behavior.
Snakes have long been considered solitary except for seasonal mating rituals. In a number of species, mating aggregations are large and dramatic. Territorial and dominance relationships in wild snakes is seemingly uncommon, but does occur and is probably more common than we think. Snakes, all being obligate carnivores, and most relying on large prey, compared to insectivorous lizards, are often at low densities in the wild and thus their social relationships not easily recognized or studied. Yet studies show that many species go to seasonal hibernacula to brumate over winter and individuals have preferred partners for resting and basking – even perhaps, friendships. Recent laboratory studies with Common Gartersnakes show that juvenile snakes develop social partners as well. A number of species of snakes stay with their eggs and defend them. Mother rattlesnakes, who give live birth, are known for staying with their offspring for days and there are even reports of males defending females and offspring from predators. Snakes often compete for food in captivity and this can lead to social preferences or avoidance. Some male pit vipers have dramatic wrestling matches, often to impress nearby lurking female with whom they want to mate. We are just on the cusp of finding out how social snakes can be. It is important, of course, to view snakes from their sensory and perceptual worlds, and not ours. Thus, for most snakes and many lizards, chemical cues are more important than visual and auditory cues, but these we cannot personally perceive ourselves and thus are prone to ignore. The secret lives of snakes are still largely secret.
References & Further Reading
- MJ Whiting and GM While. 2017. Sociality in Lizards. In Comparative Social Evolution, ed. D. R. Rubenstein and P. Abbot, 390–436. Cambridge: Cambridge University Press.
- JS Doody, GM Burghardt, V Dinets. 2013. Breaking the social–non‐social dichotomy: a role for reptiles in vertebrate social behavior research? Ethology 119:95-103.
- M Skinner and N Miller. 2020. Aggregation and social interaction in garter snakes (Thamnophis sirtalis sirtalis). Behavioral Ecology and Sociobiology 74:1-3.
- JJ Smith and M Amarello. 2014. SnakeBook: the Arizona black rattlesnake social network. Biology of the Pitvipers 2. Tulsa, Oklahoma. (poster)