Relatedness within and between aggregations of Prairie Rattlesnakes (Crotalus viridis) in northern Colorado
Department of Quantitative Biology
University of Texas at Arlington
Arlington, Texas USA
Department of Biology
Carlisle, Pennsylvania USA
Cryptically social animals can give us greater insight into how sociality evolved as they present social behavior in ways that have been previously unexplored. Most reptiles are solitary for much of their lives and are traditionally viewed as non-social, aggregating mainly for reproductive needs (e.g., courtship and mating). However, some temperate snakes, rattlesnakes in particular, are well known for their massive denning aggregations during winter, yet very few studies have investigated the possibility of “cryptic” (i.e., chemically mediated) social interactions at these communal dens. This study aims to gain insight into the details of Prairie Rattlesnake (Crotalus viridis) population structure in the wild. We strive to understand whether this species aggregates in a non-random fashion. This work was focused on aggregations of pregnant snakes at collective birthing sites called rookeries. We examined rattlesnakes from five rookery sites and compared these with individuals from the general population on Rattlesnake Butte in Steamboat Springs, Colorado. By genotyping microsatellite loci, we determined patterns of relatedness by calculating FST and genetic differentiation with GenePop R package. Our results showed 4 examples of high to moderate FST values across the gravid female group comparison, which was supported by significant p-values in the gravid female genetic differentiation analysis. Based on our current data, we see patterns of relatedness in gravid female aggregations, supporting the possibility for the aggregations being kin neighborhoods. Further studies need to be conducted to definitively identify the groupings as kin. These data have allowed us to further investigate population structure in cryptically social species to explore the evolution of sociality in broader contexts than have previously been documented.