Drs. Rulon W. Clark, William S. Brown, Randy Stechert, and Harry W. Greene  found cryptic sociality in timber rattlesnakes (Crotalus horridus). Timber rattlesnakes use communal winter dens and pregnant females aggregate together at rookeries to gestate their young. Clark and colleagues collected DNA samples from rattlesnakes to examine relatedness within these aggregations. While all individuals from the same den were not related, aggregations of juveniles of the same age group and pregnant females that shared rookeries were related.
Timber and Arizona black rattlesnakes are similar in many aspects of their behavior. Arizona blacks also den communally, although this behavior is not restricted to the northern part of their range as it appears to be in timber rattlesnakes [1,2]. Some female Arizona blacks use rookeries at or near their dens, although many nest alone.
So, are aggregations of Arizona black rattlesnakes related? Or like timber rattlesnakes, perhaps only aggregations of pregnant females and juveniles are related. Or maybe aggregations of Arizona black rattlesnakes are just random groups of unrelated individuals. This is one our research topics, which you can read more about here. Hopefully we’ll be able to answer the above questions over the next couple years.
- Clark, R.W., W.S. Brown, R. Stechert, and H.W. Greene. Cryptic sociality in rattlesnakes (Crotalus horridus) detected by kinship analysis. Biology Letters rsbl20111217; published ahead of print February 22, 2012. doi:10.1098/rsbl.2011.1217
- Brown, W.S. 1993. Biology, status, and management of the timber rattlesnake (Crotalus horridus): a guide for conservation. Herpetological Circular 22.