Rattlesnake sociality exists, it's complex, and likely occurs in multiple species

Drs. Rulon W. Clark, William S. Brown, Randy Stechert, and Harry W. Greene [1] 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.


An adult male with several female and juvenile Arizona black rattlesnakes basking just outside their den.

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.

1. 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
2. Brown, W.S. 1993. Biology, status, and management of the timber rattlesnake (Crotalus horridus): a guide for conservation. Herpetological Circular 22.

Drinking

Cap Mama takes advantage of some rain to take a drink of water dripping off the rock above.

Drinking is a behavior rarely seen in wild snakes. In fact, some would say that snakes don't need to drink. While it is rare to see this behavior, snakes do drink and likely need water in addition to what they acquire from their food. How important drinking is to snakes became very clear to me one day in March 2006 (Repp & Schuett 2008). Despite cold, rainy, windy, and even snowy weather, we saw more than a dozen western diamond-backed rattlesnakes drinking rain and snow outside their dens!

A poor quality video of rattlesnakes drinking snow during the long, dry winter of 2005-2006. Ugh - glad we have upgraded our cameras!

Last summer was pretty dry at our field site; the monsoon did not amount to much. In the photo at the top of this post, you can see Cap Mama snagging a drink about nine days after giving birth. The following videos were taken by our time-lapse cameras while the snakes were still pregnant:

This is Cap Mama again, about a week before she gave birth. Shortly after the rain starts, she emerges and drinks rain as it falls on her body.


Meanwhile on the other side of this rock outcrop, another pregnant female (Stache) also sneaks out for a drink. Unfortunately there is some grass in the way, but you can still get an idea of what a drinking snake looks like.

For more information on drinking and water harvesting in snakes, check out this paper:
Repp, R.A. & Schuett, G.W. 2008. Western diamond-backed rattlesnakes, Crotalus atrox (Serpentes: Viperidae), gain water by harvesting and drinking rain, sleet, and snow. Southwestern Naturalist 53: 108–114.