A report of unusual aggregation behaviour in Bullsnakes (<i>Pituophis catenifer sayi</i>) near a nest site in Saskatchewan

Abstract

We describe an unusual aggregation of Bullsnakes (Pituophis catenifer sayi) near a nest site in Saskatchewan. Bullsnake is a wide-ranging oviparous colubrid that reaches the northern tip of its continental range on the prairies and badlands of Canada. At that location, it is considered a species of Special Concern, but, until recently, has been the subject of relatively few natural history reports. This is significant, because, at the northern edge of their range, Bullsnakes may behave differently than elsewhere due to thermal limitations experienced at high latitudes. On 29 June 2019, we observed a mass of five adult Bullsnakes in a Silver Sagebrush (Artemisia cana) shrub on a slope in southwestern Saskatchewan. Aggregations of Bullsnakes are known to occur at hibernacula, during mating, and inside nest chambers before and after oviposition. However, we are unaware of the occurrence of surface aggregations in any other situation. We suggest that these Bullsnakes may have been exhibiting communal gestation, a behaviour thought to be rare in oviparous snakes whereby gravid females congregate before parturition or oviposition for thermal stability or protection from predators.

Thermoregulation by Bullsnakes (Pituophis catenifer sayi): do burrows make life easier on the prairies?

“…Despite the potential for unknown factors, a final model explained 57.2% of the variation in T b with only three simple environmental variables (bare ground T e , hours since sunrise, and day of year) demonstrating that these are useful and valid predictors of snake behaviour. Future research could investigate the influences of predators and prey (Webb et al 2009), social interactions (Johnson et al 2020), and reproduction in males and females on thermoregulation. It could also explore how different climates might impact snakes and their interactions with prey (Weatherhead et al 2012;DeGregorio et al 2015).…”