Bullsnake, <em>Pituophis catenifer sayi</em>, Nesting Biology in Alberta

Abstract

Bullsnakes were opportunistically observed at a site on Alberta’s Red Deer River at the northern extreme of their range near the town of Drumheller. This site is significant for its importance to the local nesting ecology of this snake. Data were collected from captured snakes, and individuals were marked and photographed to enable identification upon subsequent recapture. A minimum of 39 adult Bullsnakes were known to utilize a single bluff over a period spanning five years from 1998 to 2002. Fifteen gravid females were found over this span nesting in a single burrow complex. Bullsnakes were found to excavate their own nesting burrows at the site, and to show nest site fidelity. The congregation of numbers of these snakes at localized sites of importance to nesting biology renders them potentially vulnerable, and may present conservation challenges.

Variable habitat selection and movement patterns among Bullsnake (<i>Pituophis catenifer sayi</i>) populations in Saskatchewan

“…Bullsnakes are widespread throughout the United States, with their range extending northward into Canada, across southeast Alberta to southwest and southcentral Saskatchewan (Ernst and Ernst 2003). Bullsnakes nest communally or individually under rocks, logs, and within self-excavated or mammal-created burrows (Ernst and Ernst 2003;Wright 2008). Bullsnakes overwinter in extensive mammal burrows or rock crevices (Ernst and Ernst 2003;Kapfer et al 2008).…”

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

“…The mass of Bullsnakes may have consisted of gravid females that formed an aggregation for thermoregulatory advantages before oviposition. Indeed, the date of observation coincides with the typical timing of oviposition (Wright 2008;Iverson et al 2012). One of the known females in the mass had recently migrated to the nest site from its normal home range roughly 1.2 km away and was presumed gravid for this reason.…”

“…Bullsnakes have been well studied outside of their Canadian range (e.g., Fitch 1982;Moriarty and Linck 1998;Kapfer et al 2008aKapfer et al ,b,c, 2010Iverson et al 2012), and knowledge of Bullsnake ecology in Canada has expanded greatly in recent years (e.g., Didiuk 2003; Kissner and Nicholson 2003;Wright 2008Wright , 2016Martinson 2009;Fortney et al 2012;Martino et al 2012;Gardiner et al 2013;COSEWIC 2017;Somers et al 2017;Edkins et al 2018;Powell et al 2018). However, there are still important knowledge gaps in terms of whether they behave differently at the northern periphery of their range relative to ar-eas further south.…”

“…In Canada, Bullsnakes often nest communally (Wright 2008). Communal nesting is apparently widespread among reptiles (Graves and Duvall 1995) and is also found among close relatives of Bullsnake, such as Pinesnake (Pituophis melanoleucus; Burger and Zappalorti 1986) and Gophersnake (Pituophis cateni fer deserticola; Williams et al 2015).…”

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“…Communal nesting enhances thermal and hydric stability for eggs and may be especially important when suitable nesting sites are limited (Graves and Duvall 1995). Female Bullsnakes have been observed aggregating inside underground nest chambers before oviposition, and several days following oviposition (Wright 2008). However, coiled masses of female Bullsnakes outside nest chambers are apparently unusual or have gone unreported in the literature.…”