Morphology, reproduction, habitat use, and hibernation of Red-bellied Snake (<i>Storeria occipitomaculata</i>) near its northern range limit

Abstract

Northern regions limit ectotherms to relatively short periods of feeding and breeding interrupted by long periods of inactivity. This may force cool-climate ectotherms into different ecological or demographic trade-offs than their southern conspecifics. Our aim is to examine demography, morphology, reproduction, habitat use, and hibernation by populations of Red-bellied Snake (Storeria occipitomaculata) near their northern range limit. This research was conducted in southwestern Manitoba and data on summer activity were collected from April to September 2007–2009 using coverboard and pedestrian surveys. Hibernation sites were monitored over three winters (2007–2008, 2008–2009, and 2009–2010), and thermal profiles of Formica ant mounds were collected in 2008–2009 and 2009–2010. Females reached sexual maturity at a smaller size than most other populations that have been reported but appear to have similar clutch sizes to the rest of the range. The majority of adult females captured at our summer sites were gravid (96%) suggesting annual reproduction, and activity patterns suggest fall breeding. Near its northern range maxima, this species appears to use relatively warm habitat, have rapid reproduction, and co-opt ant mounds to survive in a difficult climatic environment. Much remains unknown and future studies should further examine the variation in size at maturity and the relationship between body size and clutch size. In addition, little is known about diet, benefits of fall mating, use of open prairie habitats, and late-season migration by S. occipitomaculata.

Staying warm is not always the norm: behavioural differences in thermoregulation of two snake species

“…Although T. s. sirtalis and S. o. occipitomaculata are sympatric in our study area, these species differ substantially in their life history. Thamnophis sirtalis sirtalis actively move through their habitat in search of suitable sites that allow efficient thermoregulation (Gibson and Falls 1979;Gregory 1984;Peterson 1987;Rosen 1991), whereas S. o. occipitomaculata are semi-fossorial (Brown and Phillips 2012;Cairns et al 2019) with little information about their thermal physiology available. This difference in life history was also revealed in the traits under study.…”

“…We identified S. o. occipitomaculata based on key morphological traits. These included grey, tan, or brown dorsal colourations, with a bright red-orange coloured ventral surface (Cairns et al 2019), and two darker-coloured lateral lines running along the dorsal surface (Smith 1963). Although not always present, and sometimes fused together, S. o. occipitomaculata were also identified by the presence of up to three white spots on top of the neck (Smith 1963).…”

“…The thermal biology of T. sirtalis has been a topic of interest for decades, and although historical studies have not clearly defined thermoregulatory parameters using standardized methods, evidence suggests that these snakes are active thermoregulators (Gibson and Falls 1979;Lysenko and Gillis 1980;Gregory 1984;Peterson 1987;Rosen 1991). In contrast, the relatively understudied S. o. occipitomaculata are semi-fossorial animals whose thermal biology is essentially unknown (Brown and Phillips 2012;Cairns et al 2019). Previous research indicates that legless fossorial lizards tend to display lower T b in a thermal gradient than non-fossorial lizards (Bury and Balgooyen 1976;Wall and Shine 2008).…”

Occurrence of the Red-bellied Snake (Storeria occipitomaculata) on the margins of a disjunct range

“…High densities of row crop agriculture in addition to moderate levels of residential and industrial development likely create a relatively hostile matrix for Storeria occipitomaculata dispersal within the Rainwater Basin ecoregion (Jochimsen et al 2004;Willson and Dorcas 2004;Dappen et al 2008;Row et al 2010;Biaggini and Corti 2015). S. occipitomaculata have regularly been recorded using gravel roads and trails for thermoregulation, but these can also pose a significant mortality risk for the species (Cahoe and Troelstrup 2004;Jochimsen et al 2004;Shepard et al 2008;Busby et al 2014;Cairns et al 2018). Additionally, agricultural monocultures tend to provide little habitat for herpetofaunal movements (Willson and Dorcas 2004;Shepard et al 2008, Row et al 2010Martino et al 2012;Biaggini and Corti 2015).…”

“…The two most westerly populations exist within the central Great Plains in the Black Hills of South Dakota and the Central Platte River Valley (CPRV) of Nebraska and are disjunct from the snake's larger eastern range (Ernst and Ernst 2003;Dieter and Ronningen 2017;Tye et al 2017). Additionally, in the northern Great Plains a population exists as far west as southern Saskatchewan (Cook and Nero 1961;Cairns et al 2018). Estimating the contours of a species' geographical range entails significant uncertainty, especially near the periphery (Rocchini et al 2011).…”