Motherly Instinct

By Alida Lemieux

Gray Ratsnakes, like many other snakes are oviparous, meaning they lay eggs.  Female ratsnakes usually lay a clutch of a dozen or more eggs in late June or July, and abandon them after laying.  While this may not be considered the most caring of parental behaviours, ratsnake mothers apparently make some important decisions when it comes to selecting a nest site.

An ideal nest could be a rotted stump or log, or a burrow beneath a rock pile or leaf litter.  Many wild ratsnakes choose to nest communally, which makes for a warmer nest temperature and increases the young ratsnakes’ chances for survival.  Hatchlings from warmer nests tend to hatch earlier, grow longer, and swim faster!  Here, at the northern limit of the Gray Ratsnake’s range, hatching out quickly (by late August or so) is a major advantage.  An early freeze could kill un-hatched eggs in the nest.  Research conducted in the late 1990s and early 2000s confirmed that, in a lab setting, female ratsnakes still preferred to lay their eggs at temperatures closer to those of communal nests.

A mother’s best intentions could go sour though, thanks to an inconspicuous insect.  The Pustulated Carrion Beetle (Nicrophorus pustulatus) is a parasitoid of the Gray Ratsnake.

Ratsnake eggs parasitized by carrion beetles. Photo: Gabriel Blouin-Demers.

This beetle lays its eggs on those of the ratsnakes, and when the larvae hatch out, they destroy their ratsnake-egg hosts.  When female ratsnakes nest communally, they run the risk of increasing the chances of parasitism by these carrion beetles.

For more information on the effects of nest site selection on young ratsnakes, check out Gabriel Blouin-Demers’ website at:
http://mysite.science.uottawa.ca/gblouin/publications.html

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