Chipmunk Research

For more than fifteen years, we have been working to reveal the secret lives of the eastern chipmunks (Tamia striatus) of southern Quebec. Despite a diverse diet, chipmunks rely heavily on the seeds of American beech trees (Fagus grandifolia) and red maples (Acer rubrum) for their winter survival and reproduction. However, these trees produce abundant seeds only every other year (mast years) as an anti-predator defense. During a mast year they produce so many seeds that the seed predators, such as chipmunks, are overwhelmed and therefore some seeds are able to escape predation and germinate. However, in non-mast years beech trees do not produce any seeds at all and red maple produce very few, meaning that chipmunks and other seed predators must find alternate sources of food.

In southern Quebec, chipmunks breed once a year, but the timing of breeding depends on whether it is a mast year or not. In years of high beech seed production, chipmunks mate in June and their young emerge from the maternal burrows to establish themselves in a new burrow in September, exactly when beech seeds are available. The beech mast therefore provides them with enough food to get through their first winter. Because they have accumulated a lot of seeds in their burrows, chipmunks then mate in March during the following non-mast year, and then not again until June of the following mast year.

Red maples produce seeds synchronously with beeches, but in the spring rather than the fall, and their cycle is less marked than that of beech trees, with fewer seeds being produced in non-mast years. Chipmunks eat more maple seeds in years of high fall beech seed production. Red maple seeds are excessively rich in vitamin B3, or niacin, and are believed to stimulate summer reproduction in chipmunks, as B3 would boost fertility in both males and females. We are continuing our research with an experiment to test the effects of B3 on ovulation in chipmunks.

This seed production cycle has many consequences on chipmunk demography and life history (population density and age structure, age at first reproduction, senescence and longevity), behaviour, individual specialization of ecological niches, activity rhythms, and parasitism. In recent years, due to the combined effects of a mealybug and a fungus, cortical beech disease has caused very rapid death in mature beech trees. These changes to the make-up of the forests where our populations reside are likely to have important implications. The chipmunk, which for the moment is a common species, could very well change its conservation status in the coming decades.

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Collaborators: Dany Garant, Patrick Bergeron, Mathilde Tissier, Albrecht Schulte-Hostedde

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Students: Laurie Auclair (MSc), Dominic Bourret (MSc), Megan Brownlee (MSc), Catherine Čapkun-Huot (MSc), Elene Haave-Audet (PhD), Marianne Roxbough-Lepage (MSc).