The effects of diet and photoperiod on hibernation in the woodland jumping mouse, Napaeozapus insignis (Miller)

Abstract

Woodland jumping mice, Napaeozapus insignis, were held at 9 ± 3 °C under three photoperiods: short days (8 h light: 16 h dark), long days (16 h light: 8 h dark), and a naturally changing photoperiod that approximated naturally occurring day lengths. Half the animals under each photoperiod had access to a full diet of sunflower seeds, rolled oats, and Purina rabbit chow throughout the experiment. The remainder of the animals in each photoperiod received the full diet for the first 10 days of the experiment after which they were given only rabbit chow. The patterns of torpidity of the animals in each group were analyzed with respect to two dimensions of hibernation: timing and quality. Under all photoperiods, animals that were switched to the rabbit chow diet spent significantly more time in torpor than did those that remained on the full diet. Of the animals on a full diet, those on a natural photoperiod spent more time in the torpid state than did those on either long or short days. It is suggested that jumping mice in nature respond to both decreasing photoperiod and food to adjust the proportion of time spent in torpor.