Seasonal Changes in Body Mass and Activity of Digestive Enzymes in Eptesicus nilssonii (Mammalia: Chiroptera: Vespertilionidae) during Hibernation

Hibernation can be considered as a circannual cycle of feeding and fasting. During winter, the absence of dietary substrates in fat-storing hibernators leads to a reduction in the mass of fats and digestive organs. We examined the seasonal changes in body mass and activity of digestive enzymes in the pancreas and small intestine of the torpid Eptesicus nilssonii (Keyserling & Blasius, 1839). Adult females and males were captured in autumn (November, early hibernation), winter (February, mid-hibernation) and spring (March–April, late hibernation) in northwestern Russia (Republic of Karelia). Our findings indicated that male and female E. nilssonii reduced body mass during hibernation, but females exhibited a slower decline in body mass during hibernation period than males. No significant differences in the activity of digestive enzymes were found between males and females. Pancreatic protease activity was the highest in autumn, decreased in the mid-hibernation season, and remained low during hibernation of E. nilssonii . There was no difference in the activity of amylase and lipase in the pancreas among all periods of hibernation. However, the activity of protease, amylase and lipase in small intestine was higher before the emergence from hibernation in spring than during autumn. This study provides new information of the maintenance of intestinal hydrolytic enzyme activity after months of fasting. E. nilssonii , a fat-storing hibernator, appears to maintain a digestive function during the hibernation season, apparently to allow efficient absorption of nutrients that are ingested after terminal arousal in the spring.