The effect of hibernation on the caecal flora of the thirteen-lined ground squirrel (Citellus tridecemlineatus).

Summary. The effect of hibernation on the caecal flora of the thirteen-lined ground squirrel (Citellus tridecemlineatus) was determined by comparing the flora of 7 active squirrels with that of 6 × 6 days hibernators and 2 × 42 days hibernators. Direct microscopical examination showed the presence of a wide variety of micro-organisms, including protozoa in all the animals. Using strict anaerobic techniques it was possible to isolate > 60% of the total flora of the active squirrels but only c. 30% in the hibernators. Several distinct types of anaerobic Gram negative, nonsporing rods predominated in both the active and hibernating animals. Gram positive, nonsporing rods and coccobacilli were present in the active squirrels but were not isolated from the 42 days hibernators. Atypical lactobacilli present at 106–108/g formed the major part of the aerobic flora of the active squirrels but were reduced at least 100-fold during hibernation.