Difference in glucose tolerance between phytophagous and insectivorous bats

Bats are mostly insectivorous or phytophagous. It is hypothesized that bats are evolved from small insectivorous mammals. Therefore, the digestive and metabolic systems of phytophagous and insectivorous bats must have evolved differently to adapt to their dietary habits. To investigate the difference in sugar tolerance in bats, we determined changes in blood glucose levels after intraperitoneal (i.p.) injection of glucose in three species of phytophagous and four species of insectivorous bats under resting conditions. Results showed that phytophagous bats eliminated blood glucose faster than insectivorous bats. All three species of fruit bats reduced blood glucose to fasting levels within 30-45 min, whereas all insectivorous bats failed to lower blood glucose to fasting levels even 120 min after i.p. glucose injection. Taken together, results of this study suggest that bats have undergone adaptations and become diversified in dietary habits.