Nitrogen and energy requirements of the short-tailed fruit bat (Carollia perspicillata): fruit bats are not nitrogen constrained.

Nitrogen (N) and energy (E) requirements were measured in adult Carollia perspicillata which were fed on four experimental diets. Bats ate 1.3-1.8 times their body mass.day-1 and ingested 1339.5-1941.4 kJ.kg-0.75.day-1. Despite a rapid transit time, dry matter digestibility and metabolizable E coefficient were high (83.3% and 82.4%, respectively), but true N digestibility was low (67.0%). Mass change was not correlated with E intake, indicating that bats adjusted their metabolic rate to maintain constant mass. Bats were able to maintain constant mass with digestible E intake as low as 1168.7 kJ.kg-0.75.day-1 or 58.6 kJ.. Metabolic fecal N and endogenous urinary N losses were 0.87 mg N.g-1 dry matter intake and 172.5 mg N.kg-0.75.day-1, respectively, and bats required 442 mg N.kg-0.75.day-1 (total nitrogen) or 292.8 mg N.kg-0.75.day-1 (truly digestible nitrogen) for N balance. Based on E and N requirements and digestibilities, it was calculated that non-reproductive fruit bats were able to meet their N requirements without resorting to folivory and without over-ingesting energy. It was demonstrated that low metabolic fecal requirements allowed bats to survive on low-N diets.