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

Abstract

Nitrogen (N) and energy (E) requirements were measured in adultCarollia 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 coeflicient 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.