Nitrogen and energy requirements of the North American porcupine (Erethizon dorsatum).

We measured nitrogen and energy requirements in adult North American porcupines (Erethizon dorsatum) fed three experimental diets differing primarily in crude protein content. Porcupines ingested 497.3-865.4 kJ kg-0.75 d-1, and there was no significant loss of body mass on any dietary treatment. Individuals maintained nitrogen balance on a total nitrogen intake of 389.4 mg N kg-0.75 d-1. The true digestibility of nitrogen was high (88%) but within the range for eutherians. We found metabolic fecal nitrogen to be 0.92 mg N g-1 dry matter intake and endogenous urinary nitrogen to be 223 mg N kg-0.75 d-1. The low value of metabolic fecal nitrogen found for porcupines affects the dry matter intake required for nitrogen balance, and it may allow these animals to exploit nitrogen-poor diets.