NITROGEN AND ENERGY-REQUIREMENTS OF THE NORTH-AMERICAN PORCUPINE (ERETHIZON-DORSATUM)

We measured nitrogen and energy requirements in adult North American p orcupines (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 an y dietary treatment. Individuals maintained nitrogen balance on a tota l nitrogen intake of 389.4 mg N kg(-0.75) d(-1). Th, true digestibilit y of nitrogen was high (88%) but within the range for eutherians. We f ound 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 lo w value of metabolic fecal nitrogen found for porcupines affects the d ry matter intake required for nitrogen balance, and it may allow these animals to exploit nitrogen-poor diets.