Effects of prey size, meal size, meal composition, and daily frequency of feeding on the recovery of rodent remains from carnivore scats

Abstract

Recovery of rodent bone and teeth from coyote (Canis latrans) scats (feces) varied with prey size, meal size, energy content of the meal, and the frequency with which prey were consumed. Mean percentages of mouse and rat teeth recovered ranged from 1% (SE = 0.5%, n = 5) to 24.4% (SE = 3.6%, n = 4) and from 13.8% (SE = 3.8%, n = 5) to 52.5% (SE = 16.6%, n = 5), respectively. A significant portion of this variation resulted from physiological mechanisms affecting how long prey were retained in the digestive acids of the stomach. Recovery of hair did not vary and thus it was considered to be nondigestible. Owing to the variation in the recovery of bone and teeth and the lack of variation in the recovery of hair, we recommend the use of teeth or bone to identify the small rodents present in carnivore scats, and then the use of a visual estimate of hair, or sample of hair, to apportion the scat to the prey items present. We caution against using the numbers of teeth or diagnostic bones to determine the number or amount of a prey item represented by a scat without addressing the variability in their recovery. The effects of gastrointestinal physiology should be considered when planning feeding trials to derive correction factors for scat analysis.