Coyote diets in the Chihuahuan Desert, more evidence for optimal foraging

With 7 years data on coyote prey use and availability, we tested three predictions based on optimal foraging: (1) the proportion eaten of the most profitable item is constant regardless of availability, (2) under a constant density of higher ranked prey, there is no relationship between the proportion eaten of low profitability items and their density, (3) the ratio of number consumed to availability for the highest ranking prey item should be negatively related to availability. We tested these predictions with regression analyses. We found no significant linear relationship between lagomorph availability and use. There was no significant linear relationship between percent frequency of occurrence of rodents nor arthropods and their respective availabilities for two levels of availability of lagomorphs. We found a significant negative relationship between number consumed/number available to availability for lagomorphs but not for rodents nor arthropods. The results supported the three predictions and we concluded that coyotes are foraging optimally. (C) 2002 Elsevier Science Ltd.