AN ESTIMATION OF COYOTE POPULATION SIZE FOR EVIDENCE OF A TROPHIC CASCADE

Abstract

Following the re-introduction of gray wolves (Canis lupus occidentalis) into Yellowstone National Park in 1998, a dramatic influence of the wolves on the landscape of Yellowstone ecosystem was observed over the following x decades, termed a trophic cascade. Trophic cascade is defined as the reciprocal predator-prey effects that alter the abundance, biomass, or productivity of a population, community, or trophic level across more than one link in a food web, and this effect was has been well-documented from reintroduction efforts of apex predators in the United States. In the Yellowstone wolf example, the wolves have initiated both a traditional trophic cascade, which spans across trophic levels (predator-prey-vegetation), and a carnivore cascade, which spans across a predator guild (wolf-coyote-fox). A goal of the present study was to determine whether or not the Mexican gray wolf (Canis lupus baileyi) can initiate a carnivore cascade in Arizona and New Mexico, assessed by estimation of a coyote minimum population size on the White Mountain Apache Reservation in Arizona. This was accomplished by genotyping scats collected in 2008 and 2009 for polymorphic microsatellite DNA loci, to estimate the population size through a simple genetic minimum population size using all unique individuals. Sixty-one individual coyotes were estimated using minimum population estimate in 2008 and 28 individual coyotes in 2009, on the study plot, however, the estimate did not include the influence of Mexican gray wolves on coyotes population size, due to carnivore cascades in this region.