AGE DISTRIBUTION AND SURVIVAL OF COYOTES AND GRAY FOXES IN WESTERN TEXAS
Kirk, Cassie Ann
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The coyote (Canis latrans) is one of the top predators in the state of Texas. They have been able to adapt to urbanization and continue to thrive in the wild. The coyote is also considered a top down keystone species. As such, coyote management can influence how other species are managed. Female coyotes can become sexually mature once they experience their first estrus cycle in the first year of life. Gray foxes (Urocyon cinereoargenteus) occur throughout Texas. Both male and female gray foxes can attain sexual maturity at an early age. Females on average breed for the first time at about 9-10 months of age. A better understanding of the age structure and survival rate of both species, we can better understand how many possible individuals we have that will be in prime breeding age, and how exploitation of the species may be effecting structure of the population. Given that both species are harvested in predator hunts and nuisance animal situations, I wanted to explore age structure and survival of coyotes and gray foxes in western Texas. I collected the lower canine tooth from 378 coyotes from the Panhandle and southwest areas of Texas. I also collected 288 lower canine teeth of gray fox samples from the Edwards Plateau and the Trans Pecos ecoregion. The teeth were processed for cementum annuli to access age for each individual. I then developed age distributions and used these distributions to calculate annual survival rates using a-structured regression. The overall survival of coyotes in Texas was 0.659. For females in total, annual survival was 0.709. Males annual survival was 0.686. The annual survival of all the gray foxes together is 0.650. Females annual survival was 0.647. Male’s annual survival was 0.643. The coyote and gray fox are adaptive species and can survive in different habitats and situations. The age structure in both species does suggest that exploitation is changing the age structure towards a younger dominant composition. However, these age structures also suggest that all of the populations I examined have not been over-harvested. Shifting populations to younger age classes can reduce age at maturity and increases litter sizes. Thus, the demographic strategy of these species apparently allows them to be resilient to current exploitation levels in this region.