Case Study: Using Soil Survey to Help Predict Sonoran Desert Tortoise Population Distribution and Densities

Abstract

Soils properties can affect the ability of an animal to dig burrows for habitat and survival purposes. The Sonoran (Gopherus morafkai) and Mojave Desert Tortoise (Gopherus agassizii) require burrows that are at least 20 inches deep to help them thermoregulate during the cold of winter and heat of summer. Soils that have characteristics that restrict their “digability” would be expected to limit the population density and distribution of animals such as the Sonoran or the Mojave Desert Tortoise regardless of the amount of forage vegetation being produced. The Sonoran Desert Tortoise in Mohave County, Arizona, and possibly throughout its range may seek “habitats of opportunity” within boulder piles, under exposed bedrock, and in caliche caves due to the limited “digability” of the soils endemic to this part of the Sonoran Desert. The natural availability of thermoregulating burrowing habitat and temperature/precipitation records should be considered when interpreting any fluctuations in Sonoran Desert Tortoise population densities. © 2017 The Society for Range Management