New CSP study focusing on the movement ecology of the Mojave desert tortoise - Conservation Science Partners
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New CSP study focusing on the movement ecology of the Mojave desert tortoise

Understanding patterns and drivers of animal movement is essential for the development of comprehensive conservation and management plans. Movement can be impeded by natural factors as well as by human-induced changes to the environment. For instance, the placement of buildings, roads, and fences may restrict natural animal movement processes such as foraging, dispersal, and gene flow. Similarly, climate change may impact animal movements independently or in tandem with landscape change by affecting exposure stress, limiting dispersal, and increasing disease transmission rates.

Changes to animal movement in response to human-induced changes to the environment are of growing concern in conservation. Most research on this problem has focused on terrestrial endotherms, but changes to herpetofaunal movement are also of concern given their limited dispersal abilities and specialized thermophysiological requirements.

Animals in the desert region of the southwestern United States are faced with environmental alterations driven by development (e.g., solar energy facilities) and climate change. Here, we study the movement ecology of a desert species of conservation concern, the Mojave desert tortoise (Gopherus agassizii). We collected weekly encounter locations of marked desert tortoises during the active (nonhibernation) seasons in 2013–2015, and used those data to discriminate movements among activity centers from those within them. We then modeled the probability of movement among activity centers using a suite of covariates describing characteristics of tortoises, natural and anthropogenic landscape features, vegetation, and weather.

Multimodel inference indicated greatest support for a model that included individual tortoise characteristics, landscape features, and weather. After controlling for season, date, age, and sex, we found that desert tortoises were more likely to move among activity centers when they were further from minor roads and in the vicinity of barrier fencing; we also found that movement between activity centers was more common during periods of greater rainfall and during periods where cooler temperatures coincided with lower rainfall. Our findings indicate that landscape alterations and climate change both have the potential to impact movements by desert tortoises during the active season. This study provides an important baseline against which we can detect future changes in tortoise movement behavior.

Location of the study area in the Ivanpah Valley of southern California, U.S.A.

[READ FULL PUBLICATION] – Discriminating patterns and drivers of multiscale movement in herpetofauna: The dynamic and changing environment of the Mojave desert tortoise