TORTOISES AND HABITAT CONNECTIVITY

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Why It matters

Spotting a Sonoran desert tortoise in the wild typically sparks excitement. These seldom-seen animals are important in the ecosystem, providing food for other species as well as shelter through the burrows they dig.

Unfortunately, their numbers have been declining throughout their range. As a long-lived species with slow recruitment (few young survive to adulthood), it is vulnerable to human and environmental pressures. Chief threats facing this species include habitat loss and fragmentation, removal from the wild, disease, introduced species and more. In Arizona, it is considered a special status species, and it is currently being considered for federal listing as threatened or endangered under the Endangered Species Act.

Little is known about the tortoise population in McDowell Sonoran Preserve or what factors might be affecting it. Understanding how human activities might influence this sensitive species will help the Conservancy and the City of Scottsdale make appropriate management decisions to protect the tortoise and the Preserve ecosystem.

The Conservancy’s Work

Through generous support from the Heritage Fund, the Conservancy is studying the local tortoise population using a combination of surveys and radio telemetry. Trained teams survey for tortoises in the Preserve, with the goal of attaching radio transmitters to at least 20 animals. All animals are weighed, measured, marked, and given a health assessment, which helps monitor for evidence of disease or other potential issues.

Transmittered animals are then located weekly. Once equipment becomes available, these animals will receive GPS trackers, which will provide a location every hour for each individual. These trackers do not affect tortoise behaviors or movements. Tracking desert tortoise movements provides a better understanding of how tortoises are using the Preserve and what factors might affect their population. Information about this population also helps understand trends throughout this species’ range and how to best protect it into the future.

Additionally, this project feeds into our knowledge of how the Preserve acts as a habitat linkage within the larger region. The Preserve provides a vital connection for nearly 3 million acres of protected landscapes, extending from Tonto National Forest through the Preserve and into McDowell Mountain Regional Park. Understanding how species such as tortoises, mule deer and more move about the landscape is essential for determining management needs to maintain that connectivity and ensure these species continue to thrive in this area.

What’s Been Found

This is a new project! Field work began in April 2021 and has been very successful. Seventeen tortoises have been marked, and several others have been observed or reported by other individuals. Transmitters have been attached to 12 adults; juveniles do not receive transmitters.

Thus far, these tortoises have been making short but frequent movements, often occupying a new location each time they are found. A couple individuals have moved up to 400 meters in one week. Tortoises are typically less active during the dry season and make larger movements during the monsoon season, so it has been interesting to see these frequent movements during May and June.

Continued tracking will allow us to determine areas typically used by each individual, overlap between those areas, short- and long-distance movement patterns, and much more. From this information, the influence of natural and human factors can be teased out to help inform management needs.

How You Can Help

  1. Tortoises are protected in the state of Arizona. If you see one, please do not touch, handle or move it, unless it is in imminent danger (e.g., on a busy road).
  2. Please report any sightings of tortoises while adventuring in nature! You can document them in iNaturalist.
  3. Learn more about the Sonoran desert tortoise.
  4. Support McDowell Sonoran Conservancy with a gift or volunteer as a Conservancy Science Steward

McDowell Sonoran Conservancy Staff Contact:

Tiffany Sprague | 480-998-7971 ext. 105 | Tiffany@mcdowellsonoran.org
7729 East Greenway Road, Suite 100, Scottsdale, AZ 85260 | 480.998.7971


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