Tortoise Crossing: Our History with the Sonoran Desert Tortoise and our mission to watch them cross Oracle Road

Written by Jonni Zeman

The Sonoran Desert tortoise (SDT) is one of the most resilient and adaptable animals in the Sonoran Desert. With a life span of up to 80 years, the Sonoran Desert tortoise takes full advantage of the resources available in its habitat. A master of water conservation, these tortoises can go for up to a year and without water. To stay cool and conserve energy, they spend hot days in their burrows, but are most active during monsoon season, when water is plentiful, and they will eat their fill of cactus fruits and flesh. These reptiles rely on the Sonoran Desert scrublands for finding food, water, building burrows, and starting families.

Photo of a desert tortoise with a prickly pear fruit by David Wrench

Unfortunately, many factors threaten the life and abundance of Sonoran Desert tortoises, including habitat loss and fragmentation and an increased mortality due to roadkill. As with most wildlife species, roads are a nearly impenetrable barrier to Sonoran Desert tortoises. These reptiles rarely attempt to cross roads but when they do, they suffer high mortality rates. (1) In accordance with Pima County’s Multi-Species Conservation Plan, the protection of these tortoises requires diligence to connect and restore its habitat here in the Sonoran Desert.

Sonoran Desert tortoise found in the wildlife underpass during construction (1)

The Coalition has worked collaboratively with Pima County, Town of Oro Valley, Arizona Department of Transportation (ADOT), and Arizona Game and Fish (AZGF), alongside our community to achieve our common goal of protecting the Sonoran Desert tortoise, and many other animals, by keeping our roadways safe for both wildlife and people. One area that long been a focal point is the barrier of Oracle Road (also called State Route 77 or SR-77) within the Catalina-Tortolita Mountains wildlife linkage. With data from our roadkill surveys, we knew animals wanted to cross Oracle Road and many failed to do so. We worked hard to provide them a safe crossing opportunity that we know now as the Oracle Road wildlife crossing bridge and underpass. Little did we know just how eager animals were to cross – in the early stages of construction, workers relocated multiple Sonoran Desert tortoises from the site, including one that tried to cross through the underpass in October 2015. (1)

The Sonoran Desert tortoise population near the Oracle Road wildlife crossings provided an opportunity to witness the combined effectiveness of a bridge, underpass, and wildlife funnel fencing in minimizing road-kill while also increasing the connectivity of the surrounding habitats (1). Even though there were many SDT in the area, it was unlikely for us to see them from the wildlife cameras, as they often pass below where cameras are positioned. Luckily, GPS telemetry allowed us to track the SDTs, their movements, and location with radio collars harmlessly attached to their shell (1). AZGF began tracking the movements of 30 SDT in the area with this method.

Tortoise outfitted with GPS telemetry unit

In 2017, when AZGF began the radio telemetry research, we met Calypso, a healthy desert tortoise of about 25-30 years. He was named by a caring, bright 7-year old, whose family found him on their front doorstep no less than three times – after several kindly reminders to return to Big Wash and to stay on his side of the street. AZGF biologists joined CSDP Conservation Science Director Jessica Moreno and placed a tracker on Calypso’s shell using special putty, offered him a drink, and returned him with ceremony once again to Big Wash, carrying him low as they crossed back over Oracle Road. (2)

A Sonoran Desert tortoise, affectionately nicknamed “Calypso” by the family that found him, gets ready to be released back into the wild with a tracking device affixed by the Arizona Game and Fish Department. (2)

On April 27, 2019, NBC’s, “1st Look,” aired a segment after Saturday Night Live about the Coalition and our work on the Oracle Road wildlife crossingsCSDP Conservation Science Director Jessica Moreno spent a day in the field with the crew and host of the show, Johnny Bananas, giving them a tour of the Oracle Road wildlife crossings. AZGF Wildlife Biologist Scott Sprague demonstrated how they use the GPS telemetry device to monitor the tortoises in the area.

Tortoise segment begins at time-stamp 3:49!

As time and monitoring progressed, we had hopes that SDTs in the area would start using the wildlife crossings, but none of the 30 tortoises equipped with GPS transmitters crossed Oracle Road without human assistance (1). It seemed these reptiles were still, unfortunately, using the more dangerous route. After the monitoring season ended, AZGF removed the GPS units from the tortoises in the project area in 2021(1).

Then, later in 2021, AZGF’s roadkill surveys confirmed a growing hotspot of animals being killed on the highway south of the underpass crossing, where there were gaps in the wildlife funnel-fence near an adjacent neighborhood. (3) These gaps allowed for animals, such as Calypso the tortoise, to sneak past the wildlife fencing and crossing structures to attempt to cross Oracle Road. With lives on the line, the Regional Transportation Authority, the Coalition for Sonoran Desert Protection, the Rancho Vistoso HOA, and the Town of Oro Valley joined together with neighbors to find the best fencing solution.

After years of planning and construction, in April 2023, the Town of Oro Valley hosted a ribbon cutting to celebrate a new wildlife gate at Big Wash Overlook Place. This project succeeded in its goal to preserve scenic views, address the wildlife fencing gaps, and safeguard wildlife along Oracle near the wildlife underpass (3).

“This has been quite an effort on the part of groups with a wide variety of needs. Biologists, government agencies, and wildlife connectivity advocates were at odds with Oro Valley residents’ concerns about scenic views at the start of this project, with no solution seemingly possible. But collaboration won the day, with groups working literally for years to find a solution that works for both wildlife and residents. Today is a celebration of that effort”

Carolyn Campbell, Executive Director
Pat Miller, a CSDP Desert Monitor volunteer and a local resident involved with the project, took this photo of the completed wildlife gate at Big Wash Overlook Place, one of two automatic gates installed near the wildlife underpass that closed gaps in adjacent wildlife fencing.

With these gaps filled, we continued to wait and watch for Sonoran Desert tortoise activity on the wildlife crossings. At this point, there had been thousands of successful crossings by many other species, but still no tortoises were detected. Then, this past fall, a group of Coalition volunteers and staff were hard at work improving native habitat on the wildlife bridge during our 2023-2024 Habitat Restoration Days project. With excitement, they spotted a female Sonoran Desert tortoise moving near the south wall of the bridge. Finally, after 9 years, we had the first concrete evidence of a tortoise using these crossings! 

Female Sonoran Desert tortoise using the Oracle Road wildlife crossing bridge.

This tortoise is a tangible reminder that this work matters. While we often have to play the long game, our collective persistence pays off. Will the tortoise we found using the Oracle Road wildlife bridge be the first of many desert tortoises to use wildlife crossings throughout the Sonoran Desert? We hope so.

Your support funds our advocacy for constructing more wildlife crossings over and under local roads and ensures there are connected and protected open spaces leading to and from each wildlife crossing.

  • Wildlife crossings full of healthy, native habitat with the help of our Desert Wildlife Crossing Crew.
  • New wildlife crossings in the Tucson Mountains at Rattlesnake Pass, across I-10 connecting the Tucson and Tortolita Mountains, and across Route 86 north of Kitt Peak.
  • Increased connectivity of landscapes for wildlife with the removal of barbed wire fences by the Desert Fence Busters.
  • Continued health and biodiversity of the Sonoran Desert in the light of climate change.

Supporters like you are taking part in our mission with your personal and community actions. You are restoring habitat and wildlife corridors. You are removing dangerous barbed wire fencing, connecting and protecting wildlife. You are advocating and voting loudly for policy change and protecting water and open spaces. Your donations fund these long-term projects that create positive changes for our communities and our environment. Thank you for everything you do. It matters.

Even a little support goes a long way – Sonoran Desert Tortoise stickers are available on our website for $3 each!


(1) 2021-12-30-SR-77-Progress-Report.pdf (

(2) In wonder of bighorns and tortoises – Coalition for Sonoran Desert Protection

(3) SR77 Wildlife Gate and Fencing Ribbon Cutting Event – Coalition for Sonoran Desert Protection