Look at a map of the McDowell Sonoran Preserve and it has an odd shape: the mountains in the south, the big saguaro flats in the north, and a narrow connection between them. The city’s own documents call that connection the Gooseneck, and a good share of the science done in the Preserve over the last fifteen years has been about one question. Do animals actually get through it?
Why a corridor at all
The city’s 2024 Ecological Resource Plan, declared a public record by the City Council on December 4, 2024, says the Preserve “protects wildlife corridors that connect the Tonto National Forest and Maricopa County’s McDowell Mountain Regional Park through areas that otherwise would be fragmented by various forms of urban development.” Those neighbors are large: about 2.9 million acres of national forest to the north, about 21,099 acres of county park and the Town of Fountain Hills’ roughly 824-acre preserve to the east. The Preserve itself is just over 30,580 acres.
A deer or a mountain lion in the southern McDowells that wants to reach the forest has to get through the Gooseneck. The plan’s January 2024 working draft describes it as the “wildlife linkage between the southern and northern parts of the Preserve,” and names the problem: two roads, Rio Verde Drive and 128th Street, cross it.
Walking it
The city trail map shows a Gooseneck Trail leaving from the Fraesfield Trailhead area on Rio Verde Drive. Part of it carries the Maricopa Trail designation, the 315-mile loop around the metro area that links nine county regional parks, and a Gooseneck Trail County Park Connector links it to the county park. Fraesfield has no water. It also has fewer people than any trailhead we know, which is a good thing on a trail whose whole reason for being is that animals need to pass.
What the studies found
The research on the corridor is a stack of separate projects, most run by the city, the Arizona Game and Fish Department and the McDowell Sonoran Conservancy, whose citizen-science arm has carried the Parsons Field Institute name since 2018.
- 2012: road kill. Game and Fish studied wildlife movement and roadway deaths in the Gooseneck for the city. The report is Identification of Wildlife Road Mortality Hotspots and Wildlife Activity Patterns within the Scottsdale McDowell Sonoran Preserve Wildlife Linkage (Grandmaison, November 2012).
- 2016 to 2018: mule deer collars. The city, the Conservancy and Game and Fish put radio collars on mule deer. The resulting report, Mule Deer Corridor and Habitat Use in the McDowell Sonoran Preserve (Sprague and others, May 2019), looked specifically at how deer use habitat in relation to trail use.
- 2017 to 2019: cameras. The Corridor Viability Project put 26 remote cameras across the Preserve. Mountain lions, mule deer and medium-sized carnivores turned up in every region, which the 2020 report took to mean that every part of the Preserve gives those species what they need to survive and reproduce. A 2018 Conservancy poster summarized the camera and GPS-collar results under the title “Mammal Community Composition and Connectivity through an Urban Corridor.”
- 2021 onward: tortoises. The Desert Tortoise and Habitat Connectivity study began in 2021. Twenty-four Sonoran desert tortoises were weighed, measured, marked and given health checks; transmitters went on 17 adults and two juveniles, which were located weekly that year. In spring 2022 they got GPS trackers that log a location every hour. The working draft describes that tracking as ongoing. Results haven’t been published in the plan.
- 2024: 60 cameras. The plan reports 60 cameras deployed for a long-term trap-camera study run each spring and fall.
What the plan wants next is telling. It calls for radio collars on mountain lions, which haven’t been tracked yet; for camera traps near washes, to test whether animals use drainages as travel routes; for health checks on collared tortoises, watching for upper respiratory tract disease; and for road-kill monitoring within a mile of Rio Verde Drive in the Gooseneck, repeated every few years. Its measure of success is plain: a significant change in movement between the north, the Gooseneck and the south, or along the washes, triggers a closer look.
The rest of the science
The corridor work sits inside a much larger volunteer effort. From the 2024 plan:
- Bats: monitored since 2017. Thirteen species identified (the January draft said twelve), and a maternity roost of Townsend’s big-eared bats has been found. The plan doesn’t say where, and neither will we.
- Birds: at least 190 species recorded. Since 2018 volunteers run nine daytime survey routes, three times a year, plus two night routes each late May. The working draft counted 20 species that are sensitive or in global decline.
- Butterflies: fall counts at six sites since 2014, spring counts added in 2017, 59 species. A 2024 paper from the counts found that winter rain supports butterfly diversity while monsoon rain drives how many butterflies there are afterward.
- Ground-dwelling arthropods: sampled since 2012 at paired sites, one deep in the Preserve and one near the urban edge. More than 300 taxa, with help from the Central Arizona–Phoenix Long-Term Ecological Research program. A 2024 paper in PLOS ONE titled “Living on the Edge” came out of it.
- Reptiles and amphibians: a 2011–2013 survey documented 34 species (3 amphibians and 31 reptiles: one tortoise, 13 lizards and 17 snakes). Monsoon toad monitoring since 2016 has recorded five toads: Great Plains, red-spotted, Couch’s spadefoot, Sonoran Desert and Woodhouse’s.
- Phoenix talussnail: a native land snail the plan says is being considered for Endangered Species Act listing in 2025–2026. Game and Fish has “a couple records” of it in the Preserve.
- Plants: since 2017 volunteers record flowering and fruiting at three sites at least twice a week: saguaro, buckhorn cholla, jojoba, soap tree yucca, desert senna, velvet mesquite, barrel cactus and ocotillo, plus the white-winged dove, which follows the saguaro bloom. Saguaro plots have been measured since 2023 in the area burned by the Diamond Fire.
- Game counts: Game and Fish has flown aerial counts every year since 2013.
- Water: almost nothing. The 2014 baseline inventory found one perennial spring, a few small intermittent sources, and old wildlife catchments and stock tanks. The plan admits “little is known” about any of them.
- Trails themselves: a 2018 paper in the Journal of Environmental Management measured damage to soil and biological soil crust along trails with different amounts of use, and the Conservancy has mapped degraded land for restoration.
Fire has shaped some of this ground. The city’s 2015 Cultural Resource Master Plan notes that wildfires in 1995 and 1996 swept the eastern slopes and pediment, and that what grew back has more red brome, buffelgrass and desert broom than before. The Conservancy’s own history column puts a 2,000-acre burn along the Lost Dog Wash Trail in 1993, the Ancala Fire, which local firefighters nicknamed for its cause: a surveyor burning used toilet paper on a breezy day.
What the plan is for
The 2024 plan is less a report than a schedule. It assigns each study a priority tier and a suggested frequency, calls for an Annual Report pulling all the results together, and every three to five years an Ecological Health Assessment by a panel of outside experts. It is also frank that budgets will decide how much of it happens. If you want to know how the tortoises are doing, the Annual Report is where the answer should appear. Ask the city’s Preserve office for it.
What you can do
- Stay on the trail. The mule deer study was designed around trail use for a reason. Off-trail travel is also illegal in the Preserve.
- Drive Rio Verde Drive and 128th Street like animals live there, because they do. The city paid for a road-kill study on those two roads. Dawn and dusk are when you’ll meet deer and javelina.
- Leave tortoises alone. The Preserve code forbids feeding, harassing, disturbing or collecting wildlife. Photograph from a distance and move on. Our desert wildlife field guide covers what to do about the animals that can hurt you.
- Leash the dog, six feet, always. It’s the rule, and a loose dog is exactly the disturbance these studies measure.
- Volunteer. Nearly every number above was collected by trained Conservancy volunteers. Bird routes, butterfly counts, pitfall traps and toad nights all need people, and the plan suggests the iNaturalist app for recording talussnail sightings.
The Brown’s Ranch and Fraesfield trails are the best places to see the northern half the corridor is meant to keep connected. Go early, go quiet, and look at the washes. On the evidence so far, that’s where the traffic is.