How were Southern Utah’s tortoises impacted by the area’s wet winter?

ST. GEORGE — After a wet winter, spring flowers and other plants sprouted with vigor — a double-edged sword for the threatened Mojave desert tortoise, as the same luscious vegetation they feast on could put them at risk in hot, dry Southern Utah.

A juvenile tortoise eats at the Palms Marine Corps Base, California, Jan. 8, 2020 | Photo courtesy of Joanna Gilkeson/U.S. Fish and Wildlife Service, St. George News

Increased moisture will positively impact the species by providing a greater forage variety during their active spring season, said Ann McLuckie, a wildlife biologist with the Utah Division of Wildlife Resources. Tortoises are more likely to be out and about as they feed.

Additionally, this year’s juveniles will have a better chance of survival as “when they break out of their eggshell and come to the surface, there’s going to be additional forage for them,” McLuckie said.

More precipitation can also increase growth rates, so these young reptiles are more likely to reach adulthood, she added.

While potential flooding may put some species at risk, McLuckie said this isn’t a great concern with tortoises. Even though dry washes they inhabit can flood quickly, they also dry quickly, and while drowned reptiles have been found occasionally, there is less potential for these kinds of deaths in their habitats.

A baby Mojave desert tortoise hatches, location unspecified, Sept. 13, 2023 | Photo courtesy of K. Kristina Drake/ U.S. Geological Survey, St. George News

Mojave desert tortoises may take advantage of steep slopes over portions of their range to avoid periodic flooding, according to the U.S. Forest Service. Additionally, the species may choose soils that hold more water and are not prone to flooding.

However, surface disturbances, like flooding, grazing and wildfire, can cause habitat shifts or alter substrates, like soil, to such an extent that they are no longer viable for creating burrows and nests, according to the U.S. Fish and Wildlife Service. Such occurrences can also destroy existing burrows.

Wildfire poses a significant risk to tortoise populations, McLuckie said. And this year, the risk could be higher due to an abundance of vegetation — particularly invasive grasses, which become fuel during Southern Utah’s dry summers.

For instance, many of Washington County’s hills and roadsides are covered in Sahara mustard plants and red brome, also called foxtail brome — both invasive species that increase wildfire risk.

A tortoise crawls into a burrow in this file photo, St. George, Utah, Aug. 23, 2022 | Photo courtesy of Mike Schijf, St. George News

Tortoises can survive fire within their deep burrows, but not on the surface, and conflagrations can cause regional and local declines of 15-16%, according to a Utah Department of Natural Resources report following devastating wildfires near Turkey Farm Road, Cottonwood Trail and other areas in 2020.

Not only does wildfire kill tortoises directly, but long-term impacts on vegetation negatively affect a population’s recovery, the report reads.

Long-term wildfire impacts on tortoises include injuries from exposure to high temperatures, reduced forage and low-quality habitat, higher surface temperatures due to ground cover and shelter loss, and increased exposure to predators, the report states.

The Washington County Habitat Conservation Plan continues its efforts to reduce wildfire risk by monitoring and removing invasive plant species.

In this file photo, a tortoise sits in red sand near a burn scar, Washington County, Utah, date not specified | Photo courtesy of Ann McLuckie, St. George News

With the Utah Department of Transportation right-of-ways as its highest priority, 26 miles of such areas near or inside the Red Cliffs Desert Reserve were treated with herbicides in 2020-2021. This method appears to be effective at limiting invasive grass growth, according to the Washington County Amended HCP 2022 Annual Report.

In 2022, the conservation plan continued its partnership with the Utah Division of Wildlife Resources on aerial herbicide treatments on up to 523 acres of habitat within the reserve and adjacent to UDOT right-of-ways near Washington City and North of Green Spring, the report states.

Other mitigation strategies include using similar treatments to create fuel breaks and protect unburned habitats, and manually removing invasive species.

For instance, the Bureau of Land Management and the Utah Conservation Corp removed over 18,000 Sahara Mustard plants near Cottonwood Springs Road earlier this year, as St. George News reported.

Southern Utahns can also do their part to prevent wildfires by practicing “good behavior,” McLuckie said.

Red brome grows on a slope in Washington County, Utah, May 14, 2023 | Photo by Alysha Lundgren, St. George News

“In other words, don’t throw out cigarette butts, make sure you’re not dragging chains from your vehicles and creating sparks and make sure when you drive off the side of the road that your catalytic converter doesn’t start a fire,” she said. “So just be very cautious when summer comes of the increased fuel out there.”

Additionally, fireworks should only be lit in approved, paved areas, away from dry vegetation, McLuckie added.

Mojave desert tortoises are listed under the Endangered Species Act and protected by Utah law. According to Red Cliffs’ website, the Habitat Conservation Plan was developed to protect the state’s population and nearly 70,000 acres have been set aside as part of the reserve since 1996 to that effect.

Copyright St. George News, LLC, 2023, all rights reserved.

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