Salt River wild horse study to test limits on herd size

Key Points:

• The Arizona Board of Regents recently approved a $325,000 grant to conduct a genetic study of the Salt River horse herd

• Officials from the Arizona Department of Agriculture want to study the herd’s genetics as they make decisions about managing it

• Researchers will gather fecal samples from all 267 horses to determine how small the herd can sustainably be kept

The fate of Arizona’s iconic Salt River wild horses may hinge on newly funded genetic testing to determine how many of the animals can remain in the wild without putting the herd’s long-term viability at risk.

The Arizona Board of Regents unanimously approved a $325,000 grant on Aug. 27 for researchers from the University of Arizona and Northern Arizona University to study the animals. The study comes as state officials prepare to decide the herd’s future after Gov. Katie Hobbs recently announced a pause on removing horses from the wild.

Researchers plan to collect genetic information by sampling feces from all 267 horses. Ideally, that information will tell researchers how many horses can stay in the wild while maintaining enough genetic diversity to remain healthy.

The data collected from that research, the details of which were released this week, could shape the extent of future removals and the size of the herd for years to come.

“The department’s interest in the study is to ensure that decisions involving the herd are informed by sound, objective science and the best available information,” said Mykaela Martin, a spokesperson for the Arizona Department of Agriculture.

The herd has been a popular draw for tourists who can often catch a glimpse of the animals while floating on the river near Mesa and Phoenix. But critics and some environmentalists say the horses, which are descended from Spanish colonial steeds, damage the local ecosystem and can pose a hazard to motorists.

Hobbs had previously caught flak from Salt River horse advocates who argued that a February decision to reduce the herd size to about 120 within five years could wreck its genetic diversity and cause its extinction. The first removal of 25 horses was set for this month.

The governor’s office did not respond to a request for comment.

The Salt River Wild Horse Management Group, the volunteer organization that helps protect and manage the herd, counted 267 horses as of July 31, according to its mid-year report. The AZDA awarded the group a contract in February to help relocate the horses, despite its objections to any removals.

As that process started, state officials realized they had no genetic information about the herd, Martin said.

How the study will work

Salt River Wild Horse Management Group volunteers will help students, staff and faculty from the University of Arizona and Northern Arizona University collect the samples. The U.S. Geological Survey’s Fort Collins Science Center and Southern Arizona Experiment Station will also participate in the research.

Simone Netherlands, the president of the volunteer organization, said the group is assisting the study by providing its insight and documentation on each horse.

Sample collection is expected to begin this fall, according to the proposal.

The University of Arizona’s PANDA Genomics and Microbiome sequencing facility will assemble the genome, or complete genetic instructions, for each horse, per the proposal. Using that data, the researchers will run simulations to project the herd’s numbers under various population management strategies.

“We’re excited to find out more about the genetic diversity of the Salt River wild horses,” Netherlands said.

Hobbs also announced an amendment to AZDA’s management plan to cap the herd size at 170, up 50 from before.

Giving the herd ‘a fair shake’

The previous figure of 120 risked causing the horses’ extinction if the herd became too inbred, Netherlands said. Researchers have previously identified between 150 and 200 horses as the standard herd size for genetic viability.

“That’s exactly what people were complaining about, that we cannot remove horses before you really know if they are viable into the future,” she said.

While Netherlands said the Salt River Wild Horse Management Group would rather avoid any horse removals, it appreciates the governor’s administration raising the planned herd size to 170 and pausing removals ahead of the study.

Craig Downer, an ecologist who has studied the Salt River wild horses, said the study will be useful. However, he suggested that this research should be complemented by studies on the Salt River ecosystem’s carrying capacity for the herd and the horses’ contributions to their environment.

“Since nature is very complicated, it’s very easy to fool people that don’t have a good overview of the life community and make it seem like they’re a damaging presence,” Downer said.

He said he just wants the herd to get “a fair shake.”

Read on: Salt River wild horse study to test limits on herd size | Arizona Capitol Times

Photo courtesy of Susie Bell