What Happened to the Prescott Valley Pronghorn Antelope Herd? – Bill Williams

Photo courtesy of George Andrejko

Dispelling the myths and rumors about the Arizona Game and Fish Department’s roundup and relocation of the antelope

Most of the antelope herd is now on the far east side of Prescott valley. Photo: Bill Williams

The fastest land animal in North America can make it seem effortless, reaching a top speed of 55 mph, then being able to coast at 30 mph for miles. When they get their wheels rolling, there isn’t a predator that can keep up with them, let alone catch them, but there is one thing however that pronghorn roaming the Glassford Hill area near Prescott Valley cannot outrun — development, according to Glen Dickens, Vice President of the Arizona Antelope Foundation – the only foundation of its kind in America.

On a cold January morning in 2019, volunteers, local private landowners, and Arizona Game and Fish Department (AGFD) personnel gathered at an antelope capture site in Prescott Valley, Arizona. They  were divided into four teams, two of which had fence construction materials to build a temporary woven fence in an alleyway configuration. The other two teams positioned on both sides of the capture alley, hidden in nearby brush to become “drivers.” Everyone hiding was breathless with anticipation when a helicopter fired up and began moving the nearby herd of pronghorn. Fifty-five pronghorns were herded into the ‘wing trap’ and down ‘the alley’ which had been erected a couple months earlier (see video). Volunteers quickly erected a woven fence with ‘the drivers’ who would move the herd at the ready. When the alley trap doors were swung shut, the herd was driven into the capture pens. The teams decided that 45 antelope of the 55 would be the best number to place on trucks for the move south.

AGFD reduced the size of the Glassford Hill (Prescott Valley, Arizona) pronghorn antelope herd – in order to save the herd. They called it translocation, which in layman’s terms means they herded them with a helicopter into a very tall fenced area, put blindfolds over their eyes temporarily (to calm them) and nudged them into a truck for transport to southern Arizona where other healthy pronghorn herds were living. “Our research showed this was the most humane way to get the job done,” said Callie Cavalcant, Big Game Management Program Supervisor, Arizona Game and Fish Department.

The idea was to save the herd from high density housing developments adjacent to Glassford Hill Road and from collisions with cars, in Prescott Valley, and to boost, and add genetic diversity to southern Arizona pronghorn populations.

Rumors and speculation regarding the trapping and moving of the pronghorn have been rampant throughout the population of humans in Prescott Valley, so this reporter sought the final report and conclusions from the experts. From erroneous high numbers of fatalities to risking the herd more than development and automobiles, to speculation that AZGFD did not know what they were doing, and the helicopter harmed the animals… Prescott Valley became the epicenter of pronghorn antelope rumors without facts.

The relocation project was a success

Each pronghorn was inspected for signs of stress, injury, or disease. They were treated for stress if needed, and given a broad-spectrum antibiotic and an anti-parasite drug. Blood samples for standard disease monitoring were obtained by wildlife biologists and veterinarians. Each pronghorn was marked with a colored, numbered ear-tag and some were fitted with radio-collars. Blindfolds were removed immediately prior to being loaded into the transport vehicles.

“The Prescott Valley antelope absolutely joined the other herds down south,” said Rana Murphy, Big Game program leader with AZGFD, Tucson Region. “The colored ear tags, along with the collar data show them mixing, plus their habitat use and even mortality rates.”

Where the antelopes now roam

On the afternoon of that January day, vehicles started south to their respective release sites in Southern Arizona. In the game and fish region known as ‘The Buenos Aires,’ teams released four mature pregnant does, two equipped with radio collars, and Dickens says that went off without a hitch later that evening. The pronghorn destined for the Willcox, AZ. area arrived the next morning at Bonita/Allen Flat and the Monk Ranch. That same morning three mature pregnant does and one buck, without collars were released in the center of the San Bernardino Valley region by Douglas Wildlife Manager Mike Richins.

The data from the radio collars is uploaded at least 4 times daily and analyzed by a Geographic Information System (GIS) Game Specialist periodically. The focus will be on learning where pronghorn are fawning, breeding, and the key zones they utilize seasonally for foraging. The first and last time pronghorn were reintroduced to this area was in 1944-45 when a total of 46 pronghorn were released.

The numbers in the balloons on this graphic/map represent how many animals were released at two sites, total, and how many collars were affixed

This map shows the paths the pronghorn took including a quick visit to Mexico and back

Post-release mortalities and monitoring showed one mature doe died in the Prescott Valley to Tucson area transport and one collared doe and one collared buck at the Bonita release site died most likely of ‘capture myopathy’ within 72 hours after being released. This percentage of transplant mortality is well within acceptable biological limits according to Dickens. The really good news, says Dickens, is that all the other pronghorn released with collars have been observed upright, healthy and mixed in with groups of resident pronghorn.

The Antelope Foundation paid for the collars attached to bucks and does and that is paying dividends because the movement of those with collars is tracked and placed in a database and show detail such as a pair of does crossing over the Mexican border for a couple days and coming back (see map). The pronghorn are all very busy exploring the boundaries of what Dickens and the Foundation consider the available pronghorn habitat and in some cases beyond. One curious buck, with a collar began his journey a couple months after relocation from northwest of Willcox in what became a 70-mile “walk about” and was recently sighted on the north side of the Gila River northeast of Safford, Arizona.

The does fawn in May and they do teach young ones how to stay safe, but they constantly look for feed and try to keep the fawns within a mile of a water source. Maps generated by collar data indicate movement to water and vegetation and can give researchers ideas on where to set up water tanks.

This research is part of the Foundation’s 8-year Southeastern Arizona Pronghorn Enhancement project funded by the National Fish and Wildlife Foundation and the Arizona Game and Fish Habitat Partnership program.

Dickens said one of the greatest values of moving the Prescott Valley herd south was the DNA, meaning there was successful breeding with the herd in the south where they were transported.  The pronghorns’ chief predators are coyotes and mountain lions. There is a hunting season each year in August and September and hunters obtain permits from AZGFD.

This success fits the two-fold purpose. The first purpose was to “rescue” a subpopulation of  pronghorn that had become surrounded by 360 degrees of subdivisions and major highways. The herd had decreased in population from 100 animals a year earlier due largely to vehicle collisions. The second purpose was to release the captured animals into five pronghorn subpopulations in Southeastern Arizona to bolster individual herd numbers and genetic diversity.

The herd was given a death sentence by urbanization

Researchers have been monitoring Arizona herds since the 1940s. Herd size has varied in size over the years and with studies like this one, researchers can get a better gauge of how and why the size of the herd grows or contracts. Researcher  believe 30 died from car collisions along major roadways in Prescott Valley. “We saved the herd from high density development and potentially more car collisions,” Dickens said. “The Prescott Valley herd was given a death sentence by urbanization.”

“Our mission at Game and Fish is to conserve and protect all of Arizona’s wildlife,” said Erin Butler, terrestrial wildlife program manager for the department’s regional office in Kingman, AZ.

“With a four-lane, divided highway to the north, an encroaching subdivision to the east, another housing community under construction to the west, and more development to the south, the Prescott Valley herd needed our help.”

As development in the Prescott Valley area continues, and their habitat dwindles, these pronghorn will find it increasingly difficult to survive. As for the remaining pronghorn near Glassford Hill, AZGFD expects the lower-elevation grassland habitat to be completely developed within the next five to 10 years, resulting in a decrease in the population.

For more on the Antelope Foundation, see https://www.azantelope.org/

Photos have been graciously provided courtesy of Betty Dickens; and Arizona Game and Fish Department which provided the graphics as well.