By BEN NEARY
NMWF Conservation Director
The U.S. Fish and Wildlife Service has prohibited grazing in select areas around New Mexico to preserve populations of the New Mexico Jumping Mouse. Now the agency is gearing up to monitor what it hopes will be a robust recovery of the mouse population.
The New Mexico Jumping Mouse doesn’t tolerate intense livestock grazing on its habitat. It requires healthy streams and tall grass to survive. The mice grow up 9 inches long, with more than half of that length consisting of their tails. They can jump up to 30 inches. They hibernate for nine months a year.
The population of the mouse has fallen drastically in recent decades.
The USFWS listed the mouse as endangered in 2014. Two years later, the agency designated 14,000 acres of critical habitat for the mouse, mostly in New Mexico but also with parcels in Colorado and Arizona. Early this year, the USFWS published its recovery plan for the species.
Mark Brennan, fish and wildlife biologist, is assigned to the New Mexico Jumping Mouse recovery. He will give a free presentation on his agency’s recovery efforts on Sept. 13 in Albuquerque as part of the New Mexico Wildlife Federation’s Wildlife Wednesday series. His talk will start at 5:30 p.m. at Marble Brewery’s Northeast Heights Taproom, at 9904 Montgomery Blvd NE, Albuquerque.
Although the New Mexico Jumping Mouse was listed as endangered nearly 10 years ago, Brennan said the nature of the mouse makes it difficult to gauge how well the recovery effort is going.
“With a lot of species of this type — small, cryptic animals — it’s hard to really know the populations’ trends,” Brennan said. Now that a recovery plan is in place, he said The Fish and Wildlife Service hopes to work with outside scientists to do the necessary long-term mapping and recovery work.
In its 2016 published designation of critical habitat for the mouse, the USFWS stated that most livestock grazing is likely to be incompatible with the persistence of jumping mouse populations because of their sensitivity to habitat disturbance.
“Although livestock grazing can be managed in many different ways, the best available scientific and commercial data indicate that the jumping mouse does not persist in areas when its habitat is subjected to heavy grazing pressure,” the designation stated.
The Northern New Mexico Stockman’s Association and Otero County Cattleman’s Association sued the USFW over the critical habitat designation. The ranchers argued that the agency had failed to consider the economic effects of its decision and failed to consider ranchers’ water rights.
The ranchers lost their case in federal court and appealed. Last year, the 10th Circuit Court of Appeals ruled against the ranchers, upholding the USFWS’s critical habitat designation.
Although Brennan said it’s difficult to gauge current population trends of the Mexican Jumping Mouse, he said it’s clear their numbers have fallen dramatically over time.
“It’s greatly reduced, there’s no question about that,” Brennan said. He said there are no studies from the 1940s or 1950s that would allow scientists today to calculate precisely how much the population has declined. He said studies starting in the 1980s show the current population has declined significantly.
“It’s been greatly reduced and a lot of it is because of land management and grazing and water diversion and some of these other basic habitat modifications that have happened in the past few decades,” Brennan said of the mouse population.
The mouse is found as far south in New Mexico as the Sacramento Mountains in the south central part of the state, in the Bosque del Apache along the Rio Grande. They exist across northern New Mexico, from the San Juan Basin, the Sangre de Cristo range and east into the Canadian River Basin.
Removing livestock from critical habitat areas has shown dramatic improvements in mouse habitat and populations, Brennan said.
“We get incredible habitat response,” Brennan said. “And, knock on wood, we’re seeing in some places immediate, within a couple of years, immediate New Mexico jumping mice.”
Once livestock grazing is curtailed, Brennan said mouse numbers increase enough that scientists are able to detect populations through putting out tracking devices and live traps.
“On federal land, primarily Forest Service lands that are managed for grazing, we’ve had allotments for quite a while that have not had riparian habitat excluded,” Brennan said. “Those are places we saw the mouse disappearing from rapidly, that had historic records.”
Brennan said the Forest Service has been scrambling for years to try to get the money for fencing around riparian areas designated as critical habitat.
Once cattle are excluded from riparian zones to benefit the New Mexico Jumping Mouse, Brennan said other species benefit as well, including aquatics and fish species. Leopard frogs, the Southwest Willow Flycatcher and several snake species are all among the species that require riparian habitat, he said.
Remaining mouse populations have been identified in 19 known locations among six geographic areas among the three states, Brennan said. “We want to expand them back into areas that have gotten degraded and where they’ve gotten greatly reduced in,” he said.
The USFWS recovery plan calls for increasing to eight distinct populations over a period of time to show a stable, or increasing trend. Brennan said that if that level can be maintained for 12 years, the mouse species can be downlisted from its current status as a critically endangered species. In order to delist the species entirely, he said the 12 populations will have to be maintained for 16 years.
Brennan said the USFWS is working to conserve as much habitat for the mouse as possible while making sure that designated habitat stays functional.
“This species is a riparian obligate and doesn’t live in the upland areas,” Brennan said.
Brennan said he sees a role for the public in supporting his agency’s work on the New Mexico Jumping Mouse. “We get a lot of voices in this state who are opposed to what we’ve done for the New Mexico jumping mouse,” he said. “We also get an occasional letter in favor of the conservation needs for the state, especially riparian habitat, which is a very fragile and limited habitat in the Southwest.”
Anyone can ask their congressional delegation to express support for the recovery planning going on for the New Mexico Jumping Mouse, Brennan said. “That alone will help congresspeople in this state take this to their desks on Capitol Hill and petition for the funds we need,” he said. “That’s the biggest thing we need, funds for more research, more habitat modification,” he said.
Brennan said getting the recovery plan in place this year will allow his office to seek more money for recovery work. “Now that we’ve got that guidance in place and approved, I’m hoping we’ll have the ability to get more funding in,” he said.
Aside from its intrinsic value as a species, conserving the New Mexico Jumping Mouse is important because of what its survival says about how well we’re managing riparian areas, Brennan said.
“Deer mice, voles, other small mammals, they’ll be in that same habitat, but they’re certainly not dependent on it,” Brennan said. “So this one is pretty much our red flag species for functional riparian habitat.”