New Mexico meadow jumping mouse Zapus hudsonius luteus
ESA status: candidate for listing
The New Mexico meadow jumping mouse is a unique subspecies of meadow jumping mouse; it is a water-loving animal that lives only along the banks of southwestern streams. It is semi-aquatic, and its large back feet may assist it with swimming as well as jumping. Unlike other subspecies of meadow jumping mouse, it is never found in meadows or grasslands without suitable perennial water and riparian habitat. It is rarely found more than a few feet (1.8 m) from running water.
These small creatures are not called jumping mice for nothing; they can make leaps of up to three feet, ten times the length of their bodies. They are also unique because of the amount of sleep they need. New Mexico meadow jumping mice that live in the mountainous areas of their range may hibernate for 10 months out of the year. Valley jumping mice have longer active periods, but still sleep from early November to late April. Because they spend so much time in hibernation, the preparations they make for their long sleep are crucial to their overwinter survival. And that is part of the key to their water-loving nature – it is along the banks of streams that these mice can most easily and quickly find the rich food sources they need to fatten up for hibernation. They spend their nights foraging in territories that stretch for up to 300 feet along stream banks (sometimes overlapping the territories of other New Mexico meadow jumping mice), eating fruits, the seeds of grasses and forbs, insects, snails, slugs, and millipedes. Moist habitats provide the mouse with a cornucopia of options, as well as dense vegetation that hides them from predators and regulates the moisture and temperature of their environment.
These mice are naturally rare and scattered across isolated population centers, and no wonder – riparian areas make up less than 1 percent of the landmass in the Southwest. But these precious arteries of life are in decline, and the jumping mouse along with them. The mouse has been extirpated from 70 to 80 percent of its historic range, which extended from the San Juan Mountains in southwestern Colorado into the Rio Grande Valley in New Mexico and the White Mountains in Arizona. These days, they are found only in 5 isolated mountain ranges in Colorado, New Mexico, and Arizona, and in the Rio Grande Valley. In all historical locations surveyed since 2000, populations have undergone large declines and in some cases may have completely disappeared. Overgrazing by livestock is the primary driver of this decline – cattle grazing, even with low numbers of cows, destroys sensitive streamside habitat through loss of vegetation, alteration of the vegetative community by selective grazing of certain species, soil compaction, and general destruction from trampling. A mouse in grazed habitat generally cannot collect enough food during its short active period to make it through the winter. During surveys in 2005 and 2006, every population of New Mexico meadow jumping mice was found in areas inaccessible to livestock.
In addition, the removal of beaver from the southwest has had terrible repercussions for the jumping mouse. Beaver dams create complex wetland habitats with saturated soils and dense vegetation, perfect habitat for the New Mexico meadow jumping mouse. But trapping nearly eliminated beaver from New Mexico during the 1890s. Despite their role as ecosystem engineers, beaver are often deemed a pest species and continue to be removed and persecuted by humans, further reducing potential jumping mouse habitat. In addition, off-road vehicle recreation, camping, fire and subsequent erosion, flooding, water diversion for agricultural and urban use, ongoing drought, and climate change all contribute to degradation of the mouse’s habitat, turning the situation from bad to worse.
The mouse became a candidate for listing under the Endangered Species Act in December 2007, but it is still waiting for the legal protection it needs to survive. The U.S. Forest Service (USFS) still allows grazing in jumping mouse territory (both historic and current) in the Santa Fe and Lincoln National Forest; in some places allowing ranchers to graze vegetation down to just 4 inches, despite the jumping mouse’s need for vegetation approximately 33 inches high. In many historic jumping mouse localities that were fenced from cattle, the fences have been cut, left open, or fallen down, and the USFS is not planning to improve their care of the New Mexico meadow jumping mouse any time soon.
According to the U.S. Fish and Wildlife Service (FWS), the USFS is not planning any new management measures to protect the mouse, does not regularly inspect or maintain livestock exclosures in current mouse habitat, and does not plan to reduce livestock grazing in the National Forests. And without the legal enforcement provided by listing the mouse under the Endangered Species Act, the USFS cannot be made to change their ways. While the mouse waits for listing, its habitat is neglected and mowed down by cattle. The existing populations are already so small, and their habitat so fragmented, that the FWS believes populations are not self-sustaining and expansion into additional habitat is not possible. If this mouse is not listed under the ESA, it may well jump into the chasm of extinction.
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photo credit: J. N. Stewart/Flickr