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My Nevada 5: The Critters that Capture My Imagination
In 1946, the eminent mammalogist E. Raymond Hall wrote in the preface of his classic book Mammals of Nevada that "Mammals are abundant in Nevada, even in the most sandy areas which, because they appear to be barren, have but slight if any appeal to the casual visitor."
Nevada is full of areas that appear barren. But at the right time of day and season, even a casual visitor will find that superficial "barrenness" filled with extraordinary species that exist nowhere else on Earth. Unfortunately, some of these species are in imminent danger of disappearing.
Most of the mammals I study are rodents, but not the rats and mice that seek out human landscapes (and deservedly earn a reputation for their association with our less sanitary spaces). Rather, rodents that populate the vast desert and mountain landscapes of western North America. These generally unseen members of our native wildlife reveal fascinating stories about the turbulent geological and climatic history that produced the biological diversity we see in Nevada today.
Any number of species could have been included on my list of favorite Nevada mammals, but these four rodents and one rabbit offer at least one trait (ecological, evolutionary) illustrating the uniqueness of our state's mammals, and thus why this is a special place to be a mammalogist.
1. Grasshopper mice (Onychomys)
Imagine a mouse that sits up on its haunches and howls like a coyote -- a high-pitched, squeaky howl, but a howl nonetheless. Nevada is home to two species of grasshopper mice, and while neither is unique to the state, they represent important and fascinating residents of those barren areas. In addition to the howling, grasshopper mice share with their better-known dog and cat-like carnivores a preference for animal diets. They are voracious hunters of ground insects, scorpions, and centipedes -- having developed predatory tactics for avoiding spray from bombardier beetles and scorpion stingers.
2. Kangaroo mice (Microdipodops)
Now imagine a mouse that looks like a walking and hopping head, about the size of a large chicken egg.While not literally all head, kangaroo mice have the largest head-to-body ratio of any other mammal on Earth. Nearly all populations of the two species of kangaroo mice occur in Nevada. This incredible mammal, seemingly drawn from the imagination of Lewis Carroll, is quite rare and specialized for a very unique set of sandy desert habitats. We may lose many populations of these species through development of solar energy farms before gaining the widespread realization that Nevada is uniquely situated to help retain global biological diversity by ensuring their sustainability.
3. Great Basin pocket mouse (Perognathus parvus species group)
A few of my colleagues, including three former graduate students, described a new species in this group and in so doing are forcing mammalogists and ecologists to use a new taxonomy (ecologists are not generally very happy about such things). Pocket mice share an ancient ancestry in North America with kangaroo rats and kangaroo mice. Thus their genes hold clues -- if only we discover how to read them -- to the roles of geological and climatic history in the origination of modern species. When we read the genes of the Great Basin pocket mouse, we discovered that it actually included two very old species -- one centered on Nevada, and the other on the Columbia Plateau in eastern Washington. We have a lot more work to do to flesh out other details, but value this species for its record of evolution in and around Nevada over the past 8 million years or so.
4. Chisel-toothed kangaroo rat (Dipodomys microps)
Kangaroo rats, kangaroo mice, and pocket mice are what we call "granivores" -- they specialize in sifting the seeds of grasses and shrubs from the soil and carrying them in fur-lined cheek pouches back to the relative predator safety of their burrows. The Chisel-toothed kangaroo rat is an evolutionary and ecological individualist. This species has developed flattened lower incisors beneficial for scraping the waxy and salty outer surface from the leaves of a shrub called saltbush. Digestive adaptations enhance their capacity to digest leaves in addition to seeds. Nevada represents most of the territory occupied by this biologically and ecologically unique mammal.
5. Pygmy rabbit (Brachylagus idahoensis)
There is a rabbit that digs burrows in the big sagebrush habitats that once stretched many miles across central and northern Nevada. It is small enough as an adult to fit into the palm of your hand. Not much is known about the origins of this species, but fossils demonstrate they once ranged as far east as Colorado and New Mexico. Nevada thus represents a large portion of the remaining populations of this tiny rabbit, which is unlike any other on Earth. Due to a combination of forces that is rapidly eliminating the vital big sagebrush habitats, Nevada is in grave danger of losing its remaining populations of both the pygmy rabbit and the Greater sage grouse.
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