A new species in a studied state
Arizona’s mammals were supposed to be a finished list. Then in 2003, mammalogists examining small gray shrews from the southeastern corner of the state announced something new: a desert shrew distinct from Crawford’s gray shrew, named for the mammalogist E. Lendell Cockrum. It was the first new mammal species named from Arizona since 1977.
The animal itself is minute even by shrew standards, around 3 inches long with the tail and light enough to balance against a penny. It is a red-toothed shrew, pale gray above and whitish below, and separating it from Crawford’s gray shrew by eye alone is expert work. Range helps: this species is the gray shrew of the desert grasslands and thornscrub edges of southeastern Arizona and adjacent Sonora.
Desert life at shrew scale
Shrews burn energy fast, and a desert shrew faces the extra problem of heat and drying. Cockrum’s gray shrew hunts small insects and other invertebrates in the litter and soil of arid grassland, most active when temperatures allow, and shelters in cover and burrows through the harshest hours. Like other desert shrews it can ease its metabolism when conditions demand, a trick that lets a high-strung little predator live where water is scarce.
The record set is genuinely small. A handful of confirmed Arizona localities mark the known US range, and every new record refines it. Read the sparse record as a portrait of how rarely this animal is caught and identified, not as proof it lives only at those spots.
How a species stays hidden until 2003
The shrew’s late discovery follows from its looks. Small gray shrews of the Southwest are maddeningly similar, and it took careful measurement and comparison to prove this one was distinct. Specimens sitting in museum trays under older names may yet expand the known range once re-examined.
The IUCN lists the species as Least Concern, though with so few records that rating rests more on its habitat being widespread than on direct knowledge of the animal. Desert grassland across southeastern Arizona remains extensive, and there is no particular reason to think the shrew is rare within it. For now, Cockrum’s gray shrew stands as evidence that even the best-known states haven’t finished yielding their mammal fauna.
