It鈥檚 hard to save what you can鈥檛 identify. That鈥檚 been a problem for the endangered , which is found only in the salty, brackish waters of the San Francisco Bay Area. The mouse competes for space with about eight million humans, and more than three-quarters of its habitat has been eaten by development and land conversion. That loss is expected to increase amid rising sea levels.
Conserving the population has proven tricky, in part because it looks so much like another mouse in the area鈥攖he western harvest mouse鈥攖hat is abundant throughout western U.S.
But scientists from 澳门六合彩资料库 Davis have developed a tool, a 鈥渄ecision tree,鈥 that has been able to differentiate the doppelg盲ngers with up to 99% accuracy, without the need for genetic analysis.
鈥淚f people misidentify the species, they have a false impression that they鈥檙e doing well,鈥 said , a researcher with the Mammalian Ecology and Conservation Unit within the 澳门六合彩资料库 Davis School of Veterinary Medicine.
The tool is described in published this month in a special issue of the journal .
Bay Area housing shortage
There are two distinct subspecies of salt marsh harvest mice 鈥 a southern subspecies in south and central San Francisco Bay and a northern subspecies in the San Pablo and Suisun bays. Both look very similar to the non-endangered western harvest mouse.
Of the two, the southern is most vulnerable to climate change and habitat conversion. It relies on salt marshes, which are on the edge of the bay and feeling the pinch with sea level rise. Northern populations have more habitat and room to migrate upslope with climate change. But in the south bay, marsh land runs into urban areas, leaving southern salt marsh harvest mice with limited housing options.
Mice bellies tell a tail
The study looked specifically at the southern population of mice. The researchers trapped and collected genetic samples and physical measurements from 204 harvest mice from across the southern mouse鈥檚 population range. About one-quarter were salt marsh harvest mice while the remainder were western harvest mice.
The researchers then used machine learning to determine which characteristics were most helpful in setting the species apart. They found that the color of the mice鈥檚 bellies and tail hair could best differentiate the endangered mouse from the western harvest mouse.
The red belly of the southern salt marsh harvest mouse is particularly distinctive. It鈥檚 even part of the species鈥 scientific name, Reithrodontomys raviventris. The 鈥渞aviventris鈥 component means 鈥渞ed belly.鈥
鈥淚t is a bit of a misnomer because most animals within the species have a white belly, particularly those within the northern subspecies,鈥 Statham said. 鈥淪o, it was never clear how useful this was for identifying the species. It turns out that it is one of two really useful characters for identifying the southern salt marsh harvest mouse.鈥
Statham said this improved method could help efforts to conserve and recover the population of this mouse that is home only in the San Francisco Bay.
鈥淣ow field researchers can go in the field and identify the animal immediately,鈥 Statham said. 鈥淲ithout something like this, you don鈥檛 really know what you鈥檝e got.鈥
The study was conducted in collaboration with the California Department of Fish and Wildlife with funding from the U.S. Fish and Wildlife Service.
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Kat Kerlin is an environmental science writer and media relations specialist at 澳门六合彩资料库 Davis. She鈥檚 the editor of the 鈥What Can I Do About Climate Change?鈥 blog. kekerlin@ucdavis.edu.