Phillips's Small-eared Shrew is known only from a handful of localities in the mountains of Oaxaca. All these sites lie within an area so small that it would fit several times inside a single large city.
It lives in the humid undergrowth of pine-oak forest and mid-mountain cloud forest, where it spends its life almost completely hidden under leaf litter and moss.
Like other shrews in its group, Phillips's Small-eared Shrew never stops moving for long. Its accelerated metabolism requires it to eat almost constantly.
It is one of many examples of a species with an extremely restricted distribution, a result of the isolation of the various mountain ranges forming Oaxaca's mountainous geography.
A small Phillips's Small-eared Shrew with uniform dark brown fur, a long, mobile snout, and tiny eyes barely visible in the fur. It is confused with other broad-clawed shrews from the mountains of Oaxaca. Reliable separation often requires cranial or genetic analysis given the great recent diversification of the group in the region.
Tiny track, barely 1 cm, rarely visible except on very fine substrate. Tiny, dark droppings, a few millimetres long, containing insect chitin remains, left scattered along surface runways under damp leaf litter. Phillips's Small-eared Shrew builds surface runways under leaf litter and spherical nests in hollows under fallen logs or roots. These are typical of the damp mountain undergrowth where Phillips's Small-eared Shrew lives.
Pine-oak forest and mid-mountain cloud forest, with damp soil and abundant leaf litter, generally between 2000 and 3000 m altitude.
Endemic to a very small and fragmented area of the Sierra Madre de Oaxaca, in southern Mexico.
Phillips's Small-eared Shrew is insectivorous, feeding on insects, earthworms and other invertebrates from the damp soil of mountain forests.
Phillips's Small-eared Shrew is active continuously in short bursts throughout the day and night, driven by its very fast metabolism. It exhibits solitary and territorial behaviour. Its strong dependence on the constant humidity of mountain forest greatly limits its ability to move between separated habitat fragments.
Its known home range, barely 6000 km² and highly fragmented, combined with continued habitat loss from overgrazing and deforestation, places its populations in continued decline.
Deforestation and overgrazing in the pine-oak forest and cloud forest on which Phillips's Small-eared Shrew depends, and the extreme fragmentation of its already very reduced home range.
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