The Pacific Water Shrew is the largest shrew in the province. It is an attractive mammal, with dorsal fur that varies from dark brown to black, and dark brown ventral fur that does not contrast sharply with the dorsal fur. The tail is a unicoloured dark brown above and below. The feet have a stiff fringe of hairs about one millimetre long, although the hairs may be missing on old adults.
The relatively large skull has a rostrum that is curved in ventral profile. There are five upper unicuspid teeth; the third is distinctly smaller in size than the fourth. The upper unicuspids have a pigmented ridge that extends to the cingulum. The upper incisor has a large medial tine that is positioned within the pigmented region on the face of the incisor.
IdentificationThe large body size (total length greater than 130 mm; hind foot greater than 18 mm), large skull (skull length greater than 19.0 mm; palatal length greater than 8.2 mm) and the fringe of stiff hairs on the feet distinguish the Pacific Water Shrew from all our shrew species except the Water Shrew (Sorex palustris). The Water Shrew can be identified by its dark grey to black dorsal fur with a silver-grey belly, a bicoloured tail that has a paler underside, and a longer, more conspicuous fringe of hairs on its feet. The skull of the Water Shrew is smaller, does not have a ventrally curved rostrum, and has upper incisors with indistinct, medial tines.
Dental Formulaincisors: 1/1
Measurementstotal length: 154 (137-176) n = 107
tail vertebrae: 70 (61-81) n = 106
hind foot: 19 (16-21) n = 105
ear: 8 (6-9) n = 10
weight: 13.2 (10.0-20.0) n = 24