In Washington, the Shrew-mole has a lengthy breeding season that begins in February and extends to late September, although few animals are in breeding condition after mid May. The length of the gestation period has not been determined for this species. Females probably produce only one litter per year; the litter size ranges from one to four. Breeding data for British Columbia are limited to information from a few museum specimens. Four pregnant females, with three or four embryos each, were taken between 1 April and 15 June. Four nursing females were trapped between 30 April and 12 June. These data are consistent with a breeding season that extends from March to June.
Shrew-moles are born naked with no vibrissae, their teeth are not erupted and their digits lack nails. Newborn young weigh less than a gram; their total length is about 26 millimetres and their tail length is about 5 millimetres. Growth and maturation of the young have not been studied, but the young probably reach sexual maturity in the spring following their birth.
| Earthworms are usually the major prey; they accounted for 42 to 82 per cent of the stomach remains in Shrew-moles captured in Oregon and Washington. Other important prey types are insect larvae, adult beetles, grasshoppers, sowbugs (wood lice), snails, slugs and centipedes. Seeds and other plant material are eaten on occasion. A study from the Cascade Mountains of Washington found that, in September, invertebrates formed 75 to 88 per cent of the diet; in July, however, conifer seeds (36 per cent) and lichens (32 per cent) were the major foods, and invertebrates (18 per cent) were minor. Captive Shrew-moles readily consumed conifer seeds, especially Sitka Spruce seeds, and various species of fungi.
Remarkably, the Shrew-mole is completely blind and is dependent on its sense of touch to locate food and find its way. In addition to the sensitive bristles on the nose, it has bristle hairs on the tail that are probably sensitive to touch. The role of sound in the behaviour of this species is not known, but there is circumstantial evidence suggesting it is adapted to hearing high-frequency sounds (8 to 30 kilohertz). The Shrew-mole's sense of smell is poorly developed, and the nose acts primarily as a tactile organ. When searching for food, it swings its nose from side to side, tapping the surface of the ground. Insect pupae and sowbugs are flipped over and pounced upon. Earthworms are bitten along their entire length and eaten whole or chewed into smaller pieces. The Shrew-mole has a voracious appetite. A 10-gram mole was observed to eat a 1.3-gram earthworm in ten seconds; another consumed 4.7 grams of worms in two hours.
| The Shrew-mole's association with forests of different ages is not clear; it has been captured in recent clearcuts, second growth and old-growth forests. Several studies in the Douglas-fir forests of Oregon and Washington have demonstrated that this mole has a strong affinity for moist old-growth forests. However, studies in other parts of the western United States revealed no clear relationship between Shrew-mole abundance and forest age. In a major survey of small mammals in the Greater Vancouver region watersheds in the southern Coast Mountains, Dale Seip found the Shrew-mole most common in second growth forest, but his results were based on only 48 captures.
Unlike our other moles, the Shrew-mole is frequently active above ground. When walking, it bends its front claws inward and supports its weight on the backs of them. This mole is surprisingly agile and can move quickly when disturbed. A captive Shrew-mole climbed twigs and the side of its cage; it was also a powerful swimmer.
The Shrew-mole constructs shallow runways and deep burrows. Surface activity takes place in a network of runways about four centimetres in diameter, just two centimetres below the top of the surface litter. The burrows are about two centimetres in diameter and run between one and twelve centimetres deep. Small ventilation ducts bring in air from the surface. The Shrew-mole's digging actions are very similar to those of other moles: alternate side-to-side movements of the front feet. Rather than pushing the dirt above ground to form molehills, this mole presses it into the sides of the burrow. Having no well-defined activity period, the Shrew-mole is active at all hours, taking intermittent brief rests lasting one to eight minutes.
Little information is available on actual population numbers, but densities of 12 to 15 Shrew-moles per hectare have been reported in ideal habitats in Washington. It seems to be a relatively uncommon species in British Columbia; most researchers report less than one capture per 100 trap nights of effort. Dale Seip, for example, captured only 48 Shrew-moles in 13,722 trap nights using pitfall traps. Similarly, of the 999 small mammals captured by Carlos Galindo-Leal and Gustavo Zuleta in the lower Fraser River valley, only 16 were Shrew-moles. Home range and movements have not been determined.
Because it is often active above ground, this species is more vulnerable to predators than our other moles. Owls (the Barn Owl, Great Horned Owl, Western Screech Owl and Northern Saw-whet Owl) are probably the major predators. Garter snakes and a few mammals, such as Racoons and domestic cats, also prey on Shrew-moles.
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