Gaspé shrew (Sorex gaspensis) COSEWIC assessment and status report: chapter 6
Little is known about the biology or life history of either S. gaspensis or S. dispar. The following information is mainly based on information gleaned from the physical examination of captured specimens, or inferred from biological studies on other, similar shrew species.
Life cycle and reproduction
Both S. gaspensis and S. dispar are insectivorous, consuming mainly small invertebrates such as centipedes, spiders, beetles, flies and grasshoppers (Richmond and Grimm 1950). In Canada, the stomach contents of S. dispar contained spiders and centipedes (1 specimen, August, McAlpine et al. 2004) and S. gaspensis spiders, beetles, flies, Trichoptera and Lepidoptera (two specimens, Hamilton and Hamilton 1954, 64 specimens Whitaker and French 1984). Spiders are possibly the most important food items (Whitaker and French 1984).
Both species most likely live for 14-17 months, attaining sexual maturity in the second summer after birth. In S. dispar the reproductive season appears to extend from early spring to late summer (Kirkland 1981), and based on the sexual maturity of captured specimens is probably of similar length in S. gaspensis (French and Kirkland 1983; McAlpine et al. 2004). Courtship in shrews is generally rudimentary, with males pursuing females until contact is made. Females in oestrus will allow males to mount; otherwise the male’s advances will be met with aggression. Females are probably in oestrus for a few hours every three weeks or so. Repeated copulation may be necessary to stimulate ovulation. The gestation period is probably 22-25 days. Embryo counts suggest litters range from 2-6 (Richmond and Grimm 1950; Kirkland and Van Deusen 1979; French and Kirkland 1983). Young are probably fully weaned by 22-25 days old. Two litters per breeding female may be possible if the first litter is conceived by early May.
We presume that both species are largely solitary. Female shrews generally have fixed home ranges where they remain for most of their life. However, males may wander widely during the breeding season, possibly abandoning their territories, in search of females in oestrus. Meetings between shrews may result in aggressive reactions such as postures and vocal signals, and often a fight. Although these interactions would rarely be fatal, a shrew prevented from feeding for a period of time may be at risk of starvation. Aggressive interactions are likely highest in mid-summer when juveniles are competing with adults for territories and nesting sites, and population density is high.
Owls, weasels, cats and short-tailed shrews have been observed catching and eating small shrews like S. dispar and S. gaspensis. Shrews are not usually depredated because of distasteful secretions located in their dermal glands. Dispersing shrews are probably most vulnerable to predation, when they may be active on the ground surface rather than in subsurface tunnels and runways. To our knowledge, no information exists on the specific effects of predation on either S. gaspensis or S. dispar.
High metabolic rates and voracious appetites are characteristic of shrews. Generally active both day and night, they require food every 2-3 hours to maintain their high metabolism. To maintain body temperature in winter, shrews increase their metabolic rates as well as reduce heat loss by undergoing a pre-winter moult, which produces a longer and thicker pelage. Use of subterranean space by both species should mitigate the effects of harsh winter weather, as the talus and snow layer have an important moderating influence on temperature. Possibly due to their elevated metabolism and activity levels, shrews usually have a high evaporative respiratory loss, resulting in relatively high water requirements (Churchfield 1990).
In Sorex generally, young disperse from their natal areas as soon as they are weaned, and may wander widely in search of their own home range. Establishing themselves quickly within a home range is important for juvenile survival by ensuring access to food and nesting sites, and minimizing predation and aggressive interactions with conspecifics. The dispersal distances of S. gaspensis and S. dispar are unknown.
Both S. gaspensis and S. dispar have been captured in association with other small mammal species, including red-backed vole (Clethrionomys gapperi), masked shrew (Sorex cinereus), water shrew (S. palustris), smokey shrew (S. fumeus), pygmy shrew (Microsorex hoyi), short-tailed shrew (Blarina brevicauda), deer mouse (Peromyscus maniculatus), woodland jumping mouse (Napaeozapus insignis), meadow vole (Microtus pennsylvanicus) and rock vole (Microtus chrotorrhinus) (Roscoe and Majka 1976; Kirkland and Schmidt 1982; Whitaker and French 1984; Scott 1987; Scott and van Zyll de Jong 1989; McAlpine et al. 2004). The extent to which these species compete for habitat and food with S. gaspensis and S. dispar is unknown.
Shrews are host to a wide variety of external and internal parasites. Whitaker and French (1982) describe 18 ectoparasites found on 67 S. gaspensis individuals trapped at Mt. Carleton Provincial Park in New Brunswick, and Whitaker and French (1988) and O'Connor (1985) describe the ectoparasites found on S. dispar in New York and Tennessee. However, there is little evidence that parasite loads affect mortality in shrews (Churchfield 1990).
Nothing is known about the adaptability of either species.
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