Neurotrichus gibbsi, Gunther, 1880

Russell A. Mittermeier & Don E. Wilson, 2018, Talpidae, Handbook of the Mammals of the World – Volume 8 Insectivores, Sloths and Colugos, Barcelona: Lynx Edicions, pp. 52-619 : 603

18.

American Shrew Mole

Neurotrichus gibbsi

French: Taupe naine / German: Amerika-Spitzmull / Spanish: Topo musarana americano

Other common names: Shrew Mole

Taxonomy. Urotrichus gibbsii Baird, 1858 ,

“White River, Cascade Mountains, W. T.

[= Washington Territory],” Washington, USA.

Neurotrichus gibbsii is the only extant species of Newrotrichus. Three subspecies recognized.

Subspecies and Distribution.

N.g.gibbsuiBaird,1858—SWBritishColumbia(Canada)andNWUSA(WCWashington,WOregon,andNWCaliforniaasfarSasSanBenitoCounty);alsoonDestructionI,Washington.

N.g.hyacinthinusBangs,1897—WCCalifornia(USA). N. g. minor Dalquest & Burgner, 1941 — extreme SW British Columbia (Canada) and coastal zone of Washington (USA).

Descriptive notes. Head-body c.63-71 mm, tail 29-50 mm, hindfoot 13-18 mm; weight 6-14-5 g. There is no secondary sexual dimorphism in size. As its name implies, the American Shrew Mole superficially looks like a shrew ( Soricidae ). It is small, with moderately long tail of ¢.35% of head-body length. Scaly tail is thick, constricted at base, and densely covered with 2-5mm hairs. Blunt tip of tail terminates in a 4-4mm tuft. Head is large, and snout is long, flattened dorso-ventrally, and fringed with bristles. Nostrils open laterally. Eyes are minute (0-7-1 mm in diameter) and subcutaneous; there is no palpebral opening. External meatus is slit-like (dimensions 4 x 2 mm). Feet are moderately small, each with five clawed fingers; palm is longer (5-4 mm) than wide (4 mm). Claws are not broad and depressed as they are in truly fossorial moles. Palms and soles are naked and have tubercles. Pelage is thick and soft. Guard hairs are c.10 mm and are twice as thick as underfur. Coloris nearly uniform, varying from dark brownish gray and blackish gray to sooty blue black. Females have five pairs of mammae: one pectoral, two abdominal, and two inguinal. Skull shows proportions characteristic of a mole. Braincase is rather deep, and rostrum is narrow. Dental formula is 13/3, C 1/1, P 2/2, M 3/3 (x2) = 36. I' is larger than posterior two incisors, and last premolar and molars are robust. Karyotype is 2n = 38.

Habitat. Preferring black-slit soils with high humus content covered with moist layer of vegetative litter (twigs, leaves, and logs) from sea level to elevations of ¢.2440 m. Main habitat of the American Shrew Mole is turf-free gullies, covered by riparian alder (Al nus, Betulaceae ) and thickets of alder and salmonberry ( Rubus spectabilis, Rosaceae ). It also occupies lakeshore swamps and willow ( Salix , Salicaceae ) thickets; conifer riparian hardwood; Douglas fir ( Pseudotsuga menziesii) and yellow pine ( Pinus ), both Pinaceae ; forests and forest edges; wet pastures; scrub habitats; and montane areas with low cover of lichens. It frequents stream banks and avoids dry habitats. American Shrew Moles occasionally occupy logged areas.

Food and Feeding. Earthworms are the main diet (48-5% of volume) of the American Shrew Mole, followed by gastropods, centipedes (Chilopoda), isopods (Isopoda), insects (mainly dipterans and beetles), seeds, fungi, and lichens. American Shrew Moles either start eating a live earthworm at one end or cut it into pieces first. Being completely blind, they locate prey with their prehensile snout. Captive American Shrew Moles ate dead mice and amphibians but rejected live frogs. They consumed large amount of food in a short time; e.g. an American Shrew Mole weighing 10 g ate a 1-3g worm in ten minutes, another consumed 4-7 g of worms in two hours, and another consumed 14-4 g of food in twelve hours. An individual died eleven hours after food deprivation. Speed of digestion is extremely rapid; it takes only 30-45 minutes from ingestion of food to its defecation. Excrements are c¢.4 mm long and less than 1 mm wide and disintegrate rapidly. Average area of the stomach is 3-5: cn’.

Breeding. Breeding season of the American Shrew Mole occurs in February—October and peaks between early March and mid-May. Length of gestation is unknown, but it is assumed to be longer than 15 days. Females carry 1-5 embryos (mean 3). Neonates are naked, with eyes and ears sealed and without vibrissae. They are 26 mm long and weigh 0-49-0-67 g.

Activity patterns. The American Shrew Mole is less fossorial and excavates less extensive galleries than do fossorial moles. Entrances to tunnels are left open. In humid soil, American Shrew Moles construct runways that are 38 mm wide and 20 mm deep and covered with dead leaflitter. Deep tunnels are less common and

are narrower (less than 25 mm in diameter) and descend 12.7-30.5 cm underground. Burrow system usually includes a larger (127 x 75 cm) chamber that is constructed close enough to the water table to remain humid. American Shrew Moles move more slowly than shrews. They can swim and climb but are unable to jump. Ordinary movements consist of slow walk and momentary pauses. Claws of forefeet bend under feet so that an individual actually walks on backs of front claws. American Shrew Moles climb well but always descend tail first. While swimming, they propel feet on each side of body alternately, resulting in undulating motion of body and tail. American Shrew Moles are active at all hours of the day. Short (2-18 minutes) periods of activity are interrupted by even shorter (1-8 minutes) periods of rest. They sleep in simple nests constructed from small pieces of vegetation. While sleeping, they keep feet under their bodies and fold snout and head below their bodies between forelegs. Great majority of active time is spent in quest of food. Basal rate of metabolism of the American Shrew Moles is close to that of shrews and 2-3times greater than predicted for similar-sized placental mammals. Body temperature (38:4°C) is higher than in other Nearctic moles. Average rate of respiration is 3-4 breaths/second. American Shrew Moles apparently can lower metabolic heat production by 21:2-27-8% and body temperature by 6-8°C below normal. Hypometabolic stage is of short duration.

Movements, Home range and Social organization. Size and stability of home ranges are unknown. Densities in favorable habitat are 12-15 ind/ha. In an experiment where other small mammals were removed from the study plot, density of the American Shrew Mole reached 247 ind/ha. Reproductively active males emit a musky smell. The American Shrew Mole is more social than other moles. Some observations suggest it travels in loose groups. When an individual is under threat,it assumes a defensive posture. Some authors reported that captive American Shrew Moles were vocal, emitting high-pitched squeals, but others claimed that they were silent.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Population of the American Shrew Mole on the Destruction Island, Washington, declined after introduction of the European Rabbit (Oryctolagus cuniculus).

Bibliography. Campbell & Hochachka (2000), Carraway & Verts (1991a), Carraway et al. (2002), Dalquest & Orcutt (1942), Kremsater et al. (1993), Maseret al. (1981), Nagorsen (2002), Verts & Carraway (1988).

Figures

1. Equivalent-teeth Shrew Mole (Uropsilus aequodonenia), 2. Anderson’s Shrew Mole (Uropsilus andersont), 3. Gracile Shrew Mole (Uropsilus gracilis), 4. Inquisitive Shrew Mole (Uropsilus investigator), 5. Chinese Shrew Mole (Uropsilus soricipes), 6. Snow Mountain Shrew Mole (Uropsilus nivatus), 7. Black-backed Shrew Mole (Uropsilus atronates), 8. Gansu Mole (Scapanulus oweni), 9. Hairy-tailed Mole (Parascalops breweri), 10. Coast Mole (Scapanus orarius), 11. Townsend’s Mole (Scapanus townsend), 12. Broad-footed Mole (Scapanus latimanus), 13. Mexican Mole (Scapanus anthonyi), 14. Eastern Mole (Scalopus aquaticus), 15. Long-tailed Mole (Scaptonyx fusicauda), 16. Japanese Shrew Mole (Urotrichus talpoides), 17. True’s Shrew Mole (Dymecodon pilirostris), 18. American Shrew Mole (Neurotrichus gibbsi), 19. Star-nosed Mole (Condylura cristata), 20. Russian Desman (Desmana moschata), 21. Pyrenean Desman (Galemys pyrenaicus)

Subspecies and Distribution. N.g.gibbsuiBaird,1858—SWBritishColumbia(Canada)andNWUSA(WCWashington,WOregon,andNWCaliforniaasfarSasSanBenitoCounty);alsoonDestructionI,Washington. N.g.hyacinthinusBangs,1897—WCCalifornia(USA). N. g. minor Dalquest & Burgner, 1941 — extreme SW British Columbia (Canada) and coastal zone of Washington (USA).