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Sorex fumeussmoky shrew

By Makayla Beckner

Geographic Range

Smoky shrews (Sorex fumeus) are native to the eastern United States, with a range running along the Appalachian Mountains and extending as far north as southern Canada. Their boundaries include far north as southeastern Canada (southern Ontario, Quebec) with the Atlantic coast as the eastward limit. It extends westward to Lake Superior in the north. The range continues southward, through the northeastern and mid-Atlantic United States, as far south as northern Georgia. The westward bounds include Tennessee, Kentucky, Indiana, and Ohio. (Cassola, 2016; Hamed and Laughlin, 2015; Owen, 1984; Felix, et al., 2009)

Habitat

Smoky shews are often found in higher elevations, typically above 700 m, in or around deciduous montane forests. At the southern edge of their geographic range, it's been reported that they exists at elevations as low as 300 m. They occur in a variety of forest types, on talus slopes, and occasionally some wetter areas (bogs, swamps, bankside of rivers). However, although it appears that they are more abundant in moisture-rich forests, they are much less common (or absent) in seasonally or permanently inundated wetland habitats.

Smoky shrews typically either take over other small mammals burrows to make use of them for themselves, or build rounded nests ca. 5.08 centimeters in diameter on the forest floor, often underneath forest debris. Nests are built using various mammal hair and vegetative matter on sheltered forest floors. (Cassola, 2016; Choate, et al., 1994; Laerm, et al., 2007; Merritt, 1987; Nowak, 1999; Owen, 1984; Webster, et al., 2004)

  • Aquatic Biomes
  • rivers and streams
  • Range elevation
    300 (low) m
    984.25 (low) ft
  • Average elevation
    >700 m
    ft

Physical Description

The average total length of smoky shrews is 111.4 millimeters, with an average weight of 7.6 grams. Average tail length is 43.8 millimeters, and their hind feet are, on average, 13.2 millimeters long. Both male and female shrews are similar in size. Newborn shrews are blind, toothless, lack fur and weigh 0.14 grams. By one month old, they weigh 4 grams. Smoky shrews have a generally flattened skull. Like all shrews, the snout of smoky shrews is elongated, and they have ears that are often concealed within their fur. Smoky shrews have 32 teeth with a dental formula of incisors 1/1, canines 5/1, premolars 1/1, and molars 3/3.

The coloration of smoky shrews is an identifying feature among similar species. In the summer months, the dorsal fur is brown, with a yellow tint, and the ventral fur is pale brown. Their winter coat is dark gray on the dorsal side with silver hues on the ventral side. Smoky shrews molt twice annually, once in preparation for winter and again in preparation for summer. The molt for winter happens in October for a thicker fur as well as a change of color to accommodate surroundings; the other in preparation for summer happens in April or May for a thinner coat with brown fur. The tail of smoky shews is consistently bicolored, following the different hues among the months. The tail is a light brown with yellows hues in the summer months, and dark brown with silver hues in the winter months.

Older shews tend to have fur with whiter tips. The younger shrews are distinguished from the older shrews not only because they are smaller, but also because they have long hairs on the tips of their tails that disappear once maturing to adults. (Best and Dusi, 2014; Choate, et al., 1994; Kurta, 1995; Merritt, 1987; Naughton, 2012; Owen, 1984)

  • Sexual Dimorphism
  • sexes alike
  • Average mass
    7.6 g
    0.27 oz
  • Average mass
    7.5 g
    0.26 oz
    AnAge
  • Average length
    114.4 mm
    4.50 in

Reproduction

Although it has not been studied in smoky shrews, there are observations of the mating techniques of the masked shrew, Sorex cinereus. Males use high-pitched vocalizations to complete with other males when looking for mates. Usually in groups of three, the male masked shrews will jump in a breeding chase. It’s likely that smoky shrews have a similar mating system. (Maier and Doyle, 2006)

Smoky shrews use leaf litter and other vegetative matter to build a nest in protected habitats (i.e., rotting logs or stumps). Alternately, they may take advantage of an abandoned nest. The nests are 10 to 48 centimeters below the ground or under downed logs. Breeding occurs year-round but is primarily in early spring to early fall, March to October. Smoky shrews have 2 to 3 litters year-round with a gestation period of 19 to 22 days. They produce 2-8 young each litter. Female shrews experience post-partum estrous, when females go into heat immediately after giving birth to a litter. Newborn shrews are blind, toothless, lack fur and weigh 0.14 grams. By one month old, they weigh 4 grams. After one month, the pups are fully weaned and own their own. Most often these shrews do not breed within their first year of life and reach sexual maturity after their winter as young. (Brown, 1997; Elbroch and Rinehart, 2011; Laerm, et al., 2007; Merritt, 1987; Naughton, 2012; Owen, 1984)

  • Breeding interval
    Smoky shrews breed 2 to 3 times yearly.
  • Breeding season
    Smoky shews primarily breed from March to October.
  • Range number of offspring
    2 to 8
  • Average number of offspring
    5
    AnAge
  • Range gestation period
    19 to 22 days
  • Range weaning age
    1 (low) months
  • Range time to independence
    1 (low) months
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    304 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    1 years
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    304 days
    AnAge

The mothers groom, nurse, and regurgitate food for their young. Females take care of the young for up to a month after the young are fully weaned. Young stay in the nest until the mother leaves to mate again. At this point, the young leave the nest to find new nesting sites. Beyond mating, males have no parental investment. (Churchfield, 1990; Elbroch and Rinehart, 2011; Naughton, 2012)

Lifespan/Longevity

Juvenile and adult smoky shrews are distinguished by weight and tooth, tail, and hair wear. Because smoky shrews do not breed within the year they are born, they most often survive until the subsequent breeding season and live a total of 14 to 17 months. The lifespan on smoky shrews in captivity has not been reported and is not currently known. (Kurta, 1995; Churchfield, 1990; Kurta, 1995; Thompson-Jackson, 1961)

  • Typical lifespan
    Status: wild
    14 to 17 months

Behavior

Smoky shrews are constantly active through all hours of the day, and throughout the year. Colder temperatures do not semm to be limiting, as they have been captured in the snow. These shrews typically are not social, but clustering of captures suggest that they might live in colonies. They do not migrate.

When smoky shrews are disturbed, they release a high-pitched squeaking noise, throw themselves onto their backs, and wave their limbs. When searching for food, smoky shrews produce a faint twittering noise. (Elbroch and Rinehart, 2011; Owen, 1984)

Home Range

Home range has not been reported for smoky shrews, and territory size also is unknown. (Owen, 1984)

Communication and Perception

When smoky shrews are disturbed, they emit a high-pitched squeaking noise, throw themselves onto their backs, and wave their limbs. When searching for food, smoky shrews produce a faint twittering noise, which might be a crude form of echolocation. This has not largely been studied in smoky shrews, but other shrews in Sorex have been known to echolocate. Common shrews Sorex araneus are able to use echolocation to find objects up to 200 mm away. Echolocation is especially helpful to shrews when they inhabit abandoned burrows, as it allows them to sense if the burrow is empty. It is also used to aid in finding protective cover when being pursued by a predator. (Forsman and Malmquist, 1988)

Food Habits

Smoky shrews are insectivores feeding on various invertebrates. A North Carolina study reported that centipedes (36.5% of stomach contents, by volume) were the most common food item, followed by earthworms (19%) and adult lepidopterans (19.5%), and ground beetles in the family Scarabidae (10%). Insects (adults and larvae), spiders, isopods, and some fungi are included in the diets of smoky shrews. In captivity, the shrews also could eat salamanders and snails.

Although it has not been directly studied in smoky shrews, the hearts of other shrews in the genus Sorex have been found to beat 800-1200 beats per minute. Due to a high metabolism, shrews must feed day and night to support their appetites. (Choate, et al., 1994; Laerm, et al., 2007; Owen, 1984; Sipe and Browne, 2004; Webster, et al., 2004; Whitaker Jr. and Hamilton Jr., 1998)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • terrestrial worms
  • Other Foods
  • fungus

Predation

Smoky shrews molt their fur twice annually so they have brown with a hint of yellow coat in the summer and gray and white in the winter which provides cryptic coloration. Smoky shrews dwell mostly on the forest floor, small enough to maneuver leaf and other vegetative matter. This habitat allows them natural camouflage. When disturbed, smoky shrews produce a high-pitched noise. The main predators of smoky shrews are bobcats (Lynx rufus), red foxes (Vulpes vulpes), gray foxes (Urocyon cinereoargenteus), hawks, falcons, long-eared owls (Asio otus), weasels, northern short-tailed shrews (Blarina brevicauda), and timber rattlesnakes (Crotalus horridus). (Choate, et al., 1994; Clark, 2002; Hamilton Jr., 1941; Laerm, et al., 2007; Merritt, 1987; Owen, 1984)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Smoky shrews are insectivores who prey on many insects and their larvae. They are also prey for snakes, owls, weasels, hawks and larger shrews. Smoky shrews are hosts to many parasites including mites (Amorphacarus hengererorum, Orycteroxenus soricis, Xenoryctes nudus, Myobia, Haemogamasus, Protomyobia, Myonyssus jamesoni, Haemolaelaps glasgowi, Euhaemogamasus liponyssoides, Hirstionyssus talpae), chiggers (Euschoengastia whitakeri, Euschoengastia jamesoni), and nematodes (Capillaria hepatica). (Choate, et al., 1994; Laerm, et al., 2007; Merritt, 1987; Owen, 1984)

Commensal/Parasitic Species
  • nematodes (Capillaria hepatica)
  • mites (Amorphacarus hengererorum)
  • mites (Orycteroxenus soricis)
  • mites (Xenoryctes nudus)
  • mites (Myobia species)
  • mites (Haemogamasus species)
  • mites (Protomyobia species)
  • mites (Myonyssus jamesoni)
  • mites (Haemolaelaps glasgowi)
  • mites (Euhaemogamasus liponyssoides)
  • mites (Hirstionyssus talpae)
  • chiggers (Euschoengastia whitakeri)
  • chiggers (Euschoengastia jamesoni)

Economic Importance for Humans: Positive

Smoky shrews may aid in the population control of insects. Masked shrews (Sorex cinereus) have been known to aid in the population control of the larch sawfly (Pristiphora erichsoni). It's likely smoky shrews could have a similar impact. (Dent, 2000; Fryxell, et al., 2014; Whitaker Jr. and Hamilton Jr., 1998)

Economic Importance for Humans: Negative

There are no known adverse effects of Sorex fumeus on humans.

Conservation Status

Smoky shrews are listed as a species of “Least Concern” on the IUCN Red List. CITES and the US Federal List list smoky shrews as no special status. The Michigan Natural Features Inventory states that smoky shrews are "Threatened," because there have been fewer than half a dozen captures of these individuals in the state. Current management efforts are in place to maintain forest cover and leaf litter on the forest floor. It's likely that these efforts positively impact smoky shrews. (Cassola, 2016)

Contributors

Makayla Beckner (author), Radford University, Karen Powers (editor), Radford University, Alex Atwood (editor), Radford University, Marisa Dameron (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal
  1. active during the day, 2. lasting for one day.
echolocation

The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

year-round breeding

breeding takes place throughout the year

References

US Forest Service. Influence of elevation and forest type on community assemblage and species distribution of shrews in the Central and Southern Appalachian Mountains. None. None Provided: International Society of Shrew Biologists. 2005.

Best, T., J. Dusi. 2014. Mammals of Alabama. Tuscaloosa, Alabama: The University of Alabama Press.

Brown, L. 1997. A Guide to Mammals of the Southeastern United States. Knoxville, Tennessee: The University of Tennessee Press.

Cassola, F. 2016. "Sorex fumeus" (On-line). IUCN Red List of Threatened Species 2016: e.T41396A22312838. Accessed September 12, 2016 at http://www.iucnredlist.org/details/41396/0.

Choate, J., K. Jones Jr, C. Jones. 1994. Handbook of Mammals of the South-Central States. Baton Rouge, Louisiana: Louisiana State University Press.

Churchfield, S. 1990. The Natural History of Shrews. Ithaca, New York: Cornell University Press.

Clark, R. 2002. Diet of the timber rattlesnake, Crotalus horridus. Journal of Herpetology, 36/3: 494-499.

Dent, D. 2000. Insect Pest Managment. Cambridge, Massachusetts: CAB International.

Elbroch, M., K. Rinehart. 2011. Peterson Reference Guide to the Behavior of North American Mammals (Peterson Reference Guides). New York, New York: Houghton Mifflin Harcourt.

Felix, Z., L. Gatens, Y. Wang, C. Schweitzer. 2009. First records of the smoky shrew (Sorex fumeus) in Alabama. Southeastern Naturalist, 8/4: 750-753.

Forsman, K., M. Malmquist. 1988. Evidence for echolocation in the common shrew, Sorex araneus. Journal of Zoology, 216: 655-662.

Fryxell, J., A. Sinclair, G. Caughley. 2014. Wildlife Ecology, Conservation, and Management (3rd edition). Hoboken, New Jersey: John Wiley & Son Ltd.

Hamed, K., T. Laughlin. 2015. Small-Mammal mortality caused by discarded bottles and cans along a US National Forest Service road in the Cherokee National Forest. Southeastern Naturalist, 14/3: 506-516.

Hamilton Jr., W. 1941. The food of small forest mammals in eastern United States. Journal of Mammalogy, 22/3: 250-263.

Kurta, A. 1995. Mammals of the Great Lakes Region: Revised Edition. East Lansing, Michigan: The University of Michigan Press.

Laerm, J., W. Ford, B. Chapman. 2007. Smoky shrew. Pp. 95-98 in M Trani, W Ford, B Chapman, eds. The Land Manager's Guide to Mammals of the South. Durham, North Carolina: USDA Forest Service & The Nature Conservancy.

Maier, T., K. Doyle. 2006. Aggregations of masked shrews (Sorex cinereus): Density- related mating behavior?. Mammalia, 70/1-2: 86-89.

Merritt, J., S. Vessey. 2000. Shrews-small insectivores with polyphasic patterns. Pp. 235-251 in S Halle, N Stenseth, eds. Activity Patterns in Small Mammals: An Ecological Approach, Vol. 141. New York, New York: Springer-Verlag Berlin Heidelberg.

Merritt, J. 1987. Guide to Mammals of Pennsylvania. Pittsburgh, Pennsylvania: University of Pittsburgh Press.

Naughton, D. 2012. The Natural History of Canadian Mammals. Toronto, Canada: University of Toronto Press.

Nowak, R. 1999. Walker's Mammals of the World, 6th Edition: Volume 1. Baltimore, Maryland: Johns Hopkins University Press.

Owen, J. 1984. Sorex fumeus. Mammalian Species, 215: 1-8.

Sipe, T., R. Browne. 2004. Phylogeography of masked (Sorex cinereus) and smoky shrews (Sorex fumeus) in the southern Appalachians. Journal of Mammalogy, 85/5: 875-885.

Thompson-Jackson, H. 1961. Mammals of Wisconsin. Madison, Wisconsin: University of Wisconsin Press.

Webster, D., J. Parnell, W. Biggs Jr.. 2004. Mammals of the Carolinas, Virginia, and Maryland. Chapel Hill, North Carolina: The University of North Carolina Press.

Whitaker Jr., J., W. Hamilton Jr.. 1998. Mammals of the Eastern United States. Ithaca, New York: Comstock Publishing Associates.

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