Long-tailed weasel

Long-tailed weasel
Long-tailed weasel
Conservation status
Least Concern (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Carnivora
Family:	Mustelidae
Subfamily:	Mustelinae
Genus:	Mustela
Species:	M. frenata
Binomial name
Mustela frenata Lichtenstein, 1831
Long-tailed weasel range

The long-tailed weasel (Mustela frenata), also known as the bridled weasel or big stoat is a species of mustelid distributed from southern Canada throughout all the United States and Mexico, southward through all of Central America and into northern South America.

Evolution

Skulls of a long-tailed weasel (top), a stoat (bottom left) and least weasel (bottom right), as illustrated in Merriam's Synopsis of the Weasels of North America

The long-tailed weasel is the product of a process begun 5–7 million years ago, when northern forests were replaced by open grassland, thus prompting an explosive evolution of small, burrowing rodents. The long-tailed weasel's ancestors were larger than the current form, and underwent a reduction in size to exploit the new food source. The long-tailed weasel arose in North America 2 million years ago, shortly before the stoat evolved as its mirror image in Eurasia. The species thrived during the Ice Age, as its small size and long body allowed it to easily operate beneath snow, as well as hunt in burrows. The long-tailed weasel and the stoat remained separated until half a million years ago, when falling sea levels exposed the Bering land bridge, thus allowing the stoat to cross into North America. However, unlike the latter species, the long-tailed weasel never crossed the land bridge, and did not spread into Eurasia.^[2]

Physical description

The long-tailed weasel is one of the largest members of the genus Mustela in North America, with a total length of 300–350 mm and a tail comprising 40–70% of the head and body length. In most populations, females are 10–15% smaller than males,^[3] thus making them about the same size as large male stoats.^[4] The eyes are black in daylight, but glow bright emerald green when caught in a spotlight at night.^[5] The dorsal fur is brown in summer, while the underparts are whitish and tinged with yellowish or buffy brown from the chin to the inguinal region. The tail has a distinct black tip. Long-tailed weasels in Florida and the southwestern US may have facial markings of a white or yellowish colour. In northern areas in winter, the long-tailed weasel's fur becomes white, sometimes with yellow tints, but the tail retains its black tip.^[3] The long-tailed weasel moults twice annually, once in autumn (October to mid-November) and once in spring (March–April). Each moult takes about 3–4 weeks and is governed by day length and mediated by the pituitary gland. Unlike the stoat, whose soles are thickly furred all year, the long-tailed weasel's soles are naked in summer.^[4] The long-tailed weasel has well-developed anal scent glands, which produce a strong and musky odour. Unlike skunks, which spray their musk, the long-tailed weasel drags and rubs its body over surfaces in order to leave the scent.^[6]

Behavior

Reproduction and development

The long-tailed weasel mates in July–August, with implantation of the fertilized egg on the uterine wall being delayed until about March. The gestation period lasts 10 months, with actual embryonic development taking place only during the last four weeks of this period, an adaptation to timing births for spring, when small mammalsare abundant. Litter size generally consists of 5–8 kits, which are born in April–May. The kits are born partially naked, blind and weighing 3 grams, about the same weight of a hummingbird. The long-tailed weasel's growth rate is rapid, as by the age of three weeks, the kits are well furred, can crawl outside the nest and eat meat. At this time, the kits weigh 21–27 grams. At five weeks of age, the kit's eyes open, and they become physically active and vocal. Weaning begins at this stage, with the kits emerging from the nest and accompanying the mother in hunting trips a week later. The kits are fully grown by autumn and, by this time, the family disbands. The females are able to breed at 3–4 months of age, while males become sexually mature at 15–18 months.^[6]

Denning and sheltering behaviour

The long-tailed weasel dens in ground burrows, under stumps or beneath rock piles. It usually does not dig its own burrows, but commonly uses abandoned chipmunk holes. The 22–30 cm diameter nest chamber is situated around 60 cm from the burrow entrance, and is lined with straw and the fur of prey.^[6]

Diet

The long-tailed weasel is a fearless and aggressive hunter which may attack animals far larger than itself. When stalking, it waves its head from side to side in order to pick up the scent of its prey. It hunts small prey, such as mice, by rushing at them and kills them with one bite to the head. With large prey, such as rabbits, the long-tailed weasel strikes quickly, taking its prey off guard. It grabs the nearest part of the animal and climbs upon its body, maintaining its hold with its feet. The long-tailed weasel then manoevres itself to inflict a lethal bite to the neck.^[7]

The long-tailed weasel is an obligate carnivore which prefers its prey to be fresh or alive, eating only the carrion stored within its burrows. Rodents are almost exclusively taken when they are available. Its primary prey consists of mice, rats, squirrels, chipmunks, shrews, moles and rabbits. Occasionally, it may eat small birds, bird eggs, reptiles, amphibians, fish, earthworms and some insects. The species has also been observed to take bats from nursery colonies. It occasionally surplus kills, usually in spring when the kits are being fed, and again in autumn. Some of the surplus kills may be cached, but are usually left uneaten. Kits in captivity eat from ¼–½ of their body weight in 24 hours, while adults eat only one fifth to one third. After killing its prey, the long-tailed weasel laps up the blood, but does not suck it, as is popularly believed. With small prey, also the fur, feathers, flesh and bones are consumed, but only some flesh is eaten from large prey. When stealing eggs, the long-tailed weasel removes each egg from its nest one at a time, then carries it in its mouth to a safe location where it bites off the top and licks out the contents.^[7]

Subspecies

As of 2005^[update],^[8] 42 subspecies are recognised.

Subspecies	Trinomial authority	Description	Range	Synonyms
Bridled weasel Mustela f. frenata (Nominate subspecies)	Lichtenstein, 1831	A large subspecies with a long tail, relatively short black tip and has a black head with conspicuous white markings[9]	Mexico	aequatorialis (Coues, 1877) brasiliensis (Sevastianoff, 1813) mexicanus (Coues, 1877)
Mustela f. affinis	Gray, 1874	A large, very dark subspecies with very little white marking on the face[10]		costaricensis (J. A. Allen, 1916) macrurus (J. A. Allen, 1912) meridana (Hollister, 1914)
Mustela f. agilis	Tschudi, 1844			macrura (J. A. Allen 1916)
Black Hills weasel Mustela f. alleni	Merriam, 1896	Similair to arizonensis in size and general characters, but with yellower upper parts[11]	Black Hills, South Dakota
Mustela f. altifrontalis	Hall, 1936			saturata (Miller, 1912)
Arizona weasel Mustela f. arizonensis	Mearns, 1891	Similair to longicauda, but smaller in size[12]	Sierra Nevada and Rocky Mountain systems, reaching British Columbia in the Rocky Mountain region
Mustela f. arthuri	Hall, 1927
Mustela e. celenda	Hall, 1944
Mustela f. aureoventris	Gray, 1864			affinis (Lönnberg, 1913) jelskii (Taczanowski, 1881) macrura (Taczanowski, 1874)
Mustela f. boliviensis	Hall, 1938
Mustela f. costaricensis	Goldman, 1912			brasiliensis (Gray, 1874)
Mustela f. effera	Hall, 1936
Chiapas weasel Mustela f. goldmani	Merriam, 1896	Similair to frenata in size and general characters, but with a longer tail and hind feet, darker fur and more restricted white markings[13]	Mountains of southeastern Chiapas
Mustela f. gracilis	Brown, 1908
Mustela f. helleri	Hall, 1935
Mustela f. inyoensis	Hall, 1936
Mustela f. latirostra	Hall, 1896			arizonensis (Grinnell and Swarth, 1913)
Mustela f. leucoparia	Merriam, 1896	Similair to frenata, but slightly larger and with more extensive white markings[14]
Common long-tailed weasel Mustela f. longicauda	Bonaparte, 1838	A large subspecies with a very long tail and short black tip. The upper parts are pale yellowish brown or pale raw amber brown, while the underparts vary in colour from strong buffy yellow to ochraceous orange[15]	Great Plains from Kansas northward
Mustela f. macrophonius	Elliot, 1905
Mustela f. munda	Bangs, 1899
Mustela f. neomexicanus	Barber and Cockerell, 1898
Mustela f. nevadensis	Hall, 1936			longicauda (Coues, 1891)
Mustela f. nicaraguae	J. A. Allen, 1916
Mustela f. nigriauris	Hall, 1936			xanthogenys (Gray, 1874)
Mustela f. notius	Bangs, 1899
New York weasel Mustela f. noveboracensis	Emmons, 1840	A large subspecies, with a shorter tail than longicauda. The upper parts are rich, dark chocolate brown, while the underparts and upper lip are white and washed with yellowish.[16]	Eastern United States from southern Maine to North Carolina and west to Illinois	fusca (DeKay, 1842) richardsonii (Baird, 1858)
Mustela f. occisor	Bangs, 1899
Mustela f. olivacea	Howell, 1913
Oregon weasel Mustela f. oregonensis	Merriam, 1896	Similair to xanthogenys, but larger, darker in colour and has more restricted facial markings[17]	Rogue River Valley, Oregon
Mustela f. oribasus	Bangs, 1899
Mustela f. panamensis	Hall, 1932
Florida weasel Mustela f. peninsulae	Rhoads, 1894	Equal in size to noveboracensis, but with a skull more similair to that of longicauda. The upper parts are dull chocolate brown, while the underparts are yellowish[18]	Florida Peninsula
Mustela f. perda	Merriam, 1902
Mustela f. perotae	Hall, 1936
Mustela f. primulina	Jackson, 1913
Mustela f. pulchra	Hall, 1936
Cascade Mountain weasel Mustela f. saturata	Merriam, 1896	Similair to arizonensis, but larger and darker, with an ochraceous belly and distinct spots behind the corners of the mouth[19]
Mustela f. spadix	Bangs, 1896	Similair to longicauda, but much darker[20]
Mustela f. texensis	Hall, 1936
Tropical weasel Mustela f. tropicalis	Merriam, 1896	Similair to frenata, but much smaller and darker, with less extensive white facial marking and an orange underbelly[21]	Tropical coast belt of southern Mexico and Guatemala from Vera Cruz southward	frenatus (Coues, 1877) noveboracensis (DeKay, 1840) perdus (Merriam, 1902) richardsoni (Bonaparte, 1838)
Washington weasel Mustela f. washingtoni	Merriam, 1896	Similair to noveboracensis in size, but with a longer tail and shorter black tip[22]	Washington state
California weasel Mustela f. xanthogenys	Gray, 1843	A medium sized subspecies with a long tail, a face marked with whitish and ochraceous underparts[17]	Sonoran and Transition faunas of California, on both sides of Sierra Nevada

References

Notes

1. ^ Reid, F. & Helgen, K. (2008). Mustela frenata. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 29 March 2010. Database entry includes a brief justification of why this species is of least concern
2. ^ Macdonald 1992, p. 205
3. ^ ^{a b} Feldhamer, Thompson & Chapman 2003, p. 651
4. ^ ^{a b} Merritt & Metinko 1987, p. 280
5. ^ Schwartz & Schwartz 2001, p. 303
6. ^ ^{a b c} Merritt & Metinko 1987, p. 282
7. ^ ^{a b} Schwartz & Schwartz 2001, pp. 306–307
8. ^ Wozencraft, W. Christopher (16 November 2005). "Order Carnivora (pp. 532-628)". In Wilson, Don E., and Reeder, DeeAnn M., eds. Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Baltimore: Johns Hopkins University Press, 2 vols. (2142 pp.). ISBN 978-0-8018-8221-0. OCLC 62265494. http://www.bucknell.edu/msw3/browse.asp?id=14001381. 
9. ^ Merriam 1896, pp. 26–28
10. ^ Merriam 1896, pp. 31–32
11. ^ Merriam 1896, p. 24
12. ^ Merriam 1896, pp. 22–24
13. ^ Merriam 1896, pp. 28–29
14. ^ Merriam 1896, pp. 29–30
15. ^ Merriam 1896, pp. 20–21
16. ^ Merriam 1896, pp. 16–18
17. ^ ^{a b} Merriam 1896, pp. 25–26
18. ^ Merriam 1896, p. 19
19. ^ Merriam 1896, pp. 21–22
20. ^ Merriam 1896, p. 21
21. ^ Merriam 1896, pp. 30–31
22. ^ Merriam 1896, pp. 18–19

Bibliography

• Coues, Elliott (1877). Fur-bearing Animals: A Monograph of North American Mustelidae. Government Printing Office. http://www.archive.org/details/furbearinganima00couegoog 
• Feldhamer, George A.; Thompson, Bruce Carlyle; Chapman, Joseph A. (2003). Wild mammals of North America: biology, management, and conservation. JHU Press. ISBN 0801874165 
• Kurtén, Björn (1980). Pleistocene mammals of North America. Columbia University Press. ISBN 0231037333 
• Macdonald, David (1992). The Velvet Claw: A Natural History of the Carnivores. New York: Parkwest. ISBN 0563208449 
• Merriam, Clinton Hart (1896), Synopsis of the weasels of North America, Washington : Govt. Print. Off., http://www.archive.org/details/synopsisofweasel00merriala 
• Merritt, Joseph Anne; Matinko, Ruth F. (1987), Guide to the mammals of Pennsylvania, University of Pittsburgh Press, ISBN 0822953935 
• Schwartz, Charles Walsh; Schwartz, Elizabeth Reeder (2001), The wild mammals of Missouri, University of Missouri Press, ISBN 0826213596