Natural History of the Gray Wolf

Canis lupus - The gray wolf

By Tanya Dewey and Julia Smith
 

Geog­raphic Range

The origin­al range of Canis lupus con­sis­ted of the major­ity of the Northern hemisphere -- from the Arctic con­tinu­ing south to a latitude of 20° S, which runs through sout­hern Centr­al Mexico, northern Af­rica, and sout­hern Asia. Howev­er, due to habitat de­struc­tion, en­viron­ment­al chan­ge, per­secu­tion by humans, and other bar­ri­ers to popula­tion growth, gray wolf popula­tions are now found only in a few areas of the con­tigu­ous Uni­ted States, Al­as­ka, Canada, Mexico (a small popula­tion), and Eurasia.

Habitat

Gray wol­ves are one of the most wide rang­ing land an­im­als. They oc­cupy a wide variety of habitats, from arctic tundra to forest, prairie, and arid landscapes.

Phys­ical De­scrip­tion

The lar­gest of approximate­ly 41 wild spe­cies of canids, gray wol­ves vary in size based primari­ly on geog­raphic loc­al­ity, with sout­hern popula­tions general­ly small­er than northern popula­tions. Total body length, from tip of the nose to tip of the tail, is from 1000 to 1300 mm in males, and 870 to 1170 mm in females. Tail length ran­ges bet­ween 350 to 520 mm. Males can weigh from 30 to 80 kg, with an average of 55 kg, females can weigh from 23 to 55 kg, with an average of 45 kg. Height (measured from base of paws to should­er) general­ly ran­ges from 60 to 90 cm. Dis­tan­ce bet­ween the canines is around 4 cm.

Fur color of gray wol­ves also va­ries geog­raphical­ly, rang­ing from pure white in Arctic popula­tions, to mix­tures of white with gray, brown, cinam­mon, and black to near­ly uni­form black in some color phases.

North American popula­tions have three dis­tinct color phases. The norm­al phase is charac­terized by vary­ing mix­tures of white with shades of black, gray, cin­namon, and brown on the upper parts of the an­im­al. The back is usual­ly more pro­found­ly black, and the muzzle, ears, and limbs have cinam­mon col­ora­tion as well. Under parts are whitish and the tail is con­spicuous­ly black over the tail gland, and paler below to the tip, which is near­ly pure black. The black phase of North American popula­tions is charac­terized by the upper parts vary­ing from brown to black, with specks of white; the un­der­parts are paler in tone, and there is often a pure white medi­al pec­tor­al spot. The third color phase oc­curs dur­ing the first pelage of young wol­ves. The upper parts are drab-gray, over­laid with brownish-black. The un­der­parts are paler as well, and the ears vary from black to buffy, de­pend­ing on the sub­spe­cies (Young 1944).

Gray wol­ves have a dense un­der­fur layer, pro­vid­ing them with ex­cel­lent in­sula­tion against cold con­di­tions.

Gray wol­ves can be dis­tin­guis­hed from red wol­ves (Canis rufus) by their larg­er size, broad­er snout, and short­er ears. They are dis­tin­guis­hed from co­yotes (Canis lat­rans) by being 50 to 100% larg­er and hav­ing a broad­er snout and larg­er feet.
  • Sexual Dimorphism
  • male larger
  • Range mass
    23.0 to 80 kg
    50.66 to 176.21 lb
  • Range length
    870 to 1300 mm
    34.25 to 51.18 in

Re­produc­tion

The dominant pair in a grey wolf pack are the only mem­b­ers that breed. This pair is mono­gam­ous al­though, with the death of an alpha in­dividu­al, a new alpha male or female will em­er­ge and take over as the mate.
Breed­ing oc­curs bet­ween the months of Janua­ry and April, with northern popula­tions breed­ing later in the season than sout­hern popula­tions. Female gray wol­ves choose their mates and often form a life-long pair bond. Gray wolf pairs spend a great deal of time togeth­er. Female gray wol­ves come into estrus once each year and lasts 5 to 14 days, mat­ing oc­curs dur­ing this time. After mat­ing oc­curs, the female digs a den in which to raise her young. The den is often dug with an en­tran­ce that slopes down and then up again to a high­er area to avoid flood­ing. Pups are born in the den and will re­main there for sever­al weeks after birth. Other dens are under cliffs, under fall­en trees, and in caves.

The ges­ta­tion per­iod lasts bet­ween 60 and 63 days, lit­t­er size ran­ges from one to four­te­en, with the average size being six or seven pups. Pups re­main in the den until they are 8 to 10 weeks old. Females stay with their pups al­most ex­clusive­ly for the first 3 weeks. Pups are cared for by all mem­b­ers of the pack. Until they are 45 days old the pups are fed re­gur­gitated food by all pack mem­b­ers. They are fed meat pro­vided by pack mem­b­ers after that age.

Female pups reach matur­ity at two years of age, while males will not reach full matur­ity until three years of age. Most young gray wol­ves dis­per­se from their natal pack when they are bet­ween 1 and 3 years old.
  • Breeding interval
    Gray wolves breed once each year.
  • Breeding season
    Gray wolves breed between January and March, depending on where they are living.
  • Range number of offspring
    5.0 to 14.0
  • Average number of offspring
    7.0
  • Average number of offspring
    6
    AnAge
  • Range gestation period
    63.0 (high) days
  • Average weaning age
    45.0 days
  • Range age at sexual or reproductive maturity (female)
    2.0 to 3.0 years
  • Range age at sexual or reproductive maturity (male)
    2.0 to 3.0 years
Gray wolf pups are born blind and deaf. They weigh approximate­ly 0.5 kg and de­pend on the moth­er for warmth. At ten to fif­te­en days of age, the pups' blue eyes open, but they only have con­trol over their front legs, thus crawl­ing is their only mode of mobil­ity. Five to ten days later, the young are able to stand, walk, and vocal­ize. Pups are cared for by all mem­b­ers of the pack. Until they are 45 days old the pups are fed re­gur­gitated food by all pack mem­b­ers. They are fed meat pro­vided by pack mem­b­ers after that age. Dur­ing the 20th to 77th day, the pups leave the den for the first time and learn to play fight. In­terac­tions at this time, as well as the dominan­ce status of the moth­er, ul­timate­ly de­ter­mines their posi­tion in the pack hierarchy. Wolf pups de­velop rapid­ly, they must be large and ac­complis­hed en­ough to hunt with the pack with the onset of wint­er. At approximate­ly ten months old, the young begin to hunt with the pack.
  • Parental Investment
  • no parental involvement
  • altricial
  • pre-fertilization
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • post-independence association with parents
  • extended period of juvenile learning
  • maternal position in the dominance hierarchy affects status of young

 

 

 

 

 

 

 

 

 

Li­fes­pan/Lon­gev­ity

Gray wol­ves may live thir­te­en years in the wild, though average li­fes­pan is 5 to 6 years. As adults they usual­ly die from old age or from in­ju­ries re­ceived while hunt­ing or fight­ing with other wol­ves. In cap­tiv­ity they may live to be fif­te­en years of age.

Be­havior

Gray wol­ves are high­ly soci­al, pack-living an­im­als. Each pack com­prises two to thirty-six in­dividu­als, de­pend­ing upon habitat and ab­un­dance of prey. Most packs are made up of 5 to 9 in­dividu­als. Packs are typical­ly com­posed of an alpha pair and their of­fspr­ing, in­clud­ing young of pre­vi­ous years. Un­related im­mig­rants may also be­come mem­b­ers of packs.

There is a strong dominan­ce hierarchy with­in each pack. The pack lead­er, usual­ly the alpha male, is dominant over all other in­dividu­als. The next dominant in­dividu­al is the alpha female, who is sub­or­dinate only to the alpha male. In the event that the alpha male be­comes in­jured or is ot­herw­ise un­able to main­tain his dominan­ce, the beta male will take his place in the hierarchy. Alpha males typical­ly leave the pack if this oc­curs, but this is not al­ways the case. Rank with­in the pack hierarchy de­ter­mines which an­im­als mate and which eat first. Rank is de­monstrated by post­ur­al cues and faci­al ex­press­ions, such as crouch­ing, chin touch­ing, and roll­ing over to show the stomach.

Each year, gray wolf packs have a stationa­ry and nomadic phase. Stationa­ry phases occur dur­ing the spr­ing and summ­er, while pups are being rea­red. Nomadic phases occur dur­ing the fall and wint­er. Wolf move­ments are usual­ly at night and cover long dis­tan­ces. Daily dis­tan­ce traveled can be up to 200 km, the usual pace is 8 km/hr. Wol­ves can run at speeds up to 55 to 70 km/hr.

Home Range

The ter­rito­ry of a pack ran­ges from 130 to 13,000 square kilomet­ers, and is de­fen­ded against in­trud­ers.

Com­munica­tion and Per­cep­tion

Rank is com­municated among wol­ves by body lan­guage and faci­al ex­press­ions, such as crouch­ing, chin touch­ing, and roll­ing over to show their stomach.

Vocaliza­tions, such as howl­ing al­lows pack mem­b­ers to com­municate with each other about where they are, when they should as­semble for group hunts, and to com­municate with other packs about where the boun­da­ries of their ter­rito­ries are. Scent mark­ing is or­dinari­ly only done by the alpha male, and is used for com­munica­tion with other packs.

Food Habits

Gray wol­ves are car­nivores. They hunt prey on their own, in packs, steal the prey of other pre­dators, or scaven­ge carr­ion. Prey is loc­ated by chan­ce or scent. An­im­als in­cluded in the diet of gray wol­ves va­ries geog­raphical­ly and de­pends on prey availabil­ity. Wol­ves primari­ly hunt in packs for large prey such as moose, elk, bison, musk oxen, and re­in­de­er. Once these large un­gulates are taken down, the wol­ves at­tack their rump, flank, and should­er areas. Wol­ves con­trol prey popula­tions by hunt­ing the weak, old, and im­ma­ture. A wolf can con­sume up to 9 kg of meat at one meal. Wol­ves usual­ly util­ize the en­tire car­cass, in­clud­ing some hair and bones. Small­er prey such as be­av­ers, rab­bits, and other small mamm­als are usual­ly hun­ted by lone wol­ves, and they are a sub­stan­ti­al part of their diet. Wol­ves may also eat li­ves­tock and gar­bage when it is avail­able.
  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates

Pre­da­tion

Few an­im­als prey on gray wol­ves. Wol­ves and co­yotes are high­ly ter­ritori­al an­im­als so wol­ves from other packs and co­yotes will at­tack wol­ves that are alone or young. They will kill pups if they find them.

Ecosys­tem Roles

As top pre­dators, gray wol­ves are im­por­tant in re­gulat­ing popula­tions of their prey an­im­als.

Economic Im­por­tance for Humans: Positive

His­torical­ly, the fur of grey wol­ves was used for warmth. As top pre­dators in many ecosys­tems, wol­ves are im­por­tant in con­troll­ing popula­tions of their prey.

Wol­ves are im­por­tant in our cul­ture, many peo­ple be­lieve they sym­bol­ize the spirit of wil­der­ness. Wolf pro­ducts, in­clud­ing post­ers, books, and t-shirts are very popular. Wolf ecotour­ism is a major sour­ce of re­venue for parks and re­ser­ves.
  • Positive Impacts
  • body parts are source of valuable material
  • ecotourism

Economic Im­por­tance for Humans: Negative

Gray wol­ves may some­times kill li­ves­tock. The ex­tent of li­ves­tock loss to wol­ves is often over­stated, wol­ves typical­ly pre­f­er their wild prey.

Con­ser­va­tion Status

"Few an­im­als have ever haun­ted our dreams or fired our im­agina­tions more than the wolf. Un­for­tunate­ly, by the early part of this cen­tu­ry, man had al­most ex­ter­minated the wolf from the lower 48 states. The re­cove­ry of the wolf is be­com­ing an im­pres­sive con­ser­va­tion suc­cess story and a gift to fu­ture genera­tions" (Bruce Bab­bitt, Sec­reta­ry of the In­terior).

Wol­ves play an im­por­tant role in the ecosys­tem by con­troll­ing natur­al prey popula­tions and re­mov­ing weak in­dividu­als. As settle­ment in­creased, the be­lief that li­ves­tock was end­an­gered by wolf popula­tions also in­creased. As such, the frequen­cy of hunt­ing the gray wolf ex­ploded. The popula­tions were near­ly eradicated. Cur­rent­ly in the lower 48 Uni­ted States, about 2,600 gray wol­ves exist, with near­ly 2,000 in Min­nesota (com­pared to the few hundred li­v­ing there in the mid-20th cen­tu­ry). Suc­cess­ful re­cove­ry plans have been de­veloped throug­hout the co­unt­ry. These plans evaluate the popula­tions to de­ter­mine dis­tribu­tion, ab­un­dance, and status. The main cause of popula­tion de­clines has been habitat de­struc­tion and per­secu­tion by humans. But the re­introduc­tion of gray wol­ves into pro­tec­ted lands has great­ly in­creased the li­kelihood of their sur­viv­al in North America. Popula­tions in Al­as­ka and Canada have re­mained steady and are fair­ly numer­ous. Cur­rent­ly the State of Al­as­ka man­ages 6,000 to 8,000 gray wol­ves and Canada's popula­tions are es­timated at about 50,000. The wol­ves in Canada are man­aged by pro­vin­ci­al govern­ments and are not cur­rent­ly threatened.

In wes­tern Eurasia gray wolf popula­tions have been re­duced to isolated re­mnants in Poland, Scan­dinavia, Rus­sia, Por­tug­al, Spain, and Italy. Wol­ves were ex­ter­minated from the British Isles in the 1700's and near­ly dis­ap­peared from Japan and Green­land in the 20th cen­tu­ry. Green­land's wolf popula­tions seem to have made a full re­cove­ry. The status of wolf popula­tions throug­hout much of eas­tern Eurasia is poor­ly known, but in many areas popula­tions are pro­bab­ly st­able.

Gray wol­ves are li­sted were until re­cent­ly li­sted as end­an­gered by the U.S. Fish and Wildlife Ser­vice and as threatened by the state of Mic­higan DNR. Most U.S. popula­tions of gray wol­ves have now been de­lis­ted, ex­cept for ex­periment­al popula­tions of Mexican gray wol­ves in the southwest. They are in CITES Ap­pendix II, ex­cept for popula­tions in Bhutan, India, Nepal and Pakis­tan, which are in Ap­pendix I.

Other Com­ments

Ex­cept for red wol­ves (Canis rufus), all li­v­ing North American wol­ves are con­sidered to be Canis lupus -- a total (as of 1997) of 32 re­cog­nized sub­spe­cies.
Gray wol­ves are wide­ly re­cog­nized to be the an­ces­tor of all domes­tic dog breeds (Canis lupus familiaris), in­clud­ing feral forms such as di­ngos (Canis lupus dingo) and New Guinea sing­ing dogs (Canis lupus halstromi). Genetic evi­d­ence sug­gests that gray wol­ves were domes­ticated at least twice, and per­haps as many as 5 times, by humans. Ar­tifici­al selec­tion by humans for par­ticular traits, in­clud­ing size, ap­pearan­ce, aggres­sive­ness, loyal­ty, and many de­sir­able, specialized skills, has re­sul­ted in an as­tonish­ing array of domes­tic dog morpholog­ies. Domes­tic dogs vary in size from di­minutive, 1.5 kg chihuahuas to 90 kg giant mas­tiffs.

Con­tributors

Tanya Dewey (aut­hor, editor), An­im­al Di­vers­ity Web.
Julia Smith (aut­hor), Uni­vers­ity of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, 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
Palearctic
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
World Map
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.
carnivore
an animal that mainly eats meat
carrion
flesh of dead animals.
chaparral
Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.
chemical
uses smells or other chemicals to communicate
cooperative breeder
helpers provide assistance in raising young that are not their own
diurnal
  1. active during the day, 2. lasting for one day.
dominance hierarchies
ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates
ecotourism
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
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.
fertilization
union of egg and spermatozoan
forest
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
holarctic
a distribution that more or less circles the Arctic, so occurring in both the Nearctic and Palearctic biogeographic regions.
World Map
Found in northern North America and northern Europe or Asia.
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).
monogamous
Having one mate at a time.
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
nomadic
generally wanders from place to place, usually within a well-defined range.
scrub forest
scrub forests develop in areas that experience dry seasons.
seasonal breeding
breeding is confined to a particular season
sexual
reproduction that includes combining the genetic contribution of two individuals, a male and a female
social
associates with others of its species; forms social groups.
tactile
uses touch to communicate
taiga
Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.
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).
terrestrial
Living on the ground.
territorial
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
tundra
A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.
viviparous
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

Re­fer­ences

"A Short Co­ur­se on Gray Wol­ves" (On-line). Ac­cessed De­cemb­er 9, 1999 at http://www.boomer­wolf.com/graycors.htm.
July 1998. "Gray Wolf (Canis lupus)" (On-line). Ac­cessed De­cemb­er 9, 1999 at http://www.fws.gov/r3pao/­wolf/wol­findx.html.
Janua­ry 16, 1997. "Gray Wolf" (On-line). Ac­cessed De­cemb­er 9, 1999 at http://www.kats-korner.com/graywolf.html.
Dog Breed Info Cent­er, 2000. "Dog Breeds in Al­phabet­ical Order" (On-line). Ac­cessed Feb­rua­ry 16, 2002 at http://www.dogbreedin­fo.com­/abc.htm.
Kind­er, A. 1995. "An­im­al Di­vers­ity Web, Canis lupus dingo (Dingo)" (On-line). Ac­cessed Feb­rua­ry 19, 2002 at http://animal­diver­sity.ummz.umich.edu/ac­counts/canis/c._lupus_din­go$nar­rative.html.
McIn­tyre, R. 1993. A Society of Wol­ves: Nation­al Parks and the Battle Over the Wolf. Stillwat­er, MN: Voyageur Press.
Mech, L. 1999. Gray Wolf. Pp. 141-143 in D Wil­son, S Ruff, eds. The Smithsonian Book of North American Mamm­als. Was­hington and Lon­don: Smithsonian In­stitu­tion Press.
Shet­al, B. 1995. "An­im­al Di­vers­ity Web, Canis lupus familiaris (Dog)" (On-line). Ac­cessed Feb­rua­ry 19, 2002 at http://animal­diver­sity.ummz.umich.edu/ac­counts/canis/c._lupus_familiaris$nar­rative.html.
Straub­er, J. June 12, 1997. "The Gray Wolf" (On-line). Ac­cessed De­cemb­er 9, 1999 at http://www.hillsborough.k12.nj.us/hhs/endspeci/­canis­lupus.html.
Young, S., E. Goldman. 1944. The Wol­ves of North America. Was­hington D.C.: The American Wildlife In­stitute.
Zgurski, J. 2002. "The Be­havior and Ecology of Wol­ves" (On-line). Ac­cessed Feb­rua­ry 16, 2002 at http://www.ual­berta.­ca/~jzgurski/.
Zgurski, J. 2002. "The Origin of the Domes­tic Dog" (On-line). Ac­cessed Feb­rua­ry 16, 2002 at http://www.ual­berta.­ca/~jzgurski/­dog.htm.
Zgurski, J. 2002. "Wolf Taxonomy" (On-line). Ac­cessed Feb­rua­ry 16, 2002 at http://www.ual­berta.­ca/~jzgurski/­taxa.html. 

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