Yellowstone Wolf Facts

KINGDOM: Animalia

PHYLUM: Chordata

CLASS: Mammalia

ORDER: Carnivora

FAMILY: Canidae (dog family)

GENUS: Canis (Latin word meaning "dog")

SPECIES: lupus (Greek word meaning "wolf")

COMMON NAMES: gray wolf, timber wolf

NAMES IN OTHER LANGUAGES: Spanish: Lobo, French: Loup, Italian: Lupo, Swedish: Varg, Norwegian: Ulv

GROUP OF WOLVES: pack/ family (one of few eusocial species)

AVERAGE LIFE SPAN (YNP): 4-5 years

AVERAGE LIFE SPAN (OUTSIDE YNP): estimated 2-3 years

OLDEST WOLF KNOWN IN YNP: 12.5 years - 478F of the Cougar Creek pack

OLDEST WOLF KNOWN IN THE ROCKIES: B2 released in Idaho at estimated 4 years of age;died at age 13.8 of unknown causes

CAUSES OF MORTALITY IN ADULTS (YNP): natural causes 77% (intraspecific 42%, natural unknown 15%, interspecific 8%, malnutrition 5%, other 4%, disease 3%); human causes 17% (harvest 7%, vehicle 6%, illegal 2%, control 1%, other 1%); unknown causes 6%

CAUSES OF MORTALITY IN ADULTS (GYE): human causes 77%;natural causes 23%

PROPORTION OF POPULATION >5 YEARS OLD: 18%

SEX RATIO: 50:50

PELAGE: gray or black (ratio 50:50), rarely white

BLACK COAT COLOR: caused by K-locus gene thought to have originated from historic hybridization with domestic dogs 500-14,000 years ago

LOCOMOTION: tetrapedal, digitigrade

AVERAGE RATE OF SPEED: 5mph

TOP SPEED: 35mph

AVERAGE BODY MASS: males- 110 lbs (50 kg); females-90 lbs (41 kg)

HEAVIEST KNOWN WOLF IN YNP: 148 lbs (wolf 760M of Yellowstone Delta pack with no food in stomach)

HEIGHT AT SHOULDER: males-81 cm average, females-77 cm average

LENGTH: 181 cm average

BODY TEMPERATURE: 100-102.5 F (37.3-39.1 C)

RESPIRATION: 10-30 breathes per minute

HEART RATE: 70-120 beats per minute

EYES: blue at birth, light yellow to gold to brown as an adult

NUMBER OF BONES: 319 males, 318 females

NUMBER OF TEETH: 42

SMELL: excellent, although unmeasured. Estimated to be thousands of times better than humans

VISION: excellent night vision; no red or green cones, but have blue and yellow cones

HEARING: little is known, but probably similar to dogs (relatively normal hearing abilities compared to other mammals)

DENTAL FORMULAE: incisors 3 top/3 bottom, canines 1/1, premolars 4/4, molars 3/2 (on each side)

FEEDING HABITS: generalist carnivore; scavenges when possible and has been known to eat small amounts of vegetation

PRIMARILY FEED ON (YNP): Winter: elk (>96%), bison (3-4% and increasing in recent years; deer (1.5%); Spring: elk (89%), bison (7%), deer (7.1%); Summer: elk (85%), bison (14.1%), deer (<1%)

ELK KILLED PER MONTH PER WOLF: 1.83 elk/wolf/month during winter

ELK KILLED PER YEAR PER WOLF: 18-22 elk/wolf/year (all age classes, including neonate calves)

KILOGRAM PER WOLF PER DAY NEEDED FOR SURVIVAL: 3.25 kg/wolf/day; can eat 15-20% of body weight in one sitting

CURRENT YNP POPULATION: 99 in 10 packs

CURRENT GREATER YELLOWSTONE POPULATION: 510

CURRENT NORTHERN ROCKIES POPULATION: 1,782

CURRENT NORTH AMERICAN POPULATION: 67,100-74,100 (53,600-57,600 of these in Canada)

AVERAGE HOME RANGE SIZE IN YNP (NORTHERN RANGE): 274 km² (range=58-1,151 km²)

AVERAGE HOME RANGE SIZE IN YNP (INTERIOR): 620 km² (range=105-1675 km²)

AVERAGE HOME RANGE SIZE IN YNP (PARKWIDE): 428 km²

AVERAGE PACK SIZE (YNP): 9.8

PERCENT OF POPULATION THAT ARE LONE WOLVES (YNP): 2-5%

PERCENT OF POPULATION THAT ARE LONE WOLVES (NORTH AMERICA): 10-15%

HIBERNATORS?: No, active all year

MATING SYSTEM: usually monogamous, but about 25% of packs have multiple breeding pairs under polygymous matings

PERIOD OF COURTSHIP: mid-February

GESTATION: 63 days

BIRTH PERIOD: mid-April

BIRTH LOCATION: den

TYPICAL DEN TYPES: excavated under large roots, boulders, hillsides, caves with a tunnel leading to an enlarged chamber; several entrances and chambers may be present

DEN EMERGENCE: 10-14 days

AVERAGE LITTER SIZE (YNP): 4.4 at den emergence, 3.2 survive until late December

MAXIMUM LITTER SIZE RECORDED (YNP): 11

SPLIT LITTERS?: multiple fathers per litter have not been detected in wild gray wolves

WEANING: 5-9 weeks from milk, then brought food (regurgitation) for another 3 months

MILK CONTENT: 6.6% fat; 144 kCal per 100 grams

RENDEZVOUS SITES: used as wolf pups get older as a central homesite; time spent there and number of homesites varies widely between packs

AVERAGE FEMALE AGE AT FIRST LITTER (YNP): 2.7

ONSET OF FEMALE REPRODUCTIVE SENESCENCE: 4-5 years

INTERBIRTH INTERVAL: can be every year

EYES OPEN: 12-14 days

WOLVES SEEN IN YNP: 3,573 consecutive days (February 2001-November 2010)

BITE PRESSURE: 1,200 psi

DISPERSAL: both sexes, YNP average age 2 years, 1 month; range 1-4 years

HOWLING FUNCTION: many uses, including intrapack communication, advertising territory, coordinating social activities

DISTANCE HOWLING CAN BE HEARD: forest=11km (6.6 mi), open areas=16 km (9.6 mi)

LONGEST TERM PACK: Crystal Creek/Mollie's, 1995-present

LONGEST TIME AS ALPHA MALE: 8 years; 712M, currently alpha male of the Canyon pack

LONGEST TIME AS ALPHA FEMALE: 8 years; uncollared white alpha female of the Canyon Pack

LARGEST PACK RECORDED IN YNP: Druid Peak, 37 wolves (2001); may be the largest ever recorded (42 wolves seen together in Wood Buffalo National Park (1974) but unknown if they were a single pack)

MOST PUPS BORN TO A SINGLE PACK IN YNP: Leopold pack, 25 pups, at least 4 litters (2008)

Bibliography

Anderson, T. M., B. M. vonHoldt, S. I. Candille, M. Musiani, C. Greco, D. R. Stahler, D. W. Smith, b. Padhukasahasram, E. Randi, J. A. Leonard, C. D. Bustamante, E. A. Ostrander, H. Tang, R. K. Wayne, and G. S. Barsh. 2009. Molecular and evolutionary history of melanism in north american gray wolves. Science 323:1339-1343.

Mech, L.D. 1970. The wolf. The Natural History Press, Garden City, New York, USA

Mech, D. and L. Boitani. 2003. Wolves: behavior, ecology, and conservation. First edition. The University of Chicago Press, Chicago, Illinois, USA.

Metz, M.C., D.W. Smith, J.A. Vucetich, D. R. Stahler, and R.O. Peterson. 2012. Seasonal patterns of predation for gray wolves in the multi-prey system of Yellowstone National Park. Journal of Animal Ecology 81:553- 563.

Smith, D.W., E.E. Bangs, J.K. Oakleaf, C. Mack, J. Fontaine, D. Boyd, M. Jimenez, D. H. Pletscher, C.C. Niemeyer, T.J. Meier, D. R. Stahler, J. Holyan, V.J. Asher, and D.L. Murray. 2010. Survival of colonizing wolves in the Northern Rocky Mountains of the United States, 1982–2004. Journal of Wildlife Management 74:620-634.

Stahler, D.R., D.R. MacNulty, R.K. Wayne, B. vonHoldt, and D.W. Smith. 2013. The adaptive value of morphological, behavioural and life-history traits in reproductive female wolves. Journal of Animal Ecology 82:222- 234.

Theberge, J.B. and J.B. Falls. 1967. Howling as a means of communication in timber wolves. American Zoologist 7:331-338.

artwork by Emily Harrington