A study analyzed feces to determine the natural prey of arctic wolves (Canis lupus) in Nansen Land North Greenland and Hold with Hope East Greenland. Muskoxen (Ovibos moschatus) is the major food of wolves in both Nansen Land and Hold with Hope.
Diet of wolves (Canis lupus) in North America has been subject to intensive study. These investigations have established that wolves kill a variety of prey. Most of the diet typically consists of large ungulates such as moose (Alces alces), caribou (Rangifer tarandus), and deer (Odocoileus). Small mammals such as beavers (Castor canadensis), snowshoe hares (Lepus americanus), and microtines may be seasonally or locally important prey (Mech, 1991).
A variety of techniques has been employed to evaluate diets of wolves. The most effective methods are direct observation of kills and examination of kill sites. Nonetheless, these procedures are not always feasible, so analysis of feces is frequently used despite inherent short-comings. First, an investigator is unable to distinguish between scavenging and predation. Second, analysis of prey species that differ markedly in size can result in overrepresentation of the proportion of smaller animals eaten relative to larger prey because of varying surface:volume ratios. Smaller prey has a higher surface: volume ratio and is covered by more hair or feathers per mass of flesh relative to larger prey. Because hair and feathers constitute the primary identifiable remains in carnivore feces, the contribution of smaller prey may be overestimated....
Food habits of wolves at high latitudes in the Arctic have not been subject to intensive study; only a single investigation has been published...reported that 83.3% contained remains of arctic hares (Lepus arcticus) and only 16.7% contained remains of muskoxen. There are no empirical data published on food habits of wolves in Greenland....
This paper presents data on the food habits of arctic wolves in Greenland as part of a broader study of the ecology of wolves in the eastern Arctic (Marquard-Petersen, 1994, 1995). This study was undertaken to: 1) provide data on the extent of wolf predation on muskoxen, 2) assess relative abundance of the different prey species in the diet of wolves, and 3) evaluate geographic variation in the diet of arctic wolves in north and east Greenland. The population of muskoxen in northeastern Greenland has decreased significantly since the early 1980s, when wolves moved into Greenland. Whether wolf predation played a role in this decline is not known....
MATERIALS AND METHODS
Study area.-- Prior to our initial field work in 1991, little was known about distribution and core areas of wolves in Greenland. No information was available suggesting localities where enough feces could be collected for a study of food habits of wolves. Therefore, I analyzed 136 observations of wolves made by military personnel and government scientists during 1978-1990. This analysis suggested that wolves occurred in several areas. I selected two areas, from which I assumed that a sufficient sample size of feces could be obtained: Nansen Land in North Greenland, and Hold with Hope in East Greenland.
The first study area was located in Siriuspasset (825 deg N, 41 deg 30'W), a valley transecting southeastern Nansen Land from J. P Koch Fjord to Brainard Sund, 6-7 km wide and 24 km long. The valley consisted of clay soils derived from Cambrian siltstone. The surrounding topography was characterized by high-alpine terrain with mountain peaks to an elevation of 1,300 m. Numerous glaciers descended into the valley. Siriuspasset was considered true polar semidesert but was one of the few areas in North Greenland with relatively luxuriant vegetation....There were few meteorological data for the area; annual precipitation was believed to be <50 mm with a mean annual temperature of -16 deg C. The only extant ungulate was muskoxen. Greenland caribou (Rangifer tarandus) did not occur in North and East Greenland. Collared lemmings (Dicrostonyx groenlandicus), arctic hares, and arctic foxes (Alopex lagopus) were common. The population of lemmings in North and East Greenland was cyclic, and variation in density was likely critical in availability of prey for wolves. Little is known about population fluctuations of arctic hares and arctic foxes in northeastern Greenland.
The second study area was located in Hold with Hope including Badlanddalen (73 deg 30'N, 21 deg 45'W), a valley 7-12 km wide and 21 km long, transecting western Hold with Hope from Loch Fyne to Mackenzie Bay. Badlanddalen consisted of quaternary marine deposits of 7297% sand (Marquard-Petersen, 1994) with a complex of ridges, river valleys, and ponds. Part of the valley had a desert-like appearance and was subject to severe sandstorms....The surrounding topography was characterized by highalpine terrain with mountain peaks >1,250 m. There were few recent meteorological data for the area. The nearest weather station was in Daneborg ca. 100 km to the north, which reported a mean annual temperature of -9.9 deg C and a mean annual precipitation of 285 mm. Yearly precipitation could be substantial depending on the extent of ice cover on the Greenland Sea. The fauna was rich and varied. Wolves, muskoxen, collared lemmings, arctic hares, and arctic foxes were common and occurred in the area year-round. Greenland caribou became extinct in this area around 1900. Avifauna consisted of 38 species; most were present from mid-May through August (Elander and Blomqvist, 1986). Both study areas were located in the Northeast Greenland National Park.
Field collections.-Wolf feces were collected opportunistically....North and east Greenland were frequented by sled dogs of the Danish military who patrolled the region. Therefore, methods were developed to differentiate between feces of dogs and wolves....Feces of wolves were assumed to represent the yearround diet because they were collected away from den sites and varied in age as evidenced by varying degrees of desiccation.... Calculations of frequency of occurrence were based on number of occurrences of each type of prey divided by the total number of feces and were expressed as a percentage of the total sample.
Nansen Land, North Greenland.-Identifiable prey occurred in 107 of 110 feces. Prey species included muskoxen, lemmings, arctic hares, wolves, and arctic foxes. Results indicated that the major food of wolves was muskoxen with a frequency of occurrence of 79.4%. Lemmings constituted the second most important food with a frequency of occurrence of 19.6%, followed by arctic hares with a frequency of occurrence of 7.5%.....
Hold with Hope, East Greenland.-Identifiable prey occurred in 344 of 351 feces. Prey species identified included muskoxen, barnacle geese (Branta leucopsis), pink-footed geese (Anser brachyrhynchus), lemmings, arctic hares, and beetles (Coleoptera). Results suggested that the major food of wolves was muskoxen with a frequency of occurrence of 65.4%. Geese and other birds were the second most important food (35.5%)....
Most studies of food habits of wolves in North America indicate that ungulates are a primary prey, which is likely related to availability of prey and energetic costs of capturing and handling prey. Although capturing larger prey requires increased effort relative to small animals, more food is secured when a kill is made. When large ungulates become unavailable, a functional response of wolves causes increased reliance on smaller prey. Availability and vulnerability are important factors in selection of prey. When these factors vary between areas, a difference in diets of wolves is likely to exist.
There is little published information on wolf predation on muskoxen, so a quantitative comparison with my results is difficult. Tener (1952) reported that 16.7% of feces of wolves collected on Ellesmere Island contained remains of muskoxen, but new methods suggested that these findings may not reflect a reliance on arctic hare as the primary prey. Kuyt (1972) reported that wolf predation on muskoxen in the Thelon Game Sanctuary, Northwest Territories, Canada, was insignificant (1.8%), perhaps due to the availability of caribou. More recently, analysis of 98 feces collected at two dens in Ellesmere Island National Park Reserve revealed that 97.5% contained remains of muskoxen.
In addition to energy requirements, the most likely reason for the high frequency of occurrence of muskoxen in feces of wolves from both study areas was related to availability of prey. Unfortunately, accurate data on population sizes of muskoxen were not available. No comprehensive census has been conducted in either study area and guesses vary. Boertmann et al. (1992) reported 1-50 muskoxen in Nansen Land. I counted 56 muskoxen in central Nansen Land during wolf surveys in July-August 1991, and groups of [twelve or less] muskoxen have been observed in western Nansen Land, an area I did not visit. Therefore, population size may be closer to...50-100.... Overall density of muskoxen in North Greenland was extremely low, ca. 1.7 muskox/100 km2....Nonetheless, overall density in Nansen Land is probably closer to 3.4-4.5 muskoxen/100 km2, assuming the population consisted of 75-100 animals....Relative to ungulate herds in lower latitudes, the population of muskoxen in Nansen Land appeared extremely small, but many areas of North Greenland consisted of large plateaus essentially devoid of vegetation and mammals. The prey base for wolves in Nansen Land could be evaluated based on this information.
Availability of prey to wolves in Hold with Hope was substantially higher than in Nansen Land. The population of muskoxen was estimated at 1,000-2,000 animals, including muskoxen in adjacent Hudson Land and Gauss Peninsula....Although those densities were remarkably similar between years, muskoxen density in Badlanddalen may not be representative of the entire Hold with Hope region. The central northern part of the valley was almost devoid of vegetation and thus offered little forage for muskoxen. Overall muskoxen density in the Hold with Hope region was between 13.6 and 27.2/ 100 km2 following the population estimate by Boertmann et al. (1992)....Thus, muskoxen density in this southern study area was at least four times higher compared with Nansen Land, but feces from Hold with Hope suggested that wolves relied less on muskoxen for primary prey than wolves in North Greenland. This outcome may be related to the high occurrence of birds, probably predominately geese...suggesting that this abundant summer food may act as a buffer to predation of muskoxen....
My data indicate that both study areas were capable of sustaining a sufficiently large population of muskoxen to sustain wolves, but this is uncertain given the lack of data on movements of wolves. Both areas have good habitat for muskoxen and there is mounting evidence that the areas also are important habitat for wolves. Wolves were first detected in Nansen Land in April 1984 and have been observed every year since, except in 1988 and 1990. Known pack sizes have ranged from two in 1995 to seven in 1984....In Hold with Hope, wolves were first observed in March 1980, and known pack sizes have ranged from two in 1980 to nine in 1992.
My finding that muskoxen constituted the major prey of wolves correlates well with what is known about core areas for wolves in Greenland; wolves tend to occur where muskoxen are common. In areas where muskoxen density is low, there are correspondingly few observations of wolves. For example, Hall Land (81 deg 43'N, 60 deg 00'W) lacks muskoxen and no wolves or tracks have been reported observed there since 1965. In contrast, in Peary Land, where muskoxen are common, wolves are observed yearly in packs numbering up to eight animals....
The most likely reason why avian fauna constituted an important secondary prey during both the 1990 and the 1992 denning season probably can best be explained in terms of availability and vulnerability (ease of capture)....Vulnerability is likely variable depending on species. For example, barnacle geese usually nest colonially at highly protected sites (e.g., cliff ledges), whereas nests of pinkfooted geese are on top of river banks or large hummocks and may be more accessible to wolves. During molting of flight feathers, adult post-breeding pink-footed geese remain flightless for ca. 25 days in July-August, and barnacle geese become flightless for 3-4 weeks starting in early July (nonbreeders), or between mid-July and mid-August for postbreeders. This period corresponds to the second half of the denning season, where the nutritional demands of young wolves are great and where adult wolves must secure enough food to ensure survival of their litter. The 297 feces collected at the two dens at Hold with Hope, representing two different denning seasons, suggest that geese are highly vulnerable to wolf predation during the flightless period. This conclusion is supported by observations from the Copper River Delta, Alaska, where two wolves were observed killing three molting dusky Canada geese (Branta canadensis occidentalis) on one occasion.
Lemmings appeared to be a secondary prey of wolves in Nansen Land but were of less importance to wolves in Hold with Hope. Other researchers have reported a comparable occurrence. Clark (1971) noted that wolves on Baffin Island, Northwest Territories, Canada, during summers 1966 and 1969 frequently ate lemmings (13.2% and 11.5%, respectively). Kuyt (1972) made no attempt at distinguishing lemmings from other microtines but reported an overall occurrence, including Dicrostonyx, of 12.8%. Occurrence of arctic hares was low in feces from both study areas. Occurrence of arctic hares in the 297 wolf feces collected at dens in Hold with Hope also was low, suggesting a consistently low dependence on arctic hares in summer.... Perhaps predation on arctic hares in Hold with Hope in summer is buffered by the presence of thousands of vulnerable geese.
A substantial amount of wolf hair and parts of a tooth and claw from an arctic wolf occurred in a single fece from Nansen Land, suggesting conspecific aggression or scavenging of a wolf carcass. Most natural mortality among wolves in lower latitudes is conspecific, but it is not known if this also holds in the High Arctic, where wolf densities are among the lowest recorded, thereby reducing the probability of interterritorial strife.
There was no significant difference in contents between feces collected year-round in both Nansen Land and Hold with Hope, suggesting that differences between the samples from the two areas are strictly seasonal. Future research needs include...investigation of the effects of predation by wolves on the population of muskoxen in northeastern Greenland to ascertain if predation has played a role in its decline.
Figure 1: Greenland showing study areas and wolf range.
Figure 2: Frequency of occurrence of prey items in 107 wolf feces from Nansen Land, North Greenland, and 344 feces of wolves from Hold with Hope, East Greenland.
Figure 3: Frequency of occurrence of prey items in 293 feces of wolves from two dens in Hold with Hope, East Greenland.
Figure 4: Frequency of occurence of prey items in 51feces of wolves from summer and winter range in Hold with Hope, East Greenland.
Table 1: Frequency of occurrence of prey in 451feces of wolves from Nansen Land, North Greenland, and Hold with Hope, East Greenland, collected during summers 1991-1995.