Über die Autorin bzw. den Autor

L. David Mech is a senior research scientist with the Biological Resources Division, U.S. Geological Survey and adjunct professor in the Department of Fisheries, Wildlife, and Conservation Biology and the Department of Ecology and Behavioral Biology at the University of Minnesota. He is the author of The Wolf: The Ecology and Behavior of an Endangered Species, The Way of the Wolf, and The Arctic Wolf, among other books, and is coauthor of The Wolves of Denali. Luigi Boitani is a professor of vertebrate zoology and animal ecology at the University of Rome. He is the author of Dalla parte del lupo, coauthor of Simon and Schuster's Guide to Mammals, and coeditor of Research Techniques in Animal Ecology.

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Wolves

Behavior, Ecology, and ConservationBy L. David Mech

University of Chicago Press

Copyright © 2007 L. David Mech
All right reserved.
ISBN: 9780226516974
1 - Wolf Social Ecology

L. David Mech and Luigi Boitani

THE FIRST REAL BEGINNING to our understanding of wolf social ecology came from wolf 2204 on 23 May 1972. State depredation control trapper Lawrence Waino, of Duluth, Minnesota, had caught this female wolf 112 km (67 mi) south of where L. D. Mech had radio-collared her in the Superior National Forest 2 years earlier. A young lone wolf, nomadic over 100 km2 (40 mi2) during the 9 months Mech had been able to keep track of her, she had then disappeared until Waino caught her. From her nipples it was apparent that she had just been nursing pups.

?This was the puzzle piece I needed,? stated Mech. ?I had already radio-tracked lone wolves long distances, and I had observed pack members splitting off and dispersing. My hunch was that the next step was for loners to find a new area and a mate, settle down, produce pups, and start their own pack. Wolf 2204 had done just that.?

During the decades since, we have seen this process many times, and it represents one of the primary ways in which wolves become breeders (Rothman and Mech 1979). However, there are several other ways, and it is only now, after 25 years of study and the wedding of wolf radio-tracking with biochemical analyses of wolf genetics (see Wayne and Vila, chap. 8 in this volume), that we seem to have a reasonably complete picture of wolf social ecology (Meier et al. 1995; D. Smith et al. 1997; Mech et al. 1998).The basic social unit of a wolf population is the mated pair. Known variations include a mature male and two mature females; a mature male, his yearling son from a previous mating, and a new mate; and a mature female with a new mate and his younger brother (Mech and Nelson 1990b). There is no reason to believe that other similar combinations of a mated pair with various relatives of one or both members are not also possible.

There are two reports of packs of males, but these packs are not well documented or understood, and presumably are temporary until a mate is found. Ballard et al. (1987) reported without documentation that a pack of three males occupied a 3,077 km2 (1,200 mi2) area of Alaska for over a year. Two radio-collared males split off from a Montana pack and lived together from June to September before being joined by a third animal of unknown age and sex (Ream et al. 1991).

The most unusual type of pack ever recorded formed in Yellowstone National Park 7 years after wolf reintroduction (D. W. Smith, unpublished data). During winter 2001?2002, three packs were formed of various assortments of at least twelve dispersers from four packs. Each new pack included a Druid Peak pack female born in 1997. Individuals moved among these packs, sometimes daily. By late spring, one pack contained two males from the Chief Joseph pack and four Druid Peak females. These wolves produced two litters in separate dens, merged in midsummer into six adults and four pups, and remained such at least into winter. Less is known about the other two new packs.

Mech also once recorded an adult male, his yearling son, and his three pups remaining together for 10 weeks after his mate (wolf 5091) was killed by other wolves (Rothman and Mech 1979). This situation can be considered a temporary exception; a new mature female (5079) joined the pack after 10 weeks and remained with it, producing pups the next spring.

The natural extension of the mated wolf pair is the pair with its collection of offspring, or family, as earlier workers surmised (Olson 1938; Murie 1944; Young and Goldman 1944) and numerous radio-tracking studies have documented. In a thriving population, a wolf pair produces pups every year (Fritts and Mech 1981; Mech and Hertel 1983; Peterson, Woolington, and Bailey 1984; but cf. Mech 1995d). The offspring usually remain with their parents for 10?54 months, but except under special circumstances, all offspring disperse (Gese and Mech 1991; Mech et al. 1998). Packs therefore may include the offspring of as many as 4 years. A wolf pack, then, is some variation on a mated pair, and packs have contained as many as forty-two members, although most include far fewer (see table 1.1).

Adoptees

One poorly understood exception to the above basic rule is that strange wolves sometimes join packs already containing a breeding pair, at least temporarily (Fritts and Mech 1981; Peterson, Woolington, and Bailey 1984; Messier 1985b; Ballard et al. 1987; Mech 1991b; Boyd et al. 1995; Meier et al. 1995). We will refer to these animals as ?adoptees? (Meier et al. 1995) to distinguish them from wolves that enter a pack to replace a lost breeder (see below). Most adoptees are males, and most adoptions take place from February through May (Messier 1985b; Meier et al. 1995).

One of the main mysteries of this behavior is why strange wolves are sometimes allowed to join packs, whereas in so many other cases they are chased, attacked, or killed (Mech 1993a, 1994a; Mech et al. 1998). A clue may be the fact that most adoptees are 1?3 years old (Messier 1985b; Meier et al. 1995), whereas a high percentage of wolves killed by other wolves are adults (Mech 1994a; Mech et al. 1998). Tests with captive wolves confirm that degree of aggressiveness depends on the rank, age, and residency status of the wolves involved (Fox et al. 1974).

The incidence of packs adopting strange wolves would be very difficult to measure without sampling each wolf in every pack of a population and resampling over time. Based on genetic determinations, nine of twenty-seven packs from three study areas included apparent adoptees (Lehman et al. 1992). However, most members of most packs were not sampled, and the sampling was done over several years. In an Alaskan population subject to harvesting by humans, over 21% of the wolves that dispersed over a 7-year period were accepted into other packs (Ballard et al. 1987). These diverse sampling schemes, plus the fact that adoptees remain in packs for periods of only a few days to over a year, preclude an estimate of the proportion of adoptees at any given moment. A rough guess might be 10?20%, and this proportion could well vary by time and place. (Additional information about adoptees can be found in the discussion of multiple breeding below.)

Pair Formation

As in the case of wolf 2204, described above, one of the main methods of pair formation is for dispersing wolves of the opposite sex to find each other. However, there are several other methods (?strategies?) of pair formation.

To understand the various breeding strategies wolves use, we must first make it clear that every wolf is a potential breeder, and as each begins to mature (see Kreeger, chap. 7 in this volume), its tendency will be to try to breed. This idea is contrary to earlier views that some wolves relinquish breeding ?for the good of the species? (Rabb et al. 1967; Woolpy 1968; Mech 1970; Van Ballenberghe et al. 1975; Haber 1977).

Detailed studies of captive (Packard and Mech 1980; Packard et al. 1983, 1985) and wild wolves (Mech 1979a; Fritts and Mech 1981) show that many young wolves merely defer reproduction while still in their natal packs. In the basic social life of the wolf, this strategy can now be seen as merely a natural result of breeding competition, much like the failure to breed of many young male ungulates that lose in their competition with mature...