Ecological Influences of Canis lupus arctos and Canis lupus of Yellowstone National Park

1. Ecological Influences of Canis lupus arctos and Canis lupus of Yellowstone National Park Joanna Denninghoff Winter Ecology – Spring 2005 Mountain Research Station – University of Colorado, Boulder

2. Purpose • How have the varying habitats and ecosystems between arctic wolves and the gray wolves of Yellowstone been affected by wolf predation? • How do the different ecosystems affect these wolf populations as well as ungulates and scavengers throughout the separate latitudes?

3. Introduction • The extreme differences between the habitats of arctic wolves (above 67* lat.) and the gray wolves of Yellowstone allowed for the opportunity to research the differences of wolves’ behavioral differences and environmental effects caused by their differing habitats and resource availabilities. • Although these two species of wolves may seem somewhat abstract to one another, the genetic diversity between them is very insubstantial. The arctic wolf is just one of the subspecies of the gray wolf, Canis lupus (Marquard-Petersen, 1998). Because of this, the differences between the wolves can be considered to be due to their varying environments and the ecological pressures each faces.

5. Gray Wolves of Yellowstone • Re-introduced in 1995 and 1996 with about 31 wolves; now at around 177 wolves. • Re-introduction gave way to major changes in ungulate populations as well as scavengers’ populations and behavior (Wilmers, 2004). • Prior to re-introduction, carrion availability was due to hunters kills and end-of-winter die-offs (resulting in overwhelming amounts of carcasses—wasted) (Wilmers, 2004) • Wolves provided for constant and dispersed sources of carrion for scavengers (coyotes, ravens, magpies…beetles, vegetation).

7. Gray Wolf Behavior • Wolves preferably feed on young, weak, sick, or older prey (the more vulnerable), so as to gain food with the least amount of energy loss. (Wilmers, 2004; Ripple, et. al., 2003) • Wolves do not hibernate and hunt in packs year-round. In lower elevations (food is more abundant) wolves will not guard or defend their kills after they are finished gorging, leaving scavengers to take their fill. • As a result of the reintroduction of wolves, both scavenger health and, indirectly, potential prey (ie: elk) health has increased (Wilmers, 2004).

8. Benefits due to the Re-introduction of Wolves • The re-introduced gray wolves has proven (despite conflicting opinions of hunters) to be beneficial to the entire ecosystem of YNP. • Wolves have had a positive effect on both the fitness and population sizes of certain ungulates, which allows more available food sources for foraging ungulates during winter Wilmers, 2004). • Ravens, along with myriad scavengers are able to feed throughout winter, thus remain in better health than before wolves. • With the continuous hunting of wolves, there are much less wasted resources (Wilmers, 2004).

9. Yellowstone Conclusions • Thus, it appears to be obvious that wolves prove to be extremely beneficial to environments populated with unchecked ungulates especially during winter months. • Overpopulation of foraging ungulates caused crashes in years prior to wolf re-introduction. The only check on browse species in winter, before was snow depth, winter severity and hunting (Wilmers, 2004). • Although other predators exist in these areas: coyotes, bears and cougars—they had no documented effects on winter patterns of elk populations and herbivory (Ripple, et. al., 2003). • After re-introduction, elk started foraging at sites that allowed for earlier detection and successful chance for escape.

10. Yellowstone Conclusions • Had not wolves been absent from YNP for decades, the observed data provided insight into the importance of such a key predator. Re- introduction of wolves decreased the overpopulation of ungulates, thus increasing available herbivory for foragers, which in turn led to and increase in such populations as beavers and avian species that rely on un- browsed herbivory in later months, and also and increase in many faunal species (Ripple, et. al., 2003). All of these interactions in this ecosystem are greatly a result of the presence of wolves.

11. Artic Wolves: Introduction • Arctic wolves have significant differences from gray wolves despite their genetic similarities. Unfortunately, arctic wolves have not been under intensive studies (Mech, 2000). • These observations used methods of direct observation of kills and examination of kill sites. Also, feces samples were often used to determine the diets of these wolves (Marquard-Petersen, 1998). • In contrast to the accessible, protected, and highly observed wolves of YNP, arctic wolves have not been under intense observation, possibly because their ranges are so remote. Most data in the past has come from hunters, Inuits, and such (Mech, 2000).

12. Adaptations and Behavior • Arctic wolves live in the regions above 67* latitude. This environment/land is covered in ice and snow all year round except for a couple months in mid summer (Marquard-Petersen, 1998). • This “summer” period is very influential on ungulate prey densities, which in turn may affect wolf populations. • Arctic wolves have adapted well to their harsh environments: they are covered in long, thick fur to keep warm in temperatures as low as -70* F. They also minimize heat loss by having more rounded ears, shorter muzzles, shorter legs, smaller/stockier stature and have fur between the pads of their feet (Unknown, 2005). • These wolves do have similarities to their cousins such as living, hunting in packs, living in a social hierarchy and hold territories (Mech, 2000).

14. Habitat • The habitat of arctic wolves is extremely different from their southern counterparts. They live in harsh winter environments almost year-round (~3 months of “summer”). • Prey consists of muskoxen, lemmings, arctic hares, and arctic foxes. Wolves are rarely killed from conspecific aggression (probably due to the low density of arctic wolves) (Marquard-Petersen, 1998). • Wolves tend to occur where muskoxen are common. In areas where muskoxen density is low, there were fewer observations of wolves (Marquard-Petersen, 1998).

15. Denning Behavior • Because of higher latitudinal locations, females birth 2-3 pups in late May, early June. This contrast southern relatives in that the southerners birth about one month earlier to about 5-6 pups. The lower number of pups may be due to scarcity of prey in the arctic (Gray, 1993). • Because of permafrost, arctic wolves must den in rock outcroppings, caves, or shallow depressions, in contrast to wolves of Yellowstone who are able to dig dens (Gray, 1993). • With arctic wolves the observed time of extensive travel of pups with the pack was much earlier than most southern wolves. Also, pups used kill sites as temporary rendezvous sites after the pack has begun traveling which provides not only a place to meet but allows pups to rest, feed explore and gain experience while adults continue hunting (Gray, 1993).

16. Arctic Wolves’ Hunting Behavior • In the Arctic, densities of mammals are much lower than those of mammals inhabiting lower latitudes (this also reflects in smaller litter size, probably due to lack of an abundance of resources), so population and productivity declines are more serious (Ripple, et al, 2003). • Because of low animal densities, prey densities, naturally, are also low in the arctic because there is a scarcity of grazing plants which requires animals to roam large areas (Marquard-Petersen, 1998). • This requires arctic wolves to have territories of well over 1,000 sq. mi.—well over the ranges of their southern counterparts.

17. Hunting Continued • Although capturing larger prey requires increased effort relative to small animals, more food is secured with larger kills (feeding a pack for around 6 days) (Marquard-Petersen, 1998). • However, arctic wolves will respond if large prey becomes unavailable; then relying more on small mammals for food (Marquard-Petersen, 1998). • In contrast to the Yellowstone wolves, arctic wolves will prey on anything and eat the entire carcass (including fur, bones, skull…) (Mech, 2000). • In this environment, it is the wolves, rather than the scavengers, that are most benefited (or harmed) by ungulate populations and predation.

18. Environmental Influences • Arctic wolf populations and productivity are easily affected by ungulate populations (because of low animal densities) (Marquard-Petersen, 1998; Mech, 2000). • These lower densities can cause much more detrimental and serious affects if populations become even less dense, which, then effects the wolves (Marquard-Petersen, 1998). • Early onset of winter might cause adverse demographic effects in arctic herbivores by shortening their summer replenishment period; which on average is only about 3 months (Ripple, et. al., 2003; Mech, 2000). • If winter sets in during August, ungulates will go into winter without enough energy reserves causing starvation of the ungulates, and thus, in turn, the wolves (Marquard-Petersen, 1998).

19. Discussion/Conclusion • Arctic wolves are influenced by their environment and have been for the time they have existed in such harsh terrain. A decline in arctic prey can severely damage arctic wolf populations (since mammalian densities of all inhabitants are at such low densities already). • Gray wolves of Yellowstone, however, have greatly influenced their environment, rather than being influenced so much by the environment. • The reintroduction of wolves in Yellowstone National Park has had great, advantageous impacts on the ecology of and around the park. The environmental affects on these wolves plays a much less important/determining role on their behaviors and such (thus far), in contrast to the arctic wolves of the north.

21. Bibliography • Author unknown. Arctic Wolves. Wolfsong Alaska Online. http:www.arctic-wolves.com 2005. • Gray, D.R. December 1993. Use of muskox kill sites as temporary rendezvous sites by arctic wolves with pups in early winter. Arctic 46 (4): 324-330. • Marquard-Petersen U. February 1998. Food habits of arctic wolves in Greenland. Journal of Mammalogy 79 (1): 236-244. • Mech, L. David. 2000. Lack of reproduction in muskoxen and arctic hares caused by early winter? Arctic 53 (1): 69-71. Jamestown, ND: Northern Prairie Wildlife Research Center Online. http:www.npwrc.usgs.gov/resource/2000/muskarc/muskarc.htm • Ripple, William J., Beschta, Robert L. 2003. Wolves and the ecology of fear: can predation risk structure ecosystems? Bioscience 54 (8): 755-766. • Wilmers, Christopher C., Getz, Wayne M. September 2004 Simulating the effects of wolf-elk population dynamics on resource flow to scavengers. Ecological Modeling 177 (1-2): 193-208.