Presentation on theme: "Carrion: It’s what’s for dinner"— Presentation transcript:
1 Carrion: It’s what’s for dinner Wolves As Keystones
2 Canis lupis“Who would not give a year of his life to see a wild wolf or a whole pack of wolves trailing down an elk or deer?” Edmund Heller 1925
3 IntroductionWolves viewed as competitors, threats to safety, symbols of evilEarly 20th Century: gray wolves eradicated from 42% of range in North AmericaHunted to local extinction in Yellowstone National Park by 1926Reintroduced in 1995By 2006, the wolf population in the park was at least 136 wolves in 13 packsToday U.S. Fish and Wildlife reports 653 wolves in 130 verified packs
4 Timeline History of Gray Wolves in Yellowstone Park 1872 YNP is established by an act of the U.S. CongressWolves in and around YNP are killed for pelts, to protect humans and livestock, and for sport.1918 The newly formed National Park Service takes control of YNP and continues to hunt wolves.1926 Wolves are exterminated from YNP1973 The U.S. govt. lists the gray wolf as an endangered species.Thirty-one wolves are reintroduced into YNPwolves, in 130 verified packs, and breeding pairs.
6 Wolves as KeystonesImportant to restore the gray wolf to Yellowstone because it is a keystone species.A keystone in an arch's crown secures the other stones in place.Keystone species play the same role in many ecological communities by maintaining the structure and integrity of the community.
8 Keystone SpeciesWolves have facilitated the recovery of beavers in Yellowstone.In the 1890s, human trappers decimated beaver populations
9 Keystone Species After wolves were removed, Elk populations grew Competition for willow increasedSuppressed beaver population recovery
10 Keystone Species After wolves restored to YNP: Predation, hunting and drought have reduced elk populations.
11 Keystone Species Elk have thus changed behavior Move to coniferous forests for protection when they detect wolvesNo longer near streams to compete with beavers
12 Keystone SpeciesFewer elk in the willow habitat have resulted in increased beaver colonies on the northern range of YNP from one in to nine in 2003
13 Winter on the Northern Range In YNP, daytime winter temperatures range from -40oC to -5oC and snow can exceed 7 m at high elevations (NPS 2006)In the autumn, elk in northern YNP migrate from high elevation to a milder habitat
14 Winter on the Northern Range Winter isn’t easy for the elkDifficult to dig and move in deep snowIn severe winters, elk regularly starve to death
15 Winter on the Northern Range Carcasses-particularly those of elk- are an important food source for Yellowstone carnivoresCarnivores, like bears and eagles, scavenge carrion during winter and early spring.Ravens have learned to track wolves to kill sites
16 Winter on the Northern Range Carrion availability depended on winter severity w/out wolvesDeep snow and low temperatures, elk carrion was plentifulMild winters, carrion was sparse.During the rest of the year, carrion is negligible.
17 Winter on the Northern Range Even with wolves, snow plays a big role.Wolves leave more carrion for scavengers when snow is deepElk are easier to kill and wolf packs eat a smaller proportion of each kill.
18 Winter on the Northern Range Presence of wolves = carrion available year- roundCarrion is a more predictable resource for scavengers
19 Winter on the Northern Range Change in the timing and predictability of carrion benefits:Small scavengers (e.g. foxes), which have small stores of body fat and need to feed frequentlyLarge scavengers (e.g. bears), which require a high energy food source before hibernation
20 Winter on the Northern Range No other carnivores in Yellowstone fill the ecological role of the gray wolf.Coyotes occasionally kill elk, but they feed primarily on small mammals and carrionBears prey on elk only during some parts of the year.Cougars are a major year-round predator of elk, but they defend their kills from scavengers more fiercely than wolves and hide uneaten prey
21 Winter on the Northern Range Human huntersProvide large amounts of carrion in the form of gut piles on park borders during hunting season.Bears in hibernation cannot take use thisScavenging coyotes have difficulty finding the gut piles and are often shot by human hunters
22 QUESTIONAs global temps increase, what will happen to the snow depth and snow season?How will this affect the elk population?How will this affect the availability of carrion?Can wolves act as a “buffer” against climate change by delaying the detrimental effects of declining snow cover such that other species have more time to adapt to their changing environment?