Transcript Ecological Influences of Canis lupus arctos and Canis

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
Purpose
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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?
Introduction
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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.
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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).
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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).
Benefits due to the Re-introduction
of
Wolves
 The re-introduced gray wolves has proven
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(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).
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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.
Yellowstone Conclusions
Had not wolves been absent from
YNP for decades, the observed data
provided insight into the importance
of such a key predator. Reintroduction 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 unbrowsed 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.
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Artic Wolves: Introduction
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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).
Adaptations and Behavior
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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 (MarquardPetersen, 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).
Habitat
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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).
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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).
Arctic Wolves’ Hunting Behavior
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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.
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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.
Environmental Influences
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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).
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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.
Bibliography
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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): 755766.
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.