"What do killer whales, polar bears(Wolves, Grizzlies, Coyotes) and humans have in common?"............ "They are adaptable predators with the ability to select new prey when their favourite food is in low supply".............. "But this change can disrupt entire ecosystems"................The plight of the fading Caribou population in North America is a first hand account of so-called "Prey-Switiching..........As we humans carve up the remaining boreal forests where the historic suite of Caribou, Wolves and Grizzly Bears reside, we create "linear paths" for those Wolves and Grizzlies to migrate deeper into once harder to reach interior forests where Caribou once found enough safe haven to maintain stable populations.............Along those same linear paths of habitat alteration and enhanced by a warming climate come Caribou's sympatric hoofed browsers, deer and Elk.............As the Caribou are somewhat slower and less adapt at eluding Wolves and Griz than Deer and Elk, suddenly the Wolves and Bears determine that a Caribou meal serves them up just as many valuable calories as Elk and Deer, with a significantly reduced energy output ratio of "pursuit to capture".......Crashing down in population size go the Caribou as a result!......A classic prey switching paradigm has accordingly taken place with the once stable Caribou-driven system thrown into disarray by the manipulations of man, simultaneously taken advantage of by the Wolves and the Bears............So should we be killing off Wolves and Griz to save Caribou or like U. of Saskatchewan researcher Gordon Stenhouse puts forth---"We're trying to look at ways to put habitat conditions back that are more favourable to Caribou"............"(As) there’s limited resources to do that, so we want to make sure we go in and put the recovery into the places that will have the greatest impact".................."If we’re going to go in and, say, plant more trees, or revegetate these areas, we know now where the best places to do that are"-------#predator and prey, # prey switching, # trophic cascades, # human alteration of the landscape crashes biodiversity

http://feedproxy.google.com/~r/sciencedaily/plants_animals/~3/5fzno4Wrrn0/151006085230.htm?utm_source=feedburner&utm_medium=email

The predator survives –

 but the ecosystem crashes

The killer whales' main prey used to be newborn whale

 calves. When whale populations fell dramatically due to

 intensive hunting, they began to hunt seal instead. Then

 when the seal population was quickly eradicated, the killer

 whales moved on to sea otters. This reduced the pressure

 on sea urchins, the preferred diet of the sea otters. As a

 result, the sea urchins grazed down the kelp beds that

 have served as nurseries for many different fish species

 and small marine animals
-------------------------------------------------------------------

http://www.thestarphoenix.com/technology/researcher
+plants+seeds+caribou+recovery/11419023/story.html

Researcher plants seeds of 

caribou recovery

BY JONATHAN CHARLTON, THE STARPHOENIX OCTOBER 6, 2015

Gordon Stenhouse, adjunct professor at U of S, has been studying

 how human-made features affect wildlife.

Caribou and grizzly bear populations are low in Western
Canada, and a University of Saskatchewan researcher has
been trying to figure out an effective way to help them.

Gordon Stenhouse has spent three years studying how
 linear features — power lines, seismic lines and roads
 that criss-cross boreal forest — affect the predators and
 prey in Alberta. This week, he’s presenting his findings
 at the Sustainable Forestry Initiative Annual Conference
in California. The StarPhoenix called him up for a biology
 lesson. This interview has been condensed and edited.

First off, what’s the relationship between grizzly bears
and caribou?

You’ve got predators and prey. Caribou are the prey
 species, and grizzly bears and wolves are predators
 that eat caribou.

The challenge for caribou has been that usually
when you modify forest conditions you increase the
 number of other prey species like white-tailed deer
 and moose, and when you increase the number of
 prey species you get a concurrent increase in the
number of predators like wolves and bears.

Mother Griz and cubs

We’re trying to look at ways to put habitat conditions
back that are more favourable to caribou to encourage
their recovery.

How are man-made features making life hard for caribou?

Those linear features make it easier for predators to
move around the landscape.

Think of building trails when you’re in the bush —
it’s much easier for you to walk on a trail than through
 the bush. So by making all these linear features, or
 trails, through the bush, you’ve increased the hunting
 efficiency of predators, and that increase in efficiency
 has had a detrimental effect on caribou ... We found
that specifically more for wolves than grizzly bears.
Grizzly bears will use them, but grizzly bears will hunt
 (caribou) where they find them. Wolves are more a
 species that moves around the landscape looking for
 prey.

Caribou very vulnerable to road cuts encouraging predation

If these trails are bad news for caribou, wouldn’t they

 help predators?

These same access corridors provide access for
 people — and people are the predators for grizzly
 bears. So as you put more linear features and
access to high quality bear habitat, there’s usually
 more poaching events that occur and more bears
 die at the hands of humans.

What’s next?

Caribou in unfragmented forest better able to withstand
predation


Our work has been focused on trying to identify

 which lines can be recovered. It’s all about wise
 use of a conservation dollar — so when we’re
 trying to recover a species there’s limited
 resources to do that, so we want to make
 sure we go in and put the recovery into the
 places that will have the greatest impact ...

If we’re going to go in and, say, plant more

 trees, or revegetate these areas, we know

 now where the best places to do that are.

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https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0CCgQFjABahUKEwi7ycLs6bHIAhXG2B4KHadgDCw&url=http%3A%2F%2Fwww.conservationnw.org%2Fwhat-we-do%2Fpredators-and-prey%2Fcarnivores-predators-and-their-prey&usg=AFQjCNHLPCLtRcgaaToIlyZzUaYJtGHwPw

Predators & prey: Where have all the mule deer gone?

Researchers from Washington State University wanted to understand the reasons for long-term mule deer declines in the intermountain West. Hunters had long been blaming cougars. They were right...sort of. Cougars do kill mule deer. So do wolves, coyotes, bobcats, black bear, and grizzly bears.

But as with all natural systems, nothing’s that simple.

It turns out that the open, mixed forest habitat preferred by mule deer
 has been so dramatically altered in the West through irrigated
agriculture that it’s provided wonderful white-tailed deer habitat.
 White-tails, historically rare in Washington, now outnumber mule
 deer in eastern Washington.  

And as white-tailed deer numbers grow, mule deer decline. It
 appears as though landscape level habitat changes have created
 the white-tailed equivalent of tenements for cockroaches. It also
 appears that cougars have responded in kind.

But while there may be a slight uptick in cougar numbers as a
 result of increased ungulate numbers, cougar numbers have
 not exploded as some people seem to think.  

"It's particularly striking how little difference there is in resident
cougar densities across cougar range in western North America,"
 says Gary Koehler, carnivore biologist, Washington Department
 of Fish and Wildlife. According to Dr. Koehler and his colleagues,
"North American cougars exist in densities of about 1 to 2 adult
 animals per 100 sq. km everywhere they live—almost without fail.
 Female cougars are limited by prey availability, but males are
 limited by the availability of females in their territories, which
 they defend vigorously."

However, the WSU researchers have found that cougar predation
is having a greater impact on mule deer than on white-tails and
 occurs in the summer when white-tails move into higher
elevation mule deer habitat. Mule deer are the "secondary" prey,
 but as they're already in decline, predation is having a greater
effect on them.   

A similar dynamic has happened with mountain caribou in British
 Columbia’s inland rainforest. As the caribou's historically
 extensive old-growth forest habitat has been increasingly
 fragmented, it’s opened more niches for deer, elk, and moose.
 Cougars and wolves follow and opportunistically prey on caribou
 which cannot withstand the “new normal.” For centuries the
mountain caribou old forest and high elevation niche was at
 the heart of their predator avoidance strategy. Predators simply
 weren’t able to get to them enough to make a difference in
 caribou numbers.

Like steelworker jobs in Pittsburgh, jobs for mountain caribou
 have diminished. Now the wolves are literally at the door and
 it’s forced some tough choices for managers and
 conservationists alike until the habitat and historic prey
 species numbers are restored.

Woodland caribou are considered one of the most
 endangered large mammals in North America. Loss
 of old-growth habitat to logging and other development
 have removed old growth and reduced mountain caribou
 herds to just 1,900 animals.

Tree lichens are caribou food

In B.C., logging, road building, and motorized
 recreation are still caribou's chief threats. Caribou
rely in winter on arboreal lichens which develop only
 in old-growth forests. The continuing proliferation of
motorized recreation in winter such as snowmobiling
 stresses mountain caribou during a season when their
 health is weakest. This can force caribou are
 into poorer habitat, where predation rises.