Seems like strategically placed wildlife overpasses and culverts can get 20% of the Black and Grizzly Bears in Banff National Park in Canada to "take a stroll to get on through to the other side".............Montana State biologist Mike Sawaya who did the research on this phenomena feels that if more than 10 per cent of a population can cross the highway then there is sufficient connectivity to maintain a healthy ecosystem for bears(solid flow of genes passing through successive generations of offspring)..................

Study finds bears embrace

 wildlife crossings in Banff

Data shows structures help keep

 habitat from being fractured by roads

BY CATHY ELLIS, CALGARY HERALD 

STORY 

A news study shows about 20 per cent of grizzly 

and black bear populations in Banff are making 

use of wildlife crossings structures on the

 Trans-Canada Highway.

BANFF — A significant portion of Banff’s grizzly bear
 population is using wildlife crossings to safely get
 across the busy Trans-Canada Highway and access
important habitat, according to a new landmark study.

The study identified 15 individual grizzly bears and
17 individual black bears that used the highway
crossings over a three-year period — close to 20
 per cent of the estimated population.

Researchers say it’s encouraging that a highway
 punctuated with 25 different crossings did not
fragment the habitat in a way that prevented
 bears from seeking food, shelter and dispersal
 areas on either side of the highway.

Mike Sawaya, co-author of the study, said
 movement of more than 10 per cent of a
 population across the highway signals there
 is sufficient connectivity to maintain a healthy
 ecosystem for bears.

“This is meaningful from a population perspective
. This is a substantial portion of the population that
 is using the crossing structures,” said Sawaya,
 a 2012 graduate of Montana State University.

“One of the unique results, to me, is we were able
 to discover that these crossings are really allowing
 access, especially for female grizzlies, to areas
 like important low-elevation Bow River habitat.”

One of the world’s most developed and
 well-known wildlife crossing systems is found in
 Banff National Park, where more than three million
visitors arrive every year and an average of 18,000
 cars a day travel the highway.

Two overpasses and 23 underpasses were built
 in the 1980s and 1990s to reduce the number
of animals killed by vehicles and to maintain
wildlife movement across the four-lane highway.

Wide-ranging carnivores such as grizzlies
 are susceptible to fragmentation because
 of roads due to their low densities and
 reproduction rates, as well as large home ranges.

Roads are the most common form of man-made
 disruption to wildlife habitat and, in the case of
 the Trans-Canada Highway, pose a direct threa
t to a threatened Alberta grizzly bear population.

This latest work looked into whether wildlife
 crossings provide demographic connectivity
 for grizzly and black bears in Banff National
Park. It was recently published in Conservation
 Biology, a peer-reviewed scientific journal.
The study was part of Sawaya’s doctoral work,
 for which he teamed up with Tony Clevenger,
 a local wildlife biologist and a senior research
scientist at MSU’s Western Transportation
Institute, and Steven Kalinowski, an associate
 professor of ecology at MSU who was Sawaya’s
 adviser.

In 2006, researchers began setting out
 non-invasive hair snags — strands of barbed
 wire strung across the crossings that collect
 samples from bears lured to a scent, and rub
 trees with wire attached.

Over the next three years, hair samples were
 collected from 20 crossings, 420 hair traps
 and 497 rub trees. They ended up with more
 than 10,000 genetic samples.

Their research found that 15 grizzlies (seven
 female and eight male) and 17 black bears
 (eight female and nine male) used the crossings
 to access habitat on both sides of the highway.
The researchers believe those numbers are
actually conservative, noting it’s probable there
 were bears that managed to evade the hair
 collection traps at the crossings.

Peak use of Banff’s wildlife crossings for both
bear species occurred in July, when high rate
s of searching for food coincide with mating season.

The results concluded grizzly bears used
 overpasses more often than they travelled
 through underpasses, such as culverts or
 under bridges. In fact, they preferred
overpasses 90 per cent of the time.

Grizzly bear crossings were highly concentrated
 at two overpasses and one larger open-span
 underpass west of the Banff townsite, whereas
black bear use was evenly distributed and more
concentrated to the east.

“You can put in underpasses cheaper, but this
 data means you can justify putting in overpasses,”
 said Sawaya. “If you want female movement,
 you’ve got to put in overpasses.”

In a news release, Clevenger said the landmark
study is the first time extensive genetic sampling
 has been done to address unanswered questions
 about the use of highway crossings by bears.

“We knew that bears used the crossings, we just
 didn’t know how many, what percentage of each
 species’ population uses them, whether there is
 a preference by males or females to use crossings
, and if there was a gender or species preference
 for overpasses or underpasses,” he said.

Another paper from the study due this fall will break
 down what ecologists call gene flow between bear
populations in the Banff ecosystem. That data should
help gauge how well the crossing structures perform
 in allowing different bears to find mates in an
environment bisected by a major highway.

“By collecting the genetic data on each bear
using the crossings, we have a much more powerfu
 tool for gauging the effectiveness of the crossing
 structures to provide connectivity within the ecosystem,”
said Clevenger.

Clevenger, who has been tracking the number of
 bear crossings on the Trans-Canada Highway
structures for more than a decade as part of the
Banff Wildlife Crossings Project, said the study’s
 findings are a breakthrough.

“This is confirmation of what our previous
 investigations have suggested but couldn’t
 confirm,” Clevenger said. “We were pretty
 certain that the numbers of bears using the
 crossings had steadily increased. Now we know.”

In addition to bears, Banff’s crossings have
seen documented use by deer, elk and moose,
 as well as wolves, wolverines, lynx, cougars
 and a host of other animals.