in the Canadian
Rockies
Bears and
Habitat
Bears and
Roads
Bears and
Science
Roads, Railways
and Bear
Mortality
Bears and
Roads
Roads and railways are a source of direct and indirect mortality for bears. Direct mortality refers to being struck and killed by a train or vehicle. Many bears also die because of the adverse effects roads and railways can have other than direct collisions. Such deaths are considered indirect mortalities.
Direct
mortality
Obtaining reliable
data on the numbers of bears that are killed by vehicles or trains is
difficult because:
-
not all train- or vehicle-wildlife collisions are reported;
-
reports that are filed are often inconsistent or incomplete; and
-
not all bears die immediately from their injuries; if they disappear into the forest after being struck, it is impossible to confirm their death.
Black bears
The
following statistics demonstrate that vehicles and trains kill significant
numbers of black bears in the Canadian Rockies.
-
a minimum of 30 black bears have been killed on the railway between Field and Revelstoke in British Columbia between 1993-1997. A minimum of 102 black bears have been killed on the Trans-Canada Highway (TCH) in the same area between 1964 and 1997. (Munro 1999)
-
65% of the railway mortalities occurred in May, a time when black bear use of railway and highway right-of-ways is greater than expected. (Munro 1999)
-
in the Bow Valley of Banff National Park, the TCH was the largest single source of mortality for black bears between 1995-1999. (Serrouya 1999)
-
from 1989-1999 vehicle-wildlife collisions was the highest cause of black bear mortality in the Bow Valley. (Serrouya 1999)
Several biologists studying road-related black bear mortality have concluded that the growth along highway and railway right-of-ways of plant species that are attractive to bears (e.g., dandelions), contributes significantly to this mortality. (Munro 1999 and Gibeau and Heuer 1996)
Grizzly bears
The numbers of grizzly bears killed on the highways
or railways in the Canadian Rockies are lower than those for black bears.
For example, between January 1997 – November 1999, 12 black bears were
killed on the Trans-Canada Highway (TCH) in Banff and Yoho National Parks
compared to 0 grizzly bears. (Clevenger 1999)
Reasons for the difference in numbers
include:
-
relative abundance of the species in the Bow Valley and in vicinity of the highway: grizzly bear populations have lower densities than black bear populations. Radio-monitoring of grizzly bears showed that they rarely interact with the TCH. This is particularly the case for adult females, many whose home ranges don’t overlap the TCH and remain 500 to 1500m distant from it.
-
habitat selection: grizzly bears are not as dependent on valley bottom or “montane” habitat as are black bears. Therefore, the number of interactions with the TCH and the number of collisions with vehicles are higher for black bears compared to grizzlies.
(Clevenger 2001)
Since 1980 there have, however, been 7 grizzly bears killed in collisions with vehicles on Highways 93 (in Banff and Jasper National Parks) and 40 (in Kananaskis Country). These highways experience smaller traffic volumes than the TCH and do not affect grizzly bear movement to the same extent as the TCH. Therefore, there are a greater number of grizzly bear interactions with (and crossings of) these highways, and occasionally, roadkills do occur. (Clevenger 2001)
Indirect
mortality
Two major ways that roads and railways
indirectly contribute to bear mortality are by: (1) facilitating the
process of human-habituation and human food-conditioning through the
presence of natural or unnatural bear attractants; and (2) providing
access to hunters, recreationists, settlers, poachers and industry, all of
whom are potentially lethal to bears.
Attractants
The presence of natural and unnatural attractants and the resulting process
of roadside human habituation – especially within the Mountain National
Parks – have been well-documented.
NATURAL
ATTRACTANTS
Grasses, dandelions and berries are examples of
important bear foods that grow well in cleared, open right-of-ways,
relative to adjacent habitats where the forest canopy reduces the amount
of sunlight that can reach the forest floor. These open areas are of
particular importance to and, hence, are especially attractive to bears in
the spring because snow melt occurs earlier in them. (Gibeau
and Herrero 1998 and Gibeau and Heuer 1996)
Gibeau and Herrero also note that
“in places like the Bow River Valley where fire suppression has created a
predominantly closed canopy forest, the edges of road and rails right of
ways have become some of the better berry producing areas during poor
years”, and that these areas attract both black and grizzly bears.” 1
The carcasses of previously killed ungulates on the highway or railway also attract bears to feed in these areas, putting them in danger of being struck and killed themselves or of becoming habituated to humans.
UNNATURAL
ATTRACTANTS
The primary unnatural attractant associated with
roads and railways in the Central Canadian
Rockies is grain that has spilled or leaked from
rail cars or from transport trucks. Researchers with the Eastern Slopes Grizzly Bear
Project documented 6 out of the 7 radio-collared
bears in the Bow River Valley who came into contact with the rail line,
feeding at one time or another on spilled grain. (Gibeau and
Herrero 1998)
National Park warden files also document numerous incidences
of both grizzly and black bears feeding on spilled grain.
ROADSIDE HUMAN HABITUATION
AND HUMAN FOOD-CONDITIONING
Bears who feed on natural
and/or unnatural attractants along roads and railways are highly exposed
to humans. In a place like Banff National Park which has very high numbers
of tourists, road- and rail-side bear-viewing opportunities are especially
dangerous to bears. In 1998 and 1999 alone, there were a minimum of 375
“bear jams” – traffic jams that form when people stop their cars to watch
bears – in Banff. (The Friends of Banff 2000)
This exposure to people “sets the stage” for human habituation, human
food-conditioning and the associated risks to the bear of having to
eventually be killed or otherwise removed from the ecosystem. (Gibeau and Herrero 1998)
Access
McLellan and
Shackleton have documented the potential ways that access into bear
habitat, provided by industrial roads, can result in bear mortalities.
These include:
-
increased vulnerability to hunters
-
increased vulnerability to poachers
-
risk of being killed by industry personnel if bears gain access to industrial camp food or garbage
-
risk of being struck and killed by a vehicle
Of these possible contributors to bear mortality, they found that vulnerability to hunters and poachers due to road access was the most significant in their study area (Flathead River drainage of southeastern British Columbia and adjacent Montana). Between 1979 and 1988, all of the 29 known and suspected adult and sub-adult grizzly deaths were due to legal or illegal hunting, and most bears were shot from roads.
They also noted that industry policy probably helped to lessen some of these and other potential road-related effects on grizzly bears in the Flathead area. For example, Shell Canada had an employee policy that restricted the use of private vehicles and disallowed the possession of firearms in the area. Shell also had a policy of incinerating camp garbage on a daily basis to avoid conflict with bears.
(Source for all: McLellan and
Shackleton 1988)