1. I wish those two dogs would stop barking
2. That is not even their territory (judging from the distance of their barks); I wish they would stop barking the whole flaming night
Open Access
Original research article
Grizzly bear diet shifting on reclaimed mines
- Under a Creative Commons license
Abstract
Industrial
developments and reclamation change habitat, possibly altering large
carnivore food base. We monitored the diet of a low-density population
of grizzly bears occupying a landscape with open-pit coal mines in
Canada. During 2009–2010 we instrumented 10 bears with GPS radiocollars
and compared their feeding on reclaimed coal mines and neighboring Rocky
Mountains and their foothills. In addition, we compared our data with
historical bear diet for the same population collected in 2001–2003,
before extensive mine reclamation occurred. Diet on mines (n=331
scats) was dominated by non-native forbs and graminoids, while diets in
the Foothills and Mountains consisted primarily of ungulates and Hedysarum spp. roots respectively, showing diet shifting with availability. Field visitation of feeding sites (n=234
GPS relocation clusters) also showed that ungulates were the main diet
component in the Foothills, whereas on reclaimed mines bears were least
carnivorous. These differences illustrate a shift to feeding on
non-native forbs while comparisons with historical diet reveal emergence
of elk as an important bear food. Food resources on reclaimed mines
attract bears from wilderness areas and bears may be more adaptable to
landscape change than previously thought. The grizzly bear’s ready use
of mines cautions the universal view of this species as umbrella
indicative of biodiversity.
Keywords
- Brown bear;
- Environmental impact;
- GPS clusters;
- Mine reclamation;
- Scat analysis;
- Ursus arctos
1. Introduction
Occurrence
and persistence of many wildlife populations are largely determined by
the availability and distribution of food and habitat resources (Manly et al., 2002 and Stephens et al., 2007). To avoid starvation, animals must be able to track information on food distribution (Dall and Johnstone, 2002 and Dall et al., 2005).
Locating adequate food resources can be challenging when original
habitat is altered by human-caused landscape change. As human
populations rise, so does the consumptive footprint (Houghton, 1994) even at lowered population growth rates (Ehrlich et al., 1999), leading to habitat change through conversion of natural areas to agriculturally and industrially modified landscapes (DeFries et al., 2004 and Foley et al., 2005).
Open-pit
(surface) mining provides a clear-cut example of habitat modification
due to resource exploitation by humans. Following closure of open-pit
mines, often a principal goal of mine reclamation is provision of
habitat for wildlife (Erickson, 1995 and Kennedy, 2002). In this context, reclaimed mines are accepted as dynamic landscapes colonized by species from nearby undisturbed areas (Hobbs and Harris, 2001 and Choi et al., 2008). Colonization of mines by focal species is commonly used as a measure of reclamation success (Scott et al., 2001 and Cristescu et al., 2012a).
Terrestrial focal species chosen to monitor reclamation effectiveness
are typically plants, invertebrates, amphibians, reptiles and birds (McCoy and Mushinsky, 2002 and Cristescu et al., 2012a). Small mammals (Larkin et al., 2008) and ungulates (e.g., Jansen et al., 2009) are less commonly selected, although in natural systems foraging by ungulates can slow ecological succession (Mysterud, 2006) and substantially alter ecological processes (Frank, 1998).
On reclaimed mines, ungulate foraging also slows or even prevents
ecological succession to a more natural vegetation community, especially
when combined with harsh abiotic conditions characteristic of mined
landscapes (Smyth, 1997, Paschke et al., 2003 and del Moral et al., 2007) and low dispersal and competitive abilities of native plants compared to non-natives (Holl, 2002 and Zipper et al., 2011).
If
ungulates are killed by large carnivores on reclaimed mines, then
carnivores could facilitate ecological succession thus helping
conversion of mines back to a more natural ecosystem state. Monitoring
carnivores on and near mines could therefore provide valuable
information for gauging reclamation success. However, data on large
carnivore diet on reclaimed mines are absent from the peer-reviewed
literature.
Canada is no
exception to the global conservation crisis, with habitat loss being the
single most important threat to species persistence (Venter et al., 2006).
Extractive industries such as open-pit mining are forecasted to expand
substantially in response to high demand from rapidly growing world
economies (MiHR, 2010).
To provide insights into large carnivore adaptation to industrially
exploited and subsequently reclaimed landscapes, the Foothills Research
Institute designed a monitoring program on grizzly bears in west-central
Alberta, Canada, working in collaboration with universities and
industry in Canada. Low grizzly bear population estimates found along
with ongoing human activities led to grizzly bear designation as
threatened in Alberta in 2010 (Festa-Bianchet, 2010).
The grizzly bear’s distribution is driven primarily by foods and human persecution (Mattson and Merrill, 2002, Laliberte and Ripple, 2004 and Proctor et al., 2012). The carnivorous digestive system and relatively poor ability to digest plant matter (Schwab et al., 2009 and Schwab et al., 2011)
suggest that although bears can consume vegetation extensively, meat is
an important component in their diet. In Yellowstone National Park,
grizzly bears have greater impacts on elk calf survival than wolves and
other predators (Barber-Meyer et al., 2008), and substantial predatory impact by grizzly bears has been documented in Alaska (Boertje et al., 1988) and Yukon (Larsen et al., 1989). In addition, grizzly bears frequently scavenge on wolf, cougar and human hunter-killed ungulates.
Our
objective was to investigate bear diet in relation to availability of
foods on a landscape with natural habitats and open-pit mining
industrial disturbance. The research was carried out on and adjacent to
two coal surface mines of west-central Alberta, where Munro et al. (2006)
found that grizzly bears consumed a variety of food items. However that
study occurred during 2001–2003, when mine reclamation had lower
extent; did not explicitly address bear diet on reclaimed mines or
differences in food consumption on vs. outside mines; and did not
provide a detailed assessment of food availability on mines, in the
mountains and foothills. Nonetheless, the Munro et al. (2006)
study offered a unique opportunity to investigate differences in diet
for the same bear population, which we studied during 2009–2010, once
the mines had been largely reclaimed. Given the threatened status of
grizzly bears in Alberta and continuing industrial development,
documenting how bears have adapted to modification in the availability
of foods associated with mine reclamation is informative for the
conservation of this species.
