The Impact of Wolf Predation on Western Canada Boreal Woodland Caribou Populations: A Critical Review of the Evidence
Gilbert PROULX
Alpha Wildlife Research & Management Ltd., 229 Lilac Terrace, Sherwood Park, Alberta, T8H 1W3, Canada. Email: gproulx@alphawildlife.ca
Dr. Gilbert Proulx, PhD, CWB
Director of Science
Alpha Wildlife Research & Management Ltd.
VISIT MY NEW BLOG= WILDLIFE CONSERVATION– LET’S WISH FOR THE BEST IN 2016!
Editor-in-Chief
Canadian Wildlife Biology & Management
Cell: 780-953-6931
Fax: 780-417-0255
Was the impact
of wolves on boreal
caribou populations
oversold?
In the past, it has been argued that changes in the forest age structure may compromise the ability of caribou to avoid other prey species and their predators because young forests support higher densities of alternate ungulate species such as moose (Rempel et al. 1997; Wiwchar and Mallory 2012) that in turn support higher predator densities and wolf size, leading to increased predation on caribou (Bergerud and Elliot 1986; Seip 1992). However, data show that caribou are not an important food item of wolves. Would a 15%- predation rate threaten a caribou population? It would likely threaten a population that has dwindled to a few animals, or when the females fail to reproduce. However, the majority of boreal caribou populations encompass hundreds of animals (Table 1) and ≥85% of the adult females usually are pregnant (Stuart-Smith et al. 1997; Rettie and Messier 1998; McLoughlin et al. 2003).
In the Little Smoky range where the population is relatively small (≤80 animals; Callaghan et al. 2011), it is unlikely that wolf predation compromised the caribou population. In fact, aerial surveys indicated that the population increased from 43 in the late 1990s to 74 in 2003 in the absence of any wolf control program (ASRD/ACA 2010). Obviously, predation did not impede the population from increasing in numbers, even though it was a slow growth. After killing nearly 1,000 wolves during a 7-year period, Hervieux et al. (2014) failed to generate growth in the Little Smoky caribou population. Clearly, something other than predation interfered with the growth of the population.
In the Little Smoky range where the population is relatively small (≤80 animals; Callaghan et al. 2011), it is unlikely that wolf predation compromised the caribou population. In fact, aerial surveys indicated that the population increased from 43 in the late 1990s to 74 in 2003 in the absence of any wolf control program (ASRD/ACA 2010). Obviously, predation did not impede the population from increasing in numbers, even though it was a slow growth. After killing nearly 1,000 wolves during a 7-year period, Hervieux et al. (2014) failed to generate growth in the Little Smoky caribou population. Clearly, something other than predation interfered with the growth of the population.
While methodological limitations and non-replicated treatments likely impacted on the ability of researchers to properly evaluate the mechanism of caribou population declines (Hayes et al. 2003; Brown et al. 2007; Proulx et al. 2017), I believe that wolves have been wrongly singled out as the proximate factor for the decline of boreal caribou populations. There is no doubt that wolves are opportunistic predators and they will kill caribou or any other prey they may encounter while hunting moose or deer. However, past researchers have not demonstrated that wolves caused the decline of boreal caribou populations. In the Little Smoky range, no studies have shown that wolves were limiting the caribou population. There were no recent studies on food habits, rates of predation or wolf densities (M. Besko, Director, Wildlife Management, Alberta, 8 February 2017, personal communication). As is the case for many other populations, conjectures about wolves impacting on caribou populations have been qualitative, anecdotal, and prejudicial (Proulx et al. 2017). Hebblewhite et al. (2006) also recognized that future research was needed on some of the assumptions underlying predator-prey models including multi-prey wolf numeric responses, wolf kill-rates of caribou, and caribou mortality by other predators. al. 1996; Hayes et al. 2003; Boutin 2017), any reduction of predator or competitor populations should also result in an increase of boreal caribou populations.
Controlling bears (Ursus spp.) would likely reduce calf mortality (Rettie and Messier 1998; Latham et al. 2011; Pinard et al. 2012) and therefore contribute to population growth. Decreasing densities of moose, and thus provoking a decline in the density of predators, may also result in an increase in the survival of caribou (Serrouya et al. 2017). Eliminating beavers (Castor canadensis) would likely decrease incidental caribou kills by wolves in spring and summer (Latham et al. 2013). Destroying predators and their prey to increase boreal caribou populations is a simplistic and relatively inexpensive approach employed by some managers hoping for a short-term victory for their single- species management program. The notion of killing predators and prey, and destroy an entire wildlife community, to save a species at risk is not coherent with contemporary ecosystem and biodiversity conservation principles (Proulx and Brook 2017).
Thick, unbroken forest habitat, the key, to Caribou thriving
I believe that wolf killing programs were oversold, and such programs are misleading the public and the scientific community by shrouding the real cause of the decline of boreal caribou populations – habitat loss and disconnection. On the subject of limiting factors on caribou populations, Leopold and Darling (1953) stated: “We cannot agree with the viewpoint…that the game program must be directed towards controlling the action of predators, both men and wolves, rather than improving the range. To ignore range limitations for caribou is to ignore the crux of the problem”. Hindsight indicates that Leopold and Darling were right. Habitat loss and disconnection is the ultimate factor impacting on the survival of boreal caribou populations (Donovan et al. 2017). One may kill all the wolves and alternate prey of an ecosystem, and farm caribou in an enclosure in order to save the species (Alberta Government 2016) but without functional and accessible habitat, caribou are unlikely to persist over the long term.
Thick, unbroken forest habitat, the key, to Caribou thriving
I believe that wolf killing programs were oversold, and such programs are misleading the public and the scientific community by shrouding the real cause of the decline of boreal caribou populations – habitat loss and disconnection. On the subject of limiting factors on caribou populations, Leopold and Darling (1953) stated: “We cannot agree with the viewpoint…that the game program must be directed towards controlling the action of predators, both men and wolves, rather than improving the range. To ignore range limitations for caribou is to ignore the crux of the problem”. Hindsight indicates that Leopold and Darling were right. Habitat loss and disconnection is the ultimate factor impacting on the survival of boreal caribou populations (Donovan et al. 2017). One may kill all the wolves and alternate prey of an ecosystem, and farm caribou in an enclosure in order to save the species (Alberta Government 2016) but without functional and accessible habitat, caribou are unlikely to persist over the long term.
Boreal woodland caribou are now faced with climate change involving the drying of peatlands, and the “icing” of winter ranges where interludes of mild weather result in the formation of crusted snow and basal ice that restricts access to forage (Tyler 2010; Proulx 2015a). Where muskegs have been disconnected, caribou must venture on roads and through upland forests where they may be killed by predators or become victims of accidents (Proulx, personal observations). Human activities and infrastructures are the cause here, not the wolves.
Caribou are capable of adapting and coexisting in areas affected by human development provided that adequate habitat exists (Weclaw and Hudson 2004; O’Brien et al. 2006). By maintaining and interconnecting black spruce- tamarack muskegs and adjacent lichen-rich pine (Pinus spp.) stands, caribou can find food and security from adverse weather, predation, competition from other ungulates and accidents.
The plea from wildlife professionals to conserve boreal woodland caribou habitat is based on scientific evidence, not on speculations or prejudices (Proulx et al. 2017). Developing a caribou recovery program based on habitat conservation is addressing the ultimate factor responsible for the decline of boreal caribou populations, and will solve issues associated with proximal mortality factors. Habitat conservation has been recommended by a plethora of wildlife biologists. Nearly 30 years ago, Edmonds (1988) recommended habitat conservation to ensure the future of the Little Smoky caribou population. Her recommendation was echoed by Cumming (1992), Weclaw and Hudson (2004), O’Brien et al. (2006), Proulx (2015a), Proulx and Powell (2016), and many others. We should no longer postpone the implementation of habitat conservation programs with the excuse that some caribou populations are presumably unsustainable, or their current range is highly fragmented and it may take another 40 years to bring back large intact forests. Caribou will persist if, and only if, we act now by conserving and further improving their habitats, and eliminating or at least minimizing habitat loss and alteration caused by industry (Proulx 2015b).
In conclusion, I believe that wolf predation on boreal woodland caribou was oversold by government agencies and some academics. Instead of scapegoating wolves for the demise of boreal woodland caribou populations, wildlife managers should implement a comprehensive caribou recovery program aimed at conserving, restoring, expanding and connecting critical habitats across landscapes (Proulx et al. 2017).
Posts
No comments:
Post a Comment