Wolf Awareness is a non-profit Canadian organization dedicated to the conservation of wolves through research and public education about wolf ecology.

Wolf Trophic Cascades and Kinship

Image Peter A. Dettling© – Terra Magica

The decline of large carnivores, including wolves, in North America and around the world has disrupted ecosystems, causing cascading changes that have resulted in a decrease in biodiversity and created artificially inflated ungulate populations as documented in Yellowstone (USA) and Banff (Canada) National Parks.

Where wolf populations have been extirpated or exploited in North America, a cascade effect is observed in which small mammals, fish, insects, birds, amphibians, ungulates, tree species and vegetation all suffer.

As wolves’ decline, ungulate density increases and adversely affects the growth of plants they feed on such as aspen and willow.   With reduced plant biomass,  a reduction of active beaver lodges results which in turn negatively affects songbird abundance and diversity.  Various species of fish, amphibians, insects, birds and mammals are also effected in the trophic cascade that wolves facilitate, as was observed in Yellowstone National Park, after wolves were intentionally wiped out in the 1920’s.

Although wolves were returning naturally to Yellowstone National Park (Wyoming USA) and the surrounding area gradually since their extirpation,  the relocation of wolves from northern BC and Alberta in 1995 and 1996 bolstered what has been referred to as the “greatest ecological restoration project in North American history”.  Researchers  William J. Ripple and Robert L. Beschta have documented changes to the entire Yellowstone ecosystem since wolves began enriching the landscape through a return of their presence

Several indirect effects were documented with the return of wolves to this system, including mesopredator control.  Ripple and Beschta also theorize that the mere presence of wolves on a landscape can affect the behaviour of ungulates, influencing vegetation growth, stream morphology, and overall biodiversity. 

Yellowstone image

Yellowstone image – The Ecology of Fear. National Geographic Magazine©, March 2010

 

In an article that appeared in Bioscience August  2004 Vol. 54 No. 8, Ripple and Beschta coin the question “Wolves and the Ecology of Fear: Can Predation Risk Structure Ecosystems?”  Watch this video to find out how they CAN: “How Wolves Change Rivers“.

The combined role of the wolf pack as an umbrella and keystone species merits added protection for this species, as ecological studies have shown that loss of a keystone species is more apt to cause a series of linked extinction events, resulting in a degraded ecosystem where biological diversity suffers.

Hebblewhite’s 1995 Master’s of Science Thesis titled “Wolf and Elk Predator-Prey Dynamics in Banff National Park” provides evidence and information on how wolves can control ungulate populations.  However, the longest ongoing predator-prey study in history on Isle Royale shows that the relationship between wolves and moose in a simple system are unclear.  Wolves on Isle Royale are now facing an extinction vortex, with numbers so low that inbreeding pressure has become a major  threat to their survival. Learn more about this situation and the Wolves and Moose of Isle Royale

Wolf Awareness and many biologists believe that the conservation of wolves requires maintaining not only viable populations, but also naturally-functioning populations and vibrant natural ecosystems.

Dr. Linda Rutledge’s research in Ontario’s Algonquin Provincial Park indicates that this may even benefit ecosystems more; “fitness is likely to be optimized when evolutionary adaptation is driven by natural rather than artificial (ie human mediated) selection pressures”.

Rutledge and others (2010) state that this “social component may stimulate natural regulation at other trophic levels” and is “evolutionarily important”.

Canada is an important stronghold for wolves, as the species has been decimated or completely extirpated from many areas of its former range. Merely having wolves present is one thing, but preserving the species as part of a functioning ecosystem is a more challenging yet sound management decision.

Social chaos vs. pack stability

A disruption of wolf social structure often leads to increased conflicts with humans and livestock, similar to people reacting to war zone (stealing, cheating, killing).  Disrupting stable wolf family units can even effect the ecological role of the wolf PACK as an apex predator, as documented by Dr. Linda Rutledge and her team in Ontario’s  Algonquin Provinical Park.

Ecological & Ethical Arguments for Wolf Conservation

Rutledge et al (2010) state that this “social component may stimulate natural regulation at other trophic levels” and is “evolutionarily important”.

  • “Lethal control” of wolves breaks social structure, and can lead to: changes in age composition; group size; survival rates of other wolves; pack hunting abilities; territory size and stability; social behaviour; genetic identity and diversity; a higher proportion of young, breeding pairs and litters due to lack of structure which regulates breeding

  • Packs experiencing control and/or hunting had higher mortality rates and thus pack sizes are smaller, home ranges less stable and occupied at variable times, more pups produced

  • packs dominated by young more likely to attack domestic stock (inexperience)

  • may breed earlier and produce more pups in exploited population

  • growing pups have greater energy requirements and must consume more

If an alpha, or leading parent, is killed by human influences, there will more likely be dispersing wolves.  Territories may dissolve.  Learning of young pups or juveniles may be lost (the chance to pass on important information is taken or disrupted).  This can lead to cause an alteration in social behaviour eg. cooperative hunting techniques, reuse of den sites.

PAD575

Image courtesy Peter A. Dettling

Dr.’s  Gordon Haber, Chris Darimont, Paul Paquet, John Theberge and Linda Rutledge are among several wolf biologists whom urge that conservation of wolves and ecosystems requires managing the species at the level of the family unit.  This will require maintaining not only viable populations, but also naturally-functioning populations where “fitness is likely to be optimized when evolutionary adaptation is driven by natural rather than artificial (i.e. human mediated) selection pressures” (Rutledge et al 2010 and personal communication).

The stability of wolf packs may be as important to their role as a keystone species as population size, but this critical factor is not often considered in conservation-management plans for wolves  in  North America. 

  • Wallach et al. (2009) indicated that the longer an area was allowed to recover from lethal control of dingos, the more they returned to using indicators of social stability (scent marking and howling).  These indicators for social communication were lost in areas with high persecution. 

(Note; scent marking through urine, scat, ground raking communicates pack size and composition, individual social and breeding status, and helps define territory).

  • Rutledge et al. (2010) provided evidence through research on Eastern wolves in Agonquin provincial park (following implementation of Buffer Zones 2001) combining ecological and genetic data to show that reducing human-caused wolf mortalities (through hunting and trapping) restored the natural structure of wolf packs (kin-based families) without a marked increase in population (natural mortality replaced human caused deaths).

  • Groups stopped recruiting ‘foreigners” when not exploited and Rutledge and team saw a reduction in unrelated adopted animals in 17 packs (80% pre-ban unrelated vs. 6% post-ban unrelated) (Rutledge et al 2010).

  • provides evidence that even protected areas can act as sinks if not large enough, and with non-stable social units less able to adapt to evolutionary changes and function in ecological role (fitness benefits accompany social unit, experience and learning are important).