Grad Publication: Carolyn Shores takes a very close look at what wolves eat

As a BioGrad, Carolyn Shores worked in Sam Wasser's lab, AKA the UW Center for Conservation Biology, finding new and better ways to look at wolf poop! Carolyn's work, co-authored by Samrat Mondol (former Post-doc, now at the Wildlife Institute of India) and Sam Wasser, recently appeared in Conservation Genetics Resources. Carolyn is continuing her research on the effects of predators in the Predator Ecology Lab in the UW School of Environmental and Forest Sciences. Here she describes what the recent study was all about.

Adult gray wolf traveling through snow as seen
through sight scope. Photo: Carolyn Shores
Large carnivores have the unlucky honor of being some of the most well-recognized but controversial wildlife in the world. This is partly due to their cultural significance in myths and legends, but also because their diet often puts them into direct conflict with humans. Apex carnivores depend on large herbivores such as deer, elk and moose that are hunted by humans, and carnivores may also attack livestock if wild prey is scarce.

Given how the diet of large carnivores defines their interaction with humans, it is essential for their conservation and management that we understand their dietary ecology. In a paper recently published in Conservation Genetics Resources with my co-authors Drs. Samrat Mondol and Samuel Wasser, we developed a molecular method to study the diet of wild wolves (Canis lupus) in northeastern Alberta, Canada. This is the first time genetic methods have been used to study the diet of wild wolves.

Pack of wild gray wolves (Canis lupus). Photo: Shane White
Our study site in northeastern Alberta is also home to the Alberta oil sands, a site of extensive oil development and the largest supplier of foreign oil to the United States. Wolves in northeastern Alberta are partially blamed in the recent decline of woodland caribou (Rangifer tarandus), a threatened species in Canada, although there is extensive debate over the role wolf predation and oil extraction play in the caribou’s decline. Our aims for this study were to develop a molecular dietary analysis method, compare it to traditional dietary analysis methods, and determine the proportional amount of caribou in wolves’ diets in the Alberta oil sands.

Wolf scat samples were collected by the hard-
working Conservation Canine Crew during
the winter in northeaster Alberta. Here,
Orienteer Nick Bromen collects a scat sample
while doghandler Canyon rewards CK9 Chester
by playing fetch! Photo: Jennifer Hartman
The traditional way to study carnivore diet is a laborious (and smelly) process that involves picking through scats and identifying remains of prey, such as hair or bone. This method is affordable, but is also prone to observer bias and misidentification. After using identifying prey hair in the wolf scat, we developed species-specific mitochondrial DNA primers for the prey of wolves in our study area. This included caribou, moose (Alces alces), deer (Odocoileus sp.), beaver (Castor canadensis) and snowshoe hare (Lepus americanus). Since the prey DNA is degraded in the wolf scat after going through the wolves’ digestive system, we designed our primers to amplify short <200 base pair sequences. In addition to cross-species standardization tests to ensure primer specificity, we sequenced a subset of the PCR products to ensure we were amplifying target prey DNA.
We found that DNA methods detected significantly (p<0.01) more prey than morphological methods overall and for every prey species except deer. The difference in detection rates with DNA was greatest (8.75 times higher) for moose. This significant difference in prey composition between the two methods could lead to very different management of wolf populations. Two of our prey species, deer and caribou, had strikingly similar hair cell patterns which made them difficult to differentiate with morphological analysis if color had been leached from the hair. With DNA analysis, the issue of differentiating similar taxa was eliminated. Deer was the dominant prey under both methods, making up 43% of the diet using DNA methods. Under DNA analysis, moose made up 26% of the wolf diet, while caribou was present in only 16.2% of wolf scats. Snowshoe hare and beaver both made up less than 10% of prey species.

Our results contribute to previous research that suggests a significant shift in the prey of wolves in the boreal forest of the Canadian oil sands. In the mid-1990’s, wolves ate primarily moose in northern Alberta, and deer made up only a tenth of their diet. However, in the past decade, deer have become the primary prey of wolves, and aerial ungulate surveys confirm a 17.5 fold increase in the deer population. This could be due to a combination of the destruction of older boreal forest by industry and climate change, which has allowed deer to expand north outside of their normal range. The increase in deer may present already threatened caribou with a novel competitor, not to mention the influx of disease vectors that could jump to caribou.

Woodland caribou in northeaster Alberta on a seismic line cut through the
boreal forest to test for the presence of oil. Photo: Jennifer Hartman 
Our research presents an objective, easily reproducible method for studying the diet of wild carnivores. DNA analysis showed a marked increase in the detection of prey. We hope our development of prey-specific primers designed for diet analysis will make it easier for other wildlife biologists and ecologists to implement this method when studying wolves. Since the diet of wolves regularly leads them into conflict with humans, it is key to wolf conservation that we have an accurate way to assess their diet to better understand their place in the ecosystem.

The full citation for the article is: Shores, C; S Mondol; S Wasser (2015). Comparison of DNA and hair-based approaches to dietary analysis of free-ranging wolves (Canis lupus). Conservation Genetics Resources. 7(4): 871-878. 


The direct link to the article is found here (paywall). You can request an electronic reprint from Carolyn through her ResearchGate profile.
If you enjoyed reading about what we can learn from animal poop, you might also want to check out Jen Day's post on hunting jaguar scat.

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