Talk like a conservation ecologist

Game species — animals hunted by humans

Mortality — the number of deaths in a population

Snow water equivalent — the amount of water produced when a given volume of snow is melted (i.e., a measure of the density of the volume of snow)

Statistical modelling — applying statistical analyses to a dataset to find patterns and relationships among variables

Sustainable harvesting — hunting animals to manage their population

Winter severity index — a metric to quantify the harshness of a winter season

From grizzly bears roaming the Rocky Mountains to herds of bison grazing the Prairies, Canada is home to an incredible diversity of wildlife. But despite their ‘wild’ nature, many of these species are closely managed by humans. “Game species (e.g., deer, elk, moose) are managed for hunters,” explains Professor Mark Boyce, a conservation ecologist at the University of Alberta. “Other species are managed to reduce risks to livestock (e.g., wolves) or crops (e.g., boar), or for their own protection (e.g., grizzly bears in Alberta).”

However, knowing the best method for managing wildlife is not straightforward. “Often, wildlife management decisions are made with insufficient evidence because it’s expensive to accurately monitor populations,” says Mark. “Or political interference can mean decisions are based on public opinion rather than advice from scientists.” For example, people in urban areas generally favour wolf protection, while people in wolf-inhabited areas generally favour wolf hunting to protect their livestock and pets.

Population management: follow the science

Wildlife populations change size according to their rates of reproduction and mortality, which are influenced by numerous factors such as availability of food, predator and prey interactions, weather conditions, disease and hunting. Complex mathematical equations can incorporate these variables into models that predict how populations will change over time. In the Boyce Lab, Mark and his team develop such models to investigate how wildlife populations will respond to different management strategies.

There are many forms of wildlife management, including direct management (killing or protecting animals), or indirect management (managing habitats, e.g., planting native species or removing vegetation through controlled burning). But before making management decisions, it is important to have a robust understanding of their likely effects. History is littered with stories of when wildlife management went wrong. A famous example is the introduction of cane toads to Australia – they were introduced to control crop pests but soon became invasive and had catastrophic effects on native species. Wildlife management strategies can have unanticipated outcomes, which is why Mark is a strong advocate for science-based management built on real-world data and mathematical models.

Surprising population changes

Population ecology models have revealed counterintuitive phenomena which mathematically explain why some management strategies fail. The Hydra Effect is named after the many-headed monster in Greek mythology – each time a head was cut off, two more grew in its place. “For certain populations, we find that low to moderate levels of hunting can actually result in increased abundance of the species,” says Mark.

The Hydra Effect occurs because surviving individuals have less competition for resources, leading to a ‘baby boom’ and increased population. This has significant implications for wildlife management. “For game species, the increased abundance caused by low to moderate hunting is good news for hunters,” says Mark. “On the other hand, for species in conflict with humans, hunting can be counterproductive.” For example, hunting wild boar in an attempt to stop them damaging crops actually leads to increased boar populations and greater crop damage.

Another counterintuitive effect is the Volterra Principle. “When both predator and prey species have an increase in mortality, the prey species then increases while the predator species decreases,” explains Mark. “This has implications for how we manage predator and prey populations as it calls into question the use of predator control to manage game species.” For instance, a wildlife manager may want to kill wolves to increase the deer population for hunters, but according to the Volterra Principle, both predator and prey should be targeted.

Winter is coming

Canada is a country of seasonal extremes, where winters can be very harsh. This has a significant impact on white-tailed deer populations, a species that provides over $35 million to the Albertan economy through the hunting industry. Kathryn Vaughan, a master’s student in the Boyce Lab, developed a winter severity index to help manage deer populations. “A winter severity index is a tool to measure the harshness of a winter season, based on factors like temperature and snow conditions,” she explains. “Colder weather means deer use more energy to stay warm, and deeper snow makes it harder for them to move around to find food and shelter.”

Wildlife managers need to understand the effects of winter on deer populations to decide how to manage them, but traditional winter severity indices are overly simplified. “To make a more accurate and flexible index, I used 20 years’ worth of satellite data of temperature and snow water equivalent,” says Kathryn. “Snow water equivalent is a measure of how dense the snow is, which gives us a better understanding of the amount of energy deer use to move through it.”

Kathryn used her new winter severity index to explore whether sustainable harvesting could help with white-tailed deer management to prevent population crashes after severe winters. “Interestingly, I found that areas with more hunting tended to have more stable and even slightly higher average abundance,” says Kathryn. “This suggests that consistent hunting may help prevent overpopulation, by decreasing competition for food and shelter when they are limited during tough winters.”

Preventing sheep disease

Preventing the spread of diseases between domestic and wild animal populations is a key part of wildlife management. Gillian Power, a PhD student in the Boyce Lab, is exploring disease transmission to wild bighorn sheep, a species famous for dramatic head-butting dominance displays. “Domestic sheep and goats carry a bacterium that can cause pneumonia in bighorn sheep,” Gillian explains. If wild bighorn sheep come into contact with domestic animals, pneumonia outbreaks can devastate their populations, which take generations to recover.

It is essential to understand how these outbreaks occur to effectively manage and protect wild populations. “We are placing radio collars on bighorn sheep, which allow us to track and analyse their movements,” explains Gillian. “I will use statistical modelling and machine learning simulations to understand the patterns within their movements.” She will supplement these data with real-life observations, spending time in the field to document the behaviours and interactions of wild bighorn sheep.

Gillian hopes to identify priority locations for surveillance, so wildlife managers can prevent contact between wild bighorn sheep and domestic animals. “Due to the severity of this disease, our best chance for maintaining healthy bighorn sheep populations is by preventing it from entering wild populations in the first place,” says Gillian. “I hope this project brings together people with passions for wildlife and domestic animals – by working together, we can make a bigger impact.”

As Mark, Kathryn and Gillian’s work highlights, conservation ecologists are essential for providing the scientific evidence required for making effective wildlife management decisions.

Professor Mark Boyce
Boyce Lab, Department of Biological Sciences, University of Alberta, Canada

Website: grad.biology.ualberta.ca/boyce

Research project: Modelling wildlife population dynamics to inform management strategies

Kathryn Vaughan
Master’s student (now graduated)

Research project: Developing a winter severity index to help manage white-tailed deer populations

Gillian Power
PhD student

Research project: Tracking bighorn sheep movement to prevent the spread of disease from livestock to bighorn sheep

Fields of research: Conservation ecology; wildlife management

Funders: Natural Sciences and Engineering Research Council of Canada (NSREC); Alberta Conservation Association (ACA)