UW-Madison study finds wolves can bring benefits to ecosystem, but are not a 'cure all'

A new study by a University of Wisconsin-Madison team of researchers looking at wolves on an island in Lake Superior is helping shed light on the role that certain species play in helping shape an entire ecosystem.

The conclusion was those species do play a role, but those effects may be temporary, and humans also play a role.

The real story, though, was the process of reaching that conclusion.

The summer of 2020 was unusual in many ways. COVID restrictions were in place even in remote Isle Royale, one of the least visited national parks in the U.S. That meant researcher Mauriel Rodriguez Curras spent the monthlong research trip in a tent, facing temperatures that got below freezing, and grueling treks as long as 20 miles.

But at least he was doing what he loved — collecting scat and bits of hair, specifically from foxes, American marten and grey wolves.

For Rodriguez Curras, a graduate student at the UW-Madison at the time, working with scat is a badge of honor. Every sample he collected has a wealth of information. It helps researchers understand where animals go, what they eat, how they interact with each other and how to conserve them.

Isle Royale is a remote archipelago in Lake Superior. For more than five decades, researchers had been observing the island's wolves and the moose they hunted. This long-term study has produced useful insights into predator-prey dynamics. But then, in 2015, the wolf population collapsed. By 2018, there were only two adults left, and they were related to each other. As far as scientists were concerned, wolves on Isle Royale were functionally extinct.

The National Park Service quickly jumped into action, introducing 19 wolves to Isle Royale in 2018 in an attempt to revive the population.

Jonathan Pauli, a professor at the UW-Madison, watched all these developments from the sidelines. He was not particularly interested in wolves, but when he caught a whiff of the National Park Service's plans, he sensed an opportunity to study how wolves impact other animals on the island.

For the last eight years, Pauli has been studying American martens on the island. The tiny ferret-like creatures, also known as pine martens, were hunted to near extinction for their pelts. Management efforts have brought their numbers back in many states, but they are still considered endangered in Wisconsin, and scientists are concerned about the effect of climate change on them.

To add to their woes, martens on Isle Royale face direct competition for food and territory from one of the most versatile carnivores on the planet — foxes. Martens stay among the trees and more wooded areas of the forest to avoid confrontations with these larger animals.

Despite all of this going on in the forest, most conservation efforts tend to focus on what are known as keystone species, like wolves. The idea is that such species bring overall benefits to the ecosystem.

Pauli wanted to understand how the foxes and martens of Isle Royale would react to the near extinction, and subsequent reintroduction, of wolves. Would the wolves bring balance to the ecosystem? Or is the importance given to keystone species unwarranted?

The work, led by Rodriguez Curras with significant support from the National Park Service, was recently published in Frontiers in Ecology and the Environment. It highlights the importance of an interconnected, holistic long-term approach to conservation. Large, top-of-the-food-chain predators like wolves can have huge impacts on ecosystems, but only temporarily.

In 2018, before the reintroductions, Pauli's team had already collected a bunch of scat and hair. They repeated the exercise in 2019 and again in 2020 after Rodriguez Curras joined the team.

Each time Rodriguez Curras came across a piece of scat, he swabbed it and bagged it. Later, he would extract DNA from the swab to identify the individual and examine the contents. In addition, he also collected bits of hair that animals unwittingly left behind on strategically placed brushes along the forest floor. An analysis of the hair told researchers what the animal ate.

All these bits of information put together a picture of how foxes, martens and wolves interacted with each other, and their environment in those three years.

Wolves are known as pack animals, but in that first year on Isle Royale, the newly arrived wolves went solo. They were "moving around a lot more, killing smaller prey and being really territorial," Rodriguez Curras said.

With the wolf social life in disarray, foxes were pushed closer to human campsites in 2019. The hair samples he collected told Rodriguez Curras they ate a lot more human food that year. At the same time, marten populations shot up and the researchers began to see their scat in new areas.

With their larger competitors out of the way, the smaller, less numerous martens had some breathing room.

It would seem wolves had brought some balance, but it was only temporary.

The next year in 2020, everything just went back to normal. "The first year we saw this really strong impact from wolves, the second year, those effects subsided." Rodrigues Curras said.

The wolves established two packs with clearly defined territories on the eastern and western ends of the island respectively, foxes were all over the place and martens were once again restricted themselves to the densely forested parts of the island.

What this tells Pauli, who oversees a network of sites across Wisconsin, Minnesota, and Michigan focused on the recovery of martens, is that no one species is a cure all. Keystone species can have huge impacts on the ecosystem, but at least in some instances those can be temporary. While he remains focused on martens, he is now thinking about what other species they interact with and how they could affect each other in the different sites he looks at.

Human presence can benefit some species more than others. Foxes can rummage around in human trash when they can't find food elsewhere, but the two other species the team studied tend to avoid humans.

Rodriguez Curras also hopes this study brings focus on how humans can indirectly shape interactions between species.

This article originally appeared on Milwaukee Journal Sentinel: UW-Madison study finds wolves can bring benefits to ecosystem, but are not a 'cure all'