Muskrats are an indicator for a drying delta – Eurasia Review

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The muskrat, a stocky brown rodent the size of a Chihuahua – with a mouse-like tail, beaver-like teeth, and an exceptional ability to bounce back from a quick death – has lived for thousands of years in the one of the largest freshwater deltas on Earth. , in northeastern Alberta, Canada.

Today, this delta sits in one of the largest tracts of protected land in North America: a national park five times the size of Yellowstone that is home to the largest free-roaming bison herd on the planet and the last natural nesting place for the whooping crane, an endangered species. . It is also central to the culture and livelihoods of Indigenous peoples, including the Mikisew Cree First Nation, Athabasca Chipewyan First Nation and Métis Local 125.

New research focusing on muskrat population dynamics in the Peace-Athabasca Delta, published June 24 in Communications biology, demonstrates the vulnerability of this landscape, even the most protected, to anthropogenic changes in hydrological systems and the global climate.

“A little muskrat in the middle of this northern part of Canada is an indicator of human impacts at local, regional and global levels,” said Elizabeth Hadly, environmental biologist at Stanford University, co-principal investigator of the study. “Climate change and dams have altered the ability of this exemplary species – and many plants, animals and people who depend on the same ecosystem – to thrive in this vast area. “

The research follows a draft United Nations finding that Wood Buffalo National Park of Canada – the park and World Heritage site that contains the Peace-Athabasca Delta – is likely threatened by governance threats as well as hydroelectricity and oil. development of sands upstream of the delta. Previous research has implicated climate change as a long-term drying factor in the delta and hydroelectric dams on the Peace River as a cause of reduced flooding.

“Our results speak to the biotic environmental impacts of long-term drying – whatever the cause – and this has implications for environmental science and policy,” said Stanford hydrologist Steve Gorelick, co – Principal investigator of the study and principal investigator at the Stanford Woods Institute for the Environment.

Eruption and wasting

Muskrat (Ondatra zibethicus) populations have always followed a cycle of boom and bust, with numbers collapsing in dry years and peaking after major floods. But in recent decades, booms – and the area of ​​the delta inhabited by muskrats during wet years – have diminished. The authors found that the most recent year of net population increase after the floods, 2014, was less productive than any other year of growth dating back to the 1970s.

While many creatures depend on the dynamic nature of wetlands for survival, muskrats rely heavily on floodwaters, rivers, and streams to move and disperse beyond their native ponds. “In a big flood, a lot of muskrats will drown. Some will be swept up into the trees and stay put, ”said lead author of the study, Ellen Ward, who worked on the research as a PhD student in Earth System Science at Stanford. “But some will stay in the water, floating or clinging to debris, and get swept away quite far.”

As floodwaters recede, scattered muskrats benefit from habitat gains that support larger populations. They graze plants near the shore intensely, strongly influencing the plant life in the area and providing prey for foxes, lynxes, mink and other predators.

Canary in a coal mine

Because the behavior and dispersal of the muskrat is so closely related to the distribution and abundance of freshwater, their genetic data offers hard evidence of how changes in the aquatic environment have affected a population. real over time. “They’re kind of like a canary in a coal mine,” said Hadly, Paul S. and Billie Achilles professor of environmental biology and senior researcher at the Stanford Woods Institute for the Environment.

In a year of flooding, the DNA of a pair of closely related muskrats ended up nearly 40 kilometers apart, suggesting the animals may roam or be transported far to the search for suitable habitat beyond their place of birth. During dry years, the authors found that population size and density decreased as the number of individuals migrating through a given location increased, suggesting that overpopulation in the remaining habitat patches results in long and long migrations. perilous in search of a viable territory.

“Our work shows that they can travel great distances – much longer than their home range – and that they reproduce so prolifically that their population rebounds, but not like before,” said Gorelick, Professor Cyrus Fisher Tolman at the Stanford School. Earth, Energy and Environmental Sciences (Stanford Earth).

Computer simulations and tail tissue

The new estimates are the result of a collaborative effort combining computer simulations of freshwater habitat in the Delta and muskrat behaviors, along with genetic analysis of 288 muskrat tail tissue samples collected and donated by native trappers who captured the animals for their fur and meat. “Our modeling takes into account all stages of the muskrat’s life: their journeys, their diet, their reproduction and the many ways in which they can perish and perish. They can freeze, drown, starve, be eaten or eat each other, ”Gorelick said.

Modeling and genetic analysis suggest that delta muskrats today are likely clustered into many smaller populations that, taken as a whole, have a long history of rapid mortality and what scientists call bottlenecks. genetic strangulation. “Even when the population grows to the enormous sizes that we see in peak years, there is not as much genetic diversity in the population as we expected,” explained the co-lead author of the study Katherine Solari, postdoctoral researcher in biology.

According to the authors, no part of the delta is most important for muskrat persistence. “You can’t just go to a lake and say, ‘We’re going to protect all the fish and muskrats here,’ because it’s going to be completely different next year,” Hadly said. “It challenges us to think about how we preserve the vibrancy of this landscape in the face of altered hydrology and climate. “

Gorelick also heads the Global Freshwater Initiative at the Stanford Woods Institute for the Environment. Hadly is director of the Jasper Ridge Biological Preserve faculty at Stanford, a member of Bio-X and a courtesy professor of Geological Sciences. Co-author Amruta Varudkar worked on this project as a postdoctoral researcher in the Department of Biology at Stanford.


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