The muskrat is a brown, stocky rodent about the same size as a Chihuahua. It has lived thousands of years in northeastern Alberta in Canada, where it can be found in one of the largest freshwater deltas on Earth.This delta is located within one of the most protected areas in North America. It's home to five times as many Yellowstone-sized bison, the world's largest free-roaming herd, and the last natural nesting site for the endangered whooping crane. It is also central to the culture, livelihoods, and culture of Indigenous peoples like the Mikisew Cree First Nation (Athabasca Chipewyan First Nation), Mtis Local 125, and the Mikisew Cree First Nation (Miskisco Chipewyan First Nation).The vulnerability of this most protected area to human-driven climate and water system changes, according to new research published in Communications Biology on June 24, 2014, shows that even the Peace-Athabasca delta's muskrat population dynamics, is vulnerable.Elizabeth Hadly, an environmental biologist at Stanford University, was co-principal investigator for the study. "A little muskrat is in the middle of the northern part of Canada. This is an indicator of human effects at the local, regional, and global levels." Climate change and dams have affected the ability of this exemplar animal, as well as many other species and animals that depend on this ecosystem to thrive in such a large area.This research follows a draft United Nations finding that Canada's Wood Buffalo National Park, a park and World Heritage Site that includes the Peace-Athabasca delta, is at risk from threats to governance and hydropower development upstream. Climate change has been implicated in long-term drying of the delta and the hydroelectric dams along the Peace River as the cause of decreased flooding."Our results speak about the impacts of long-term drying on the biotic ecosystem -- regardless of the cause -- and these have implications for science and environment policy," stated Steve Gorelick (Stanford hydrologist and senior fellow at Stanford Woods Institute for the Environment).AdvertisementEruption or die-offMuskrat (Ondatra Zibethicus), populations have been subject to a boom-and–bust cycle. Their numbers plummet in dry years, and then rise after major floods. In recent decades, the booms and the area in which muskrats live during the wet years have been decreasing. According to the authors, the 2014 year with the greatest net population growth after flooding was less productive than any other such year since the 1970s.Many creatures depend on the dynamic nature and strength of wetlands for survival, but muskrats rely heavily on rivers, floodwaters and streams to move and disperse outside their natal ponds. Many muskrats can drown in a flood. Ellen Ward, a Stanford PhD student in Earth systems science, was the lead study author. She said that some will be swept up into trees but others will stay put. "But others will remain in the water, floating or clinging on to debris and get swept along quite a distance."The floodwaters recede and the dispersed marsh muskrats are able to enjoy habitat gains that allow them to support larger numbers. They are a strong influence on the ecosystem by grazing heavily on the plants close to the shore. This provides prey for predators such as foxes, lynxes, mink, and other predators.Canary in a coalmineBecause muskrat dispersal and behavior are closely tied to freshwater abundance and distribution, their genetic data provides hard evidence that changes in the environment have had an impact on a population. Hadly, the Paul S. & Billie Achilles Professor of Environmental Biology and a senior fellow with Stanford Woods Institute for the Environment, said that muskrats are "a bit like a canary within a coal mine."AdvertisementOne flood year saw DNA from two closely related muskrats found nearly 25 miles apart. This suggests that the animals can move far to find suitable habitat. The authors discovered that population size and density declined in dry years while more individuals moved through a given area. This suggests that overcrowding in habitats leads to long, dangerous migrations in search for viable territory."Our research shows that they can travel great distances, far greater than their home range, and that their breeding is so prolific that their population bounces back, but not as high as it was before," Gorelick, the Cyrus Fisher Tolman professor in Stanford's School of Earth, Energy & Environmental Sciences, (Stanford Earth) said.Computer simulations and tail tissueThese new estimates are based on a collaboration that combined computer simulations of freshwater habitat and muskrat behavior, as well as genetic analysis of 288 tail tissue samples taken from muskrats captured by Indigenous trappers for their fur and meat. "Our modeling covers all aspects of muskrat's life, including their travels, diet, reproduction, and the many ways in which they may die. Gorelick stated that they can freeze, drown or starve and be eaten, or eat one another."Both genetic analysis and modeling suggest that muskrats living in the delta today may be grouped into smaller populations. These smaller populations, when taken together, have a long history involving rapid die-offs, or what scientists refer to as genetic bottlenecks. Katherine Solari (postdoctoral researcher in biology), co-lead author of the study. "Even though the population grows to the enormous sizes we see in peak year, there isn't as much genetic diversity as we would anticipate."According to the authors, muskrat persistence is not dependent on a single part of the delta. Hadly stated that it is impossible to just say "We're going all to protect the fish and muskrats in this lake," because it will change next year. It challenges us to consider how we can preserve the landscape's dynamism in the face climate change and altered hydrology.Gorelick is also the director of the Stanford Woods Institute for the Environment's Global Freshwater Initiative. Hadly is a faculty member at Stanford's Jasper Ridge Biological Preserve and a member of BioX. She also teaches Geological Sciences. Amruta Varudkar, a Stanford postdoctoral scholar, was a co-author.Stanford Woods Institute for the Environment provided funding for the research through an Environmental Venture Project Grant. Graduate student support was provided by Stanford Freeman Spogli Institute for International Studies and Stanford Graduate Fellowship program.
