Abstract
Wetlands worldwide are under threat from anthropogenic impacts. In large protected North American areas such as Yellowstone and Wood Buffalo National Parks, aquatic habitats are disappearing and wetland-dependent fauna are in decline1–3. Here we investigate population dynamics of an indicator species in Canada’s Peace-Athabasca Delta (“the delta”), a World Heritage Site. Based on population surveys, habitat mapping and genetic data from 288 muskrats, we use agent-based modeling and genetic analyses to explain population expansion and decline of the semi-aquatic muskrat (Ondatra zibethicus). Simulations quantify a large population (~500,000 individuals) following flood-induced habitat gains, with decreased size (~10,000 individuals) during drying. Genetic analyses show extremely low long-term effective population size (Ne: 60–127), supporting a legacy of population bottlenecks. Our simulations indicate that the muskrat population in the delta is a metapopulation with individuals migrating preferentially along riparian pathways. Related individuals found over 40 km apart imply dispersal distances far greater than their typical home range (130 m). Rapid metapopulation recovery is achieved via riparian corridor migration and passive flood-transport of individuals. Source-sink dynamics show wetland loss impacts on the muskrat metapopulation’s spatial extent. Dramatic landscape change is underway, devastating local fauna, including this generalist species even in a protected ecosystem.
Highlights
Wetlands worldwide are under threat from anthropogenic impacts
Agent-based simulations show that the number of muskrats in the delta is characterized by a series of peak population values followed by sharp declines in the population, concordant with the population survey record (Fig. 1c)
Agent modeling results show muskrat population dynamics characterized by periods of eruptive population growth followed by die-offs that emerge from the simulated life sequence of up to 546,619 individuals on the floodplain (Fig. 1c)
Summary
Wetlands worldwide are under threat from anthropogenic impacts. In large protected North American areas such as Yellowstone and Wood Buffalo National Parks, aquatic habitats are disappearing and wetland-dependent fauna are in decline[1,2,3]. Previous work has attributed drying in the delta to the effects of climate change, upstream hydropower development on the Peace River, or a combination of both drivers[5,6,7,8] This habitat loss is concurrent with a dramatic decline in the delta’s muskrat (Ondatra zibethicus) population over the past half century, a trend long reported by local Indigenous trappers[9,10]. The muskrat shares habitat requirements of other wetland species, including fish and waterfowl, requiring vegetation maintained at early successional stages by flooding Their numbers rise and fall rapidly with changes in the floodplain as they thrive on nearshore vegetation before declining rapidly in “die-offs”, often attributed to their intensive herbivory[11]. Muskrat reorganize their home range locations in the spring “shuffle”
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