Drying drives decline in muskrat population in the Peace-Athabasca Delta, Canada

Abstract

Empirical and anecdotal reports suggest that muskrat are in decline across North America, including in the Peace-Athabasca Delta (‘Delta’), Canada, one of the largest inland deltas in the world and part of a World Heritage Site with ‘in Danger’ status pending. Muskrat are a key ecological indicator in the Delta. We investigate whether the large-scale loss of critical habitat over the past half-century could be driving a decline in muskrat abundance in the Delta. To do this, we use the Landsat record (1972–2017) to construct a 46 year record of inundation, and compare changes in the extent of critical habitat to the survey record for muskrat (1970–2016) over this 5500 km2 region. Results show that the declines in critical habitat and muskrat numbers in the Delta are synchronous: ∼1450 km2 of temporarily inundated regions that support critical habitat have diminished by ∼10 km2 yr−1 over the past 46 years, while the muskrat population density (houses/km2) has also declined and is significantly related to critical habitat area (km2) (R2 = 0.60, P = 0.0001). These findings have implications for the Delta, a Ramsar Wetland of International Importance in part for its role as a habitat for nearly 200 species of birds, many of which rely on the aquatic habitat considered here. Our results further suggest that the loss of wetland habitat is a primary driver of the decline of muskrat across the species’ native range.