Empirical evidence for declines in muskrat populations across the United States

Ahlers, Adam A.; Heske, Edward J.

doi:10.1002/jwmg.21328

Cited by 32 publications

(29 citation statements)

References 52 publications

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“…Pelt price, in particular, has been used widely as an indicator of trapper effort in studies of harvest trends in multiple furbearer species [33,35,36]. In a recent range-wide analysis of muskrat (Ondatra zibethicus) harvest where pelt price was only occasionally reported by states, Ahlers & Heske [37] found that pelt price was similar across localities and thus an average value could be applied to all states and provinces to correct for trapping effort. We converted Canadian weasel pelt prices to US dollar amounts using a year-specific conversion rate and corrected the pelt price for inflation using the Consumer Price Index (CPI; www.bls.gov/data/) adjusted to 2017 US dollar values.…”

Section: Plos Onementioning

confidence: 99%

Tracking the decline of weasels in North America

et al. 2021

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Small carnivores are of increasing conservation concern globally, including those formerly thought to be widespread and abundant. Three weasel species (Mustela nivalis, M. frenata, and M. erminea) are distributed across most of North America, yet several recent studies have reported difficulty detecting weasels within their historical range and several states have revised the status of weasels to that of species of conservation concern. To investigate the status and trends of weasels across the United States (US) and Canada, we analyzed four separate datasets: historical harvests, museum collections, citizen scientist observations (iNaturalist), and a recent US-wide trail camera survey. We observed 87–94% declines in weasel harvest across North America over the past 60 years. Declining trapper numbers and shifts in trapping practices likely partially explain the decline in harvest. Nonetheless, after accounting for trapper effort and pelt price, we still detected a significant decline in weasel harvest for 15 of 22 evaluated states and provinces. Comparisons of recent and historical museum and observational records suggest relatively consistent distributions for M. erminea, but a current range gap of >1000 km between two distinct populations of M. nivalis. We observed a dramatic drop-off in M. frenata records since 2000 in portions of its central, Great Lakes, and southern distribution, despite extensive sampling effort. In 2019, systematic trail camera surveys at 1509 sites in 50 US states detected weasels at 14 sites, all of which were above 40o latitude. While none of these datasets are individually conclusive, they collectively support the hypothesis that weasel populations have declined in North America and highlight the need for improved methods for detecting and monitoring weasels. By identifying population declines for small carnivores that were formerly abundant across North America, our findings echo recent calls to expand investigations into the conservation need of small carnivores globally.

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Section: Plos Onementioning

confidence: 99%

Tracking the decline of weasels in North America

et al. 2021

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“…However, robust empirical data on long-term trends in muskrat populations based on field observations are generally scarce in the literature. Thus, more information is needed to confirm that declines in muskrat harvest correspond to real declines in muskrat abundance (Ahlers and Heske, 2017). Fortunately, we learned of annual muskrat field surveys having been conducted at multiple locations in Ontario, Canada between 1950 and and sought to exploit this untapped source of historic muskrat population data.…”

Section: Introductionmentioning

confidence: 99%

Historical surveys reveal a long-term decline in muskrat populations

Sadowski

Bowman

2021

Preprint

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The muskrat (Ondatra zibethicus) is an iconic species in Canada, valued for both its fur and its integral role in wetland ecosystems, and widely regarded for its perseverance. However, the resilience of this semi-aquatic mammal seems to be in question now as increasing evidence points to widespread population declines. Recent analyses of harvest data across North America suggest a reduction in their numbers, but this has not been widely corroborated by population surveys. In this study we replicated historic muskrat house count surveys at two large Great Lakes coastal wetlands and present confirmation that declines in muskrat harvest correspond to actual declines in muskrat abundance. At the Point Pelee National Park marsh and the Matchedash Bay-Gray Marsh wetland we found that mean muskrat house counts declined by 93% and 91% respectively between historic surveys 40-50 years ago and contemporary surveys over the past five years. The factors responsible for these dramatic declines remain unclear but there may be a relationship with changes in the habitat quality of these wetlands that have occurred over the same time frame. Not only is the loss of muskrats an issue for the resulting loss of the wetland ecosystem services they provide, but it may be an indication of broader marsh ecosystem degradation. As such, a scarcity of muskrats should be considered a red flag for the state of biodiversity in our wetlands. Continued surveys and ongoing research are needed to shed more light on the current status of muskrat populations and their marsh habitats across their native range. Keywords: Fur harvest; Muskrat; Ondatra; Population decline; Typha; Wetlands

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“…Muskrats Ondatra zibethicus are ecologically and economically important semi‐aquatic mammals whose populations appear to be declining throughout their native range in North America (Roberts & Crimmins 2010, Ahlers & Heske 2017, Greenhorn et al 2017, Gregory et al 2019). They are also an invasive species in Europe, South America, and Asia (Anderson et al 2006, Xu et al 2006).…”

Section: Introductionmentioning

confidence: 99%

How do muskratsOndatra zibethicusaffect ecosystems? A review of evidence

Bomske

Ahlers

2020

Mammal Review

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Muskrats Ondatra zibethicus are reported to have wide‐ranging effects on wetland habitats, sometimes earning them the labels ‘keystone species’ or ‘ecosystem engineers’. We conducted an extensive review of the scientific literature and evaluated evidence for muskrats as potential keystone species or ecosystem engineers, and more generally, their known impacts on wetland ecosystems. We identified 363 publications (peer‐reviewed articles, books, theses, and reports) regarding muskrats, 202 of which were in an ecological context. Only 6% (n = 13) of these explicitly considered muskrats as ecosystem engineers (n = 9) or keystone species (n = 4). Our review found that muskrat populations may have broad effects on both wetland flora and fauna. However, studies generally occurred over small spatiotemporal scales and used dissimilar methods and reporting, which limited our inference regarding muskrats’ influence on wetland ecosystems. Research explicitly identifying muskrats as ecosystem engineers or keystone species is limited, but published evidence suggests that muskrats may have an effect on plant species diversity and habitat heterogeneity, which in turn may influence other animal species. However, long‐term and experimental research is needed to uncover impacts that muskrats have on ecosystems.

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Empirical evidence for declines in muskrat populations across the United States

Cited by 32 publications

References 52 publications

Tracking the decline of weasels in North America

Tracking the decline of weasels in North America

Historical surveys reveal a long-term decline in muskrat populations

How do muskratsOndatra zibethicusaffect ecosystems? A review of evidence

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