Persistence of fishers in riparian forests in North Dakota, USA following a severe flood event

Abstract

Historically, the distribution of fishers (Martes pennanti) in North America included portions of eastern North Dakota, USA; however, the population was reported to have become extirpated by the early 1900s. Verified reports, road-killed and incidentally trapped individuals, indicate that fishers have been re-establishing populations in riparian forests (the only areas with substantive forest cover in the region) over the last 10 years. During the summers of 2008 (16 Jun–1 Aug) and 2009 (1 Jun–18 Aug), we conducted presence–absence sampling using remote cameras and enclosed track-plates to determine the distribution of fishers along 237 km of the Red River of the North in North Dakota. Between sampling events, the Red River experienced an extreme flood with peak flooding above major flood stage, which inundated all riparian forests within the study area from approximately 23 Mar–22 May. Because of the severity of the flood, we anticipated that fishers could have perished or been displaced from much of the study area, resulting in lower detection rates in 2009 than 2008. However, fishers were detected throughout the study area during both years and, unexpectedly, detection rates were higher in 2009 than 2008 (28 out of 35 sites [80%] and 25 out of 57 sites [44%], respectively). Our study demonstrates that fishers existing in what traditionally would have been considered marginal habitat for the species were able to persist following a severe, multi-month flood that inundated >95% of the forest habitat.