Indirect effects of bioinvasions in Yellowstone Lake: The response of river otters to declines in native cutthroat trout

Abstract

Nonnative species threaten ecosystems throughout the world -including protected reserves. In Yellowstone National Park, river otters Lontra canadensis depend on native cutthroat trout as prey. However, nonnative lake trout and whirling disease have significantly reduced the abundance of these native fish in the park's largest body of water, Yellowstone Lake. We studied the demographic and behavioral responses of otters to declining cutthroat trout on Yellowstone Lake and its tributaries. From 2002-2008, we monitored otter activity at latrine (scentmarking) sites, collected scat for prey identification, and used individual genotypes from scat and hair samples to evaluate survival and abundance with capture-recapture methods. Otter activity at latrines decreased with declines in cutthroat trout, and the prevalence of these fish in otter scat declined from 73% to 53%. Cutthroat trout numbers were the best predictor of temporal variation in apparent survival, and mean annual survival for otters was low (0.72). The density of otters in our study area (1 otter per 13.4 km of shoreline) was also low, and evidence of a recent genetic bottleneck suggests that otter abundance might have declined prior to our study. River otters in and around Yellowstone Lake appear to be responding to reductions in cutthroat trout via changes in distribution, diet, and possibly survival and abundance. Our results provide a baseline estimate for monitoring the broader outcome of management efforts to conserve native cutthroat trout and emphasize the indirect ecosystem consequences of invasive species.

A Portfolio Framework for Prioritizing Conservation Efforts for Yellowstone Cutthroat Trout Populations

“…Furthermore, this population of Yellowstone Cutthroat Trout has been documented to have high ecological value that extends across ecosystems (Crait et al. ; Tronstad et al. ), suggesting that the overall conservation benefits far outweigh the considerable monetary costs to control invasive Lake Trout.…”

“…Within our framework, this population of Yellowstone Cutthroat Trout ranks in the top 10% of all populations, as it is genetically pure and occupies over 750 km covering a diversity of streams, including access to Yellowstone Lake, where thermal stratification provides an important contemporary and future coldwater refuge (Goyer et al 2014). Furthermore, this population of Yellowstone Cutthroat Trout has been documented to have high ecological value that extends across ecosystems (Crait et al 2015;Tronstad et al 2015), suggesting that the overall conservation benefits far outweigh the considerable monetary costs to control invasive Lake Trout. This post hoc assessment supports the ongoing efforts (Syslo et al 2011) and justifies further expenditures aimed at reducing the major threat to this important population.…”

Fisheries Volume 43 Number 10 October 2018

“…Within our framework, this population of Yellowstone Cutthroat Trout ranks in the top 10% of all populations, as it is genetically pure and occupies over 750 km covering a diversity of streams, including access to Yellowstone Lake, where thermal stratifi cation provides an important contemporary and future coldwater refuge (Goyer et al 2014 ). Furthermore, this population of Yellowstone Cutthroat Trout has been documented to have high ecological value that extends across ecosystems (Crait et al 2015 ;Tronstad et al 2015 ), suggesting that the overall conservation benefi ts far outweigh the considerable monetary costs to control invasive Lake Trout. This post hoc assessment supports the ongoing efforts (Syslo et al 2011 ) and justifi es further expenditures aimed at reducing the major threat to this important population.…”

Small‐clawed otters (Aonyx cinereus) in Indonesian rice fields: latrine site characteristics and visitation frequency

“…Therefore, frequently used latrine sites provide a relative measure of the intensity of use of different latrine sites and their associated habitat characteristics (Hutchings and White 2000). For this reason, researchers have studied otter visitation at latrine sites to assess habitat quality (Prenda and Granado-Lorencio 1996) and fish prey availability (Crait et al 2015), and to determine the locations of latrine sites relative to the home range of otters (Barocas et al 2016).…”

“…In this study, we sought to determine which land use factors are important for explaining the occurrence of latrine sites of small-clawed otters in Indonesian rice fields. Because the frequency of visitation to latrine sites may differ depending on local environmental conditions, such as prey availability (Crait et al 2015), we subsequently investigated which land use and local environmental factors best explain the visitation frequency of small-clawed otters to latrine sites. This study is the first to document the visitation frequency of small-clawed otters to latrine sites.…”