Moose movement rates are altered by wolf presence in two ecosystems

Abstract

Predators directly impact prey populations through lethal encounters, but understanding nonlethal, indirect effects is also critical because foraging animals often face trade‐offs between predator avoidance and energy intake. Quantifying these indirect effects can be difficult even when it is possible to monitor individuals that regularly interact. Our goal was to understand how movement and resource selection of a predator (wolves; Canis lupus) influence the movement behavior of a prey species (moose; Alces alces). We tested whether moose avoided areas with high predicted wolf resource use in two study areas with differing prey compositions, whether avoidance patterns varied seasonally, and whether daily activity budgets of moose and wolves aligned temporally. We deployed GPS collars on both species at two sites in northern Minnesota. We created seasonal resource selection functions (RSF) for wolves and modeled the relationship between moose first‐passage time (FPT), a method that discerns alterations in movement rates, and wolf RSF values. Larger FPT values suggest rest/foraging, whereas shorter FPT values indicate travel/fleeing. We found that the movements of moose and wolves peaked at similar times of day in both study areas. Moose FPTs were 45% lower in areas most selected for by wolves relative to those avoided. The relationship between wolf RSF and moose FPT was nonlinear and varied seasonally. Differences in FPT between low and high RSF values were greatest in winter (−82.1%) and spring (−57.6%) in northeastern Minnesota and similar for all seasons in the Voyageurs National Park ecosystem. In northeastern Minnesota, where moose comprise a larger percentage of wolf diet, the relationship between moose FPT and wolf RSF was more pronounced (ave. across seasons: −60.1%) than the Voyageurs National Park ecosystem (−30.4%). These findings highlight the role wolves can play in determining moose behavior, whereby moose spend less time in areas with higher predicted likelihood of wolf resource selection.

Ecological Effects of Wolves in Anthropogenic Landscapes: The Potential for Trophic Cascades Is Context-Dependent

“…Our findings are supported by recent studies showing that human-modified attributes and environmental factors are more important for moose abundance and browsing damage than wolf presence and time since wolf territory establishment (Gicquel et al, 2020). These results contrast with studies from protected areas where wolves have both density and behaviorally mediated effects on lower trophic levels (Fortin et al, 2005;Ripple and Beschta, 2012;Ripple et al, 2015;Ditmer et al, 2018). In protected areas such as Yellowstone National Park, there is often little to no anthropogenic activity and therefore, the relative importance of wolves to shape the dynamics and functions of an ecosystem is potentially higher (Mech, 1966(Mech, , 2013McLaren and Peterson, 1994;Berger et al, 2001a;Terborgh and Estes, 2010;Kuijper et al, 2016).…”

“…A recent study found that moose browsing damage on Scots pine in south-central Sweden was higher inside wolf territories than outside (Gicquel et al, 2020). These results contrast with several studies of wolf-moose-plants systems in North America (Fortin et al, 2005;Ripple and Beschta, 2012;Ditmer et al, 2018). Such a difference may be explained by different degrees of anthropogenic impact in these systems (Kuijper et al, 2016), which may change or reduce the ecological effects of wolves on other trophic levels.…”

Wolf predation risk and moose movement in eastern Finland

“…Thus the situation has been similar to that in our study system. Ditmer et al (2018) suggested that antipredator behaviors like increased movement rates could reduce the time available to critical activities like foraging, breeding and finding thermal shelter and are therefore likely to involve costs to moose. Therefore it seems plausible that these behaviors will be preserved only in conditions where they are regularly needed.…”

“…The antipredator behaviors may impose tradeoffs for the prey animals such as forcing prey to forage in safer but possibly nutritionally lower quality habitats and decreasing the time spent foraging. As a consequence the energy intake and condition of the prey animals may decrease (Ditmer et al 2018). When affecting the amount and distribution of plant consumption, the behavioral modifications of foraging prey may have effects also on community level i.e.…”

De wolf terug in Nederland : Een factfinding study

“…Ze kunnen dichtheden van grote herbivoren reduceren (Ripple & Beschta, 2012), waardoor de kans op aanrijdingen met deze hoefdieren afneemt (Mech, 2017). Anderzijds verandert het habitatgebruik van hoefdieren in de aanwezigheid van wolven, zoals blijkt uit veranderingen in vegetatie als gevolg van veranderingen in graasdruk (Smith & Ferguson, 2012;White et al, 2012;Ditmer et al, 2018). Dit kan, in potentie, leiden tot het frequenter of juist minder frequent oversteken van wegen door hoefdieren, maar hier zijn in Nederland nog geen aanwijzingen voor gevonden.…”