HUMAN ACTIVITY MEDIATES A TROPHIC CASCADE CAUSED BY WOLVES

By Mark Hebblewhite, C. White, Clifford G. Nietvelt, J. A. Mckenzie, Tomas E. Hurd, J. Fryxell, S. Bayley, Paul C. Paquet. Ecology, 2005

516 citations recorded by the source corpus.

Experimental evidence of trophic cascades initiated by large vertebrate predators is rare in terrestrial ecosystems. A serendipitous natural experiment provided an opportunity to test the trophic cascade hypothesis for wolves (Canis lupus) in Banff National Park, Canada. The first wolf pack recolonized the Bow Valley of Banff National Park in 1986. High human activity partially excluded wolves from one area of the Bow Valley (low-wolf area), whereas wolves made full use of an adjacent area (high-wolf area). We investigated the effects of differential wolf predation between these two areas on elk (Cervus elaphus) population density, adult female survival, and calf recruitment; aspen (Populus tremuloides) recruitment and browse intensity; willow (Salix spp.) production, browsing intensity, and net growth; beaver (Castor canadensis) density; and riparian songbird diversity, evenness, and abundance. We compared effects of recolonizing wolves on these response variables using the log response ratio between the low-wolf and high-wolf treatments. Elk population density diverged over time in the two treatments, such that elk were an order of magnitude more numerous in the low-wolf area compared to the high-wolf area at the end of the study. Annual survival of adult female elk was 62% in the high-wolf area vs. 89% in the low-wolf area. Annual recruitment of calves was 15% in the high-wolf area vs. 27% without wolves. Wolf exclusion decreased aspen recruitment, willow production, and increased willow and aspen browsing intensity. Beaver lodge density was negatively correlated to elk density, and elk herbivory had an indirect negative effect on riparian songbird diversity and abundance. These alternating patterns across trophic levels support the wolf-caused trophic cascade hypothesis. Human activity strongly mediated these cascade effects, through a depressing effect on habitat use by wolves. Thus, conservation strategies based on the trophic importance of large carnivores have increased support in terrestrial ecosystems.

Subfields: Ecology

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Citations in the corpus

Linking a cougar decline, trophic cascade, and catastrophic regime shift in Zion National Park (2006, background): “These landscape-scale refugia are consistent with behaviorally mediated trophic cascades theory involving predation risk effects (Ripple and Beschta, 2004; Hebblewhite et al., 2005 ).”
Modelling wildlife–human relationships for social species with mixed‐effects resource selection models (2007, background): “Wolf avoidance of human activity also has important trophic implications because ungulates may increase in areas of high human activity because of reduced wolf use, with resultant trophic cascades to plants (Hebblewhite et al. 2005).”
Large predators and trophic cascades in terrestrial ecosystems of the western United States (2009, methodology): “In some national parks where wolves have recolonized, elk have become concentrated near areas of human development in an apparent attempt to reduce predation risk (Hebblewhite et al., 2005; Beschta and Ripple, 2006b).”
Effects of sampling regime on the mean and variance of home range size estimates. (2006, background): “A useful approach to address this question is to understand the dynamics of animal movements in relation to state-dependent social and ecological factors ( Hebblewhite et al. 2005; Whitehead & Rendell 2004).”
Can we save large carnivores without losing large carnivore science (2017, background): “…from the massive scales that large carnivores utilise, they can and have been done in some places (e.g. Eldridge et al., 2002; Hayes et al., 2003; Hebblewhite et al., 2005; Allen et al., 2013a; Marshall et al., 2013; Allen et al., 2014b; Christianson and Creel, 2014; Ford et al., 2014; Hervieux…”
Rewilding – A New Paradigm for Nature Conservation in Scotland? (2011, background): “After wolves recolonised Banff National Park in Canada in 1986, cascading effects were identified on elk survival rates and population density, aspen and willow recruitment, beaver density, and riparian songbird diversity and abundance (Jones 2002; Hebblewhite et al. 2005).”
Facts From Feces: Nitrogen Still Measures Up as a Nutritional Index for Mammalian Herbivores (2008, background): “and Leslie and Starkey (1985), Hobbs (1987) echoed concerns of Robbins et al.”
Lasting behavioural responses of brown bears to experimental encounters with humans (2013, background): “population redistribution; Beckmann & Berger 2003) and ecosystem level, after altering interactions between species (Hebblewhite et al. 2005).”
Does a top‐predator provide an endangered rodent with refuge from an invasive mesopredator? (2009, background): “This top-down control of trophic webs can have positive benefits for biodiversity conservation, by reducing the impacts of herbivores and mesopredators (Crooks & Soulé, 1999; Hebblewhite et al., 2005; Berger & Gese, 2007; Berger et al., 2008).”
Do wild ungulates experience higher stress with humans than with large carnivores? (2018, background): “Ungulate prey can also profit from the proximity to humans, as it reduces predation risk from large carnivores (Hebblewhite et al. 2005; Berger, 2007, Atickem et al. 2014; Kuijper et al. 2015).”
Human Activity Differentially Redistributes Large Mammals in the Canadian Rockies National Parks (2011, background): “…however, responses were more variable; where some authors reported avoidance (Cassirer et al. 1992, Gagnon et al. 2007), others reported selection for areas near human activity (Hebblewhite et al. 2005), suggesting that both avoidance and trophic interaction may occur in different populations.”