Movement Responses of Caribou to Human-Induced Habitat Edges Lead to Their Aggregation near Anthropogenic Features

The assessment of disturbance effects on wildlife and resulting mitigation efforts are founded on edge-effect theory. According to the classical view, the abundance of animals affected by human disturbance should increase monotonically with distance from disturbed areas to reach a maximum at remote locations. Here we show that distance-dependent movement taxis can skew abundance distributions toward disturbed areas. We develop an advection-diffusion model based on basic movement behavior commonly observed in animal populations and parameterize the model from observations on radio-collared caribou in a boreal ecosystem. The model predicts maximum abundance at 3.7 km from cutovers and roads. Consistently, aerial surveys conducted over 161,920 km2 showed that the relative probability of caribou occurrence displays nonmonotonic changes with the distance to anthropogenic features, with a peak occurring at 4.5 km away from these features. This aggregation near disturbed areas thus provides the predators of this top-down-controlled, threatened herbivore species with specific locations to concentrate their search. The edge-effect theory developed here thus predicts that human activities should alter animal distribution and food web properties differently than anticipated from the current paradigm. Consideration of such nonmonotonic response to habitat edges may become essential to successful wildlife conservation.

[1]  R. Courtois,et al.  Habitat selection by black bears in an intensively logged boreal forest , 2008 .

[2]  C. Dussault,et al.  Habitat selection by forest-dwelling caribou in managed boreal forest of eastern Canada: Evidence of a landscape configuration effect , 2009 .

[3]  D. S. Ouren,et al.  Roadless Space of the Conterminous United States , 2007, Science.

[4]  S. Kalinowski,et al.  Evaluating prey switching in wolf-ungulate systems. , 2007, Ecological applications : a publication of the Ecological Society of America.

[5]  Jochen A. G. Jaeger,et al.  Comment on "Roadless Space of the Conterminous United States" , 2007, Science.

[6]  Leslie Ries,et al.  A PREDICTIVE MODEL OF EDGE EFFECTS , 2004 .

[7]  R. Courtois,et al.  Effects of forest disturbance on density, space use, and mortality of woodland caribou , 2007 .

[8]  Paul R Moorcroft,et al.  Mechanistic home range models capture spatial patterns and dynamics of coyote territories in Yellowstone , 2006, Proceedings of the Royal Society B: Biological Sciences.

[9]  Marie-Josée Fortin,et al.  Understanding avian responses to forest boundaries: a case study with chickadee winter flocks , 2000 .

[10]  Christian Nellemann,et al.  Effects of Petroleum Development on Terrain Preferences of Calving Caribou , 1996 .

[11]  Juan Manuel Morales,et al.  Behavior at Habitat Boundaries Can Produce Leptokurtic Movement Distributions , 2002, The American Naturalist.

[12]  W. Murdoch.  Switching in General Predators: Experiments on Predator Specificity and Stability of Prey Populations , 1969 .

[13]  Stan Boutin,et al.  Quantifying barrier effects of roads and seismic lines on movements of female woodland caribou in northeastern Alberta , 2002 .

[14]  R. Plummer.  The Adaptive Co-Management Process: an Initial Synthesis of Representative Models and Influential Variables , 2009 .

[15]  E. Laca,et al.  Mechanisms that result in large herbivore grazing distribution patterns. , 1996 .

[16]  R. Holt,et al.  Individual behaviour, space and predator evolution promote persistence in a two-patch system with predator switching , 2005 .

[17]  Darcy R. Visscher,et al.  Scales of movement by elk (Cervus elaphus) in response to heterogeneity in forage resources and predation risk , 2005, Landscape Ecology.

[18]  Simon Benhamou,et al.  Animal movements in heterogeneous landscapes: identifying profitable places and homogeneous movement bouts. , 2008, Ecology.

[19]  J. Witman,et al.  BEHAVIORAL INDIRECT INTERACTIONS: MULTIPLE PREDATOR EFFECTS AND PREY SWITCHING IN THE ROCKY SUBTIDAL , 2004 .

[20]  R. Courtois,et al.  Calving rate, calf survival rate, and habitat selection of forest‐dwelling caribou in a highly managed landscape , 2012 .

[21]  Mark S. Boyce,et al.  Cumulative Effects of Human Developments on Arctic Wildlife , 2005 .

[22]  J. Schaefer.  Long‐Term Range Recession and the Persistence of Caribou in the Taiga , 2003 .

[23]  K. Steenhof,et al.  Dietary Responses of Three Raptor Species to Changing Prey Densities in a Natural Environment , 1988 .

[24]  R. Didham,et al.  The Effect of Fragment Shape and Species' Sensitivity to Habitat Edges on Animal Population Size , 2007, Conservation biology : the journal of the Society for Conservation Biology.

[25]  Guangshun Jiang,et al.  Habitat use and separation between red deer Cervus elaphus xanthopygus and roe deer Capreolus pygargus bedfordi in relation to human disturbance in the Wandashan Mountains, northeastern China , 2008 .

[26]  Mark S. Boyce,et al.  Scale for resource selection functions , 2006 .

[27]  R. Didham,et al.  Confounding factors in the detection of species responses to habitat fragmentation , 2005, Biological reviews of the Cambridge Philosophical Society.

[28]  Robert M Ewers,et al.  Synergistic interactions between edge and area effects in a heavily fragmented landscape. , 2007, Ecology.

[29]  Daniel Fortin,et al.  Multi-level functional responses for wildlife conservation: the case of threatened caribou in managed boreal forests , 2012 .

[30]  T. Hughes,et al.  A theoretical framework for Petrov-Galerkin methods with discontinuous weighting functions: application to the streamline-upwind procedure. , 1982 .

[31]  M. Boyce,et al.  WOLVES INFLUENCE ELK MOVEMENTS: BEHAVIOR SHAPES A TROPHIC CASCADE IN YELLOWSTONE NATIONAL PARK , 2005 .

[32]  H. Wittmer,et al.  Changes in landscape composition influence the decline of a threatened woodland caribou population. , 2007, The Journal of animal ecology.

[33]  R. Courtois,et al.  Cumulative effects of forestry on habitat use by gray wolf (Canis lupus) in the boreal forest , 2010, Landscape Ecology.

[34]  R. Courtois,et al.  Limiting factors might obscure population regulation of moose (Cervidae: Alces alces) in unproductive boreal forests , 1997 .

[35]  Leslie Ries,et al.  Ecological Responses to Habitat Edges: Mechanisms, Models, and Variability Explained , 2004 .

[36]  V. Křivan,et al.  Alternative Food, Switching Predators, and the Persistence of Predator‐Prey Systems , 2001, The American Naturalist.

[37]  J. Cronin,et al.  Edge behaviour in a minute parasitic wasp. , 2010, The Journal of animal ecology.

[38]  R. Courtois,et al.  Winter selection of landscapes by woodland caribou: behavioural response to geographical gradients in habitat attributes , 2008 .

[39]  R. Forman,et al.  ROADS AND THEIR MAJOR ECOLOGICAL EFFECTS , 1998 .

[40]  Christine M. Schonewald,et al.  Patterns of human disturbance and response by small mammals and birds in chaparral near urban development , 1998, Urban Ecosystems.

[41]  S. Pimm,et al.  Dispersal of Amazonian birds in continuous and fragmented forest. , 2007, Ecology letters.

[42]  Mark Hebblewhite,et al.  Caribou encounters with wolves increase near roads and trails: a time‐to‐event approach , 2011 .

[43]  L. Ries,et al.  Do edge responses cascade up or down a multi-trophic food web? , 2011, Ecology letters.

[44]  M. Boyce,et al.  Grizzly bears for the Bitterroot: predicting potential abundance and distribution , 2003 .

[45]  L. Boitani,et al.  Winter habitat and travel route selection by wolves in the northern Apennines, Italy , 2003 .

[46]  EVELYN H. MERRILL,et al.  HABITAT SELECTION BY ELK BEFORE AND AFTER WOLF REINTRODUCTION IN YELLOWSTONE NATIONAL PARK , 2005 .

[47]  Elizabeth E. Crone,et al.  EDGE-MEDIATED DISPERSAL BEHAVIOR IN A PRAIRIE BUTTERFLY , 2001 .

[48]  R. Courtois,et al.  Historical Changes and Current Distribution of Caribou, Rangifer tarandus , in Quebec , 2003 .

[49]  Adrian C. Newton,et al.  Progressive impact of piecemeal infrastructure development on wild reindeer , 2003 .

[50]  R. Courtois,et al.  Demographic and behavioural response of woodland caribou to forest harvesting , 2008 .

[51]  Olav Strand,et al.  Winter distribution of wild reindeer in relation to power lines, roads and resorts , 2001 .

[52]  Stephen M. Krone,et al.  Analyzing animal movements using Brownian bridges. , 2007, Ecology.

[53]  T. Tscharntke,et al.  Spillover edge effects: the dispersal of agriculturally subsidized insect natural enemies into adjacent natural habitats. , 2006, Ecology letters.

[54]  Douglas H. Johnson.  THE COMPARISON OF USAGE AND AVAILABILITY MEASUREMENTS FOR EVALUATING RESOURCE PREFERENCE , 1980 .

[55]  D. Haydon,et al.  Multiple movement modes by large herbivores at multiple spatiotemporal scales , 2008, Proceedings of the National Academy of Sciences.

[56]  R. Courtois,et al.  An Aerial Survey Technique for the Forest-Dwelling Ecotype of Woodland Caribou, Rangifer tarandus caribou , 2003 .

[57]  Robert J. Whelan,et al.  THE EDGE EFFECT AND ECOTONAL SPECIES: BIRD COMMUNITIES ACROSS A NATURAL EDGE IN SOUTHEASTERN AUSTRALIA , 2002 .

[58]  R. Didham,et al.  Pervasive impact of large-scale edge effects on a beetle community , 2008, Proceedings of the National Academy of Sciences.

[59]  Glenn D. Sutherland,et al.  Scaling of Natal Dispersal Distances in Terrestrial Birds and Mammals , 2000 .

[60]  B. Manly,et al.  Resource selection by animals: statistical design and analysis for field studies. , 1994 .

[61]  G. Gale,et al.  Human disturbance affects habitat use and behaviour of Asiatic leopard Panthera pardus in Kaeng Krachan National Park, Thailand , 2007, Oryx.

[62]  R. Courtois,et al.  Landscape management for woodland caribou: the protection of forest blocks influences wolf-caribou co-occurrence , 2009, Landscape Ecology.

[63]  M. McPheeHeather,et al.  Hierarchical predation: wolf (Canis lupus) selection along hunt paths and at kill sites , 2012 .

[64]  Daniel Fortin,et al.  Foraging strategies by omnivores: are black bears actively searching for ungulate neonates or are they simply opportunistic predators? , 2011 .

[65]  M. Boyce,et al.  Relating populations to habitats using resource selection functions. , 1999, Trends in ecology & evolution.

[66]  R. E. Strauss,et al.  Reliability Estimates for Ivlevˈs Electivity Index, the Forage Ratio, and a Proposed Linear Index of Food Selection , 1979 .