Elsevier

Biological Conservation

Volume 159, March 2013, Pages 230-239
Biological Conservation

Human-caused mortality influences spatial population dynamics: Pumas in landscapes with varying mortality risks

https://doi.org/10.1016/j.biocon.2012.10.018Get rights and content

Abstract

An understanding of how stressors affect dispersal attributes and the contribution of local populations to multi-population dynamics are of immediate value to basic and applied ecology. Puma (Puma concolor) populations are expected to be influenced by inter-population movements and susceptible to human-induced source–sink dynamics. Using long-term datasets we quantified the contribution of two puma populations to operationally define them as sources or sinks. The puma population in the Northern Greater Yellowstone Ecosystem (NGYE) was largely insulated from human-induced mortality by Yellowstone National Park. Pumas in the western Montana Garnet Mountain system were exposed to greater human-induced mortality, which changed over the study due to the closure of a 915 km2 area to hunting. The NGYE’s population growth depended on inter-population movements, as did its ability to act as a source to the larger region. The heavily hunted Garnet area was a sink with a declining population until the hunting closure, after which it became a source with positive intrinsic growth and a 16× increase in emigration. We also examined the spatial and temporal characteristics of individual dispersal attributes (emigration, dispersal distance, establishment success) of subadult pumas (N = 126). Human-caused mortality was found to negatively impact all three dispersal components. Our results demonstrate the influence of human-induced mortality on not only within population vital rates, but also inter-population vital rates, affecting the magnitude and mechanisms of local population’s contribution to the larger metapopulation.

Highlights

► We quantified the contribution of two local populations to their metapopulations. ► Sources and sinks were operationally defined with interpopulation vital rates. ► Source populations may still depend on interpopulation movements for growth. ► Anthropogenic mortality shape source–sink dynamics via interpopulation vital rates. ► Anthropogenic mortality reduced the amount, extent, and effectiveness of dispersal.

Introduction

An understanding of how human-induced mortality affects dispersal characteristics and the role of local populations on the landscape is of immediate value to conservation (Braunisch et al., 2012). Recognizing that populations interact across heterogeneous environments (Revilla et al., 2004, Small et al., 1991, Thomas and Kunin, 1999), wildlife and fisheries managers are increasingly incorporating population spatial structure into conservation efforts (Botsford et al., 2009, McCullough, 1996, Rabinowitz and Zeller, 2010). Spatial management approaches are especially applicable when mortality operates differentially across the landscape (e.g. in and around protected areas) (Balme et al., 2010, Novaro et al., 2005, Woodroffe and Ginsberg, 1998) and for highly vagile and cryptic species (Joshi and Gadgil, 1991, McCullough, 1996).

Our understanding of stage-specific mortality effects on local population dynamics in vertebrates is well developed, with strong links between conceptual models and field data (Gaillard et al., 2000, Johnson et al., 2010, Oli and Dobson, 2003, Saether and Bakke, 2000). By contrast, few studies have explicitly linked field data to models of landscape population dynamics that account for influences of mortality on both within and among-population vital rates (Griffin and Mills, 2009, Runge et al., 2006).

Dispersal involves three distinct components: emigration from the natal range, movement between natal and breeding range, and successful establishment into that breeding range (Bowler and Benton, 2005, Howard, 1960). Due to the long and unpredictable movements inherent in dispersal events, estimating these components can be difficult (Cooper et al., 2008, Koenig et al., 1996, Morrison and Wood, 2009). If among and within-population vital rates can be derived from the field, however, the role of a local population within the multi-population context can be quantified and source and sink areas operationally identified (Griffin and Mills, 2009, Runge et al., 2006).

Pumas provide an example of the importance of inter-population processes and spatial structure for population ecology and management. Dispersal can have a prominent effect on puma population dynamics. For example, emigration can lead to local populations exhibiting lower growth rates than those expected from positive intrinsic vital rates (Cooley et al., 2009a, Robinson and DeSimone., 2011). Conversely, immigration can offset the population declines expected from negative intrinsic growth (Robinson et al., 2008). Pumas are also subject to mortality from hunting, depredation removals, and other conflicts with humans which can create source–sink dynamics (Cooley et al., 2009b, Robinson et al., 2008, Stoner et al., 2006, Thompson and Jenks, 2005).

We used long-term, large-scale demographic data from two puma populations with varying levels of human-induced mortality to determine how mortality affects spatial population dynamics. Specifically, we operationally defined the populations as sources and sinks based on within-population growth and between population exchange, and determined how these varied temporally. Additionally, we examined the effects of human-caused mortality on individual dispersal components (emigration, dispersal movement, and establishment success).

The Northern Greater Yellowstone Ecosystem (NGYE) puma population was largely insulated from anthropogenic risks. We used NGYE puma data from 2 periods. From 1987 to 1993 (hereafter “phase I”) the puma population was increasing after control efforts within Yellowstone National Park (early 20th century) and persecution as a predator in surrounding areas (up to 1971) ceased (Murphy et al., 1999). During phase II (1998–2005) of NGYE research, the puma population was relatively stable and at a higher density (Ruth and Buotte, 2007).

In contrast to the NGYE, our second population in the Garnet Mountains of Montana was exposed to higher human-caused mortality. In the first 3 years of Garnet research (1997–2000), pumas were heavily hunted throughout the study area, but in subsequent years (2001–2006) hunting was restricted (Robinson and DeSimone, 2011). However, human-induced mortality remained relatively high over all years of Garnet research compared to the NGYE (Montana Fish, Wildlife and Parks hunt reports 1988–2007; (DeSimone and Semmens, 2005, Ruth et al., 2011). We hypothesized that after puma hunting was restricted in the Garnet area the population’s per capita contribution to the region would increase in part due to higher levels of dispersal into surrounding subpopulations.

To help interpret changes in source–sink dynamics, we developed regression models of emigration, dispersal distance and establishment success to assess the influence of human-caused mortality. We tested the following predictions for how human-caused mortality could affect these three dispersal components:

  • (1)

    Emigration: Increases in the human-caused mortality rate would reduce the probability of subadults emigrating. The reduction of emigration could result from direct mortality on subadults or by opening up adult territories, thus encouraging philopatry (Cooley et al., 2009b).

  • (2)

    Dispersal distances: Dispersal distances would be shorter under higher levels of puma harvest. Harvest could influence dispersal distances directly by killing individuals as they dispersed and ending their movements. Heavy harvest could also create population turnover and open territories for settlement (Kluyver and Tinbergen, 1970, Waser, 1985) leading to settlement closer to natal areas.

  • (3)

    Establishment success: Dispersers in areas with heavy harvest would have a reduced probability of successfully surviving to establish an adult home range, due to direct mortality from harvest.

We assessed the influence of human-caused mortality on dispersal components by developing and testing competing models which also included effects of spatial/temporal variation, sex, and the presence of wolves.

Section snippets

Northern Greater Yellowstone Ecosystem (NGYE)

The primary study area covered 3779 km2, including the northern range of Yellowstone National Park, the adjoining Absorka-Beartooth Wilderness, and private and public lands in the Gardiner basin (Murphy, 1998, Ruth et al., 2011). Terrain is mountainous with steep broken canyons along the Yellowstone River and elevations ranging from 1500 to 2900 m. Documentation of dispersal movements extended out 200 km from the study area across the Greater Yellowstone Ecosystem.

Wolves were reintroduced to

Field sampling

Dependent kittens marked during research totaled 200 (NGYE n = 116; Garnet n = 84) and 113 of these kittens were monitored to subadult age (NGYE n = 61; Garnet n = 52). Additional pumas born on the study areas initially captured as subadults increased the total number of marked subadults to 126 (NGYE n = 68; Garnet n = 58). Of these marked individuals, 104 (83%) were monitored until their fate (death or successful establishment as adults) could be determined (NGYE n = 53; Garnet n = 51).

Emigration

NGYE showed no sex

Discussion

We brought together extensive field datasets from 2 study areas to quantify puma dispersal characteristics and explore the landscape-level effects of human-induced mortality on these characteristics. Furthermore, we used inter-population vital rate estimates, coupled with estimated within-population growth, to quantify each population’s contribution to landscape-level dynamics and operationally define them as sources or sinks (Griffin and Mills, 2009).

Acknowledgements

Research was supported by Craighead Beringia South, Hornocker Wildlife Research Institute, Montana Department of Fish Wildlife & Parks, Montana Cooperative Wildlife Research Unit, Panthera, Panthera-Kaplan Graduate Awards Program, Richard King Mellon Foundation, Summerlee Foundation, University of Montana, U.S. Geological Survey, Wildlife Conservation Society, and Yellowstone National Park. LSM acknowledges support from NSF DEB (0841884) and USGS National Climate Change and Wildlife Science

References (64)

  • K.P. Burnham et al.

    Model Selection and Inference: A Practical Information-Theoretic Approach

    (1998)
  • H. Cooley et al.

    Does hunting regulate cougar populations? A test of the compensatory mortality hypothesis

    Ecology

    (2009)
  • H.S. Cooley et al.

    Source populations in carnivore management: cougar demography and emigration in a lightly hunted population

    Anim. Conserv.

    (2009)
  • C.B. Cooper et al.

    Can we improve estimates of juvenile dispersal distance and survival?

    Ecology

    (2008)
  • Cougar Management Guidelines Working Group, 2005. Cougar Management Guidelines. WildFutures, Bainbridge Island,...
  • R. DeSimone et al.

    Garnet Mountans Mountain Lion Research Progress Report

    (2005)
  • W.F. Figueira et al.

    Defining patch contribution in source–sink metapopulations: the importance of including dispersal and its relevance to marine systems

    Popul. Ecol.

    (2006)
  • A.B. Franklin et al.

    Population dynamics of the California spotted owl (Strix occidentalis occidentalis): a meta-analysis

    Ornithol. Monogr.

    (2004)
  • J.M. Gaillard et al.

    Temporal variation in fitness components and population dynamics of large herbivores

    Annu. Rev. Ecol. Syst.

    (2000)
  • Griffin, P.C., Mills, L.S., 2009. Sinks without borders: snowshoe hare dynamics in a complex landscape....
  • G. Gundersen et al.

    Individual and population level determinants of immigration success on local habitat patches: an experimental approach

    Ecol. Lett.

    (2002)
  • G. Gundersen et al.

    Source–sink dynamics: how sinks affect demography of sources

    Ecol. Lett.

    (2001)
  • N.C. Harris

    Monitoring survival of young in ungulates: a case study with Rocky Mountain elk

    (2007)
  • M.A. Hixon et al.

    Population regulation: historical context and contemporary challenges of open vs. closed systems

    Ecology

    (2002)
  • W.E. Howard

    Innate and environmental dispersal of individual vertebrates

    Am. Midl. Nat.

    (1960)
  • H.E. Johnson et al.

    Population-specific vital rate contributions influence management of an endangered ungulate

    Ecol. Appl.

    (2010)
  • H.N. Kluyver et al.

    Territory and the regulation of density in titmice

  • J. Labonte et al.

    Moose dispersal and its role in the maintenance of harvested populations

    J. Wildlife Manage.

    (1998)
  • S.P. Laing et al.

    Patterns of replacement of resident cougars in Southern Utah

    J. Mammal.

    (1993)
  • K.A. Logan et al.

    Desert Puma: Evolutionary Ecology and Conservation of an Enduring Carnivore

    (2001)
  • E. Matthysen

    Density-dependent dispersal in birds and mammals

    Ecography

    (2005)
  • D.R. McCullough

    Spatially structured populations and harvest theory

    J. Wildlife Manage.

    (1996)
  • Cited by (0)

    1

    Present address: Selway Institute, PO Box 92940, Heronwood Lane, Bellevue, ID 83313, USA

    View full text