Human-caused mortality influences spatial population dynamics: Pumas in landscapes with varying mortality risks
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)
- et al.
Conservation science relevant to action: a research agenda identified and prioritized by practitioners
Biol. Conserv.
(2012) - et al.
On the role of refugia in promoting prudent use of biological resources
Theor. Popul. Biol.
(1991) - et al.
Detectability, philopatry, and the distribution of dispersal distances in vertebrates
Trends Ecol. Evol.
(1996) - et al.
A range-wide model of landscape connectivity and conservation for the jaguar, Panthera onca
Biol. Conserv.
(2010) - et al.
Estimating effects of adult male mortality on grizzly bear population growth and persistence using matrix models
Biol. Conserv.
(2001) - et al.
Edge effects and the impact of non-protected areas in carnivore conservation: leopards in the Phinda-Mkhuze Complex, South Africa
Anim. Conserv.
(2010) Dispersal of juvenile cougars in fragmented habitat
J. Wildlife Manage.
(1995)A focal species for conservation planning
- et al.
Connectivity, sustainability, and yield: bridging the gap between conventional fisheries management and marine protected areas
Rev. Fish Biol. Fisheries
(2009) - et al.
Causes and consequences of animal dispersal strategies: relating individual behaviour to spatial dynamics
Biol. Rev.
(2005)
Model Selection and Inference: A Practical Information-Theoretic Approach
Does hunting regulate cougar populations? A test of the compensatory mortality hypothesis
Ecology
Source populations in carnivore management: cougar demography and emigration in a lightly hunted population
Anim. Conserv.
Can we improve estimates of juvenile dispersal distance and survival?
Ecology
Garnet Mountans Mountain Lion Research Progress Report
Defining patch contribution in source–sink metapopulations: the importance of including dispersal and its relevance to marine systems
Popul. Ecol.
Population dynamics of the California spotted owl (Strix occidentalis occidentalis): a meta-analysis
Ornithol. Monogr.
Temporal variation in fitness components and population dynamics of large herbivores
Annu. Rev. Ecol. Syst.
Individual and population level determinants of immigration success on local habitat patches: an experimental approach
Ecol. Lett.
Source–sink dynamics: how sinks affect demography of sources
Ecol. Lett.
Monitoring survival of young in ungulates: a case study with Rocky Mountain elk
Population regulation: historical context and contemporary challenges of open vs. closed systems
Ecology
Innate and environmental dispersal of individual vertebrates
Am. Midl. Nat.
Population-specific vital rate contributions influence management of an endangered ungulate
Ecol. Appl.
Territory and the regulation of density in titmice
Moose dispersal and its role in the maintenance of harvested populations
J. Wildlife Manage.
Patterns of replacement of resident cougars in Southern Utah
J. Mammal.
Desert Puma: Evolutionary Ecology and Conservation of an Enduring Carnivore
Density-dependent dispersal in birds and mammals
Ecography
Spatially structured populations and harvest theory
J. Wildlife Manage.
Cited by (0)
- 1
Present address: Selway Institute, PO Box 92940, Heronwood Lane, Bellevue, ID 83313, USA