Demographic analysis of a declining pika Ochotona collaris population: linking survival to broad-scale climate patterns via spring snowmelt patterns.

1. Demographic analysis is essential in order to determine which factors, such as survival, fertility and other life-history characteristics, have the greatest influence on a population's rate of growth (lambda). 2. We used life-table response experiments (LTREs) to assess the relative importance of survival and fertility rates for an alpine lagomorph, the collared pika Ochotona collaris, using 12 years (1995-2006) of census data. The LTRE analysis was repeated for each of three subpopulations within the main study site that were defined by aspect (east, west and south). 3. Across the entire study site, the survival and fertility of adults contributed 35.6 and 43.5%, respectively, to the variance observed in the projected population growth rate, V(lambda), whereas juvenile survival contributed 20.9%. Adult survival and fertility contributed approximately equal amounts for each subpopulation when considered separately, although their rank order varied spatially. 4. Adult survival across the entire site was positively correlated to the Pacific Decadal Oscillation (PDO) with a time lag of 1 year, and was uncorrelated to adult density. The PDO was negatively correlated to the timing of spring snowmelt at our site, implicating the importance of earlier spring conditions and plant phenology on the subsequent winter survival of adults and therefore, population growth. 5. When subpopulations were analysed separately, survivals and fertilities were variously correlated to lagged PDO and adult densities, but the patterns varied spatially. Therefore, the mechanisms underlying V(lambda) can vary substantially over relatively short distances.

[1]  Atle Mysterud,et al.  Weather packages: finding the right scale and composition of climate in ecology , 2005 .

[2]  Hal Caswell,et al.  Elasticity: The Relative Contribution of Demographic Parameters to Population Growth Rate , 1986 .

[3]  Shripad Tuljapurkar,et al.  Structured-Population Models in Marine, Terrestrial, and Freshwater Systems , 1997, Population and Community Biology Series.

[4]  J. Parrish,et al.  Seabirds as indicators: An exploratory analysis of physical forcing in the Pacific Northwest coastal environment , 2003 .

[5]  N. Slade,et al.  Effect of density reduction on uinta ground squirrels : Analysis of life table response experiments , 2001 .

[6]  Zong-ci Zhao,et al.  Climate change 2001, the scientific basis, chap. 8: model evaluation. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change IPCC , 2001 .

[7]  R. Boonstra,et al.  Concurrent density dependence and independence in populations of arctic ground squirrels , 2000, Nature.

[8]  H. Caswell.  PROSPECTIVE AND RETROSPECTIVE PERTURBATION ANALYSES: THEIR ROLES IN CONSERVATION BIOLOGY , 2000 .

[9]  R. Sibly,et al.  Wildlife population growth rates , 2003 .

[10]  Renee J. Franken.  Demography and metapopulation dynamics of collared pikas (Ochotona collaris) in the Southwest Yukon , 2002 .

[11]  M. Forchhammer,et al.  The muskoxen Ovibos moschatus in north and northeast Greenland: population trends and the influence of abiotic parameters on population dynamics , 1993 .

[12]  D. Hik,et al.  Influence of habitat quality, patch size and connectivity on colonization and extinction dynamics of collared pikas Ochotona collaris , 2004 .

[13]  Takashi Saitoh,et al.  Seasonality, density dependence, and population cycles in Hokkaido voles , 2003, Proceedings of the National Academy of Sciences of the United States of America.

[14]  M. Oli,et al.  The Demographic Basis of Population Regulation in Columbian Ground Squirrels , 2001, The American Naturalist.

[15]  Michael D. Dettinger,et al.  Trends in Snowfall versus Rainfall in the Western United States , 2006 .

[16]  Jean-Michel Gaillard,et al.  Generation Time: A Reliable Metric to Measure Life‐History Variation among Mammalian Populations , 2005, The American Naturalist.

[17]  Andrew T. Smith.  Temporal Changes in Insular Populations of the Pika (Ochotona Princeps) , 1980 .

[18]  N. Pettorelli,et al.  The relative role of winter and spring conditions: linking climate and landscape-scale plant phenology to alpine reindeer body mass , 2005, Biology Letters.

[19]  Andrew T. Smith.  The Distribution and Dispersal of Pikas: Influences of Behavior and Climate , 1974 .

[20]  David S. Hik,et al.  Why are Arctic ground squirrels more stressed in the boreal forest than in alpine meadows? , 2001 .

[21]  N. Stenseth,et al.  Global climate change and phenotypic variation among red deer cohorts , 1997, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[22]  Carol C. Horvitz,et al.  Spatiotemporal Variation in Demographic Transitions of a Tropical Understory Herb: Projection Matrix Analysis , 1995 .

[23]  Andrew T. Smith,et al.  Colonization in a pika population: dispersal vs philopatry , 1983, Behavioral Ecology and Sociobiology.

[24]  A. Grant,et al.  How to Keep Fit in the Real World: Elasticity Analyses and Selection Pressures on Life Histories in a Variable Environment , 1996, The American Naturalist.

[25]  Erik A. Beever,et al.  PATTERNS OF APPARENT EXTIRPATION AMONG ISOLATED POPULATIONS OF PIKAS (OCHOTONA PRINCEPS) IN THE GREAT BASIN , 2003 .

[26]  N. Huntly,et al.  Habitat-specific demography: evidence for source-sink population structure in a mammal, the pika , 2003, Oecologia.

[27]  B. Sæther,et al.  Fluctuations of an introduced population of Svalbard reindeer: the effects of density dependence and climatic variation , 2000 .

[28]  C. Pfister,et al.  Patterns of variance in stage-structured populations: evolutionary predictions and ecological implications. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[29]  D. Hik,et al.  Interannual Variation in Timing of Parturition and Growth of Collared Pikas (Ochotona collaris) in the Southwest Yukon1 , 2004, Integrative and comparative biology.

[30]  J. Aars,et al.  Intrinsic and climatic determinants of population demography: The winter dynamics of tundra voles , 2002 .

[31]  J. Wallace,et al.  A Pacific Interdecadal Climate Oscillation with Impacts on Salmon Production , 1997 .

[32]  M. Oli,et al.  The Relative Importance of Life‐History Variables to Population Growth Rate in Mammals: Cole’s Prediction Revisited , 2003, The American Naturalist.

[33]  K. L. Duke.  The External Genitalia of the Pika, Ochotona princeps , 1951 .

[34]  J. Millar.  EVOLUTION OF LITTER‐SIZE IN THE PIKA, OCHOTONA PRINCEPS (RICHARDSON) , 1973, Evolution; international journal of organic evolution.

[35]  Andrew T. Smith,et al.  Dramatic decline of the threatened Ili pika Ochotona iliensis (Lagomorpha: Ochotonidae) in Xinjiang, China , 2005, Oryx.

[36]  E. Bignal,et al.  Identifying the demographic determinants of population growth rate: a case study of red‐billed choughs Pyrrhocorax pyrrhocorax , 2004 .

[37]  B. Charlesworth,et al.  Evolution in Age-Structured Populations. , 1995 .

[38]  T. H. Clutton-Brock,et al.  Why large-scale climate indices seem to predict ecological processes better than local weather , 2004, Nature.

[39]  T. Gardali,et al.  LONG-TERM DECLINES AND DECADAL PATTERNS IN POPULATION TRENDS OF SONGBIRDS IN WESTERN NORTH AMERICA, 1979–1999 , 2003 .

[40]  F. Dobson,et al.  Regulation of population size: evidence from Columbian ground squirrels , 1995, Oecologia.

[41]  Andrew T. Smith.  Comparative Demography of Pikas (Ochotona): Effect of Spatial and Temporal Age‐Specific Mortality , 1978 .

[42]  J. Millar.  Success of reproduction in pikas, Ochotona princeps (Richardson). , 1974, Journal of Mammalogy.

[43]  James H. Brown,et al.  Using Montane Mammals to Model Extinctions Due to Global Change , 1992 .

[44]  D. Schindler,et al.  EFFECTS OF CHANGING CLIMATE ON ZOOPLANKTON AND JUVENILE SOCKEYE SALMON GROWTH IN SOUTHWESTERN ALASKA , 2005 .

[45]  K. Armitage,et al.  YELLOW-BELLIED MARMOT POPULATION DYNAMICS: DEMOGRAPHIC MECHANISMS OF GROWTH AND DECLINE , 2004 .

[46]  Nils Chr. Stenseth,et al.  CLIMATIC VARIABILITY, PLANT PHENOLOGY, AND NORTHERN UNGULATES , 1999 .

[47]  D. Doak,et al.  HOW GENERAL ARE THE DETERMINANTS OF THE STOCHASTIC POPULATION GROWTH RATE ACROSS NEARBY SITES , 2005 .

[48]  C. Krebs.  Ecology: The Experimental Analysis of Distribution and Abundance , 1973 .

[49]  Peter Turchin,et al.  Complex Population Dynamics , 2003 .

[50]  J. Gaillard,et al.  Decomposing the variation in population growth into contributions from multiple demographic rates , 2005 .

[51]  J. Papineau,et al.  Wintertime temperature anomalies in Alaska correlated with ENSO and PDO , 2001 .

[52]  L. Crowder,et al.  LIFE HISTORIES AND ELASTICITY PATTERNS: PERTURBATION ANALYSIS FOR SPECIES WITH MINIMAL DEMOGRAPHIC DATA , 2000 .

[53]  Brian Charlesworth,et al.  Evolution in Age-Structured Populations. , 1983 .

[54]  A. Mysterud,et al.  Review article. Studying climate effects on ecology through the use of climate indices: the North Atlantic Oscillation, El Niño Southern Oscillation and beyond , 2003, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[55]  Eliot J. B. McIntire,et al.  Influences of chronic and current season grazing by collared pikas on above-ground biomass and species richness in subarctic alpine meadows , 2005, Oecologia.

[56]  John E. Walsh,et al.  IMPACTS OF LARGE‐SCALE ATMOSPHERIC–OCEAN VARIABILITY ON ALASKAN FIRE SEASON SEVERITY , 2005 .

[57]  C. Symon,et al.  Arctic climate impact assessment , 2005 .