Modeling amphibian energetics, habitat suitability, and movements of western toads, Anaxyrus (=Bufo) boreas, across present and future landscapes

Abstract Effective conservation of amphibian populations requires the prediction of how amphibians use and move through a landscape. Amphibians are closely coupled to their physical environment. Thus an approach that uses the physiological attributes of amphibians, together with knowledge of their natural history, should be helpful. We used Niche Mapper™ to model the known movements and habitat use patterns of a population of Western toads (Anaxyrus (=Bufo) boreas) occupying forested habitats in southeastern Idaho. Niche Mapper uses first principles of environmental biophysics to combine features of topography, climate, land cover, and animal features to model microclimates and animal physiology and behavior across landscapes. Niche Mapper reproduced core body temperatures (Tc) and evaporation rates of live toads with average errors of 1.6 ± 0.4 °C and 0.8 ± 0.2 g/h, respectively. For four different habitat types, it reproduced similar mid-summer daily temperature patterns as those measured in the field and calculated evaporation rates (g/h) with an average error rate of 7.2 ± 5.5%. Sensitivity analyses indicate these errors do not significantly affect estimates of food consumption or activity. Using Niche Mapper we predicted the daily habitats used by free-ranging toads; our accuracy for female toads was greater than for male toads (74.2 ± 6.8% and 53.6 ± 15.8%, respectively), reflecting the stronger patterns of habitat selection among females. Using these changing to construct a cost surface, we also reconstructed movement paths that were consistent with field observations. The effect of climate warming on toads depends on the interaction of temperature and atmospheric moisture. If climate change occurs as predicted, results from Niche Mapper suggests that climate warming will increase the physiological cost of landscapes thereby limiting the activity for toads in different habitats.

[1]  P. Licht,et al.  The Role of Behavioral Thermoregulation in the Growth Energetics of the Toad, Bufo Boreas , 1973 .

[2]  W. Porter,et al.  Model of Japanese serow (Capricornis crispus) energetics predicts distribution on Honshu, Japan. , 2007, Ecological applications : a publication of the Ecological Society of America.

[3]  E. Muths.  Home Range and Movements of Boreal Toads in Undisturbed Habitat , 2003, Copeia.

[4]  D. Green.  PERSPECTIVES ON AMPHIBIAN POPULATION DECLINES: DEFINING THE PROBLEM AND SEARCHING FOR ANSWERS. , 1997 .

[5]  C. Tracy.  A Model of the Dynamic Exchanges of Water and Energy between a Terrestrial Amphibian and Its Environment , 1976 .

[6]  F. Ayala,et al.  Are We in the Midst of the Sixth Mass Extinction? A View from the World of Amphibians , 2008 .

[7]  Michael J. Oimoen,et al.  The National Elevation Dataset , 2002 .

[8]  J. Karr.  Assessment of Biotic Integrity Using Fish Communities , 1981 .

[9]  Robert D. Stevenson,et al.  Integrating Thermal Physiology and Ecology of Ectotherms: A Discussion of Approaches , 1979 .

[10]  Pierre Joly,et al.  Modeling spatial distribution of amphibian populations: a GIS approach based on habitat matrix permeability , 2002, Biodiversity & Conservation.

[11]  W. Beckman,et al.  Behavioral implications of mechanistic ecology , 1973, Oecologia.

[12]  W. E. Stewart,et al.  Endotherm Energetics: from a Scalable Individual-based Model to Ecological Applications , 1994 .

[13]  D. Pilliod,et al.  Seasonal migration of Columbia spotted frogs (Rana luteiventris) among complementary resources in a high mountain basin , 2002 .

[14]  G. S. Bakken.  Arboreal Perch Properties and the Operative Temperature Experienced by Small Animals , 1989 .

[15]  C. Tracy,et al.  BEHAVIORAL THERMOREGULATION BY BUFO AMERICANUS: THE IMPORTANCE OF THE HYDRIC ENVIRONMENT , 1993 .

[16]  W. Porter,et al.  Po'ouli landscape bioinformatics models predict energetics, behavior, diets, and distribution on Maui. , 2006, Integrative and comparative biology.

[17]  W. Porter.  New Animal Models and Experiments for Calculating Growth Potential at Different Elevations , 1989, Physiological Zoology.

[18]  Raymond D. Semlitsch,et al.  Biological Criteria for Buffer Zones around Wetlands and Riparian Habitats for Amphibians and Reptiles , 2003 .

[19]  E. McCullough,et al.  Computing Clear Day Solar Radiation Spectra for the Terrestrial Ecological Environment , 1971 .

[20]  R. Olmstead,et al.  Mitochondrial DNA evolution in the Anaxyrus boreas species group. , 2009, Molecular phylogenetics and evolution.

[21]  P. Withers,et al.  The effects of hypoxia on pulmonary function and maximal rates of oxygen consumption in two anuran amphibians , 1983, Journal of comparative physiology.

[22]  David H. Douglas.  Least-cost Path in GIS Using an Accumulated Cost Surface and Slopelines , 1994 .

[23]  J. Dutoit.  The Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) , 2007 .

[24]  R. Huey,et al.  Physiological Consequences of Habitat Selection , 1991, The American Naturalist.

[25]  R. Alford,et al.  Emerging disease of amphibians cured by elevated body temperature. , 2003, Diseases of aquatic organisms.

[26]  David R. Anderson,et al.  Model selection and multimodel inference : a practical information-theoretic approach , 2003 .

[27]  R. D. Semlitsch,et al.  Demographic Consequences of Terrestrial Habitat Loss for Pool‐Breeding Amphibians: Predicting Extinction Risks Associated with Inadequate Size of Buffer Zones , 2008, Conservation biology : the journal of the Society for Conservation Biology.

[28]  Peter J. Hudson,et al.  Evaluating the links between climate, disease spread, and amphibian declines , 2008, Proceedings of the National Academy of Sciences.

[29]  Paul Stephen Corn,et al.  Effects of Amphibian Chytrid Fungus on Individual Survival Probability in Wild Boreal Toads , 2010, Conservation biology : the journal of the Society for Conservation Biology.

[30]  C. Funk,et al.  High dispersal in a frog species suggests that it is vulnerable to habitat fragmentation , 2005, Biology Letters.

[31]  P. S. Corn,et al.  Responses of pond-breeding amphibians to wildfire: short-term patterns in occupancy and colonization. , 2007, Ecological applications : a publication of the Ecological Society of America.

[32]  R. Klaver,et al.  SEXUAL DIFFERENCES IN THE POST-BREEDING MOVEMENTS AND HABITATS SELECTED BY WESTERN TOADS (BUFO BOREAS) IN SOUTHEASTERN IDAHO , 2004 .

[33]  Susan C. Walls,et al.  The Amphibian Research and Monitoring Initiative (ARMI): 5-year report , 2006 .

[34]  Randall B. Boone,et al.  Simulating wood frog movement in central Minnesota, USA using a diffusion model , 2006 .

[35]  H. Sipilä,et al.  Enhanced oxygen extraction and reduced flow heterogeneity in exercising muscle in endurance-trained men. , 2001, American journal of physiology. Endocrinology and metabolism.

[36]  M. Kearney,et al.  Modelling species distributions without using species distributions: the cane toad in Australia under current and future climates , 2008 .

[37]  Peter E. Thornton,et al.  Generating surfaces of daily meteorological variables over large regions of complex terrain , 1997 .

[38]  B. Young,et al.  Response to Comment on "Status and Trends of Amphibian Declines and Extinctions Worldwide" , 2005, Science.

[39]  Joseph K. Berry,et al.  Fundamental operations in computer-assisted map analysis , 1987, Int. J. Geogr. Inf. Sci..

[40]  Alisa L. Gallant,et al.  Global Rates of Habitat Loss and Implications for Amphibian Conservation , 2007, Copeia.

[41]  S. Ritchie,et al.  Integrating biophysical models and evolutionary theory to predict climatic impacts on species’ ranges: the dengue mosquito Aedes aegypti in Australia , 2009 .

[42]  G. Campbell,et al.  An Introduction to Environmental Biophysics , 1977 .

[43]  B. Brattstrom,et al.  Thermal acclimation in anuran amphibians as a function of latitude and altitude. , 1968, Comparative biochemistry and physiology.

[44]  P. S. Corn,et al.  Wildfire effects on water temperature and selection of breeding sites by the Boreal Toad (Bufo boreas) in seasonal wetlands , 2007 .

[45]  D. M. Gates,et al.  THERMODYNAMIC EQUILIBRIA OF ANIMALS WITH ENVIRONMENT , 1969 .

[46]  F. Burbrink,et al.  Phylogeographic and demographic effects of Pleistocene climatic fluctuations in a montane salamander, Plethodon fourchensis , 2009, Molecular ecology.

[47]  Physically modeling operative temperatures and evaporation rates in amphibians , 2005 .

[48]  David Cook,et al.  Pathogenesis of Chytridiomycosis, a Cause of Catastrophic Amphibian Declines , 2009, Science.

[49]  Michael R Kearney,et al.  Predicting the fate of a living fossil: how will global warming affect sex determination and hatching phenology in tuatara? , 2008, Proceedings of the Royal Society B: Biological Sciences.

[50]  B. Verboom,et al.  Effects of pool size and isolation on amphibian communities , 1990 .

[51]  M. Lannoo.  Amphibian Declines: The Conservation Status of United States Species , 2005 .

[52]  C. Carey.  Factors affecting body temperatures of toads , 2004, Oecologia.