title: Modeling behavioral thermoregulation in a climate change sentinel.
abstract: When possible, many species will shift in elevation or latitude in response to rising temperatures. However, before such shifts occur, individuals will first tolerate environmental change and then modify their behavior to maintain heat balance. Behavioral thermoregulation allows animals a range of climatic tolerances and makes predicting geographic responses under future warming scenarios challenging. Because behavioral modification may reduce an individual's fecundity by, for example, limiting foraging time and thus caloric intake, we must consider the range of behavioral options available for thermoregulation to accurately predict climate change impacts on individual species. To date, few studies have identified mechanistic links between an organism's daily activities and the need to thermoregulate. We used a biophysical model, Niche Mapper, to mechanistically model microclimate conditions and thermoregulatory behavior for a temperature-sensitive mammal, the American pika (Ochotona princeps). Niche Mapper accurately simulated microclimate conditions, as well as empirical metabolic chamber data for a range of fur properties, animal sizes, and environmental parameters. Niche Mapper predicted pikas would be behaviorally constrained because of the need to thermoregulate during the hottest times of the day. We also showed that pikas at low elevations could receive energetic benefits by being smaller in size and maintaining summer pelage during longer stretches of the active season under a future warming scenario. We observed pika behavior for 288 h in Glacier National Park, Montana, and thermally characterized their rocky, montane environment. We found that pikas were most active when temperatures were cooler, and at sites characterized by high elevations and north-facing slopes. Pikas became significantly less active across a suite of behaviors in the field when temperatures surpassed 20°C, which supported a metabolic threshold predicted by Niche Mapper. In general, mechanistic predictions and empirical observations were congruent. This research is unique in providing both an empirical and mechanistic description of the effects of temperature on a mammalian sentinel of climate change, the American pika. Our results suggest that previously underinvestigated characteristics, specifically fur properties and body size, may play critical roles in pika populations' response to climate change. We also demonstrate the potential importance of considering behavioral thermoregulation and microclimate variability when predicting animal responses to climate change.
authors.affiliation: Department of Biology University of Utah Salt Lake City Utah; Department of Zoology University of Wisconsin-Madison Madison Wisconsin.
authors.forename: Lucas
authors.initials: L
authors.lastname: Moyer-Horner
authors.affiliation: Department of Zoology University of Wisconsin-Madison Madison Wisconsin.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Mathewson
authors.affiliation: Department of Forest & Wildlife Ecology University of Wisconsin-Madison Madison Wisconsin.
authors.forename: Gavin M
authors.initials: GM
authors.lastname: Jones
authors.affiliation: Department of Zoology The University of Melbourne Melbourne Victoria Australia.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Kearney
authors.affiliation: Department of Zoology University of Wisconsin-Madison Madison Wisconsin.
authors.forename: Warren P
authors.initials: WP
authors.lastname: Porter
keywords: Activity; American pika; Glacier National Park; Niche Mapper; Ochotona princeps; biophysical model; elevation; protected area; temperature
references.citation: J Anim Ecol. 2010 Jul;79(4):726-46
references.pmid: 20443992
references.citation: Can J Zool. 1973 Jan;51(1):11-6
references.pmid: 4696076
references.citation: Front Biosci (Landmark Ed). 2011 Jan 01;16:1428-44
references.pmid: 21196240
references.citation: PLoS One. 2013 Sep 03;8(9):e72863
references.pmid: 24019883
references.citation: Ecol Appl. 2010 Jan;20(1):164-78
references.pmid: 20349838
references.citation: Science. 2010 May 14;328(5980):894-9
references.pmid: 20466932
references.citation: Philos Trans R Soc Lond B Biol Sci. 2012 Jun 19;367(1596):1665-79
references.pmid: 22566674
references.citation: Science. 2011 Aug 19;333(6045):1024-6
references.pmid: 21852500
references.citation: PLoS One. 2015 Mar 24;10(3):e0119327
references.pmid: 25803587
references.citation: Can J Zool. 1974 Mar;52(3):353-8
references.pmid: 4819475
references.citation: PLoS One. 2014 Aug 12;9(8):e104648
references.pmid: 25115894
references.citation: Ecology. 2011 Sep;92(9):1730-5
references.pmid: 21939069
references.citation: Science. 2008 Oct 10;322(5899):261-4
references.pmid: 18845755
references.citation: Ecol Appl. 2013 Jun;23(4):864-78
references.pmid: 23865236
references.citation: Sci Data. 2014 May 27;1:140006
references.pmid: 25977764
references.citation: Glob Chang Biol. 2013 Oct;19(10):2932-9
references.pmid: 23681970