Coping with a challenging environment: Effects of seasonal variability and reproductive status .....IntroductionMethodsStudy site and study populationAmboseli weather dataFemale reproductive stateHormone dataActivity budgetsData analysis and presentationFactors predicting fGC levelsResultsBroad patterns of variability across monthsFactors predicting GC concentrationsWithin-female comparison of wet/dry seasonsEnvironmental factors predicting fGC concentration within wet seasons or dry seasonsDiscussionIndividual and reproductive state differences in fGCEnvironmental conditions and fGC variabilityAcknowledgmentsReferencesCoping with a challenging environment: Effects of seasonal variabilityand reproductive status on glucocorticoid concentrationsof female baboons (Papio cynocephalus)Laurence R. Gesquierea,⁎, Memuna Khanb, Lili Sheka, Tim L. Wangoc,Emmanuel O. Wangoc, Susan C. Albertsd,e, Jeanne Altmanna,c,eaDepartment of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USAbDepartment of Biology, Ripon College, Ripon, WI, USAcDepartment of Animal Physiology and Anatomy, University of Nairobi, Nairobi, KenyadDepartment of Biology, Duke University, Durham, NC, USAeInstitute of Primate Research, National Museums of Kenya, Nairobi, KenyaABSTRACTARTICLE INFOArticle history:Received 12 November 2007Revised 14 April 2008Accepted 15 April 2008Available online 24 April 2008Keywords:Environmental stressorsChronic stressGlucocorticoidsReproductive statusFeeding behaviorFemale baboonsPapioHeat stressDry seasonEnvironmental stressors impact physiology and behavior in many species of animals. These effects are partlymediated through changing concentrations of glucocorticoids, which also vary with reproductive state andsocial conditions. Prior research has focused largely on seasonal breeders, but the close temporal linkagebetween season and reproductive state in these species hinders ability to disentangle environmental effectsfrom those of the animal's reproductive status. Here we assess ed the effects of environmental challenges onthe fecal glucocorticoid (fGC) levels of non-seasonal breeders, female baboons (Papio cynocephalus)ofAmboseli, Kenya. Amboseli is characterized by a long dry season, during which food and water becomescarce, and by extreme temperatures above 40 °C in the shade during some months of the year. We foundthat after accounting for female reproductive status and individual variability, females exhibited higher fGClevels during the dry season than during the wet season. Further, during the wet season, fGC levels werehigher in months of high average daily maximum temperatures. During the dry season, fGC levels wereelevated both in hotter months and in months during which the baboons spent a relatively high proportionof time feeding. In spite of these stressors, female baboons reproduce during all months of the year inAmboseli, unlike most other mammals in this environment. This may be attributable to their extremeadaptability, specifically their diversified diet, and their ability to modify their behavior, including theiractivity profiles.© 2008 Elsevier Inc. All rights reserved.IntroductionEnvironmental stressors such as drought, extremes of hot or coldtemperatures, and food shortage impact reproduction and behavior inmany species of birds (Lynn et al., 2003; Wingfield, 1984) andmammals (Bronson, 1985; Gwazdauskas, 1985; Nelson, 1993; Nelsonet al., 1989), including humans (Bronson, 1995) and non-humanprimates (Alberts et al.; 2005, Beehner et al., 2006b; Brockman andvan Schaik, 2005; Sapolsky, 1986). These effects are in part mediatedvia increases in glucocorticoid (GC) concentrations (Astheimer et al.,1992; Kitaysky et al., 2001b, 2003; reviewed by Boonstra, 2004;Landys et al., 2006; Romero, 2002 and Wingfield and Kitaysky, 2002).The classic illustration of the ecologically adaptive nature of the GCresponse (e.g. Nelson, 2005, p.15) is that of an acute stressor, such as apredator attack, where the GC response leads to an immediatelyadvantageous rapid mobilization of energy that is necessary for “flightor fight”, enhancing gluconeogenesis and shutting down processesthat are not essential for immed iate survival, such as growth,reproduction, and immune function. However, chronically elevatedGC levels can have deleterious consequences for the animal as a resultof ongoing, rather than brief, suppression of growth, reproduction,and immune defense (Boonstra, 2004; McEwen, 1998; Sapolsky et al.,2000; Wingfield, 2005 ).Several approaches have been taken to evaluate the effect ofenvironmental stressors on animal behavior and physiology. Themajority of research has been on single acute stressors, either ap-proached through experimental laboratory studies or, in a few cases,through non-experimental evaluation of acute natural stressors in thefield. In experimental laboratory studies, researchers have usuallycreated such stressors by exposing animals to various single environ-mental stressors for short period: extreme heat (Larsson et al., 1983;Lowe et al., 2002; Olsson et al.,1995,1996; review by Silanikove, 2000);Hormones and Behavior 54 (2008) 410–416⁎ Corresponding author. Fax: +1 609 2582712.E-mail address: [email protected] (L.R. Gesquiere).0018-506X/$ – see front matter © 2008 Elsevier Inc. All rights reserved.doi:10.1016/j.yhbeh.2008.04.007Contents lists available at ScienceDirectHormones and Behaviorjournal homepage: www.elsevier.com/locate/yhbehcold temperatures (DeVries et al., 1997; Filipovic et al., 2007); food orwater deprivation (Astheimer et al., 1992; Dunlap, 1995; Li et al., 2000;Lynn et al., 2003; Tsuma et al., 1996; see also review by Harvey et al.,1984). A few experiments have used a combination of two acutestressors simultaneously, e.g. heat stress in either food deprivedanimals (Olsson et al., 1995) or in water deprived animals (Lowe et al.,2002; Olsson et al., 1996, see also review by Silanikove, 2000).Another approach has evaluated acute environmental challengesin natural contexts by examining changes of GC concentrations infree-ranging animals following intense, relatively brief stressors suchas severe storms (Astheimer et al., 1992, 1995; Wingfield and Kitaysky,2002; Wingfield and Ramenofsky, 1997). As expected for an acutestressor, in all of these studies researchers observed a rapid and shortactivation of the hypothalamic–pituitary-axis (HPA), resulting inelevation of GC levels and inhibition of