title: Male endocrine response to seasonally varying environmental and social factors in a neotropical primate, Cebus capucinus.
abstract: OBJECTIVE
  Circannual variation in reproduction is pervasive in birds and mammals. In primates, breeding seasonality is variable, with seasonal birth peaks occurring even in year-round breeders. Environmental seasonality is reportedly an important contributor to the observed variation in reproductive seasonality. Given that food availability is the primary factor constraining female reproduction, predictions concerning responsiveness to environmental seasonality focus on females, with studies of males focusing primarily on social factors. We examined the influence of both environmental and social factors on male fecal testosterone (fT) and glucocorticoids (fGC) in moderately seasonally breeding white-faced capuchin monkeys (Cebus capucinus) in Costa Rica.
  
  
  METHODS
  Over 17 months, we collected 993 fecal samples from 14 males in three groups. We used LMM to simultaneously examine the relative effects of photoperiod, fruit biomass, rainfall, temperature, female reproductive status (i.e., number of periovulatory periods, POPs), and male age and dominance rank on monthly fT and fGC levels.
  
  
  RESULTS
  Male age and rank had large effects on fT and fGC. Additionally, some hormone variation was explained by environmental factors: photoperiod in the previous month (i.e., lagged photoperiod) was the best environmental predictor of monthly fT levels, whereas fGC levels were best explained by lagged photoperiod, fruit biomass, and rainfall. POPs predicted monthly fT and fGC, but this effect was reduced when all variables were considered simultaneously, possibly because lagged photoperiod and POP were highly correlated.
  
  
  CONCLUSIONS
  Males may use photoperiod as a cue predicting circannual trends in the temporal distribution of fertile females, while also fine-tuning short-term hormone increases to the actual presence of ovulatory females, which may occur at any time during the year.
authors.affiliation: Bilingual Biology Program, Multidisciplinary Studies Department, Glendon College, York University, Toronto, ON, M4N 3M6, Canada.|Department of Anthropology, Tulane University, New Orleans, LA, 70118.|Department of Anthropology, McGill University, Montréal, QC, H3A 0G4, Canada.
authors.forename: Valérie A M
authors.initials: VA
authors.lastname: Schoof
authors.affiliation: Department of Psychology, University of Lethbridge, Lethbridge, AB, T1K 6T5, Canada.|Department of Geography, McGill University, Montréal, QC, H3A 0G4, Canada.
authors.forename: Tyler R
authors.initials: TR
authors.lastname: Bonnell
authors.affiliation: Department of Anthropology, Tulane University, New Orleans, LA, 70118.
authors.forename: Katharine M
authors.initials: KM
authors.lastname: Jack
authors.affiliation: Wisconsin National Primate Research Center, University of Wisconsin, Madison, WI, 53706.
authors.forename: Toni E
authors.initials: TE
authors.lastname: Ziegler
authors.affiliation: Department of Anthropology, Washington University in St. Louis, St. Louis, MO, 63130.
authors.forename: Amanda D
authors.initials: AD
authors.lastname: Melin
authors.affiliation: Department of Anthropology, University of Calgary, Calgary, AB, T2N 1N4, Canada.
authors.forename: Linda M
authors.initials: LM
authors.lastname: Fedigan
mesh_terms: D000818:Animals; D000885:Anthropology, Physical; D002428:Cebus / Q000502:physiology*; D003364:Costa Rica; D005243:Feces / Q000737:chemistry; D005260:Female; D005938:Glucocorticoids / Q000032:analysis*; D008297:Male; D015233:Models, Statistical; D017440:Photoperiod; D012098:Reproduction / Q000502:physiology*; D012621:Seasons; D013739:Testosterone / Q000032:analysis*; D014887:Weather
chemical_list: D005938:Glucocorticoids; D013739:Testosterone
keywords: androgens; glucocorticoids; income-capital breeding; photoperiod; reproductive physiology; testosterone