Androgen in free-living arctic ground squirrels: seasonal changes and influence of staged male-male aggressive encounters

  title={Androgen in free-living arctic ground squirrels: seasonal changes and influence of staged male-male aggressive encounters},
  author={Charles Loren Buck and Brian M. Barnes},
  journal={Hormones and Behavior},
  • C. Buck, B. Barnes
  • Published 1 February 2003
  • Environmental Science
  • Hormones and Behavior

Changing seasonality and phenological responses of free-living male arctic ground squirrels: the importance of sex

The long-term phenology of hibernating male arctic ground squirrels living at two nearby sites in northern Alaska is investigated and it is suggested that the end of heterothermy in males is influenced by soil temperature and an endogenous circannual clock, but timing of male emergence from hibernation is affected by the timing of female emergence.

Plasma steroid hormones in two Arctic-breeding shorebirds: monogamy versus polygyny.

Testosterone predicts future dominance rank and mating activity among male chacma baboons

The results support the challenge hypothesis with males exhibiting elevated testosterone in association with the acquisition of high rank (ensuring access to mates), rather than with mating itself, and testosterone levels predicted future, rather than current, mating activity.



Seasonal changes in glucocorticoid and testosterone concentrations in free-living arctic ground squirrels from the boreal forest of the Yukon

The primary glucocorticoid was found to be cortisol, with corticosterone below measurable concentrations in most individuals, and values were lowest in all male classes (juveniles, nonreproductive adults, and reproductive adults), being less than half those in all female classes.

Differences in Weight Changes and the Annual Cycle of Male and Female Arctic Ground Squirrels

These data are interpreted in terms of the mating period which for males lasts for approximately three weeks, whereas for females it lasts for less than a day, and male/female differences, weights, annual cycle.

Seasonal variation in circulating testosterone and oestrogens of wild-caught California ground squirrels (Spermophilus beecheyi).

Blood samples were obtained each month for 18 months in 1984-85 from wild-caught California ground squirrels and neither juvenile males nor females differed significantly from same-sex adults with respect to plasma concentrations of oestrogen or testosterone.

Annual Cycle of Body Composition and Hibernation in Free-Living Arctic Ground Squirrels

Timing of immergence into and emergence from hibernation for arctic ground squirrels did not differ significantly from sciurid populations in temperate latitudes and fatter females emerged significantly earlier than leaner females.

Vernal Changes in the Behavioral and Endocrine Responses to GnRH Application in Male European Ground Squirrels

An exogenous pulse of GnRH can apparently release behavior in male European ground squirrels, which is normally context dependent with the emergence of females, according to the phases of the active season.

Seasonal changes in plasma glucocorticosteroids of free-living female yellow-pine chipmunks: effects of reproduction and capture and handling.

Overall, the observations suggest an important role of adrenocortical activity in the energy balance of these free-living rodents in two different contexts: (1) the seasonal regulation of physiological state, including body mass, energy reserves, and reproductive function, and (2) an acute response to stimulatory events, encompassing physiological stress.

Male mating behaviour and patterns of sperm precedence in Arctic ground squirrels

Comparison of sperm precedence patterns in ground squirrels may yield insights into the evolution of interspecific variation in male mating behaviour.

Contrasting stress response of male arctic ground squirrels and red squirrels.

The evidence suggests that the functions associated with the hypothalamic-pituitary-adrenal axis are compromised in breeding male Arctic ground squirrels, but not in red Squirrels, and it is proposed that in male red squirrels this axis has evolved in the context of a stable social system based on long-lived animals with individual territories which are needed to deal with unpredictable winter food supplies.