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I am I and my circumstances, or how social context influences the relationship between testosterone and ornamentation

One century ago, the Spanish philosopher Ortega y Gasset highlighted the importance of considering the individual context when trying to understand the individual itself and his decisions. In recent times biologists have acknowledged the importance of the –physical, ecological, social- context in the resolution of individual trade-offs aiming at achieving an optimal strategy. These trade-offs often involve complex physiological pathways, many of which are regulated by hormones that influence the expression of signals and behaviours playing roles in communication and sexual selection. Testosterone plays a key role in this kind of processes, enhancing territorial and agonistic behaviour, ornament expression, etc. However, increased testosterone levels may also convey deleterious side effects, which is key to understand the function and evolution of these traits. In a study recently published in Hormones and Behavior we studied how does social context modulates the effect of testosterone on signal expression and its associated costs. We manipulated testosterone levels in 196 male grouse (Lagopus lagopus scoticus) in high and low intrasexual competition, corresponding to contrasted levels of male-male competition for territories at the time of their independence, a vital resource for their survival and reproduction. We found that, besides the fact that treatments were identical across populations, the effects on hormone levels, size and colour of the ornaments and individual condition varied depending on the level of intrasexual competition. Specifically, young males living in low intrasexual competition contexts may afford the cost of expressing a sexual signal, whereas this becomes more difficult for individuals living in populations of higher intrasexual competition as they are perhaps more physiologically constrained and unable to confront the costs of expressing the same signal. Our results highlight that social context can influence how ornament expression responds to changes in sexual hormone levels. Also, this study support the idea that physiological pathways involved in the resolution of key life-history trade-offs are sensitive to the social context of the individual.

The results of this research have been published in the journal Hormones and Behavior, within an article authored by Jesús Martínez-Padilla, Lorenzo Pérez-Rodríguez, Francois Mougeot, Sonja Ludwig y Stephen M. Redpath, entitled “Intra-sexual competition alters the relationship between testosterone and ornament expression in a wild territorial bird ". The PDF is available on the left-side panel of this page.



  • Jesús holding a young male before release (Photo:LP-R)
  • Enjoying the weather of Moorhouse (aka Mordor). (Photo: LP-R)
  • Two testosterone implants in the breast of a grouse. (Photo: LP-R)
  • Sonja and a re-captured radiotagged male. (Photo: LP-R)
  • Radio-tagged male grouse. (Photo: LP-R)