Parasites, mate attractiveness and female feather corticosterone levels in a socially monogamous bird

Abstract

Stress is ubiquitous in the life of animals and a key determinant of their well-being and fitness. By quantifying levels of feather corticosterone in growing feathers (CORTf), we measured integrated stress responses in a monogamous game bird, the red grouse Lagopus lagopus scoticus. We investigated the effects of parasites and social mate choice on female CORTf levels during pairing, and tested the hypothesis that females with more parasites and paired with less attractive males have higher CORTf. We experimentally reduced nematode parasite abundance during pairing in females and investigated the effect of treatment on CORTf, while also considering the social mate's phenotype (male comb size, as a proxy of sexual attractiveness). The treatment was effective at contrasting parasite loads between control and dosed females, but had no apparent effect on CORTf. In experimental females, reinfection rate after a month positively correlated with CORTf. We found no evidence of assortative mating based on size, condition or ornament size, but females paired with more attractive males (displaying bigger combs) had lower CORTf during pairing. Females for which parasite load was reduced had lower CORTf than control females at all levels of male attractiveness. Social mate choice therefore appears to be an important determinant of female integrated stress responses, which may in turn modulate reinfection rate and parasitism risk. An influence of male attractiveness on female stress may be part of an adaptive response allowing females to adjust reproductive investment to their achieved social mate choice. Significance statementMate choice is often constrained by the availability of potential mates and not all females socially pair with their preferred partner. We show here that in females of a socially monogamous bird, corticosterone levels in feathers (indicative of integrated stress responses) increase with parasite infection levels but decrease with the attractiveness of the social mate. These results contribute to a better understanding of how females may adjust their reproductive investment according to their achieved mate choice.

Parasites during early life mediate the strength of phenotypic selection on sexual traits.

“…By definition, parasites impose costs on hosts that have effects, among others, at the genetic [69][70][71], physiological [72][73][74][75], behavioural [61,[76][77][78] and demographic levels [79][80][81]. However, the specific mechanism through which parasite infection during early life shapes the covariation between fitness and ornamental expression in adulthood is unknown and out of the scope of this study.…”

Estrés fisiológico en urogallos cantábricos (Tetrao urogallus cantabricus) silvestres y en cautividad: variaciones temporales e implicaciones metodológicas

“…Entre las causas que se han descrito en la literatura, el incremento en los niveles de estrés pueden deberse a variaciones en otros factores a lo largo de los años, entre los que se podrían encontrar un incremento de los predadores (Cockrem y Silverin 2002;Bennett et al 2016), parásitos (Mougeot et al 2016) o molestias humanas, pero que requeriría un estudio adicional y específico para determinar la fuente de variación de los niveles de estrés durante esos años. Podría sugerirse que el incremento de la corticosterona a lo largo de los años pueda deberse al deterioro temporal de las plumas más antiguas, reduciendo los niveles detectados.…”

“…Por tanto, la estimación de los niveles de estrés fisiológico en plumas puede ser un buen indicador de estrés fisiológico en aves en libertad. Esta técnica ya se ha utilizado en múltiples estudios de aves, también en galliformes como el lagópodo escocés (Bortolotti et al 2009;Mougeot et al 2010;Wenzel et al 2013;Mougeot et al 2016), en rapaces como el ratonero común (Martinez-Padilla et al 2013), en migradores árticos (Legagneux et al 2014) o en aves marinas (Will et al 2014;Fairhurst et al 2017) que ratifican que mayores niveles de corticosterona en plumas son indicativos de un mayor estrés ambiental, bien debido a mayores niveles de parásitos o dietas deficitarias. Debido a los efectos inmunosupresivos de los niveles de corticosterona, los individuos que mantienen niveles altos de corticosterona de modo crónico, pueden reducir su supervivencia y reproducción (Blas et al 2007;Koren et al 2012), influyendo por tanto en la dinámica poblacional.…”

The Adaptive Sex in Stressful Environments

“…In birds, more than 90% of all species are socially monogamous. Mate choice is constrained by the availability of unpaired individuals in the population and having an unattractive mate can be stressful for the female [77][78][79]. The mate attractiveness hypothesis predicts that females mated to unattractive males should produce more daughters because these daughters will not inherit their father's unelaborated sexual ornaments [80].…”