Blood corticosterone levels and intersexual selection games: Best-of-bad-job strategies of male common lizards

Glucocorticoids affect physiology and behaviour,
reproduction and potentially sexual selection as well. Shortterm
and moderate glucocorticoid elevations are suggested
to be adaptive, and prolonged and high elevations may be
extremely harmful. This suggests that optimal reproductive
strategies, and thus sexual selection, may be dose dependent.
Here, we investigate effects of moderate and high
elevations of blood corticosterone levels on intra- and
intersexual behaviour and mating success of male common
lizards Lacerta vivipara. Females showed less interest and
more aggressive behaviour towards high corticosterone
males and blood corticosterone levels affected male
reproductive strategy. Males of moderate and high corticosterone
elevations, compared with Control males, showed
increased interest (i.e., higher number of chases, tongue
extrusions, and approaches) towards females and high
corticosterone males initiated more copulation attempts.
However, neither increased male interest nor increased
copulation attempts resulted in more copulations. This
provides evidence for a best-of-a-bad-job strategy, where
males with higher corticosterone levels compensated for
reduced female interest and increased aggressive female
behaviour directed towards them, by showing higher
interest and by conducting more copulation attempts. Blood
corticosterone levels affected intrasexual selection as well
since moderate corticosterone levels positively affected
male dominance, but dominance did not affect mating
success. These findings underline the importance of female
mate choice and are in line with adaptive compensatory
behaviours of males. They further show that glucocorticoid
effects on behaviour are dose dependent and that they have
important implications for sexual selection and social
interactions, and might potentially affect Darwinian fitness.