Senescing sexual ornaments recover after a sabbatical

Abstract

Somatic deterioration in ageing animals may arise from allocation of resources to reproduction at the expense of repair and maintenance. Thus, accumulated reproductive effort is likely to progressively limit the expression of sexual ornaments at older ages. We analysed the effect of age and reproductive effort on the sexual attractiveness (foot colour) of male blue-footed boobies. Using a long-term dataset, we found that, as animals age and accumulate reproductive events, the expression of foot colour deteriorates. In addition, after non-breeding events males displayed more colourful feet compared with males that reproduced the year before, suggesting that sabbatical years facilitate recovery. Our results indirectly support the idea that allocation of resources to reproduction limits sexual attractiveness and that animals could cope with the negative effects of senescence on sexual ornaments by skipping some breeding events.

Figure 1.

Male foot colour and (a) age and (b) breeding effort (number of previous breeding attempts). Filled circles, 2004; open circles, 2005.

Figure 2.

The effect of age and skipping a breeding event on male foot colour (controlling for year). Open circles and upper line, skipping males; filled circles and lower line, non-skipping males.