Abstract
In socially monogamous species, sexual selection not only depends on
initial mate choice but also mate switching. To date, studies lack
assessment of differences between passive (widowhood) and active
(divorce) mate switching, longer-term fitness consequences, and how age
masks reproductive costs and benefits of divorce. We investigated causes
and long-term consequences of divorce and their age-dependence using
longitudinal data on Seychelles warblers (Acrocephalus sechellensis),
and experimentally test for short-term effects of mate-switching. Young
and old males, but not females, divorced most frequently. Divorce
propensity declined with pair bond duration and reproductive success in
both sexes, but mate switching did not result in short-term costs.
Divorcees did not gain short- or long-term fitness benefits compared to
non-divorcees. In fact, female early-life divorcees that lost their
breeding position had lower survival than females that never divorced.
Divorce is likely a strategy to escape poor-quality partnerships, but
not all divorcees benefit from divorcing.