Conflict and cooperation in male-male partnerships alters paternal care in the ocellated wrasse

Parental care is a critical determinant of offspring fitness. Female
presence and male competition affects paternal care, but male-male
cooperation during mating may also be an important, yet underappreciated,
driver of paternal care. In many systems, males work together to court
females or defend territories against male competitors. This male-male
cooperation can alter actual or perceived paternity of the parenting male
and could, therefore, influence how males invest in care during the
post-mating period. Here, we measured how reproductive and social dynamics
between nesting and satellite males during mating correlate with nesting
male paternal care in the ocellated wrasse (Symphodus ocellatus). Although
paternal care (fanning rates) was repeatable across days within the same
nesting cycle, it was not repeatable across different nesting cycles,
suggesting that males plastically alter care in response to the
environment. Nesting males provided care for fewer days at nests with the
most unstable relationship between the nesting and satellite male: nests
with low satellite cooperation and high male-male conflict where the
satellite eventually left or was evicted from the nest. Nesting males also
parented more intensively, but for fewer days in the warmer year,
suggesting that males may adjust care in response to temperature.
Collectively, our results suggest that there is no fixed male trait that
females can use to predict paternal care behavior. Instead, females may
use male-male interactions as a proxy for the quality of care her
offspring will receive, suggesting that sexual selection may favor the
co-evolution of paternal care with male-male cooperation.