Temporal variation in reproductive success and the effects of differential parental care on the progeny of fish with demersal eggs

A paternity test based on microsatellite analysis of eggs under the parental care of a bourgeois male Pacific sergeant major, Abudefduf troschelii, included gametes from five females and two parasitic males. The nest area was monitored for five days to evaluate variation in reproductive success, and an approximately 300% increase occurred on the first and second days after new oviposition followed by a more than 300% reduction from the second to fifth days due to predation or filial cannibalism. Finally, the egg area on the last day corresponded to the initial nest area, suggesting selective care by the male.

Coevolution influences the evolution of filial cannibalism, offspring abandonment and parental care

Understanding evolutionary patterns of parental investment and care has been a long-standing focus in studies of evolutionary and behavioural ecology. Indeed, patterns of investment and care are highly diverse, and fully understanding such diversity has been challenging. Recently, several studies have highlighted the need to consider coevolutionary dynamics in studies of parental care, as parental care is likely to co-occur and co-originate with a range of other traits. Two traits that commonly co-occur with parental care are offspring abandonment (the termination of parental investment prior to full independence in offspring) and filial cannibalism (the consumption of one's offspring). Here, we use a mathematical framework to explore how co-occurrence and coevolution among care, abandonment and cannibalism can influence the life-history conditions under which care is expected to evolve. Our results suggest that in some cases, the evolution of parental care can be inhibited by offspring abandonment and filial cannibalism. In other cases, abandonment and filial cannibalism that benefits parents can promote the evolution of parental care. It is particularly interesting that behaviours that seem so contrary to care—that is, eating or abandoning one's young—can in some cases broaden the conditions under which care can evolve. In general, our findings highlight that considering co-occurrence and coevolutionary dynamics between two or more traits is essential to understanding the evolution of trait diversity.

Behaviour of nonhuman primate mothers toward their dead infants: uncovering mechanisms

In comparative thanatology, most reports for nonhuman mammals concern mothers' behavioural responses to their dead offspring: most prominently, dead-infant carrying (sometimes of extended duration); but also inspection, proximity, maternal care such as grooming, protective behaviours and filial cannibalism. Documented across many primate species, these behaviours remain poorly understood in all. The literature is dominated by relatively brief qualitative descriptions of isolated anecdotal cases in apes and monkeys. We argue for quantitative coding in case reports, alongside analyses of longitudinal records of such events to allow objective evaluation of competing theories, and systematic comparisons within and across species and populations. Obtaining necessary datasets depends on raised awareness in researchers of the importance of recording occurrences and knowledge of pertinent data to collect. We review proposed explanatory hypotheses and outline data needed to test each empirically. To determine factors influencing infant-corpse carriage, we suggest analyses of deaths resulting in ‘carry’ versus ‘no carry’. For individual cases, we highlight behavioural variables to code and the need for hormonal samples. We discuss mothers' stress and welfare in relation to infant death, continued transportation and premature removal of the corpse. Elucidating underlying proximate and ultimate causes is important for understanding phylogeny of maternal responses to infant death. This article is part of the theme issue ‘Evolutionary thanatology: impacts of the dead on the living in humans and other animals’.