Acoustic Noise Induces Attention Shifts and Reduces Foraging Performance in Three-Spined Sticklebacks (Gasterosteus aculeatus)

Acoustic noise is known to have a variety of detrimental effects on many animals, including humans, but surprisingly little is known about its impacts on foraging behaviour, despite the obvious potential consequences for survival and reproductive success. We therefore exposed captive three-spined sticklebacks (Gasterosteus aculeatus) to brief and prolonged noise to investigate how foraging performance is affected by the addition of acoustic noise to an otherwise quiet environment. The addition of noise induced only mild fear-related behaviours - there was an increase in startle responses, but no change in the time spent freezing or hiding compared to a silent control - and thus had no significant impact on the total amount of food eaten. However, there was strong evidence that the addition of noise increased food-handling errors and reduced discrimination between food and non-food items, results that are consistent with a shift in attention. Consequently, noise resulted in decreased foraging efficiency, with more attacks needed to consume the same number of prey items. Our results suggest that acoustic noise has the potential to influence a whole host of everyday activities through effects on attention, and that even very brief noise exposure can cause functionally significant impacts, emphasising the threat posed by ever-increasing levels of anthropogenic noise in the environment

Experimental evidence that chronic outgroup conflict reduces reproductive success in a cooperatively breeding fish

Conflicts with conspecific outsiders are common in group-living species, from ants to primates, and are argued to be an important selective force in social evolution. However, whilst an extensive empirical literature exists on the behaviour exhibited during and immediately after interactions with rivals, only very few observational studies have considered the cumulative fitness consequences of outgroup conflict. Using a cooperatively breeding fish, the daffodil cichlid (Neolamprologus pulcher), we conducted the first experimental test of the effects of chronic outgroup conflict on reproductive investment and output. ‘Intruded’ groups received long-term simulated territorial intrusions by neighbours that generated consistent group-defence behaviour; matched ‘Control’ groups (each the same size and with the same neighbours as an Intruded group) received no intrusions in the same period. Intruded groups had longer inter-clutch intervals and produced eggs with increasingly less protein than Control groups. Despite the lower egg investment, Intruded groups provided more parental care and achieved similar hatching success to Control groups. Ultimately, however, Intruded groups had fewer and smaller surviving offspring than Control groups at 1-month post-hatching. We therefore provide experimental evidence that outgroup conflict can decrease fitness via cumulative effects on reproductive success, confirming the selective potential of this empirically neglected aspect of sociality

Strongly bonded individuals prefer to forage together in cooperatively breeding dwarf mongoose groups

In many social species, group members form strong social bonds. Such strong bonds are well-known to generate long-term fitness benefits, but they are also expected to influence short-term behavioural decisions. Here, we use field observations and an experimental manipulation to investigate whether variation in social-bond strength (as determined from grooming interactions) influences nearest-neighbour choices while foraging in wild dwarf mongooses (Helogale parvula). Preferred grooming partnerships (PGPs), representing particularly strong bonds, were found predominately between male–female dyads but among a range of dominance-status dyads. When searching for food, dwarf mongooses with PGPs were more likely than expected by chance to forage close to a preferred grooming partner. Foraging near a strongly bonded groupmate might reduce the predation risk or increase foraging opportunities and the transfer of social information. In addition, there could be stress-reducing benefits, although our field experiment provided no evidence that nearest-neighbour preferences for strongly bonded groupmates were additionally favoured, or indeed disrupted, in the aftermath of a short-term stressful event. Investigating the potential influence of strong social bonds on short-term behavioural decisions with potential fitness consequences is important for our understanding of social interactions and cooperation

High reproductive skew in the Neotropical paper wasp Polistes lanio

Reproductive conflicts are expected in societies where nonbreeding helpers retain the ability to produce offspring. Despite potential competition from reproductively capable nestmates in social wasps, egg laying tends to be monopolised by a single or relatively few queens. Genetic studies on reproductive partitioning in Polistes paper wasps suggest high reproductive skew in the genus. Conflict is thought to be minimal due to nestmate relatedness or the possibility of inheriting a reproductive monopoly on a nest; consequently, there are inclusive fitness opportunities for nonreproductive helpers. However, most studies are limited to temperate wasp species. Given the cosmopolitan distribution of Polistes, genetic data on group conflicts are required for a broader range of tropical species to determine whether these trends apply across climatic zones. We examined female reproductive skew in the Neotropical paper wasp Polistes lanio, genotyping a selection of adults and pupae from established post-emergence nests using single-nucleotide polymorphisms (SNPs). SNP-based pedigree analyses indicate a reproductive monopoly held by a single queen, with queen replacement from natal nestmates and evidence of possible multiple mating. Relatedness between pupal offspring was high (r = 0.71). It is likely that high reproductive skew among females is a founding trait of Polistes societies, conserved among species that have spread into new environments from Indomalayan origins