Territorial defense in a network: Audiences only matter to male fiddler crabs primed for confrontation

This is the author accepted manuscript. The final version is available from Oxford University Press via the DOI in this recordTerritorial contests often occur in the presence of conspecifics not directly involved in the interaction. Actors may alter their behavior in the presence of this audience, an “audience effect,” and audiences themselves may alter their behavior as a result of observing an interaction, a “bystander effect.” Previous work has documented these effects by looking at each in isolation, but to our knowledge, none has investigated their interaction; something that is more likely to represent a realistic scenario for species where individuals aggregate spatially. We therefore have a somewhat limited understanding of the extent and direction of these potentially complex indirect social effects on behavior. Here, we examined how audience and bystander effects work in tandem to modify resident male aggressive behavior towards intruders in European fiddler crabs, Afruca tangeri. We found that male crabs with an audience showed greater aggressive behavior towards an intruder compared with males without an audience, but only if they had acted as a bystander to an aggressive signaling interaction prior to the intrusion. Indeed, bystanding during aggressive interactions elevated aggressive responses to intruders maximally if there was an audience present. Our results suggest that bystanding had a priming effect on territory-holding males, potentially by providing information on the immediate level of competition in the local neighborhood, and that same-sex audiences only matter if males have been primed. This study highlights the fundamental importance of considering broader interaction networks in studying real-world dyadic interactions and of including nonvertebrate taxonomic groups in these studiesDanish Council for Independent Research/Natural SciencesDFFLeverhulme Trust Early Careers Fellowshi

Pair housing of dairy calves and age at pairing: effects on weaning stress, health, production and social networks

The dataset associated with this article is in ORE at http://hdl.handle.net/10871/24458This is the author accepted manuscript. The final version is available from Public Library of Science via the DOI in this record.The early social environment can influence the health and behaviour of animals, with effects lasting into adulthood. In Europe, around 60% of dairy calves are reared individually during their first eight weeks of life, while others may be housed in pairs or small groups. This study assessed the effects of varying degrees of social contact on weaning stress, health and production during pen rearing, and on the social networks that calves later formed when grouped. Forty female Holstein-Friesian calves were allocated to one of three treatments: individually housed (I, n = 8), pair-housed from day five (P5, n = 8 pairs), and pair-housed from day 28 (P28, n = 8 pairs). From day 48, calves were weaned by gradual reduction of milk over three days, and vocalisations were recorded as a measure of stress for three days before, during and after weaning. Health and production (growth rate and concentrate intakes) were not affected by treatment during the weaning period or over the whole study. Vocalisations were highest post-weaning, and were significantly higher in I calves than pair-reared calves. Furthermore, P28 calves vocalised significantly more than P5 calves. The social network of calves was measured for one month after all calves were grouped in a barn, using association data from spatial proximity loggers. We tested for week-week stability, social differentiation and assortment in the calf network. Additionally, we tested for treatment differences in: coefficient of variation (CV) in association strength, percentage of time spent with ex-penmate (P5 and P28 calves only) and weighted degree centrality (the sum of the strength of an individual’s associations). The network was relatively stable from weeks one to four and was significantly differentiated, with individuals assorting based on prior familiarity. P5 calves had significantly higher CV in association strength than I calves in week one (indicating more heterogeneous social associations) but there were no significant treatment differences in week four. The mean percentage of time that individuals spent with their ex-penmate after regrouping decreased from weeks 1-4, though treatment did not affect this. There were also no significant differences in weighted degree centrality between calves in each rearing treatment. These results suggest that early pair-rearing can allow calves the stress buffering benefits of social support (and that this is more effective when calves are paired earlier) without compromising health or production, and sheds light on the early development of social behaviour in cattle.We thank Neil Baker for providing the calves and facilities, and to all the staff at Bakers of Haselbury Plucknett Ltd, for all practical support involved in this research project. We would also like to thank Volac International Ltd for providing the weigh-band. Funded by 1. Agriculture and Horticulture Development Board - Dairy (http://dairy.ahdb.org.uk/) Grant holder – DPC, Department for Environment, Food and Rural Affairs (https://www.gov.uk/government/organisations/department-for-environment-food-rural-affairs) Grant holder – DPC, University of Exeter (http://www.exeter.ac.uk/) Grant holder – DPC 2. The Agriculture and Horticulture Development Board (AHDB)- Dairy, had some influence on the study and preparation of the manuscript; SB is employed by AHDB