Hart, J. D. | Search bioRxiv

bioRxiv2023

Biomimetic robots reveal flexible adjustment of sexual signalling in a wild invertebrate.

Sexual signals are often structured in bouts, which can be adjusted in response to changes in the signallers physical and social environment. For example, we might expect individuals to adjust their own signalling behaviour in response to changes in the signalling behaviour of rivals, because this can affect their relative attractiveness to potential mates. In this study, we used a biomimetic robot to experimentally manipulate rival waving behaviour in a wild population of fiddler crabs (Afruca tangeri), and investigated whether this leads to changes in the activity and waving behaviour of a focal male. Analysing the focal males behaviour using hidden Markov models and linear hurdle models, we found no evidence that the focal males waving rate changed in response to changes in the behaviour of the robotic rival. However, bouts of waving lasted longer when the robotic rival was waving at a fast rate. Focal males were also less likely to enter their burrow when the robotic rival was waving, and spent less time in their burrow if they did enter. These results reveal tactical adjustment of behaviour by competing signallers, and highlight the flexible nature of bout-structured sexual displays.

animal behavior and cognition↗

bioRxiv2023

High pathogenicity avian influenza (H5N1) in Northern Gannets: Global spread, clinical signs, and demographic consequences

During 2021-22 High Pathogenicity Avian Influenza (HPAI) killed thousands of wild birds across Europe and North America, suggesting a change in infection dynamics and a shift to new hosts, including seabirds. Northern Gannets (Morus bassanus) appeared especially severely impacted, but limited understanding of how the virus spread across the metapopulation, or the demographic consequences of mass mortality limit our understanding of its severity. Accordingly, we collate information on HPAIV outbreaks across most North Atlantic gannet colonies and for the largest colony (Bass Rock, UK), provide impacts on population size, breeding success, adult survival, and preliminary results on serology. Unusually high numbers of dead gannets were first noted in Iceland during April 2022. Outbreaks in May occurred in many Scottish colonies, followed by colonies in Canada, Germany and Norway. By the end of June, outbreaks had occurred in five Canadian colonies and in the Channel Islands. Outbreaks in 12 UK and Ireland colonies appeared to follow a clockwise pattern with the last infected colonies recorded in late August/September. Unusually high mortality was recorded at 40 colonies (75% of global total colonies). Dead birds testing positive for HPAIV H5N1 were associated with 58% of these colonies. At Bass Rock, the number of occupied sites decreased by at least 71%, breeding success declined by [~]66% compared to the long-term UK mean and adult survival between 2021 and 2022 was 42% lower than the preceding 10-year average. Serological investigation detected antibodies specific to H5 in apparently healthy birds indicating that some gannets recover from HPAIV infection. Further, most of these recovered birds had black irises, suggestive of a phenotypic indicator of previous infection. Untangling the impacts of HPAIV infection from other key pressures faced by seabirds is key to establishing effective conservation strategies for threatened seabird populations, HPAIV being a novel and pandemic threat.

ecology↗