No abstract

An understanding of animal grouping patterns is essential to increase knowledge about their social systems. We used a five-year continuous dataset to investigate grouping behavior in a free-ranging highly social mammal, the bottlenose dolphin. Our objective was achieved by examining the relationships between a set of oceanographic, climatic, topographic, anthropogenic and social variables and bottlenose dolphin group size. Modeling analysis revealed that bottlenose dolphin group dynamics was linked to both small-scale oceanographic variation and large-scale climatic variation. Larger groups of bottlenose dolphins were predicted with a high thermal stratification, an elevated concentration of dissolved oxygen in the water column, and a neutral NAO index. The observed link between environmental variables and dolphin group size is likely associated to changes in dolphin prey availability. Bottlenose dolphin group dynamics are likely driven by multiple factors, and social variables may act synergistically with environmental parameters. Larger groups of bottlenose dolphins were indeed also predicted with a greater number of dependent calves, likely because of enhanced care towards the calves. This study illustrates the value of using multiple variables at different scales to explore the factors that shape animal societies. The current study therefore contributes to the growing body of literature on how environmental change, occurring at different spatio-temporal scales, is indirectly related to the social behavior of a marine top predator.

No abstract

No abstract

The 2022 highly pathogenic avian influenza (HPAI) outbreak that occurred in many European countries affected several seabird species. Among them, northern gannets ( Morus bassanus ) were particularly impacted. We conducted aerial surveys in waters around the two largest gannet colonies in southwest Ireland (Little Skellig and Bull Rock, together representing 87% of the national population) in September 2022. During surveys dead and alive northern gannets were counted on survey effort. A total of 184 dead gannets were recorded on survey effort, representing 3.74% of the total number of gannets recorded. We estimated the abundance of dead gannets in the surveyed area at 1526 (95% confidence intervals (CIs) 1450–1605) individuals. The percentage of dead gannets observed was used to estimate a minimum local population mortality of 3126 (95% CIs 2993–3260) individuals across both colonies. Aerial surveys provided key information on gannet mortality from HPAI at sea. The study provides the first estimate of gannet mortality in the two largest gannetries in Ireland.