Browsing by Author "Wallraff, Kay Thorsten"
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- Behavior and fission-fusion dynamics of common dolphin (Delphinus delphis) groups with calves in the South of PortugalPublication . Wallraff, Kay Thorsten; Vinagre, Catarina; Matos, FábioFission-fusion dynamics describe animal social systems that are fluid and characterized by varying group sizes. Costs and benefits associated with grouping are considered to be the driving force for separation (fission) and joining (fusion) of individuals, resulting from ecological (e.g., food availability, predator abundance) and social (e.g., behavioral state, presence of calves) factors. The behavioral state gives insights into an animal’s ecology and allows protection of the species or population. The present study investigates which factors influence behavioral state and fission-fusion dynamics in common dolphin (Delphinus delphis) groups with calves in the south of Portugal. Between June and October of 2016, 2017 and 2019, 39 focal follows based on unmanned aerial vehicles (UAVs) were conducted, resulting in 768, 30-second behavioral samples (384 minutes). A multinomial model based on generalized estimating equations framework was used to model: i) the behavioral state by testing the responses to group size, total number of calves and month; ii) and fission-fusion dynamics assessing the effect of behavioral state, month, total number of calves and time of the day. The behavioral state of dolphin groups with calves was statistically significantly affected by the total number of calves and month. As the number of calves increased, resting behavior was less likely to occur than travelling (OR = 0.7, p = 0.015). Dolphin groups with calves were less likely to be socializing in July than to travel in June (OR = 0.1, p = 0.021). Group size had no statistically significant influence on the behavioral state in the present study. This study also revealed, that common dolphins in the south of Portugal exhibit a high rate of fission-fusion dynamics, but were not influenced by the factors considered in this study (i.e., behavioral state, month, total number of calves and time of the day). By assessing behavior and fine-scale social dynamics in common dolphins, this study enhances the current understanding of ecological and social aspects shaping grouping patterns and behavior in common dolphin groups with calves. This study also highlights the advantages of using unmanned aerial vehicles (UAVs) to assess behavioral data in wild animals.