Our results contribute to the emerging field of sociality in reptiles. The unexpected fight dynamics and regularly changing hierarchies indicate that individuals perceived the resource value of sponges differently, which was attributed to differences in their ability to assess resource abundance and/or availability of resources at alternative sites. Distinct hierarchical structuring was detected based on win outcomes and spatial area use within each year however, the number and combination of turtles frequenting the reef varied across years, with individuals only dominating for 2–3 years before departing (or returning intermittently) and being replaced. Escalation of aggression, unexpectedly, skipped the passive (evaluation) phase in half of interactions (starting with biting and chasing), with contests being primarily won by more aggressive individuals, independent of body size and duration of presence (i.e. Interactions between loggerheads represented an extremely small fraction of the activity budget, but potentially consumed two to three times more energy than swimming and foraging. Interactions generally occurred when loggerheads were adjacent to, or passing through, patches occupied by other individuals. Individual loggerheads occupied distinct (very small) patches on the reef, with low overlap when foraging. Most turtles were immature loggerheads, of which half were detected in more than 1 year. We directly observed individuals via snorkel surveys (with photoidentification and videos) supported by aerial drone surveys.

Here, we investigated how agonistic interactions influenced temporal and spatial variation in the social structuring of loggerhead sea turtles, Caretta caretta, foraging on sponges at a reef (Zakynthos, Greece) over multiple years. Interactions among individuals of the same species inform us about resource value and sociality however, for species that are difficult to observe directly, these behaviours are potentially missed or misinterpreted via remote monitoring approaches. Our results suggest that during the breeding period (1) male behaviour was primarily social and active (2) female behaviour was primarily solitary and inactive. Foraging, cleaning and female-female contests are not documented in published literature for loggerhead sea turtles at breeding areas. Social behaviour included antagonistic interac- tions and reproductive activity.

Solitary behaviour included resting, swimming, foraging and cleaning. We grouped observed activities into 4 solitary and 2 social behaviours, which were divided into 14 sub-categories. Between April and July of 2003 to 2005, turtle behaviour on initial sighting was recorded during 287 h of observation, comprising 1534 sighting events of solitary (n = 80 male, n = 1335 female) and social (n = 65 same sex, n = 54 mixed sex) activity.

The aim of this study was to document the daytime behavioural activity of loggerhead sea turtles Caretta caretta at a temperate breeding area through direct observations. Direct observation of animal behaviour is essential for the effective conservation of endangered species in their natural habitat, understanding their function within ecosystems and val- idating inferences made using remote technology.

Seaturtle behavior