The impacts of anthropogenic injury on site fidelity in Maldivian whale sharks (rhincodon typus)

Abstract

Whale sharks aggregate in predictable seasonal aggregations across the tropics. South Ari Atoll in the Maldives is one of a few year-­‐round aggregation sites. Here boating traffic matches the whale shark hotspot, increasing the probability of anthropogenic injury. Whale sharks are reported to remain faithful to this aggregation site following injury, despite the costs of injury and the risk of re-­‐injury. However, the impacts of injury on site fidelity and residency behaviour are not fully understood. Encounter data from the Maldives Whale Shark Research Programme were analysed to assess the impact of injury on site fidelity in whale sharks. There was no change in geographic site fidelity as a result of injury, but there were changes in residency timings. Injured resident whale sharks spent significantly longer at the atoll (+73 days ±8.6), less time absent from the atoll (-­‐158 days ±23.0) and were seen more consistently (+2 residency periods ±0.3) than non-­‐injured whale sharks. The residency duration, return rate and number of residency periods increased with increasing injury number and severity, whilst absence duration decreased. This implies a cost to injury, with whale sharks remaining in areas of high productivity to recover and spending less time in their pelagic phases. It highlights the importance of the South Ari Atoll aggregation, as these whale sharks do not leave, despite the risk of re-­‐injury. This emphasises the need for the management of anthropogenic activities at aggregation hotspots, to reduce the injury rate and subsequent impacts on fitness.