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Activity patterns of animals often relate to environmental variables such as food availability and predation pressure. Technological advances are providing us with new tools to monitor and better understand these activity patterns. We used animal-attached data loggers recording acceleration and depth to compare activity patterns and vertical habitat use of whale sharks ( Rhincodon typus) at Ningaloo Reef, Western Australia. Whale sharks showed a moderate reverse diel vertical migration but exhibited a clear crepuscular pattern in locomotory activity. Peak activity occurred at sunset, whereas vertical movement peaked prior to this. Typical ram surface filter feeding could be identified and occurred primarily during sunset and the first hours of night. At such times, direct observations indicated whale sharks were feeding on tropical krill swarms. Kinematic analysis of postural data and data from vertical movement suggests that whale sharks at Ningaloo spend ~8 min per day actively ram surface filter feeding. Considering the high biomass present in krill schools, it is estimated that whale sharks at Ningaloo have a similar energy intake as those at other aggregation sites. Diel patterns in activity and diving behaviour suggest that whale sharks have tuned their diving behaviour in anticipation of the formation of these high-density patches which appear to only be periodically, but predictably available at sunset. Our results confirm that diel patterns in vertical habitat selection and vertical movements do not necessarily reflect patterns in activity and foraging behaviour. Direct quantification of activity and behaviour is required in gaining accurate representation of diel activity patterns. [ABSTRACT FROM AUTHOR]

Abstract: Sensor types in animal-attached tags (e.g. accelerometers, speed sensors and compasses) now often require devices to be solidly attached to an animals’ body, which would preclude their use on many large species of shark where current attachment systems are based on tethers. A new method of attaching motion-sensitive tags securely to large sharks is presented which allows free-swimming animals to be equipped without any form of restraint. The system was tested on 11 free-swimming whale sharks (Rhincodon typus) at Ningaloo Reef, Western Australia. Devices were placed on one of two elongated arms emanating from a torsion spring which acted to force the arms together. The system was clamped to the second dorsal fin using a specially designed tagging-gun operated manually by a snorkeller. Each arm was equipped with two 1.5cm-long spikes to ensure stable, firm attachment to the fin. Data from the deployments showed that response to the tagging event varied between individuals, with some sharks showing no obvious reaction, while others exhibited a substantial reaction. Clamps remained stable on the sharks throughout the entire duration of all trials. The whole system was fitted with a corroding magnesium link to ensure that the clamp would release from the shark within weeks of deployment. [Copyright &y& Elsevier]