Fine-scale analysis of the foraging strategies of free-rangingpenguins
The large number of seabirds exploiting the Southern Ocean in relation to their status of potential competitors with human fisheries for key-species of commercial interests explain the prime importance of studies investigating the birds' feeding and foraging strategies. With this intention, pro...
| Main Authors: | , , |
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| Format: | Thesis |
| Language: | English |
| Published: |
2001
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| Subjects: | |
| Online Access: | https://ir.soken.ac.jp/?action=repository_uri&item_id=815 http://id.nii.ac.jp/1013/00000815/ |
| Summary: | The large number of seabirds exploiting the Southern Ocean in relation to their status of potential competitors with human fisheries for key-species of commercial interests explain the prime importance of studies investigating the birds' feeding and foraging strategies. With this intention, progresses in the development of new technologies have allowed researchers to monitor the behaviour of animals while at sea using loggers that measure various parameters as a function of time. In the past three years, deploying the most advanced technological devices in an integrative approach, multiple data per individual were recorded at a high sampling rate on free-ranging Adelie and King penguins. Depth utilization and swim speed as parameters of the foraging effort displayed by birds, were principally investigated in tandem with the monitoring of the oesophageal temperature, this latest being used to detect the ingestion of cold ectothermic prey, indicated by precipitous drops in the internal temperature of the predator. Thus, fine-scale foraging events could be related to feeding events. Calibration experiments on captive penguins, handfed on land and swimming in an exhibit pool, showed that the upper the sensors in the oesophagus, the higher the detection rate. Moreover, the magnitude of the temperature drop increase with the mass fed and decrease with increasing frequency of ingestion. Deployed on free-ranging birds in tandem with swim speed and depth loggers, the oesophagus temperature recording gave precious indication about the depths at which prey were taken. In addition to the feeding behaviour, several foraging strategies that may enhance the prey detection and/or capture were also revealed.Based on these data obtained on free-ranging penguins, the potential way birds locate the patch of prey within a foraging trip, possibly using chemoreception during shallow diving activity, as well as an updating of the classification of the role of dives using their depth profile will be described. Some of the most striking ... |
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