ORCID Profile
0000-0001-8424-3197
Current Organisations
The University of Auckland
,
Aarhus University
,
University of St Andrews
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Publisher: Wiley
Date: 06-02-2019
DOI: 10.1002/ECE3.4923
Publisher: Wiley
Date: 12-11-2019
DOI: 10.1111/GEB.13025
Publisher: American Association for the Advancement of Science (AAAS)
Date: 23-06-2023
Abstract: The giant rorqual whales are believed to have a massive food turnover driven by a high-intake lunge feeding style aptly described as the world’s largest biomechanical action. This high-drag feeding behavior is thought to limit e times and constrain rorquals to target only the densest prey patches, making them vulnerable to disturbance and habitat change. Using biologging tags to estimate energy expenditure as a function of feeding rates on 23 humpback whales, we show that lunge feeding is energetically cheap. Such inexpensive foraging means that rorquals are flexible in the quality of prey patches they exploit and therefore more resilient to environmental fluctuations and disturbance. As a consequence, the food turnover and hence the ecological role of these marine giants have likely been overestimated.
Publisher: Wiley
Date: 25-04-2017
Publisher: Springer Science and Business Media LLC
Date: 22-06-2020
Publisher: Acoustical Society of America (ASA)
Date: 10-2021
DOI: 10.1121/10.0006735
Abstract: Male humpback whales (Megaptera novaeangliae) sing in mating aggregations in the form of song displays, but much less is known about how both sexes use sound on their feeding grounds. Here, we test different hypotheses about the function of vocalizations in 14 foraging humpback whales tagged with sound and movement recording Dtags in Greenland. We show that this population of foraging humpback whales have an overall low call rate of 11.9 calls h−1 (inter-quartile range = 12.1) with no support for the hypotheses that they employ sound in the localization or manipulation of prey nor in the coordination of lunge feeding. The calls had a mean received level of 135 ± 5dB re 1 μPa, which is some 30 dB lower than maximum levels of song recorded on similar deployed tags, suggesting a much smaller active space of these vocalizations. This reduced active space might, in concert with low call rates, serve to mitigate eavesdropping by predatory killer whales or conspecifics competing for the same prey resources. We conclude that feeding humpback whales in Greenland produce low level, infrequent calls suggesting that calling is not a prerequisite for successful feeding, but likely serves to mediate within group social interactions.
Publisher: Springer Science and Business Media LLC
Date: 22-03-2021
DOI: 10.1038/S41598-021-85376-2
Abstract: Central place foragers are expected to offset travel costs between a central place and foraging areas by targeting productive feeding zones. Harbour seals ( Phoca vitulina ) make multi-day foraging trips away from coastal haul-out sites presumably to target rich food resources, but periodic track points from telemetry tags may be insufficient to infer reliably where, and how often, foraging takes place. To study foraging behaviour during offshore trips, and assess what factors limit trip duration, we equipped harbour seals in the German Wadden Sea with high-resolution multi-sensor bio-logging tags, recording 12 offshore trips from 8 seals. Using acceleration transients as a proxy for prey capture attempts, we found that foraging rates during travel to and from offshore sites were comparable to offshore rates. Offshore foraging trips may, therefore, reflect avoidance of intra-specific competition rather than presence of offshore foraging hotspots. Time spent resting increased by approx. 37 min/day during trips suggesting that a resting deficit rather than patch depletion may influence trip length. Foraging rates were only weakly correlated with surface movement patterns highlighting the value of integrating multi-sensor data from on-animal bio-logging tags (GPS, depth, accelerometers and magnetometers) to infer behaviour and habitat use.
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Mark Johnson.