Lunge-feeding humpback whale (Megaptera novaeanglia), Chatham Strait, Southeast Alaska, USA.
I became very familiar with the individual whales that made up the cooperative bubblenet feeding groups. I could identify them by their flukes, markings on their throats, barnacles and even sometimes by the sounds they made.
I had known Dr Fred Sharpe of the Alaska Whale Foundation for many years during his research into the cooperative bubble net feeding strategies employed by the humpback whales of Southeast Alaska. He was particularly interested in the genetic relatedness of individual whales within and between cooperative pods, in addition to the local genetic sub-structuring of the population. He discovered that social foraging humpback whale pods possess a social complexity that is rarely observed in baleen whales. For example, individuals within these groups may develop long-term associations that may last for many years. There also appears to be a division of labour, with particular whales constantly leading the group, deploying the bubble nets, and producing the feeding calls. Furthermore, on each lunge, each whale in the group maintains the same position, indicating that this is an intrinsically choreographed feeding maneuver. My own personal observations with the same feeding groups over the course of the summer also bore this out. I observed how there were always core members of a group but other individual whales appeared to join them on a much more ad hoc basis before moving off again.
He ascertained that it is only the more elusive, shoaling prey, such as Pacific herring, that require the same level of cooperative cohesiveness; easier prey such as krill do not require the same sophisticated feeding strategies as do shoaling fish.
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- © 2012 Duncan Murrell
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