Pectoral Slaps
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Also called flippering or flipper slap. This sequence is of whale 2070, Barnacles on the back side of Douglas Island in Stephens Passage on September 18, 2010. A video from August 4, 2013 is located at the bottom of this page.
More often that barrel rolling, our humpbacks do straight pectoral slaps. They swim on their backs, just under the surface with none of the belly above the water, then lift a pectoral out of the water and with a strong enough motion to bend the flexible fin, slap it onto the surface of the water. It results in a large splash and a loud noise. They usually do it more than once, but only rarely will they do more than five or six without rolling over and doing a shallow dive and cruising to another location where they will often repeat the process. Darling notes that in Hawaiian waters it can occur 20+ times in a row. I’ve never seen anywhere near that number of repeats in Juneau waters. When not barrel rolling, they slap the pectoral in the same place each time, raising it up and slapping it down. They will often hold the pectoral fin high out of the water for many moments, waving it about, before slapping it to the surface. Occasionally the fluke is lowered so slowly that it simply slides into the water and doesn’t make a splash. Some call this a pectoral wave. I do often comment to the folks on the boat when the whales do this that they are “waving” at us.
The fact that the slap results in a visual splash plus a loud noise has led to much speculation on this behavior means. Some think it might have something to do with herding their prey of small schooling fish, perhaps encouraging them to swarm in a larger school that would be easier to gulp. Watching the fish finder for “herring balls” is the only method I have for “seeing” underwater and I’ve never noticed an increase in the size of “herring balls” with pectoral slapping. Some think it may be a method of inviting other whales to join in some joint or cooperative behavior. I see this with solitary whales where this might make some sense, but I also see it in groups of whales that are already together. Here, the slapping might be a signal for the other whales to move away in a marking of some territory. I remain very skeptical about this interpretation as I’ve never seen other whales move away or leave the slapping whale.
This seems to be a very common behavior in Hawai‘i associated with pre-mating activity as nearly every whale watching company web site includes photos of it. Perhaps the whales do it here, less frequently, to keep in practice? Like the Humpback Whale Research Foundation of Bermuda, “it seems as if the whales are communicating to other nearby whales when they do this”. To say more is reaching beyond the evidence.
More often that barrel rolling, our humpbacks do straight pectoral slaps. They swim on their backs, just under the surface with none of the belly above the water, then lift a pectoral out of the water and with a strong enough motion to bend the flexible fin, slap it onto the surface of the water. It results in a large splash and a loud noise. They usually do it more than once, but only rarely will they do more than five or six without rolling over and doing a shallow dive and cruising to another location where they will often repeat the process. Darling notes that in Hawaiian waters it can occur 20+ times in a row. I’ve never seen anywhere near that number of repeats in Juneau waters. When not barrel rolling, they slap the pectoral in the same place each time, raising it up and slapping it down. They will often hold the pectoral fin high out of the water for many moments, waving it about, before slapping it to the surface. Occasionally the fluke is lowered so slowly that it simply slides into the water and doesn’t make a splash. Some call this a pectoral wave. I do often comment to the folks on the boat when the whales do this that they are “waving” at us.
The fact that the slap results in a visual splash plus a loud noise has led to much speculation on this behavior means. Some think it might have something to do with herding their prey of small schooling fish, perhaps encouraging them to swarm in a larger school that would be easier to gulp. Watching the fish finder for “herring balls” is the only method I have for “seeing” underwater and I’ve never noticed an increase in the size of “herring balls” with pectoral slapping. Some think it may be a method of inviting other whales to join in some joint or cooperative behavior. I see this with solitary whales where this might make some sense, but I also see it in groups of whales that are already together. Here, the slapping might be a signal for the other whales to move away in a marking of some territory. I remain very skeptical about this interpretation as I’ve never seen other whales move away or leave the slapping whale.
This seems to be a very common behavior in Hawai‘i associated with pre-mating activity as nearly every whale watching company web site includes photos of it. Perhaps the whales do it here, less frequently, to keep in practice? Like the Humpback Whale Research Foundation of Bermuda, “it seems as if the whales are communicating to other nearby whales when they do this”. To say more is reaching beyond the evidence.