Side Fluke
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Also called half fluke or lateral fluke display, I see this more commonly with juveniles than adults. The left photo is of an unidentified first-year juvenile taken June 12, 2012 and represents the normal pattern early in the season. The right photo is of an unidentified full adult taken on September 21, 2012 illustrating the opposite pattern by adults. The simplest explanation for this behavior is that the whale is swimming on its side very close to the surface to part of the fluke extends above the water. Most of the time this sideways swimming only lasts a short time, just a few minutes. I cannot correlate it to any pre- or post-diving behavior and it simply seems to be something the whales occasionally do.
Australian Geographic in an article on their humpbacks make the comment that “resting humpbacks may gently slice the surface with their flukes” [1998. Behavior Patterns. October-December, Issue 52, p96.]. This may be true in the fall for our adult whales, but my observations of the very active juveniles in the spring and early summer doing this lead me to a very different conclusion. I think the juveniles are simply exploring the motions their bodies can make and swimming on their side is just one of them. I don’t have anywhere near enough observations of adults doing this to come to any serious thought explaining this behavior. It is just something the whales do!
Australian Geographic in an article on their humpbacks make the comment that “resting humpbacks may gently slice the surface with their flukes” [1998. Behavior Patterns. October-December, Issue 52, p96.]. This may be true in the fall for our adult whales, but my observations of the very active juveniles in the spring and early summer doing this lead me to a very different conclusion. I think the juveniles are simply exploring the motions their bodies can make and swimming on their side is just one of them. I don’t have anywhere near enough observations of adults doing this to come to any serious thought explaining this behavior. It is just something the whales do!