Size Matters – At least it does for female Humpbacks!

We ran 3 Whale Watches yesterday under the cloudy skies. On the boat, we find it relaxing not to be in direct sunlight all day, and the whales seemed to agree with us. We saw lots of spouting and fluke dives (giving us some great shots of the unique white patterns on the ventral side of the whales’ tails). And as expected for mid-February Whale Watches, we saw lots of pods of Mom/Baby and almost all of these pods were accompanied by at least one escort. The Mom/Baby pods accompanied by more than one escort were moving much more quickly as the escorts jockeyed for the position closest to Mom. Yesterday was one of those days where no matter which direction we looked we could see spouts and splashes from surface active whales.
Captain Claire’s Humpback Whale Fact of the Day:Recent research documents that mature-sized female humpbacks associate almost exclusively with mature sized males, and have a significant preference for the largest of these males. Mature sized males, however, were less discriminating and would associate with all females regardless of size (though the males that associated with immature females were generally the smaller males). Finally, immature-sized males associate with immature-sized females. This “assortative paring” has rarely been documented in mammals – so why would whales use size as a determining factor for mate choice? Since males aren’t involved in taking care of their calves, and since research demonstrates that a bigger calf is much more likely to survive, size is much more important to a female Humpback. The sex differences in size preference by mature whales probably reflect the relatively high costs of mature females mating with small or immature males compared to the lower costs of mature males mating with small or immature females. Body size appears to influence the adoption of alternative mating tactics by males such that smaller mature males avoid the costs of competing for the highest-quality females and instead focus their attentions on smaller females that may or may not be mature.
And if it would help to sum all that up in layman’s terms….for female Humpbacks, size matters.

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