Fluke-Up Feeding in Hawaiian Waters

In the past few weeks our office has received numerous calls from concerned citizens about seeing a whale in distress.  The whale observed is spending long periods of time at the surface with its flukes extended above the water’s surface.  Some have conjectured that it is a whale using its tail flukes to sail; others have suggested it is attempting to cool down using its tail as a thermoregulatory device.

We believe a different hypothesis to be true.  The whale with the extended flukes is most likely a female humpback with a newborn calf. The mother is resting while still allowing her calf access to her mammary glands (located near the posterior portion of her body some 6-8 feet from her flukes).  By extending her tail into the air she is able to keep her body relatively close to the surface, allowing her to rest while minimizing dive depths for her young calf.  The calf is then able to nurse at will and expend less energy.

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Mother-Calf Dolphin Resight

On August 12, the research team went out on the water surveying for odontocetes and marine debris. At around 11 am, we sighted a pod of 17 bottlenose dolphins and began taking photographs, as per our protocol. We spent the maximum allowed hour with this pod, giving our interns a chance to try their photo-identification skills and collect as many dorsal fin photographs as possible, as the pod was milling about and not difficult to keep track of. While we were watching the dolphins, we noticed there were two distinct pairings in the pod.

Later that week when we were in the office cataloging and examining the photographs, our analyst Jens noticed that one of the pairs was already in our bottlenose dolphin catalog. The same two individuals had been photographed together as a mother-calf pair  in 2011.

This mother and calf pair was sighted on August 6, 2011 and again on August 12, 2014.

This mother and calf pair was sighted on August 6, 2011 and the pair was seen again on August 12, 2014.

This is pretty neat because using photo-identification we can track how long these two individuals stay together. Bottlenose dolphins have a complex social structure that is very different from odontocetes that live in stable groups like a pod of killer whales. They live in a fission-fusion society, meaning it is dynamic and always changing. However, the association between a mother and calf is one of the strongest bonds in the dolphin society. They will stay together on average for between three and six years, and we know that these two have been together for at least three years. It will be interesting to see what happens to these two individuals in the future.