Migrating Naturalist: Prop Chop

This is not the calf that had been hit, just an example of a close approach. Note that our propeller is not spinning. (The above image was taken under NOAA-Fisheries Permit #587-1767-01)

A few days ago I wrote about humpback calves (in “Calf Charisma”), and how much I enjoyed their adorably awkward antics. Unfortunately, this lack of coordination also means that their movements can be quite unpredictable. It is not uncommon for a calf to pop up suddenly right in front of you, particularly in Hawaii where the humpback population is so concentrated. These unexpected moves demand that you always keep a sharp eye out all around, and as calves tend to breathe every 2–3 minutes, you can usually spot them from afar. Unfortunately, every once in a while the driver or passengers on a boat are not watching closely enough, and a calf will be hit. If the calf is lucky, it will only bump against the boat’s hull, swimming away with a big bruise and a reason to avoid boats in the future. If the calf is unlucky, then it will make contact with the boat propeller, which can do some serious damage.

Nearing the end of our research today, we suddenly received several calls regarding a calf that had been hit by a fishing vessel close to Lahaina harbour. At least one tour boat had witnessed the incident, and two of them were following the group of whales, keeping an eye out for signs of serious injury. Blood had been seen in the water immediately after impact, and so everyone was understandably concerned. As our research boat is able to approach within the 100 yard limit maintained for all vessels, we were asked to come in and take a closer look at the calf.

On approach, we were unable to see any obvious damage to the calf. However, after a closer look, we noticed a series of prop cuts on the calf’s left side, near its pectoral fin. The calf was moving and breathing regularly, so it did not appear that the injury was life-threatening. However, the mother was being extremely protective, as was the male who was accompanying the pair. The mother was swimming quickly, continually circling to keep her calf away from our boat. After following them for a short while to obtain photos of the injury and ID photos of the two adults, we let the group move off, sending with them our best wishes. Shortly after, an NOAA vessel met us on their way to document the situation, and we passed on what we had discovered.

It is most likely that the calf will survive the incident with nothing more than some scars and a memory to stay far from boats in the future; however, not all calves are so lucky. Some will succumb to their injuries, and some will become targets for tiger sharks or other predators that dwell in these waters. Responsible boating is an absolute necessity, whether you are in Hawaii or anywhere else in the world. We must learn to share the ocean with all its creatures, and never forget that we are not alone on the water.

2 Responses to “Migrating Naturalist: Prop Chop”

  1. Keith says:

    Awesome story… Yeah that’s right I read all your blog entries!!! I hope our guests and other drivers can read this and understand why we need to keep the distance. It is also a good reason to ride on WASCO or NANUQ! These boats allow you to be higher up, giving a better view and allow us to respect the animals!

  2. Pat says:

    Another interesting episode in Diane’s Hawaiian adventure. she will be bringing back many stories to share with Wasco’s and Nanuq’s passengers next season – and much wise advice!!

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