The humpbacks have returned

The humpbacks have returned. Every year from about late August to mid-November the nearshore waters of American Samoa are taken over by amorous humpback whales (Megaptera navaeangliae). These whales, which have all migrated from their summer feeding grounds in Antarctica, come here to mate and calve.What is surprising about this journey of several thousand miles is that it is done by the same animals each year. Similar to a fingerprint in its distinctiveness, individual whales can be identified by the unique patterns on the underside of their flukes (tails). This actually gets easier with age as new scars, and scrapes aid in the differentiation. So even though they may look similar from a distance, a trained observer can easily recognize each particular whale. This is how we know that we have around 70 whales that make this arduous trip each year.During the southern hemisphere summer, the waters of the Antarctic are lush with krill and small fish, perfect for a baleen whale like the humpback. They gorge themselves all summer long putting on bulk for their long migration, because once the whales get here, there is no food for them. They fast the entire time they are here, which for the females can sometimes be several months. Once they are here then the shows really begin, humpbacks are one of the best known whales because these are the whales which fling their gigantic bodies (around 40 tons) almost entirely out of the water, called breaching. They also roll on their sides at the surface and slap the water with their huge pectoral fins, called... yup, fin-slapping. While there are many theories out there as to why the whales do this (some a little sillier than others), the honest answer is we don’t know (but we have a few pretty good guesses). It is easy to imagine that these massive 40-50 foot long animals are bulky and clumsy (especially after you see one breach). Surprisingly, underwater they are actually quite acrobatic and graceful. I suppose a few million years in the ocean will do that.What humpbacks are best known for is their singing. An unimaginably loud sound, these songs can carry for many miles underwater. They tend to last 10-20 minutes “per song” and the singing can on rare occasions go on for over 24 hours nearly nonstop. We actually hear it quite a bit this time of year while we are diving. Many times we have surfaced with thoughts of the whales being “very close”, only to find that the person on the boat saw their spouts (when they come up to breath) several hundred yards or further away. The songs are “regional dialects” and groups in different parts of the world have very different song patterns.
While males are putting on their best shows the females (which are certainly the more inquisitive sex), the girls are often curious about the things around them. They can often be seen spy-hopping, which is when them poke their heads out of the water to get a good look at things on the surface or the horizon. Sometimes they will even come right up to boats to take a peek at the curious creatures.The reason the whales make the journey to our barren and foodless water is for the good of their calves. Though they are almost 15 feet long and weigh 1 ton (2,000 lbs) at birth, these newborn whales have very little blubber to keep them warm. If they were born in the frigid waters of Antarctica, they would quickly chill. So they are born in the warm tropical waters around American Samoa where they quickly bulk up by drinking their mother’s milk which is roughly 50% fat! (whole cow milk is about 4%). Another reason is that most of the ocean is around 12,000 feet deep, while the shores immediately around our islands are about 300-800 feet deep. We are the shallow “kiddie pool” of the ocean. Once the calves have put on enough blubber, they start the long journey back south with their mothers. If all goes well, they could be back to have their own calves in as little as five years (assuming of course that they are not taken by Japanese fishermen for “scientific purposes”).One final note, all these photos were taken during a federal research trip to study the whales in American Samoa (NOAA research permit #NMFS774-1714). I was given the rare opportunity to get in the water with the whales. This is normally illegal, as these are an internationally protected endangered species. Also, I try hard to take good photos. Please do no steal these (or any other) images from our blog. If you want friends or family to see the whales that you get to see here (and I encourage this), please just make a link to this site.