In recent days, researchers have published their findings showing that humpback whales have a much more complex social structure than previously thought. Certain female individuals were known to have long-lasting associations with other females for over 6 years, the first baleen whales shown to exhibit such behaviour. At the same time, the IWC meeting is almost upon us (scientific meetings of all magnitudes are taking place behind closed doors just now!) and humpbacks are still on Greenland's wish-list! Surely this recent news of long-term associations between whales deserves some consideration when thinking of adding them to the menu?
So for the moment, some lighter reading ... WDCS's Sue Rocca introduces us to the magnificent humpback whales that she (and others) are studying on the East Coast of the USA. Over to you Sue ....
Researchers have been studying humpback whales in the Gulf of Maine for over 30 years. Every new discovery both advances our knowledge and helps us better protect this charismatic species. You would think that in over 30 years we would have them all figured out, but that couldn’t be further from the truth. But that’s what keeps it exciting – there is still so much left to discover.
We are lucky to work with a species in which individuals are so easily recognizable as humpbacks. Each humpback has a distinctive black and white pattern on the underside of their tail fluke. And we get to see this marking when humpbacks fluke up on sounding (or deep) dives. The ability to tell one apart from the other is the bases of any and all study. Without this we could not do something as simple as censes the population without worrying about counting the same individuals over and over. Before you learn how often a mother can have a calf, or at what age they reach sexual maturity, or what the life span is - you have to be able identify individuals.
So much of our work goes into recognizing and recording individuals – where they are, who they are sighted with, and what they are doing. You get enough years of this type of observational data and it’s amazing what you can tease out. Which is one of the reasons the lethal, scientific whaling conducted by Japan is such a joke. You can learn exponentially more by watching whales alive and well in their natural environment then you would ever hope to by killing it.
We know humpbacks in the western North Atlantic separate into six distinctive feeding stocks and there is some level of fidelity to which feeding stock your mother takes you to in that first year as a calf. There is a 70% sight fidelity level in the Gulf of Maine – meaning as far as we can tell 70% of the calves who’s mothers brought them to the Gulf of Maine in their first year will continue returning to the Gulf of Maine throughout their lives. We also think that all of the different feeding stocks go to the same general winter breeding grounds in the West Indies. Notice I said think…
Other things we know because we can identify individuals - humpbacks become sexual mature and can reproduce as early as 4 years of age for females. We don’t know when they stop reproducing. Salt, so named because she has white on her dorsal fin – looking as if it was covered in salt, was the first whale individually identified in 1976 because of her unique dorsal fin. We have seen Salt in the Gulf of Maine every year since, and this year she is back with her twelfth recorded calf. But there were a few years – 7 in fact – when we saw her without a calf, so we started thinking that maybe she had reach the age of on longer being able to reproduce. Then in 1998, Salt returned to the Gulf of Maine with her eighth calf. And she has continued to have four more.
And we certainly don’t know how females choose whom to mate with. Originally this was thought one of the purposes for the 30 min long, complex song the males sign. Hopefully you have heard the humpback song! No female has ever been recorded singing and once it was thought the males only sung in the breeding grounds – so you will excuse researchers from assuming the song was how male humpbacks attracted females. However, when researchers played the humpback whale songs to humpbacks it was not the females, but the males who responded. This, in addition, to the fact that humpbacks have now been recorded singing off the coast of Massachusetts when we never thought they sung in their feeding grounds, leads us to the understand that humpbacks, like all of nature, is more complicated then we originally thought.
One of the things we are hoping to better learn in the future is the life span of humpbacks and large baleen whales. Currently, our best guess is 60 to 80 years, but this is based on whaling data. It’s much better for us to see calves with their mothers in the year of their birth – know how old they are, follow then throughout their lives, and when we see entire age classes start to naturally die off we will know better.
Being able to recognize named individuals also helps people identify with the whales, which in turn increases the public’s desire to help protect all whales. Since 1984 through the Whale Adoption Project people have been helping protect whales by adopting individual humpback whales. We have supporters who have been adopting the same whale for twenty–some years and very much look forward to hearing their whale has returned to the Gulf of Maine and what they are up to. We are continually grateful and indebted to our supporters who make our work possible and carry the message of whale and ocean conservation out into the world with them.