What is Whale Poo? Is it Fertiliser?
We had an interesting day today with some quite rare sightings!
We saw a total of 5 humpback whales but spent most of the day with a mother and her 1- or 2-year-old calf that we encountered slowly cruising East along the northern beaches of Moreton Island. They were in quite shallow water (only about 5m deep) close to shore and they ended up heading South once they reached Cape Moreton. That makes them the first whales this year that we’ve seen travelling South, meaning they are already on the return journey back towards Antarctica. Quite early, all the others still seem to be heading North at the moment and usually we don’t start to see southbound whales until well into August!
Maybe the fact that they were quite early was the reason why they seemed to be taking their time, leisurely cruising along. Then they stopped to check us out, approaching our boat to within a metre, rolling at the surface. The youngster even spyhopped right next to the boat, lifting the big head above the water to get a good look at us! These kinds of encounters are always my favourite, when the whales seem as curious about us as we are about them.
But another really interesting thing that happened today was that at one point, the mum actually rolled on her side at the surface and then defecated, turning the water behind her tail a brown-green colour! Not something we see often, but that answers a question I have often been asked by guests: “Do whales poo??” Well yes, of course they do. In fact, recently there has been quite a lot of scientific interest in “whale poo”… As it turns out, whale poo actually plays a very important role in fertilising our oceans! This is particularly true for deep-diving species such as sperm whales or beaked whales. These species feed at depth, on deep water animals like giant squid, but they have a tendency to defecate when they are up near the surface. In doing so, they are actually transferring essential nutrients and minerals (for example iron and phosphates) from the unproductive deep ocean to the productive surface layer. This is where plankton can grow as it only receives enough sunlight near the surface. So the plankton is being fertilised by the whale poo, providing it with nutrients from the depth it otherwise wouldn’t be able to access. This finding has led to theories that by hunting most of the great whales to the brink of extinction, to a fraction of their original population size, humans have greatly decreased the productivity of our oceans, and the ability of plankton to trap and reuse greenhouse gases such as CO2. In other words, if we still had as many whales in our oceans as we used to, before commercial whaling started a few hundred years ago, maybe the effects of climate change we’re seeing today would be much, much weaker!
Certainly an interesting thing to consider and a good example of how our impacts on only one part of an ecosystem can have huge effects on other parts, even on ourselves!
Eco Ranger Ina