Did you know that whale poo can give us a lot of insight into what whales are eating? This activity will show you how we can use whale poo to understand the diet of Bryde’s whale (a whale seen throughout the Hauraki Gulf), and why it is important that we keep our oceans healthy if we want to look after the whales (and other sea creatures)
How big do you think a Bryde’s whale is?
Approximately how much does a whale that size need to eat each week?
How do we know what it eats?
Given that it does most of its eating under water, how do we know what it's eating?
Well, we collect their poo. The colour and texture of its poo changes according to their diet, which we have learnt using high-throughput gene sequencing. That means, that when we analyse the DNA in the poo, we get graphs that show us what the whale has been eating!
What does it eat? Feed the whale!
Drag the food types below onto the mouth of the whale to see how we can tell what they are by the colour of the whale's poo.
Great! Eating plankton soup (i.e. a mixture of zooplantkton and phytoplankton) means the whale produces a slightly tan/brown coloured poo that is a bit like a cloud.
The name plankton comes from the Greek word planktos meaning wanderers. There are two types of plankton - phytoplankton, and zooplankton
Phytoplankton are microscopic plants that live in the ocean, like seaweed and algae. They are normally found on the surface of the water, where there is a lot of sunlight. As a plant, phytoplankton rely on the sun and photosynthesis – that is, converting sunlight into energy – in order to produce their own food.
Zooplankton are animal plankton, and consist of things like tiny fish and crustaceans. Because they are animals they don’t rely on the sun for food – they rely on phytoplankton which is their chief source of food.
Krill and Mysid shrimp
Great! Krill and Mysid shrimp produces a muted pink colour poo that is a bit like a cloud.
Small schooling fishes
Great! Schooling fishes produce a brown colour poo that is a bit like a cloud – but is more sticky and has a few more lumps than other types of poo.
Keeping our oceans healthy
It’s really important that we keep our oceans healthy, because phytoplankton need a healthy ocean to survive. Without phytoplankton, the zooplankton would have nothing to eat, and without zooplankton, the smaller fishes would have nothing to eat, and without the smaller fishes the bigger fishes would have nothing to eat, and so on. And, because the whales eat plankton soup, zooplantkton swarms, and fishes, then an unhealthy ocean means no whales!
The biggest threats to our oceans are from pollution (runoff from land), climate change causing ocean acidification that means calcium carbonate structure forming organisms can’t grow (includes phyto- and zooplankton), and overfishing takes prey out of the water (think of all those pilchards used as ‘bait’, which are actually really important shark, big fish, whale, seabird and dolphin food).