Are you a whale watcher? Have you stood on cliffs along Australia’s coast searching for humpback whales and seen a spout in the distance? Maybe you’ve spotted Migaloo?
Whale of a time
Humpback whales are on their annual winter migration north along the Australian coast. The females travel from Antarctica to warmer waters to give birth. They may have one baby whale (calf) each year. The calf travels with their mother for the first year, while they learn the ways of the ocean. Then they go their own way.
Humpback whales are very special. By the time whaling of humpbacks ceased in Australia in 1965 they were critically endangered. These magnificent mammals now have an IUCN Red List conservation status of Least Concern. Although there are still significant threats, notably climate change, they have made a very hopeful (and beautiful!) return.
We’ve put together some facts about humpbacks to ponder on your whale watch this winter.
Flippin’ big flippers
Humpback whale flippers are the longest flippers amongst whales. Their sophisticated design are aerodynamic wings for lift. This helps with their unique feeding behaviour and makes them more acrobatic and manoeuvrable than other whales.
In fact their scientific genus name Megaptera means “big wing” (mega+pteron) in Greek.
Along with their larger flippers they also have other unique features that make humpbacks easy to identify. They have a distinctive bushy blow. This sprinkler spout is what most people search for to spot them out at sea.
If you get a closer look you’ll see they have unique knobs on their head and jaws called tubercles. These tubercles contain a single hair follicle.
Their tail flukes are also special. They have unique patterns on their tail fluke, which helps people identify individual humpback whales.
Humpback whales are a favourite of whale watchers because of their aerial tricks.
These include ‘breaching’ or leaping out the water. ‘Lobtailing’ which is sailing with their tail above the water. And flipper slapping.
Their acrobatics are forms of play and communication. These displays may show excitement or annoyance. They also help remove pesky parasites.
Soulful singers of the seas
Despite having no vocal cords, humpback whales are renowned for their soulful songs.
Scientists initially assumed they were mute. It was only in 1971 that it was accepted that the patterned structured sounds produced by humpback whales are essentially songs.
Only males sing these songs when on the breeding grounds. Their songs evolve and change over time. Nearby males pick up the popular hits and share some of the new song units.
Just like Eurovision, some of the songs are in different ‘languages.’ The songs humpback whales sing off Australia in the Pacific Ocean are a different dialect to those humpback whales sing in the North Pacific and in other oceanic basins.
Humpback whales undergo some of the longest known migrations of any mammal. They swim thousands of kilometres each year.
Southern hemisphere humpback whales spend their summer feeding in circumpolar waters around the Antarctic.
During winter they travel up and down the Australian coasts, going to and from the warmer tropical waters where they breed. Even though all that travel sounds like hungry work they mostly fast while on the breeding grounds.
There is no denying they have exceptional navigational skills. However, scientists don’t yet fully understand just how they navigate so efficiently.
Whale food and climate change
After all that swimming and fasting on the breeding grounds, you would be right to think they’d work up an almighty appetite. So, of course, they dine where the food is good and plentiful. What you may not know is there is southern-style food and northern-style cuisine.
Southern hemisphere humpback whales mostly feed on copepods and krill. These tiny aquatic creatures are highly nutritious and abundant in the Antarctic waters. Northern hemisphere humpbacks prefer schools of small fish like herrings and mackerel. And they have a clever way of hunting dinner using bubbles. They create bubble nets by blowing curtains of bubbles to trap schooling fish. They then lunge into the centre to feed off the captured prey.
This plentiful supply of food has been good news for whales. Centuries of commercial whaling have devastated whale populations. Now whale numbers are increasing year after year.
Humpback to the future
We used MICE (Model of Intermediate Complexity) to work out the rate of whale recovery from historical whaling. Our modelling showed humpback whales have been recovering much faster than blue or fin whales. This is probably because they have a faster breeding cycle.
It’s a positive step forward to see increasing numbers of humpback whales visiting our shores every winter. Unfortunately, our modelling results also tell us climate change poses a new and formidable threat to baleen whales.
Our modelling suggests the full recovery predicted for humpback whales is likely to be strongly reversed by 2050 due to climate change.
One of the big reasons for this prediction is the food available for whales. Krill and copepods are likely to be sensitive to increasing ocean temperatures. It is likely that the availability of food will limit their population size unless emissions are substantially reduced.