A humpback calf breaches off Mona Vale on Sydney's northern beaches. Photo: Jonas Liebschner, www.whalewatchingsydney.com.au
The humpbacks' southern migration is in full swing and plenty of mothers and calves are now on the move.
Jonas Liebschner, photographer with Whale Watching Sydney, estimates that 20,000 whales are swimming along the coast.
Their numbers are increasing by 10 per cent every year, he says.
Into the breach
Whale breach off Sydney's eastern suburbs at the weekend. Photo: Jonas Liebschner, www.whalewatchingsydney.com.au
Whale watchers should be able to see them from land as well as from boats.
Sydney played host to some spectacular action in the past few days.
Humpback whales swimming past Sydney now are coming up from their summer feeding grounds in Antarctic waters and swimming north to tropical waters to give birth and to mate, Mr Liebschner says.
It is commonly thought that the migration only occurs from mid-May to August-September because that is when whales can be seen swimming by close to land, heading north.
However, the whales that do swim past Sydney going north then come back south again as well, so the sightings continue into October and later.
When the whales do head back to Antarctica, of course there will be more of them as they will include new-born calves. Most whales swimming past Sydney at this time of year close to shore would be mothers and calves.
They might be accompanied by an escort whale (male or female) as well.
The mothers stay close to shore to protect their calves, which is best done by finding shelter in a bay or behind a reef should the weather turn bad or predators, such as orcas or the odd shark, attack.
Fully grown whales don't really have to fear an attack but calves are not strong enough yet.
Most other adult whales would be 10-15 nautical miles out to sea as they are looking for a southerly flowing current that helps them along on their journey south, which is thousands of kilometers long and will take them months to complete.
The East Australian Current (which features in the movie Finding Nemo) helps the whales along at a speed of a couple of knots, Mr Liebschner says.
That's when people usually think no whales are swimming past any more as they cannot see them from land. But October and November are the time for a lot of mothers and calves.
Any headland or beach will be a good spot to look for whales at this time of year.
"Mothers and calves are sometimes found less than a couple of hundred metres away from land and can be very playful at times, jumping out of the water for hours without stopping," Mr Liebschner says.
"This week, we watched whales going past Dover Heights, being very active. An hour later, when we were back in the harbour to pick up our passengers for the afternoon cruise, a friend texted me to say she could see a breaching whale at Bondi Beach. That would have been the same one we watched before it made its way south along the coast. So, with a bit of patience and luck, you will see a whale sooner or later.
"Humpbacks do not feed a lot during their migration because there is not too much for them to eat. We have seen whales feeding of the coast of Sydney, but it happens very rarely. We call it opportunistic feeding which means should there be a meal that presents itself to the whales they will most definitely eat it, but they can go without until they do arrive back at their feeding grounds.
"Most of their feeding happens in their Antarctic feeding grounds during summer when they eat tonnes of krill and small fish every day. They are preparing themselves for the long journey to the mating grounds up north and will build up a layer of blubber more than 20 centimetres thick that they can use up during their trip.
"A fully grown humpback whale would be about 15 metres long and can weigh up to 50 tonnes. But when we see them going past Sydney on their way south again there is a visible difference in size. They will have lost about 20 - 30 per cent of their body weight."