I’ll start off by saying I’m no expert on Orca, what I’ve learned is mostly through chatting with the researchers and reading a couple of papers about them.
Most people are surprised to hear of Killer Whales on the Ningaloo Reef, ‘aren’t they cold water creatures?’ Well, killer whales have a huge range from the poles to the tropics, although there are definitely more of them in higher latitudes (cooler waters). It seems there are at least three different orca populations in Australasian waters, A North West, South West and East Coast/NZ population, although they are potentially more subdivided than that.
The Bremer Canyon in the South West hosts a seasonal feeding event for the killer whales, and it is probably the most famous place to see these animals in Australia. People generally assume these are the same Orca we see on the Ningaloo and that they follow the whales up the coast during the winter. However, this is not the case.
The furthest south any of our Ningaloo Orca have been recorded is the Abrolhos Islands, off the coast of Geraldton, and genetic studies seem to support that these populations are distinct and it’s unlikely they are mingling. Killer whales are also often grouped into different ecotypes - animals of the same species which are ecologically and genetically different. The Ningaloo killers are genetically closer to other ‘tropical orca’, this doesn’t make them a different species, although some researchers argue there should be more than one species within the genus.
There are 26 identified Orca in the North West population (animals can be recorded and identified through photography) and there appears to be 3 related family groups which make up the population, with some animals moving between different pods. They usually time their arrival perfectly to coincide with the migrating humpback whales. There is between 30 and 40 thousand humpbacks which migrate along the coast of Western Australia each year to calve, so there is a huge amount of prey and foraging grounds for the Orca - It is believed they take more than 400 humpback calves during the migration!
Killer whales are apex predators - there is nothing out there hunting them. On the Ningaloo they predominantly feed on the humpback calves, though they have also been recorded feeding on different species of dolphins and sharks like tigers. Interestingly they have never been recorded feeding on the Ningaloo's whale sharks (maybe they know they'd get in trouble...) but in central America (Mexico, Costa Rica and Panama) Orca have been known to feed on whale sharks.
Witnessing a hunt can be both spectacular and heartbreaking as the huge animals fight to try and separate the whale calf from its mother whilst she works tirelessly to defend her calf. The battle can last for more than an hour or be over in minutes, usually the hunters will try to get the calf away and drown it, they will take turns distracting the mother, going for the calf and resting - meaning there's always one fresh predator. The humpbacks aren’t helpless against the killers, they generally travel close to the reef and if attacked while try and put the calf in really shallow water so the Orca can’t reach it. They also use their massive tails and pectoral fins to try and strike the orca - if they get a good hit in they could easily break an orca’s spine. The females will often travel with an escort male who is supposed to help protect the calf, but most of the time when I’ve seen it the escort swims off at the first sign of trouble. If they manage to get the calf, they pretty much only eat the tongue! It’s their favourite bit and its huge muscle - a big lump of protein for the hungry killers. It may seem brutal, but remember there may only be 26 Orca in the Northwest and potentially more than 40 thousand humpbacks.
Anyway, another question that is always asked about orca, is it a whale or a dolphin? Killer whales are in the family Delphinidae - Oceanic Dolphins. However Delphindae are in the order of Cetacea - Whales, so they are kind of both… All whales are dolphins, but not all whales are dolphins, make sense? Maybe.
If you’d like to try and meet one of these amazing animals on the Ningaloo, the best time is between June and September, but you need to be lucky, there aren't that many sightings throughout the season. They are occasionally sighted during the summer months, but it is even rarer. You can also see killer whales in Western Australia in Bremer Bay from January - April and it’s almost guaranteed, they even recorded the first predation on a blue whale there in 2020!
Happy whale watching :)