Last updated June 21, 2018 at 1:37 pm
Groote Eylandt rescue inspires a new collaborative project.
The discovery of a false killer whale stranded on the shores of remote Groote Eylandt in the Gulf of Carpentaria a year ago did more than just spark a successful 12-hour rescue mission by the local Anindilyakwa Land and Sea Rangers.
It also inspired a concerted effort to find out more about this mysterious mammal – a large dolphin with a deceptively whale-shaped head.
Leading the work is Carol Palmer, a marine mammal expert from Northern Territory Department of Environment and Natural Resources (DENR), who has been conducting coastal surveys in the region for more than a decade.
She mainly spots bottlenose dolphins, Australian snubfin and humpback species, but once in a blue moon a false killer whale has turned up – which surprises her because they are considered to normally be a deep ocean species.
However, further investigation revealed that researchers have been studying false killer whales in Hawaii for 15 years, finding evidence for genetically distinct in-shore and off-shore populations that don’t interact. Both are smart, active and social creatures that can live for up to 70 years and grow to six metres in length (two metres longer than a large bottlenose).
It turns out that false killers whales have been sporadically spotted in the intact marine environment around Groote Eylandt for many years; they are known to Aboriginal residents and occasional sightings have been logged by recreational fishers on the Marine WildWatch database.
Population estimated at fewer than 500
Now DENR, the Anindilyakwa Land Council (ALC) and the ranger group have joined forces in a project to tag and satellite track the false killer whale population around Groote Eylandt, which Palmer estimates at fewer than 500 in number.
They aim to put on two tags every two months over 12 months, using a dart gun to pierce the tag into the dorsal fin – a standard method developed on killer whales in the Antarctic
“They’re a tough kind of dolphin,” Palmer said. “It would be a bit like you or me getting a tetanus shot.”
The tag usually stays on for 50 to 100 days, and each time the dolphin surfaces to breathe it pings off a satellite and gives the researchers a location.
The satellite data will be overlaid onto benthic habitat maps of the marine protected area around Groote Eylandt previously created by the ALC and rangers. This will help the team assess what makes the area important for false killer whales.
According to Adrian Hogg, Land and Sea Manager of the Anindilyakwa Land and Sea Rangers, Groote Eylandt is unique in Australia. Because it lacks many of introduced animals that plague the rest of the country, there is an abundance of species that are otherwise rare.
“The underwater world here is as it was three, four, five hundred years ago,” he said. “It’s really been largely untouched, so basically the species that are here are big and in abundance.”
That is likely one of the reasons that false killer whales are drawn to the area; they need to consume about 100 kilograms of fish per day.
Health of the ecosystem
As they are top-order predators, their well-being also provides a general indicator of the health of the rest of the ecosystem. Once the team has a deeper better of this species, it will put together a management plan for a range of species in the marine protected area.
“Groote Eylandt from a marine megafauna perspective – so that means turtles, whales, dolphins, dugongs, manta rays, whale sharks – is a very important area,” Palmer said. “You want to be able to manage a place like this into the future.”
Depending on what the project shows, that may include proposing that false killer whales be listed as threatened, as they are in Hawaii, where the in-shore population is just 150.
Hogg says the project is beneficial for all involved, including the rangers. Most are local Anindilyakwa people who look after their own land, from cleaning up the marine environment to managing cultural heritage sites and assisting researchers by providing local knowledge and resources like boats.
“Aboriginal people have been aware of false killer whales for a long time,” he said. “But for the rangers to actually have a tracking device, where we can look at them on a computer and see where they go once they leave the beach, gives them a greater scientific insight.
“It’s really exciting to see the interest from the rangers and how they embrace the project.”
It’s early days, but the team is talking of also tracking other species such as whale sharks and marine turtles, though they’ll likely wrap up this project first.
“It’s quite a big effort to get out into the ocean, find whales and actually tag them,” Hogg said. “Even with the one that has a tag on right now, it’s proving quite difficult to track them down because of how quick they move!”
Anyone who encounters a false killer whale in NT waters can submit their sighting through Marine WildWatch.