The news that orcas are attacking and sinking ships off Europe’s Iberian coast has the world captivated by the strange workings of the creatures’ culture.
But these aren’t the only sleek ocean swimmers that have learned to respond to the presence of humans.
Scientists at the University of Queensland (UQ) in Australia suspect that bottlenose dolphins (Tursiops spp.) in Moreton Bay, near Brisbane, are teaching each other to ‘beg’ boats for fish.
Sometime between 2017 and 2020, marine scientists noticed dolphins approaching recreational fishing boats and feeding on the scraps tossed to them by humans on board.
“Within the dolphins’ social network, I found a cluster which would consistently patrol moored boats, waiting for recreational fishers to illegally toss them discarded bait or catches,” explains Léonie Huijser, who noticed the peculiar phenomenon while undertaking a thesis at UQ on dolphin social structures.
“Fishing is popular in the bay, and it seems some dolphins have learnt to exploit it.”
It’s currently illegal to feed dolphins in Moreton Bay, but it’s hard to actually police that law when fishing boats are out on the water, far from shore.
In another bay near Brisbane, authorities recently fined a man several hundred dollars for feeding dolphins his scraps; they warned penalties can go all the way up to AU$17,000 (US$11,252).
That might seem like a disproportionate punishment for a well-intended act, but feeding dolphins can be seriously harmful to individuals and pods.
Experts warn that tossing dolphins fish actually puts them at greater risk of behavioral changes and boat collisions.
“Some of the dolphins who boldly approach boats have evidence of propeller strike and fishing line entanglement,” says Huijser.
“During one of my first fieldwork days near North Stradbroke Island, a dolphin surfaced next to our boat but disappeared once it realized we weren’t going to feed it. Its fin had been badly mangled previously, indicating it may have been caught up in a line.”
Huijser is concerned that the begging behavior is spreading. Dolphins, like orcas, have complex cultures that can evolve and adapt over time via social learning.
If a non-begging dolphin sees its peer begging, it could mimic that behavior. Especially if the begging dolphin is successful at coaxing fish from humans above.
At least five dolphins in a pod off an island in Moreton Bay have already started showing signs of the begging behavior. They have a calf with them, too, which could mean future generations are also learning the trick.
“Not all adaptations are positive, and begging is an example of an adaptive strategy that may have short-term gain but long-term risks,” explains marine biologist Michael Noad, who supervised Huijser’s thesis.
“Dolphins risk becoming reliant on donated fish, which is like junk food to them – quick and easy, but unhealthy. It may lead to food poisoning or nutritional imbalances.”
Huijser and the team of researchers at UQ are now trying to locate ‘hotspots’ for begging dolphins in Moreton Bay to improve official surveillance in those areas.
Huijser’s thesis has been published on UQ Library’s eSpace.