Photographs of a dolphin with “strange markings”, swimming near a popular Aussie tourist beach have prompted concern. And experts believe two factors have contributed to its problem:
A string of four large white blotches were first noticed on its skin by a woman who regularly watches the pods that live off Port Macquarie on the NSW Mid North Coast. Jodie Lowe, who photographed the animal on Friday, is certain the the markings have developed quite quickly.
“These strange markings have only appeared in the last week or so,” she said. But there’s since been heavy rain which has impacted water quality, and some experts believe it could have caused the animal’s condition.
Its not the first strange find Lowe, a regular visitor to the area, has made. In an unrelated discovery, she photographed a whale with peculiar markings that stumped experts in June.
How location can make dolphins sick
Those with knowledge of dolphin illnesses believe the animal in Lowe’s photographs is most likely infected with a disease associated with freshwater. And dolphins at Port Macquarie are known to frequent the nearby Hastings and Camden Haven Rivers.
Based on an assessment of the image, cetacean researcher Dr Mike Bossley thinks the dolphin is most likely suffering from saltwater skin disease, a type of ulcerative dermatitis.
“It occurs when dolphins are exposed to reduced salinities in coastal lakes. Exactly the same thing has been happening in the Gippsland Lakes and in the Swan-Canning River,” he told Yahoo News.
Related: Seven dire reasons it might be time to leave Australia – from floods to fungus
How the dolphin skin disease develops
In 2020, a scientific report in the journal Nature described it as an “emerging clinical and pathological presentation in coastal cetaceans worldwide”.
Report co-author Dr Kate Robb, the director of the Marine Mammal Foundation, said the lesions in the photographs aren’t exactly the same as those she’s examined first-hand in the Gippsland Lakes, but that’s to be expected.
“The disease normally starts off with small pin-prick sized black lesions, and then they can ulcerate out and become secondary bacterial and fungal infections,” she told Yahoo News.
“It’s not unexpected they’d look different because secondary infections are based on the environment the animals are in. But they do form those circular lesions.”
How weather can make dolphins sick
A dolphin’s skin is the first barrier of defence against the environment it lives in. And when it comes to oceanic species, they’ve evolved to survive in salty conditions.
“If we were in a salt bath for a really long time our skin would start breaking down,” Robb said.
“Dolphins on the other hand are used to a high level of salinity. So when you put them in freshwater, at thresholds of about 10 parts per thousand their skin starts to break down.
“It creates open wounds and then they can get secondary infections. It can break down the whole skin and look like third degree burns.”
A fortnight ago, NSW experienced a deluge of heavy rain. And Robb has previously noted dolphins that experience a sudden change in water conditions can “very quickly” present with symptoms of the disease, particularly among resident pods.
“When there is a big burst of freshwater into a system that the dolphins are used to living in, they don’t necessarily know to get out — they don’t leave because it’s their home,” she said.
“I would say it’s definitely a possibility that it’s got the disease. But I’ve seen animals in worse condition survive.”
Love Australia’s weird and wonderful environment? Get our new newsletter showcasing the week’s best stories.