Two whales spotted swimming up a river in Australia may be on the run from a randy male, scientists have suggested.
The two female humpbacks were spied swimming upstream in the Brisbane River this weekend, weaving between cargo ships in the Australian river's bustling port.
An expert has theorized that the females might be avoiding a male seeking to mate and is concerned about the risk of boats and ships colliding with them.
"It could be a strategy to swim up the river and avoid a male," Olaf Meynecke, a manager and researcher at Griffith University's Whales and Climate Program, told local news ABC.
Whales and dolphins have occasionally been seen swimming up rivers, often in search of food. Sadly, many of these creatures die before they can return to the sea.
"It is possible for cetaceans to get lost up rivers. A famous case of this in California occurred in 1985 when 'Humphrey the Humpback Whale' was far up the Sacramento River, but after weeks eventually made it back down to San Francisco Bay and out into the ocean," Bill Keener, a researcher and member of the Cetacean Field Research Team at The Marine Mammal Center, told Newsweek.
During the southern hemisphere's winter months, humpback whales migrate northward from the icy waters of Antarctica to the warmer tropical waters off the coast of northern Australia, such as the Great Barrier Reef in Queensland and Ningaloo Reef in Western Australia. These regions provide safe, warm waters ideal for calving and mating. After breeding and calving, the whales begin their return journey to Antarctica around September, meaning that the whales are currently about to head back south.
The whales are gathering and mating just off the coast of Queensland, which is where the mouth of the Brisbane River is, so the females may have made a beeline into unusual freshwater territory to escape the advance of an unwanted male.
"This time of year, bulls [males] are looking to mate with females and it's that kind of behaviour where the females might try to avoid that interaction," Meynecke said.
Humpback whale mating is highly competitive, with males aggressively competing for the attention of a female. Males also often form temporary groups called "escorts" around a single female, with the strongest male, known as the primary escort, staying closest to the female, while other males, known as secondary escorts, challenge the primary escort for his position.
If a female does not want to mate with a male, she may swim away from him to escape.
"If she's already been pregnant, she might not want to be pregnant again next year, but he might not be the right one for her," Meynecke said. "There's usually competition among the males...we have mums and calves in Moreton Bay, and they go there to rest and to avoid that close interaction with those pesky males."
Both sexes will have multiple partners during this breeding period, and males may also have sex with each other.
There are concerns that the whales in the Brisbane River could risk colliding with the many boats on the river.
"There's a lot of traffic, people might not be aware that the whales are there...they have to come to the surface and there's the danger of just driving and hitting the whale," Meynecke said.
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