Two female whales may be trying to escape a pursuing male and risk colliding with boats on the Brisbane River.
Scientists have discovered two humpback female whales swimming upstream on the Brisbane River this week, weaving between cargo ships in the bustling port area of the river. Olaf Meynecke, manager and researcher in the Whale and Climate Program at Griffith University, speculated that they might be avoiding a male attempting to mate, Newsweek reported on August 12.
Two humpback whales glide on the water surface. (Photo: iStock)
Whales and dolphins sometimes swim upstream in rivers searching for food. However, many individuals die before they can return to the sea. “It’s possible that these whales are lost upstream in the river. A famous example occurred in California in 1985 when a humpback whale named Humphrey swam upstream in the Sacramento River, but after a few weeks, it returned to San Francisco Bay and out to sea,” said Bill Keener, a researcher at the Marine Mammal Center.
During the winter months in the Southern Hemisphere, humpback whales migrate north from the icy waters of Antarctica to warmer tropical waters off northern Australia, such as the Great Barrier Reef in Queensland and the Ningaloo Reef in Western Australia. These areas provide warm, safe waters for mating and nurturing their young. After the breeding season, whales begin their journey back to Antarctica around September, indicating that they are now heading south.
Whales gather and mate offshore from Queensland, where the Brisbane River meets the sea, so the two female whales may have fled to unfamiliar freshwater to escape the pursuit of a male, according to Meynecke. The mating behavior of humpback whales is highly competitive, with males often aggressively competing for the attention of females. They also form temporary groups surrounding a female, with the strongest male staying closest to the target while other males try to challenge for his position.
If a female whale does not want to mate with a male, she may try to swim away. “If the female is already pregnant, she may not want to conceive again the following year. There is always competition among males. Mother whales and their calves come to the bay to rest and avoid close interactions with bothersome males,” Meynecke explained.
Researchers are also concerned that the two female whales in the Brisbane River are at risk of colliding with boats. “People may not notice the whales. They have to come up to the surface and may collide with vessels,” Meynecke stated.
