Whaling and environmental threats
Cetaceans have conquered all the world’s oceans, from the warm tropics to ice-filled poles, from coastal shelves to deep ocean. Some even successfully returned to freshwater rivers. However, river dolphins have had to reckon with a growing list of human threats so severe they probably caused the extinction of one species, the Chinese river dolphin, or baiji (Lipotes vexillifer).
Chinese river dolphin (Lipotes vexillifer), also known as the Yangtze river dolphin, or baiji. Critically endangered and possibly extinct. This individual male, Qi-Qi, was photographed in 1988 at Institute of Hydrobiology, China. Image © Mark Carwardine/OceanwideImages.com
Found only in the Yangtze River, baiji were last seen in 2004; a 45-day search by 30 scientists in 2006 failed to locate a single individual. Like other river dolphins, baiji had especially long snouts (about four times as long as most marine dolphins), and poor eyesight, probably because they tend to live in murky water. Thought to have swum the Yangtze River for 20 million years, baiji quickly fell victim to China’s industrialisation. Four of the world’s five remaining species of river dolphin and the sole species of river porpoise are also threatened with extinction, some critically. New DNA evidence suggests that in Brazil there may be one more separate, highly endangered, species of river dolphin.
River dolphins are not alone in their plight; many other cetaceans have suffered from commercial whaling, pollution, overfishing, drowning in fishing nets, collision with ships, injury from propellers, excessive underwater noise pollution and climate change. Although conservation efforts came too late for baiji, humpback whales (Megaptera novaeangliae), show we can successfully bring whale species back from the brink of extinction.
Famous for their long, loud and complex songs, male humpbacks sometimes sing non-stop for 24 hours, possibly to serenade females. Although evolution has left most whales without any body hair (there is less friction and better streamlining without it), humpbacks are among those that still have a little. Emerging from golf-ball-sized bumps on their head, these hairs are clear reminders of the humpback’s mammal heritage.
Large-scale whaling drastically reduced humpback numbers, from an estimated 125,000 to just 5,000 individuals by 1966, when commercial hunting was banned. Humpbacks have rebounded strongly since, to an estimated 80,000 worldwide today.
A whale ship from the Cheynes Beach Whaling Station, Albany, Western Australia, harpoons a whale, 1970s. PHOTOGRAPH BY ED SMIDT, REPRODUCED COURTESY INGRID SMIDT
The popularity of whale-watching means that Australia has made more money by protecting whales than it ever made by killing them. Protective measures like the Australian Whale Sanctuary also help; this makes it an offence to harm or interfere with any cetaceans out to 200 nautical miles from Australia’s coasts. However, despite such conservation efforts as these, the populations of nearly all great whales remain at depressed levels, and many species face severe threats.
Palaeontologists have helped us look back to understand the 50-million-year evolutionary journey of cetaceans, from small forest dwellers to the mighty ocean leviathans of today. Now it’s up to the rest of us to look ahead to ensure that every living species of whale, dolphin and porpoise—each a unique product of millions of years of evolution—has a future in our oceans.
Bryant Austin’s photograph, Humpback Whale Calf III, Kingdom of Tonga, 2006. Courtesy Bryant Austin/studio:cosmos.
This portrait of a five-week-old humpback whale calf features in ‘Beautiful Whale’ an exhibition of Bryant Austin’s large-scale photography, which is on show at the museum until 1 February 2015.
About
Janice Wormworth is a science communicator with a background in biology and journalism. She has worked for NGOs, business, and government in Australia, Canada and the Netherlands, and is an author or contributor to numerous reports, articles, and a documentary on climate change and energy issues.
Credits
Images were sourced from the Australian National Maritime Museum collection, Hans Thewissen, Roman Uchytel, the University of Michigan Museum of Natural History, Wikimedia Commons, National Library of Australia, OceanwideImages.com, Shutterstock, National Oceanic and Atmospheric Administration (NOAA) Photo Library and Bryant Austin/studio:cosmos.
