Measuring lengths of up to 33 metres and weighing 190 tonnes, the blue whale is the largest animal on earth; and believed to be the heaviest animal to have existed in animal history. The mammal’s tongue, on average, is the weight of an adult elephant and may feed on 4 tonnes of krill a day during peak feeding seasons. Its intelligence matches these impressive physical characteristics; with intimate mother – calf bonds, a complex communication system and evidence of emotional awareness. Through these traits the blue whale has become an important keystone species, inspiring numerous conservation projects to help protect the species and increase their numbers. A paper published last week in Marine Mammal Science provided evidence that these conservation efforts have shown promising results, as the population of the Californian blue whale has risen over the past few decades.
Cole Monnahan and his team, from the University of Washington, estimated that numbers of Californian blue whales have recently increased to 2,200. Since whaling regulations came into effect in 1966 the Californian whale populations have steadily increased. Monnahan believes that at their current numbers, the whales have come close to their carrying capacity. This is the maximum number of whales that are sustainable within their ocean environment. The Californian blue whales are found on the eastern side of the Pacific Ocean, from the Gulf of Alaska down to Costa Rica. The other major group of blue whales are located near Japan and Russia.
To calculate their population numbers, Monnahan et al gathered whaling information from Russian whaling archives, which were only recently released. Analysing this information they were able to estimate the change in population from 1905, when the whaling industry was established, to 1966, when regulations on commercial whaling were introduced. The distinct repetitive calls of the blue whales allowed Monnahan et al to separate the Californian group from the Japanese and Russian populations. Researchers then used this information to compare current estimations of Californian whale population size with historic numbers. They concluded that their current group size is at 97% of their historic levels before 1905.
It is important to understand why this population of blue whales has increased, in order to plan effective conservation efforts for the future. Regulations on whaling have clearly had a productive effect on blue whale conservation, along with consistent monitoring of the group. One other solution has been to regulate trade ships, which may pass through primary breeding grounds. A programme has been developed from a combined effort between wildlife officials, environmentalists and air quality regulators to help protect the blue whale populations in the Santa Barbara Channel. The programme provides a monetary incentive for cargo ships to complete each trip at a slower speed. The $2,500 incentive, funded by the Santa Barbara County Air Pollution Control District and Santa Barbara Foundation, may help to sustain blue whale populations and simultaneously keep the air cleaner. The programme is currently in its trial phase and will run until the end of October, which coincides with the peak season for blue whale feeding. The trial is an opportunity to measure the impact of slowing ship speeds on blue whale numbers.
Monnahan described the blue whales as a “robust” species, their figures clearly demonstrating that they are capable of increasing their numbers after periods of whaling. However, it is vital to maintain and improve conservation efforts in order to keep their population size at carrying capacity. The California population of blue whales is a shining example of how productive, well monitored, conservation efforts to protect the species produces positive, measurable results. Other nations may learn from this research to help sustain further populations.
How else might conservationists help to protect blue whales around the world?