Sperm whales are one of the deepest diving whales on the planet and make dives of more than 2000ft below the ocean's surface lasting up to an hour while they search for the squid they feed on.
The calves, however, cannot make these dives and have to remain at the surface. This leaves the calves vulnerable to killer whales which often follow pods of sperm whales to prey upon.
Cetaceans were not limited by gravity in the buoyant marine environment and evolved multiple giant forms, exemplified today by the largest animal that has ever lived: the blue whale (Balaenoptera musculus).
There are tradeoffs, however, associated with large body size, including a higher lifetime risk of cancer due to a greater number of somatic cell divisions over time. The largest whales can have ∼1,000 times more cells than a human, with long lifespans, leaving them theoretically susceptible to cancer.
Using mercury and stable isotopes of carbon and nitrogen to obtain such information, the team were able to also analyse how the ice cover and the impact of potential toxic compounds have evolved over time.
Their findings were published in the Current Biology journal.
The tusks of the ten narwhals involved in the research were 150 to 248 cm long, and contained data from the time period 1962 to 2010.
Four of the six baleen whale species found in the western North Atlantic Ocean (humpback, sei, fin and blue) have changed their distribution patterns in the past decade.
Using 281 passive acoustic recorders moored to the sea floor from the Caribbean Sea to Greenland, researchers from the United States and Canada monitored the movements of the whales from 2004 to 2014. The findings of their study was published in the Global Change Biology journal.
Belugas are gregarious, highly sociable and they regularly form small groups, or pods, which may contain between two and 25 individuals, with an average of 10 members.
Rice's whale (Balaenoptera ricei), previously believed to be a population of Bryde’s whales, is an intermediate-sized species of baleen whale.
“I was surprised that there could be an unrecognized species of whale out there, especially in our backyard,”
—Lynsey Wilcox, geneticist with the US National Oceanic and Atmospheric Administration
We asked our contributors what their favorite marine mammal dive was and they sent us tales and images of magnificent whales, playful seals, endearing sea cows and curious dolphins.
Currently, there are only 400 of these whales left in the wild.
The first calf was seen on December 4, near Cumberland Island, Georgia. Then, on December 7, the second calf was spotted swimming alongside bottlenose dolphins off Vilano Beach, Florida.
When whaling all but exterminated the Antarctic blue whale 50 years ago, the waters around South Georgia fell silent. Between 1998 and 2018, dedicated whale surveys off the sub-Antarctic island yielded a sole blue whale sighting. But a whale expedition this year and analysis by an international research team resulted in 58 blue whale sightings and numerous acoustic detections, raising hopes that the critically endangered mammal is finally recovering five decades after whaling was banned.
After hitting a low of 300 individuals 30 years, humpback whale numbers off Australia’s east coast are soaring. Researchers from Australia’s Organization for the Rescue and Research of Cetaceans (ORRCA) are hoping for an increase in whale migration numbers this year. Census results from the past 21 years indicate an annual 10-15 per cent increase in whale migration numbers.
It’s been a quiet summer in the waters of Alaska.
With zero cruise ships carrying whale-watchers and glacier gazers—a situation which temporarily boosts the state’s population of 730,000 by 1.4m individuals—the humpback whales in the vicinity have grown much more talkative.
This is the impression that delighted researchers are getting.
