Whales

Last summer, the highly contagious strain of avian influenza, that was first detected in early winter 2021, had been spreading through North American birds made its way into marine mammals, causing a spike in seal strandings along the coast of Maine.

In June and July 2022, more than 150 dead or ailing seals washed ashore, a number that was approximately three times the normal rate for this time of the year. Of the 41 stranded seals tested for the virus, nearly half tested positive.

Cancer should be a near certainty for whales, being the longest-living and largest mammals there are. Across species, the higher the number of cells, the greater the number of cell divisions and the higher the probability of DNA damage and the transformation of a normal cell into a cancerous one.

However, the occurrence of cancer does not show a correlation with body mass. The lack of correlation between body mass and cancer risk is known as Peto’s paradox.

A study of 22 toothed whales which died in strandings along the Scottish coast shows that some of them exhibited hallmarks of Alzheimer’s disease, and this might have—at least in part—caused the stranding incident.

The dolphin species involved in the study were five species: Risso’s dolphins, long-finned pilot whales, white-beaked dolphins, harbour porpoises and bottlenose dolphins.

From March to July, phytoplankton blooms emerge along Calfornia’s Central Coast, as seasonal winds push the top layer of the waters out to sea, thereby allowing the cooler, nutrient-rich waters to rise to the surface.

Many marine animals are drawn to such oceanic upwellings, which consequently turn into their feeding grounds. For instance, krill gather to feed on the abundant phytoplankton, whilst blue whales converge to feed on the krill.

Once the upwelling ceases, these marine creatures move elsewhere.

After studying more than 23,000 sperm whale vocalisations recorded from 1978 to 2017 in the Pacific Ocean, researchers have concluded that sperm whales use distinctive vocalisations to identify themselves with specific whale clans.

Called “identity codas,” these vocalisations comprise sequences of clicking sounds that distinguish different social groups. They are different from non-identity vocalisations used across all the different whale clans.

Keeping an eye on whale behaviour is not easy, considering the fact that they travel vast distances and spend the majority of their time beneath the ocean surface.

To counter this, researchers at Oregon State University {OSU) have developed a new satellite tag that can track the whales' movements, even during dives.

Known as RDW, this new technology incorporates pressure and accelerometer sensors, thus giving the researchers the opportunity to monitor the whales’ movements underwater for several months.

Fin whales (Balaenoptera physalus quoyi) of the Southern Hemisphere were brought to near extinction by 20th-century industrial whaling. For decades, they had all but disappeared from previously highly frequented feeding grounds in Antarctic waters. Researchers estimate that by the time whaling was banned in the 1970s over 700,000 fin whales had been killed.  

For decades, Japanese whalers have known of the existence of a whale species that resembles the Baird’s beaked whale, but is smaller in size. It was only in 2019 that DNA samples taken from deceased whales were able to confirm their existence.

The new species was named Sato’s beaked whales, after researcher Hal Sato, who sent photos of deceased stranded individuals to Tadasu Yamada, curator emeritus at Japan’s National Museum of Nature and Science, in the early 2000s.

The vaquita is the world’s smallest marine mammal, measuring between four to five feet in length. A comprehensive survey conducted in 1997 counted 570 vaquitas, but today, 25 years on, a mere ten surviving vaquitas have been counted in the Sea of Cortez, the only place that the vaquita can be found.