The Amazon River Basin, known for its rich biodiversity, has witnessed a tragic event. Over the past week, 120 river dolphin carcasses have been discovered floating in its tributaries. Experts suspect that the severe drought and extreme heat are the culprits behind this mass mortality.

Dolphin Discovery

The carcasses of these dolphins were discovered floating in a tributary of the Amazon River in Brazil. The Mamiraua Institute, a renowned research group, reported that two additional dolphins were found dead near Tefe Lake.

The study, set to be published in the October 15th issue of Environmental Pollution, has provided evidence that microscopic plastic particles, which were discovered in the fats and lungs of around two-thirds of the marine mammals investigated, are not confined to the digestive tracts of these creatures but can migrate and embed themselves in their vital tissues.

In a world where facial recognition technology is becoming commonplace, it is not just humans who are being identified. A groundbreaking study has successfully applied this technology to identify individual whales and dolphins in the wild across 24 species.

Have you ever noticed that when adults speak to babies or small children, they speak in a distinctively specific manner? As if by instinct, they speak in a high-pitched voice, with clear pronunciation and longer pauses between words.

It seems that this “baby talk” is not reserved for humans. Researchers have discovered that dolphins too indulge in baby talk—by changing their characteristic whistles and frequencies—when they communicate with their offspring.

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.

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.

A new bottlenose dolphin subspecies has been identified, and it is found only in the eastern tropical Pacific Ocean, according to a study published in the Journal of Mammalian Evolution.

Called the Eastern Tropical Pacific bottlenose dolphin (Tursiops truncatus nuuanu), it is smaller than other common bottlenose dolphins, and is likely to prefer the deep offshore waters between southern Baja California and the Galapagos Islands. 

Marine mammals are not above the physical principles and processes that lead to bubble formation in tissues following decompression. Scientists once thought that diving marine mammals were immune from decompression sickness, but beached whales have been found to have gas bubbles in their tissues—a sign of the bends. In any case, how some marine mammals and turtles can repeatedly dive as deep and as long as they do has perplexed scientists for a very long time.

The Mexican government has announced the successful conclusion of a project involving the placement of 193 cement blocks on the sea floor in strategic locations in the vaquita’s habitat.

Called the Concrete Block Planting project, the objective was to discourage the setting of gillnets within the Zero Tolerance Area, where the remaining vaquita population is localised. Large steel hooks protrude from the top of the blocks, trapping any gillnets they come into contact with.

In early October, after nearly three months, the 193rd block was finally placed on the sea bed.

Researchers have discovered that male bottleneck dolphins form long-term social groups to help one another find mates and fight off competitors.

It was the first time such behaviour was observed in the animal world.

Their conclusions were based on data collected of 202 Indo-Pacific bottlenose dolphins between 2001 and 2006 in Shark Bay, Australia, using visual and auditory data. In the lab, the researchers then focused on studying the interactions of 121 of individuals for the next decade.