#monodontidae

Beluga Delphinapterus leucas

Narwhal Monodon monoceros

Narwhals inhabit the Arctic waters of Canada, Greenland and Russia. Every year, they migrate to ice-free summering grounds, usually in shallow waters, and often return to the same sites in subsequent years. Males of this species have a long tusk, which is a protruding left canine. There are an estimated 170,000 living narwhals. They have been hunted for thousands of years by Inuit in northern Canada and Greenland for meat and ivory.

The eye (and ear opening) of a Beluga whale (Delphinapterus leucas)

How it started vs. How it's going

At first the narwhal swims on the outside of the group, trying to keep up with his new friends in unfamiliar waters.

When the same group of whales is spotted a year later, the narwhal swims in the middle of the group of belugas, now officially a permanent member of their pod!

Modern beluga whales and narwhals are the only living representatives of the monodontid lineage, found only in cold Arctic and sub-Arctic waters. But this whale family actually first evolved in much warmer climates – and some of them were downright tropical.

Casatia thermophila lived about 5 million years ago during the early Pliocene, in the Mediterranean Sea around Tuscany, Italy. Although known only from a couple of partial skulls and a few vertebrae it was probably similar in size to its modern relatives, around 5m long (16'4").

It seems to have had a larger number of functional teeth than modern monodontids, and probably didn't suction feed like its modern close relatives. Instead it may have fed more like most porpoises and dolphins, relying more on speed and snapping jaws to capture prey.

It inhabited the Mediterranean at a time not long after the sea there had mostly dried up and then been rapidly refilled. The presence of warm-water marine species such as bull sharks, tiger sharks, and dugongs in the same fossil beds as Casatia indicates the local climate at the time was hotter than it is today, with tropical temperatures – and suggests that this whale's ancestors must have originally moved into the replenishing Mediterranean from lower latitudes alongside these other warmth-adapted animals.

This tropical monodontid was also much closer related to modern belugas than modern narwhals are, which raises the possibility that the two living monodontid species actually specialized for colder conditions completely independently of each other rather than descending from a cold-adapted common ancestor. Instead modern belugas and narwhals may have originated from separate warm-water monodontid ancestors who evolved similar cold-tolerant adaptations in parallel as the climate cooled during the onset of the Quaternary ice age, while the rest of their relatives all went extinct.

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Beluga Whale | Delphinapterus leucas

“Beluga whales are known for their white color and range of vocal sounds, earning them the title of "canary of the sea." They are very social animals, forming groups to hunt, migrate, and interact with each other. Beluga whales are found in the United States in Alaska and globally throughout the Arctic Ocean. They are at home in large rivers and can move between salt and fresh water. A thick layer of fat, called blubber, and thick skin helps them live in the freezing waters of the arctic and subarctic environment. Belugas also lack a dorsal fin so that they can swim under ice.

Belugas are known as the "canaries of the sea" because they produce many different sounds, including whistles, squeals, moos, chirps, and clicks. They rely on their hearing and ability to echolocate, using sound to navigate and hunt for prey. Belugas also have sharp vision both in and out of water.

MICROPLASTICS IN THE GASTROINTESTINAL TRACTS OF ALL BELUGA EXAMINED FROM ARCTIC WATERS

According to a recent published study in Marine Pollution Bulletin, researchers worked with community-based monitors and Inuvialuit hunters from Tuktoyaktuk (Northwest Territories, Canada) to sample seven beluga whales in 2017 and 2018. Microplastics were detected in the gastrointestinal tracts in every individual beluga whale, with each whale having an average of nearly 97 particles, but some of them had 147 particles.

Microplastics are plastic fragments, regularly smaller than 5 mm in size, and represent an emerging global environmental concern, as they have been detected in multiple aquatic species. However, very little is known about the presence of microplastics in higher trophic species, including cetaceans.

-Examples of microplastic particles observed within beluga gastrointestinal tracts (left: polystyrene fragment; right: polyester fibre) Bar is 0.02 cm.

Researchers do not know how microplastics enter whales, but they believe is because whales feed on fish, which have already ingested plastic.

Photo: Beluga whale by Britt Reints | Flickr

Narwhal Monodon monoceros