Beluga whales and narwhals go through menopause

August 27, 2018, University of Exeter

Scientists have discovered that beluga whales and narwhals go through the menopause—taking the total number of species known to experience this to five.

Aside from humans, the species now known to experience menopauseare all toothed whales—belugas, narwhals, killer whales and short-finned pilot whales.

Almost all animals continue reproducing throughout their lives, and scientists have long been puzzled about why some have evolved to stop.

The new study, by the universities of Exeter and York and the Center for Whale Research, suggests menopause has evolved independently in three whale species (it may have evolved in a common ancestor of belugas and narwhals).

"For menopause to make sense in evolutionary terms, a species needs both a reason to stop reproducing and a reason to live on afterwards," said first author Dr. Sam Ellis, of the University of Exeter.

"In killer whales, the reason to stop comes because both male and female offspring stay with their mothers for life—so as a female ages, her group contains more and more of her children and grandchildren.

"This increasing relatedness means that, if she keeps having young, they compete with her own direct descendants for resources such as food.

"The reason to continue living is that older females are of great benefit to their offspring and grand-offspring. For example, their knowledge of where to find food helps groups survive."

The existence of menopause in killer whales is well documented due to more than four decades of detailed study.

Such information on the lives of belugas and narwhals is not available, but the study used data on dead whales from 16 species and found dormant ovaries in older beluga and narwhal females.

Read more at: 

Heart monitors on wild narwhals reveal alarming responses to stress

As sea ice melts, new findings add to concerns about the effects of ocean noise and increased human activity on deep-diving Arctic whales

Date:  December 7, 2017

Source:  University of California - Santa Cruz

Summary:

Stress from human disturbances could cause behavioral responses in narwhals that are inconsistent with their physiological capacities, researchers say. They found that narwhals released after entanglement in nets and outfitted with heart monitors performed a series of deep dives, swimming hard to escape, while their heart rates dropped to unexpectedly low levels of three to four beats per minute.

Continued  

(Video) Scientists crack mystery of how Narwhals use their tusks

May 15, 2017

by John Hopton 

Narwhals are superb creatures - they have a great name and a striking appearance, largely due to the long and imposing tusks protruding from their heads.

But as remarkable as these whales' tusks look, it has until recently been unknown exactly how they are used.

Drone footage shot around the remote Nunavut region of Canada has put an end to the mystery, revealing that the so called "unicorns of the sea" use their tusks to stun prey.

In behavior caught on camera for the first time, narwhals are seen using the tusks as a club to hit and stun Arctic cod. Once stunned, the fish are easier to catch and eat.

Adam Ravetch of the World Wildlife Fund Canada, and researchers from Fisheries and Oceans Canada, were working in the far Northeastern region when they got the footage.

The remoteness of locations in which narwhals are found goes a long way to explaining why the behavior has not been noted before.

Three quarters of the world's population can be found in the Lancaster Sound, close (in relative terms) to where to footage was taken.

The tusks are likely multipurpose

Marianne Marcoux, a research scientist for Fisheries and Oceans Canada, said that: "Drones are very exciting, we can see things we couldn't see before."

The bigger planes previously used for such ventures often came up with incomplete footage or scared the narwhals.

"They don't jump like other whales. They are also notoriously skittish. This is an entirely new observation of how the tusk is used," said Brandon Laforest, a senior specialist of Arctic species and ecosystems with WWF-Canada.

Read more and watch videos at

Ancient Beluga Whales Enjoyed Warm Waters

An ancient beast related to today's Arctic-loving beluga whales and narwhals seemed to prefer toasty, tropical waters.

Called Bohaskaia monodontoides, the new species of toothed whale lived some 3 million to 4 million years ago during the Pliocene in warm water. Researchers aren't sure why modern belugas have left these tropical destinations and strayed pole-ward, where life would seem to be more difficult.

The fossil had been sitting in the collections of the Smithsonian's National Museum of Natural History since its discovery in a mine near Hampton, Va., in 1969. The nearly complete skull represents the only fossilized remains known of the new species. Before it was closely examined, the skull's discoverers loosely identified it as a beluga whale and left it in storage.

In 2010, Jorge Velez-Juarbe, Smithsonian pre-doctoral fellow from Howard University, finally took a close look at the skull. He compared it with the skulls of closely related toothed whales, like modern Arctic belugas and narwhals (also called unicorns of the sea for their twisted horn). While the skull shared many features, particularly in the face and snout, with modern toothed whales, the researchers say there are enough unique features to merit its placement in a new genus and species.

"We realized this skull was not something assignable to a beluga, and when we sat down, comparing the fossil side by side with the actual skulls of belugas and narwhals, we found it was a very different animal," study researcher Nicholas Pyenson, of the Smithsonian's National Museum of Natural History, said in a statement.

This and a second temperate example of a beluga-related whale indicate that the love of frosty water developed recently in these whales. [Image Gallery: Life at the North Pole]

"The fact is that living belugas and narwhals are found only in the Arctic and sub-Arctic, yet the early fossil record of the monodontids extends well into temperate and tropical regions," Pyenson said. "For evidence of how and when the Arctic adaptations of belugas and narwhals arose we will have to look more recently in time."

Velez-Juarbe said the narwhals and belugas may have changed habitats due to oceanic changes that affected the food chain: Either competition with other animals or the movement of a preferred prey species could have driven them north.  

The new analysis of the whale skull is published in the Journal of Vertebrate Paleontology.

http://news.yahoo.com/ancient-beluga-whales-enjoyed-warm-waters-140606913.html;_ylt=AqmmT.dtJjLh3HNOyFbfjQV2hMgF;_ylu=X3oDMTRhdmZzNjFxBG1pdANUb3BTdG9yeSBTY2llbmNlU0YgQW5pbWFsUGV0c1NTRgRwa2cDNzdhZTQxZTQtYTg1Yi0zOWFjLTg1MDMtZjUyNzI5ODY3MDgxBHBvcwM1BHNlYwN0b3Bfc3RvcnkEdmVyAzc2NmQ0MTZiLTc4MWEtMTFlMS05ZjczLTRmZGExYjRiZWY5ZQ--;_ylg=X3oDMTFrM25vcXFyBGludGwDdXMEbGFuZwNlbi11cwRwc3RhaWQDBHBzdGNhdAMEcHQDc2VjdGlvbnMEdGVzdAM-;_ylv=3