Critically Endangered Right Whales Are Getting Smaller Due to Climate Change; Decreasing Body Size Could Affect Ability To Breed [STUDY]

Scientists have observed that critically endangered North Atlantic right whales are actually getting smaller. This decrease in body size has also been found to affect their ability to breed.

Smaller Critically Endangered Right Whales Have Fewer Babies

In the "Decreasing body size is associated with reduced calving probability in critically endangered North Atlantic right whales" study, researchers looked into decades' worth of data and observed that smaller female right whales actually had fewer babies.

Ecologist Enrico Pirotta, the study's lead author from the University of St Andrews, shares that they offer solid evidence that the declining right whale calving trend probability is linked to the individuals' decreasing body size. Such findings also add to earlier evidence that indicates their health decline.

The scientists looked into data from the North Atlantic right whale consortium that was gathered from 1970 to 2020. This includes measurements taken through aerial shots. The researchers made use of a statistical model to look deeper into the relationship between the length, survival, health, and reproductive ability of a sexually mature female.

The researchers found that the animal's length cube was the primary factor that affected the likelihood of breeding calves. Such odds were also observed to decrease among smaller females.

It was found that, on average, a 14-meter female had a 56% likelihood of breeding, while an 11-meter female just had a 14% likelihood. Length was found to largely impact calving probability compared to health and other factors.

Whales make use of organic substance reserves known as lipids to offer sufficient energy for reproduction. Pirotta explains that having a smaller size implies that a female can accumulate less energy, which may affect her capacity for successful breeding.

North Atlantic Right Whales

Among other species, North Atlantic right whales are the most endangered. The study specifically focused on these critically endangered whales because their vulnerability to human threats implies the need for urgent protective measures. There are only 356 right whales that are thought to be alive at present.

These whales have also been getting shorter since 1981 due to certain stressors like climate change. The exact mechanisms behind their shrinking remain uncertain. However, it is believed to be associated with nutrients' reduced availability. The authors also note that size decreases as a response to climate change have been observed in both marine and terrestrial species.

The National Oceanic and Atmospheric Administration (NOAA) notes that this season, 17 North Atlantic right whales have been born. To stop the decline of the species, at least 50 calves need to be born every year.

Marine scientist Julia Singer, who is from the Oceana ocean conservation group and who did not participate in the study, explains that each right whale calf is crucial to prevent the species from becoming extinct.

Calving season typically takes place from November to April. During this season, vessel speed limits are implemented within the southeastern US. Ships must not exceed a speed of 11.5 miles per hour in order to protect both calves and mothers from possible boat strikes. Oceana calls for the government to update rules to cover smaller vessels, which have been known to collide with right whales.

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