According to a new study, one of the deep's giants
is shrinking in front of our eyes.
A study published Thursday in the journal Current Biology found that the younger generation of critically endangered North Atlantic right whales
is about three feet (one meter) shorter than whales were 20 years ago, based on data from drones and aircraft.
Entanglements with fishing
gear, collisions with ships, and climate change
shifting their food
supply north are all contributing to stress and shrinkage in these large whales, according to the study.
The whales' declining size poses a threat to the species' overall survival because they aren't having as many offspring and aren't big enough to nurse their young or even become pregnant, according to the study's authors.
According to the study, these marine mammals used to grow to an average height of 46 feet (14 meters), but the younger generation is now on track to reach only 43 feet (13 meters).
“This isn't about'short' right whales; it's about a physical
manifestation of a physiological problem, the chest pain before the heart attack
,” said Regina Asmutis-Silvia, executive director of Whale and Dolphin Conservation
North America, who wasn't involved in the study.
According to study co-author Amy Knowlton, a senior scientist at the New England
Aquarium, there are only about 356 North Atlantic right whales left, down from 500 in 2010, with other estimates putting the population at around 400, though researchers agree the population is declining.
Previously, scientists and activists focused solely on whale deaths, but now they recognize that there is a problem afflicting surviving whales that can still cause populations to dwindle further, according to study co-author Michael Moore, marine mammals director at Woods Hole Oceanographic Institute.
The problem arose during a research trip several years ago when Knowlton and others saw a few small whales and a dead one. They assumed the small whales were calves, less than a year old, due to their size, but checking revealed the whales were actually about two years old. Whale calves normally double in size in two years, according to study lead author Joshua Stewart, a National Oceanic and Atmospheric Administration researcher.
According to the study's authors, entanglement in fishing gear, particularly ropes that have become stronger and more difficult for whales to shed, is the most serious problem with smaller right whales.
“Over 83% of the species has now been entangled at least once in their lifetime, some as many as eight times,” Knowlton said, adding that “if it doesn't kill them, it will certainly affect their ability to reproduce.”
Another issue is ship collisions, which have been addressed with government regulations in some of the whales' normal feeding grounds. However, since 2010, climate change has caused the plankton that the marine mammals eat to move north and east to areas where there are no regulations, so entanglements and crashes have increased, according to Knowlton.
Moore claims that the shift in feeding grounds has added physical stress to North Atlantic right whales, which were already thin in comparison to their southern cousin species.
“We know that climate change has impacted some of their key prey sources, so entangled whales are likely experiencing a triple whammy of less food available, less ability to forage for it, and burning more energy
,” said Dalhousie University marine biologist Boris Worm, who was not involved in the study.
From Portland, Maine
, Patrick Whittle contributed.