When an Atlantic right whale is fully grown these days, it's about 3 feet shorter than a full-grown whale was in 1980. Research published Thursday in Current Biology indicates scientists have an idea why that is, NPR reports. A big reason for the whales' impaired growth is that they're getting caught up in rope and fishing gear. That can lead to drowning, fatal infections, or starvation. Even if the whales survive, they have to use energy in their struggle to survive instead of for growing or repopulating the species, the study found. "You can imagine if you had a sandbag tied to you and you had to go about your daily business, you'd be burning a lot of extra energy just dragging that sandbag around," a researcher said. Using aerial photos, the study tracked the changing conditions of 129 right whales. There were 481 right whales in 2011, the high mark on record; there are about 366 now.
The whales are less bulky now, as well, per the Guardian. "I saw pictures of 10-year-old whales that are the size of 2-year-old whales, which was shocking," the researcher said. "These are really short, stunted whales." There are other factors affecting the whales, per the AP, including collisions with ships. And climate change is causing their food supply to shift north. The combination stresses the whales, the study says. In some feeding grounds, new government regulations reduced entanglements and ship accidents. But plankton moved north and east because of climate change, drawing the right whales to unregulated areas. The problems worsened. The ropes even have gotten stronger. "Over 83% now of the species has been entangled at least once in their lifetime, some as many as eight times," a study co-author said. (Scientists are encouraged by the birth rate last winter.)