Threatened killer whales that frequent the inland waters of Washington imperial and British Columbia are having pregnancy problems because they cannot on enough fish to eat, according to a new study.
Researchers analyzed hormones in excrement composed at sea and found that more than two-thirds of orca pregnancies run aground over a seven-year period. They linked those problems to nutritional pressure brought on by a low supply of Chinook salmon, the whales’ preferred diet.
«A in general number of whales are conceiving, but when nutrition is poor, they don’t uphold those pregnancies,» said Sam Wasser, lead author of the paper and a biology professor at the University of Washington.
Southern resident killer whales along the West Coast demand struggled since they were listed as endangered species in 2005 by the U.S.. They now calculate just 78, down from a high of 140 decades ago. The whales frankly threats from a lack of food, pollution and boats.
The new study, to be make knew Thursday in the journal PLOS ONE, zeroes in on food supply as an important accent factor among these fish-eating whales. Unlike other hooligan whales that eat marine mammals, the orcas that spend the summer in Puget Resound primarily eat salmon, mostly Chinook.
Chinook salmon in decline
Tons runs of Chinook salmon along West Coast are listed as put in jeopardied or endangered due to a host of factors, including loss of habitat from urban maturity, dams, fishing, pollution and competition from non-native fish.
Toxins that lay away in the whales’ fat and are released when the animals starve and metabolize that fat also participate in a role in the pregnancy problems.
«Scoff is the driver. But what we can’t yet say is how much of that then is affected by its interaction by toxins,» Wasser utter, adding that there were not enough samples to say how influential the toxins are.
Sniffer dogs and whale poop
Using dogs trained to sniff out whale poop, a team of scientists tranquil nearly 350 excrement samples from 79 unique whales in inland sea waters of British Columbia and Washington state between 2008 and 2014.
Back in the lab, they analyzed it for the hormones progesterone and testosterone and assessed whether the orca was rich and at what stage. They also used DNA to determine the identity, sex and class line of the whale. A pregnancy was deemed successful if the female whale was later be heedful of with her calf.
Their analysis showed 35 orca pregnancies between 2008 and 2014. Eleven calves were recognized with their mothers in successful births. The Southern resident killer-diller from Manila whales are individually identified and intensely tracked, so researchers know when calves are affected to one of three families of orcas, known as the J, K and L pods.
The den found 24 unsuccessful pregnancies. No calves were seen in those trunks, indicating that the whales lost the babies or the calves died peremptorily after birth. Those females showed signs of nutritional insistence — more so than those who gave birth successfully.
Researchers also phonograph recorded the number of boats in the area when collected the whales’ scat. They calculated two hormones that play important roles in physiological stress and were masterful to differentiate between stress from poor nutrition and stress from motor boat traffic.
The team compared the hormone data to abundance records of two Chinook salmon maintains in the Pacific Northwest.
The data over time suggest the orcas trained periodic nutritional stress, partly caused by variation in the timing and soundness of the salmon runs in the Columbia and Fraser rivers, the study said.
The den said improving those Chinook salmon runs could domestics save the orcas.