When Dr. Holly Fearnbach and Dr. John Durban noticed the bodies of two female southern resident orcas widening just behind their dorsal fins, they knew it could mean only one thing: babies.
On July 26, they announced that a killer whale identified as L72 was pregnant. Soon after, they delivered news that Tahlequah, whose traumatic journey with her dead calf captured international attention two years ago, is also expecting. The world erupted in celebration. Adding newborn whales to the endangered southern resident population, which has dwindled to 73 animals, would be a big deal, and Fearnbach says she can now confirm there are pregnancies in all three pods that make up the population. But Fearnbach, marine mammal research director of Sealife Response, Rehabilitation and Research, and many whale researchers like her hesitate to celebrate.
“There are always pregnant whales in the population, but most pregnancies are not successful,” Fearnbach says, either because the pregnant whale miscarries or the calf dies. Fecal sample studies from the University of Washington show that 69 percent of pregnant southern resident whales lose their babies before birth or soon after. To the best of our limited knowledge, between 37 percent and 50 percent of calves don’t survive their first year. Scientists usually avoid announcing pregnancies at all, but Fearnbach and Durban felt the announcement could reinforce their call to give whales more space and inspire more formal requests from management agencies.
Knowing about an orca pregnancy means holding your breath. Orcas having one of the longest gestation periods of any mammal, and the southern residents have very low birth rates. There have been only two births in the three southern resident pods since Tahlequah lost her calf.
“The low birth rate in general is very concerning, so I’m not going to downplay that, but in general, wild mammals have a high calf loss rate just because it’s so hard, especially for first-time moms,” says Dr. Dawn Noren, a physiological ecologist and a research fishery biologist with the National Oceanic and Atmospheric Administration.
Each stage of early orca motherhood comes with physical and emotional hurdles, and negative human impacts on Puget Sound make things even dicier.
“One doesn’t want to be a Negative Nancy,” says Dr. Deborah Giles, a researcher with the University of Washington Center for Conservation Biology, “but there’s a lot of trepidation mixed in.”
Early days
Expectant orcas gestate for 18 months, with six-month trimesters. “I think it has to do with the complexity of their brain, but a lot of it is simply that they’re big animals,” Giles says.
Most knowledge of pregnancy comes from the veterinary study of captive orcas. Detecting early pregnancy requires blood- and urine-based hormone tests on animals in captivity, or taking breath or fecal hormone samples in the field from 6,000- to 8,000-pound females.
“Just being able to get a blood test from an orca is huge,” says clinical veterinarian Dr. Hendrik Nollens, who tracked three complete gestation periods in his 13 years as a clinical veterinarian at SeaWorld and now works on conservation medicine with the Pacific Marine Mammal Center.
NOAA’s Noren says, “We rely on chance, and it’s hard and getting harder when they’re not around as much.”
Keeping up with a pregnancy in the wild is difficult, largely because researchers can’t count on taking regular samples from whales on the move — or even seeing them. Orcas reach sexual maturity at age 12, and while they can get pregnant at any point in the year into their 40s, they tend to conceive in the spring.
Researchers like Nollens say healthy orcas are more likely to become pregnant, but a few elements need to be present: a male orca of reproductive age; a cycling female orca that’s receptive to him and doesn’t have reproductive diseases; and quiet space and time to conceive.
After conception, things quiet down for the first trimester. “Everything that happens happens internally,” Nollens says. “It is really not a terribly taxing period. You could walk past a pregnant orca and not realize it.”
Within three weeks of conception, researchers can confirm pregnancies with hormone tests, Nollens says. “But it’s entirely based on laboratory results. There’s nothing else that you would pick up on.”
Celebration, waiting game
At approximately four months, researchers can identify pregnancies from ultrasounds. At approximately six months, a pregnant orca will display that widening bump, which can be identified as a pregnancy from the air. This is how Fearnbach and Durban identified the pregnancies of L72 and Tahlequah, by analyzing drone images.
Over the next year, the fetus continues to develop into a 350-pound calf, and the mother’s progesterone levels decrease as she continues gaining between 500 and 600 total pounds — a fraction of her 6,000 to 8,000-pound weight.
The two pregnant southern resident orcas are likely in their second or third trimester, Nollens says. Van Ginneken suggests the pregnancies are late stage.
In the past two months of a cetacean pregnancy, he says, “you can start to see signs that mama’s feeling a little ‘blah’ “: decrease in appetite, discomfort and possible bacterial infections like bursella that cause late-term miscarriages in other cetacean species. But compared with everything that can go wrong at or following conception or birth, the odds that something will go wrong with these two pregnant animals in the next few months is more limited, he says.
But if the mother does lose her calf, she and the entire orca community must overcome the emotional loss. Whales are highly family bonded, and the UW’s Giles says their family members may know of a pregnancy through echolocation. “It’s like living with moving and breathing ultrasound [machines] all around you, called your mom and brother and sister,” she says. “It’s physically taxing, It’s medically taxing and dangerous, And then it’s emotionally taxing for these individuals to continuously get pregnant,” Giles says.
In some pregnancies, late-term calves can become ticking time bombs in their mothers’ bodies. If a grown calf dies, gets stuck and releases bacteria in the birth canal, the mother can die.
Calves that do make it through the birth canal need to swim to the surface and take their first breath immediately. The calves’ flukes and dorsal fins are floppy in utero, but calves come out tails first over one to two hours so their fins have time to harden in the cold water. “Calves can be successful when they’re born head first, but they don’t have that functional paddle,” Nollens says, noting calves usually get assistance from other females.
Throughout this process, there’s another threat on the perimeter: male orcas, which can become aroused during childbirth and act aggressively toward the calf if females don’t keep them away. Nollens says he’s heard reports of newborns with rake marks, and thinks it’s likely they’re from males that tried to get access to a mom or calf during birth.
The feeding challenge
Of all the stress points in a whale’s pregnancy, lactation and weaning require the most work. “Pregnancy is cheap — it’s lactation that is hard,” NOAA’s Noren says.
When orcas give birth, their caloric needs skyrocket, Nollens says, which means they must work harder to feed themselves and provide 40 percent fat whale milk to help their newborn grow quickly. “If a killer whale has unlimited access to food, the food intake within days will go up 50 percent,” Nollens says.
This responsibility can be overwhelming. “Most of these females already have other offspring that they also need to support, so it is a huge demand to support themselves, nurse their young calf and help support other offspring and family members,” Fearnbach says.
It can take two to three years, depending on whom you ask, to gradually wean a calf, which is entirely dependent upon its mother until it learns to forage. Dr. Astrid van Ginneken of the Center for Whale Research notes that where fish are scarce, weaning takes longer because calves have fewer fish to supplement their nutrition.
Dozens of researchers, policymakers and stakeholders have spent the past few years coordinating a $1.1 billion plan to save Puget Sound’s orcas from low food availability, as well as ocean disturbance and pollution. While all southern residents suffer from the effects of these factors, it’s especially pronounced for mothers and their newborns.
All of those threats compound each other, and researchers are split on which ones are worse. “I know some people are really about, ‘It’s only the prey, only the prey,’ and other people are, you know, anti-boats, I think it’s not that simple,” Noren says.
“In my opinion, to save these whales, we have to be laser focused on the food issue, and then secondarily the toxicants issue,” Giles counters.
The nearby transient orca populations, which prefer more polluted yet more abundant sea mammals (like Steller sea lions, gray whales, minke whales) over salmon but get more to eat, still have low calf mortality and smaller intervals between females’ pregnancies, which some researchers think supports the idea that food availability is the prime issue. “If the whales had enough to eat, the toxicants would not be as much of a problem,” Giles says.
To stay pregnant, an orca needs to eat up to 300 pounds of fish a day; this amount increases during pregnancy and lactation. Southern resident orcas evolved to prey on plentiful 100-pound chinook, but the average size of those salmon today is 10 to 15 pounds, and there are fewer of them.
But ocean disturbance from vessels makes foraging harder. Echolocating whales need quiet and space to be able to forage effectively, especially when their pods are spread out and they need to communicate.
“Whales and dolphins will stop eating when there’s too much noise and too many vessels around or close approaches, and that is a problem I feel like could really have a detrimental effect on a lactating female,” Noren says.
That’s the time when orca mothers need to put their energy into protecting and feeding their calf. Calves nurse from out of their mothers’ lines of sight, and mothers might not let calves nurse if they think they need to protect them, Nollens suggests.
If they don’t have good access to fish, or spend a lot of time disturbed by boats, they start relying on bodyfat to make milk. Wild whales lose weight rapidly, and oftentimes wind up skinny.
“And then you add the layer of pollution,” Nollens says. “It really is an uphill battle.”
A second try
Every miscarriage is traumatic, but there is a silver lining. Orcas have better chances at a healthy calf when they conceive soon after a miscarriage, Giles says.
Many of the legacy pollutants that pose threats to whales’ physical and neurological health are lipophilic, meaning they can stow away in that fatty blubber. The presence of those pollutants doesn’t seem to matter for a calf in utero, possibly because of the placental barrier, but it matters a lot during lactation.
When a whale mom metabolizes blubber to make milk, those legacy pollutants become milk ingredients. For first-time moms, that might mean offloading a significant portion of pollutants — collected over 12 years — into their baby’s systems.
However, if they gestate their calf for a long time, lose it, and conceive again quickly, they have less time to accumulate toxicants before nursing a second calf.
“In a way, getting pregnant and giving birth is a cleansing thing for the mom, because she’s just gotten rid of all the toxicants, which is kind of a creepy, weird thing to think,” Giles says.
For whales like Tahlequah and L72, which have both given birth before, that could be a good thing. “I’m hopeful that [Tahlequah’s] baby, because of how pregnant she is, must have been conceived fairly shortly after she let go of her other baby. And therefore she hasn’t had very much time to bioaccumulate toxicants,” Giles says.
Ultimately, a mother’s work is never done, Nollens says, and each calf adds to her workload. “Calves may become nutritionally independent at three years of age, but they’re still socially dependent on mom,” he says. “They still rely on her for guidance and protection.”
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August 31, 2020 at 03:00AM
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Here's what pregnant orcas are up against in Puget Sound - The Columbian
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