The first confirmed live birth
of twin sea lions
Credit: Alaska SeaLife Center
A Steller sea lion cow gave birth to twin pups at a rookery monitored by remote cameras outside of Resurrection Bay near Seward, in what may be the first confirmed multiple live birth for the species.
“Never before, to my knowledge, has there been definitive evidence of twin live-born pups in Steller sea lions,” said biologist John Maniscalco, of the Alaska SeaLife Center, in an email message.
But life for sea lion pups on Alaska’s rugged Pacific coast can be brutally short.
While the mom, an animal researchers call Hera, suckled one pup they nicknamed Gemini, the neglected baby flippered its way down the rocks, got “tossed around” by short-tempered females and ultimately tumbled into the pounding surf from the Gulf of Alaska.
As researchers watched in horror, the pup washed away and disappeared, Maniscalco said.
It gets worse. The second twin may have vanished too.
The unprecedented birth of twins, and the implacable aftermath, are only a few of the remarkable observations made this spring at the Chiswell Island rookery, site of a long-time study of the behavior of sea lion moms as they birth and suckle, and finally wean their pups.
A streaming video from Chiswell and other sites appears during the day at the Alaska SeaLife web site. The Seward cable TV network also carries the feed.
This high-tech spying produces amazing glimpses of sea lion motherhood at work. On June 6, for instance, two sea lion cows ended up trading their offspring after one cow stubbornly latched on to the other’s baby — and wouldn’t give it up, Maniscalco said.
The new observations come during the seventh season in an innovative project using remote cameras, blinds and — by mid summer, hydrophones — to eavesdrop and spy on the lives of endangered marine mammals off Alaska’s fecund outer coast.
Working nearly 18 hours a day from spring to fall, research associate Maniscalco, researcher Pam Parker and others have monitored the rookery and kept watch on other sea lion haul-outs at the mouth of Resurrection Bay from 2001 to this summer.
Steller sea lion bull in
the Gulf of Alaska
Credit: NOAA Photo Library
“We conducted 11,200 (hours) of observations on 782 days between 25 May and 30 October over the years 2001-2005,” Maniscalco and co-authors explained in the Journal of Ethology. “There were an average of 43 pups and yearlings on the rookery during that period.”
The first four years of results were also described in Interseasonal and Interannual Measures of Maternal Care Among Individual Steller Sea Lions in the Journal of Mammalogy.
The work was originally launched during the biggest biological investigation ever undertaken into a single species: the federal Steller sea lion project. For reasons that still remain unclear, the western population — Gulf of Alaska through the tip of the Aleutian Chain — crashed by 80 percent in the 1980s and failed to rebound in the 1990s, leading to an endangered listing and expensive restrictions to Alaska’s commercial fishing industry. During the early 2000s, hundreds of scientists from a dozen agencies and universities mounted more than 150 studies into sea lion biology, spending more than $120 million in the process.
The sea lion monitoring project allowed Maniscalco and Parker and their team to identify individual animals by their markings. Then they watched them season to season as they grew older, mated with bulls, gave birth. Some of them mastered the art of raising a pup, while others utterly failed.
Take Hera, for instance. “I’m not sure if twins could’ve been born to a worse mother out there,” Maniscalco said. “Most of the other females seem to be taking care of their pups just fine.”
Hera the Steller Sea Lion with her
twin pups. Scientists say this may
the first confirmed live birth of twins
Credit: Alaska SeaLife Center
Hera probably first gave birth in 2005, but lost her offspring into stormy surf, Maniscalco said. Another pup in 2006 disappeared after a month.
“So this female doesn’t exactly have a ‘Steller’ track record,” he said.
Then, on May 30, 2007, Hera dropped two new babies — “virtually unheard of in Steller sea lions,” Maniscalco said.
Scientists say one or two animals have been found with double fetuses in the womb. Maniscalco said one his techs possibly witnessed the birth of twins in 2004, but the second calf was stillborn and evidence wasn’t solid. And other researchers have reported evidence of twins, though sea lion mothers occasionally suckle and care for unrelated pups. (Maniscalco and his team analyzed 28 observations of this “alloparenting” in Alloparenting in Steller sea lions: correlations with misdirected care and other observations.)
“That’s not to say that twinning hasn’t happened before; it probably has but we may be the first to have sufficient evidence to prove it with our recorded video observations,” Maniscalco said.
The twins, the fourth and fifth sea lion pups of the season, appeared normal and healthy. But almost right away, Hera started favoring the second-born, an animal with a distinctive notch in its flipper.
The first-born got separated from Mom and ended up in the drink about 9:30 p.m., washed away and presumed dead. The second-born, Gemini, was suckling and doing OK. For a while.
But within a few days, Maniscalco said his team began having trouble relocating Gemini.
“It now looks as if the second pup has disappeared, probably with all the high storm surf we’ve been having today,” Maniscalco said in an email on June 7. “We still need to confirm that though.”
Pup Swapping
The “extremely strange” pup swapping unfolded on the morning of June 6.
Two adult females broke water and became agitated about the same time, evidence that they had begun labor. The one named Auburn lay a few yards above the one named Kansas, and gave birth first, according to Maniscalco.
Steller sea lions on a beach
in the Gulf of Alaska
Credit: NOAA Photo Library
“That pup immediately slid down the rock and bumped into Kansas,” he wrote in an email message. “Kansas acted as if it were her own pup and picked it up and put it beside her, vocalized and nuzzled with it.”
The biological mom, Auburn, galumphed down the slippery rocks to assert maternal rights. The two sea lions fought for an hour, slowly scooting down the rocks. But Kansas would not relinquish Auburn’s pup.
An hour later, Kansas herself gave birth. But she ignored her own newborn and turned her attention to Auburn’s pup, allowing the infant calf to slip down the rocks to the surf zone.
Pups in the surf zone don’t last long, though wave action that morning was light, Maniscalco.
Auburn flippered her way to the surf zone, sniffed her rival’s newborn, then returned to Kansas and tried once more to get her own natural offspring back. No luck.
“A few minutes later, Auburn went back to the surf zone and grabbed Kansas’s pup and carried
it back up higher the rookery,” Maniscalco wrote. “Meanwhile Kansas has started nursing
Auburn’s pup and it now looks like Auburn will keep Kansas’s pup. She started nursing it later in the morning and several times throughout the day.”
Maniscalco and Parker watched the events in real time, and recorded it all on video. The females have never been observed with pups before, but have distinctive markings and can be tracked. Not much is known about the pups yet, but they hope to follow them.
What to make the swap? Unsure.
“We believe that younger females and first-time mothers tend to have more confusion over the recognition of their own pup,” Maniscalco said.