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Surrogate-reared sea otters released by the Monterey Bay Aquarium give birth to their second pups

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7th May 2010

Romain Fonsegrives

Santa Cruz Sentinal, Santa Cruz, California, USA

MONTEREY -- California's endangered sea otter population is showing signs of hope, as two adult female reared by surrogate mothers at the Monterey Bay Aquarium recently gave birth to their second pups in the wild.

The births of sea otters "MBA 327" and "MBA 339" are a credit to the aquarium's Sea Otter Research and Conservation surrogate program, whose goal is to rescue stranded pups and return them to the wild able assimilate into the population and produce offspring. The program now counts five successful births by surrogate-reared otters in the wild.

"These births and the successful weaning of pups in the wild by surrogate-reared individuals is significant because it indicates that these sea otters are not only surviving following release, but also contributing reproductively to the wild population," said program animal care coordinator Karl Mayer. "This is the benchmark of successful rehabilitation and reintroduction efforts."

Both sea otters gave birth in the waters near Moss Landing and had already delivered male pups in March 2009 and July 2008. Mayer, who checked on them in mid-April, came back optimistic.

"The pups look healthy, bright and alert," Mayer said.

The pups' gender is unknown, but Mayer said his staff will monitor both pairs of mothers and pups regularly to document their development and collect data on mother/pup foraging behaviors and movement.

The sea otter research team started minimizing human role in raising and releasing stranded pups in 2005, using three exhibit sea otters -- Joy, Toola and Rosa -- who share duties as surrogate mothers.

Sea otters 327 and 339 were rescued after being washed ashore on the Californian coast in 2005, the staff said. Both were then returned to the wild a few months later, equipped with a radio transmitter.

"We're establishing that the methods we use to rear stranded pups enable them to reproduce as part of the wild population," Mayer said.

The program's data also suggests that surrogate-reared pups have a higher survival rate compared to the pups reared by people, the staff said. Sixty percent have survived a minimum of one year after release, compared to 30 percent for human-reared pups. Survivors are still being evaluated regarding their reproductive success.

The aquarium's research team said they are currently following seven surrogate-reared otters in the wild, including three females of breeding age that all have given birth and successfully weaned pups.

Researchers also said the tagged animals enable them to study otters' behavior, along with the causes endangering their survival.

"We can follow them for a long time. And we know that the group here is thriving, in contrast to some other groups in the area," said Mayer, who is expecting two more surrogate-reared otters to give birth in the coming months.

There are about 2,700 sea otters in California, according to recent reports. Details about the location of the mothers and their pups have not been disclosed to ensure their success in the wild, staff said.

California sea otters

The sea otter population in California was in the hundreds of thousands in the 1700s but shrank dramatically over two centuries due to the fur trade. Sea otters are now under the protection of the Endangered Species Act and need a three-year average population number of 3,090 animals to be removed from the endangered species list. The latest studies have shown sea otter population declined for the third year in 2009, averaging 2,813 animals over the past three years.
Monterey Bay Aquarium's Sea Otter Research and Conservation program has welcomed nearly 500 sea otters -- stranded pups or injured adults -- since 1984, and has developed diets and protocols to increase their survival rate.
For information about the program, visit www.montereybayaquarium.org/cr/sorac.aspx.
The latest report about sea otter population can be found at www.otterproject.org.