Two for Tilly: Oregon Zoo otter delivers her second baby

November 19, 2013 - 4:09pm

New pup is the second North American river otter born at the zoo this year

Tilly, a North American river otter at the Oregon Zoo, gave birth to another pup Nov. 8, her second this year. The new arrival weighed just shy of 5 ounces at birth and has nearly tripled that thanks to mom's naturally high-fat milk.

"We're pretty sure this pup's a male," said Julie Christie, the zoo's senior North America keeper. "But Tilly is very protective, so we can't be positive until our vets conduct a more thorough exam."

"We're confident Tilly will be a great mom to her new pup."

—Julie Christie, senior keeper

Tilly and her pup are currently in a private maternity den, and it will be another month or two before visitors can see them in their Cascade Stream and Pond habitat. Young river otters usually open their eyes after three to six weeks, and begin walking at about five weeks.

"Young river otters are very dependent on their moms, and Tilly has been very nurturing," said Julie Christie, the zoo's senior North America keeper. "She did a great job with her first pup, Mo, earlier this year. She raised him up from this tiny, helpless creature into the sleek, agile, full-grown otter he is today. We're confident Tilly will be a great mom to her new pup as well."

Surprisingly, swimming does not come naturally to river otters — pups must be taught to swim by their moms. Earlier this year, a video of Tilly teaching Mo to swim drew more than half a million views on the zoo's YouTube channel.

Keepers have yet to decide on a name for the new pup, though it is likely he will be named after a local river or waterway. (Mo is short for Molalla, after the Molalla River.)

North American river otters typically give birth from late winter to spring, but Tilly seems to be on her own schedule, keepers say. The breeding season for river otters is December through April, and actual gestation only lasts a couple of months. Unlike their European cousins however, North American river otters usually delay implantation so that the time between conception and birth can stretch to as much as a year. That hasn't been the case with Tilly.

Christie said it is also unusual — though not unheard of — for an otter to give birth to a single pup, as Tilly has now done twice. Litters usually consist of two or three pups, though the range is anywhere from one to six. Family groups typically consist of an adult female otter and her pups, with males moving away once they reach adulthood.

Since both Tilly and the pup's father, B.C., were born in the wild, they and their offspring are considered genetically important for the breeding otter population in North American zoos. Both parents are rescued animals who had a rough start to life.

Tilly, named after the Tillamook River, was found orphaned near Johnson Creek in 2009. She was about 4 months old, had been wounded by an animal attack and was seriously malnourished. Once her health had stabilized, Tilly came to the Oregon Zoo in a transfer facilitated by the Oregon Department of Fish and Wildlife, which oversees the species' protection.

The pup's father, B.C. (short for Buttercup), was found orphaned near Star City, Ark., also in 2009. He was initially taken in by the Little Rock Zoo, but transferred here the following year as a companion for Tilly. The two otters hit it off quickly and have been playful visitor favorites ever since.