They grow up so fast…. On Jan. 28, 2013, Molalla, the first river otter to be born at the Oregon Zoo, arrived. Weighing just 4 ounces, unable to see or walk, let alone swim, he was completely dependent on his mom, Tilly, for the first couple months of his life. Almost one year later, Mo — as he is known for short — is a sleek, active young adult, and will soon be moving to a new home at the Seattle Aquarium.

Visitors can see Mo through Tuesday, Jan. 21, in the Oregon Zoo’s Cascade Stream and Pond habitat, from 11 a.m. to 1:30 p.m., and from 3 p.m. to closing. He leaves for Seattle on Jan. 22.

“It’s been so much fun watching Mo grow up over the past year,” said Julie Christie, senior keeper for the zoo’s North America section. “In the wild, otter pups usually stay with their mom for about a year before striking out on their own, so the timing of this move is right. Mo’s big now, almost the size of B.C., his dad. Sometimes it’s hard for visitors to tell the two apart, especially when they’re darting around underwater, doing somersaults and backflips.”

Other than size, Christie said, the best way to tell the father and son apart is by the cream-colored patch of fur on B.C.’s throat, which is much paler than Mo’s.

Mo made a big splash with zoo visitors and otter fans worldwide when he began taking swim lessons last spring. The instructor — his mother, Tilly — didn’t go easy on him, nudging her pup to the water’s edge and then plunging in with a firm grip on the scruff of his neck, just as otter moms do in the wild. A video of young Mo’s water trials logged more than 600,000 views on the zoo’s YouTube channel, offering a rare glimpse of this major milestone on a pup’s journey to otterhood. To see the video, visit

While it is hard for Oregon Zoo staff to see Mo go, they are happy he is staying in the Northwest. Christie said animal-care staff at the Seattle Aquarium will be sending updates on the otter’s progress there, and that keepers here are already making plans to visit Mo in Seattle.

Like all river otters in accredited North American zoos, the location and reproductive status of Mo, B.C., Tilly and her new pup, Ziggy, are managed by the AZA’s Species Survival Plan. Since both Tilly and 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 Tilly and B.C. are rescue animals who had a rough start to life.

Tilly 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.

B.C. 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.

Now that the threat from fur trappers has declined, North American river otters are once again relatively abundant in healthy river systems of the Pacific Northwest and the lakes and tributaries that feed them. Good populations exist in suitable habitat in northeast and southeast Oregon, but they are scarce in heavily settled areas, especially if waterways are compromised. Because of habitat destruction and water pollution, river otters are considered rare outside the Pacific Northwest.

News release: Oregon Zoo