It’s been a tough few years for the Smithsonian National Zoo when it comes to the animals.

A two-part report I produced for CBS News last December recounted a host of problems as told by zoo insiders, some of whom were distraught over what they say as preventable injuries and deaths. While the zoo business isn’t an easy one, animal care experts and volunteers working at the National Zoo, as well as an independent expert, stated that many of the National Zoo’s animal care events were easily avoidable. The zoo withheld public documents related to animal care issues until it was pressed with my Freedom of Information Act request. Officials there say that they’ve responded properly each time problems were identified and that they’re making many improvements.

On Friday, May 9, zookeepers found a two year old sea lion dead at the bottom of her pool.

Here’s the announcement made by the zoo:

“We are sad to announce that our beloved sea lion Sophie, age 2, was found dead at the bottom of her pool this morning, Friday, May 9. Keepers reported that her behavior was normal when they checked on her last evening. Daughter of Calli, Sophie was born while the sea lions were living at Pittsburgh Zoo and PPG Aquarium while their new homes on American Trail were being built.

We don’t yet know what caused her death, but a necropsy will be performed today and results will be available in the coming weeks.

Along with her mother, Sophie lived on American Trail with female sea lions Sidney and Summer. Native to the West Coast of North America, California sea lions range from Washington state to the Baja Peninsula. Though they were once hunted for their skin, the International Union for the Conservation of Nature now classifies them as a species of least concern.”

Exclusive: Animal care problems at the Smithsonian National Zoo, Dec. 10, 2013

Part 2: Smithsonian National Zoo’s animal troubles, Dec. 11, 2013