SAN DIEGO (CBS 8) - SeaWorld is going on the offensive, defending the way it treats its animals in the wake of the critical documentary film "Blackfish."

On Friday, the theme park placed full-page advertisements in a number of newspapers, including the San Diego Union-Tribune, that describes SeaWorld as an advocate for animals.

The bullet points come five months after the documentary film "Blackfish" opened in theaters and opened the conversation about whales in captivity. In the letter, SeaWorld says it does not capture killer whales in the wild, nor does it separate killer whale moms and calves.

"They've made a decision at the executive level, 'OK, we're going to send out a round of our usual denials,' so they're doing that. But just by doing that, that's a sign of unease at the top of SeaWorld ," Howard Garrett of the Orca Network said.

Garrett says the letter doesn't ease the concerns he shared in the film about whales in captivity.

"They're completely dominated and deprived of all that is natural to them in captivity," he told CBS News 8.

But in the letter, SeaWorld offers statistics arguing its killer whales life spans are equivalent with those in the wild. SeaWorld also claims it has invested $70 million into killer whale habitats and that its research benefits animals in the wild. The Orlando-based company declined requests for an on-camera interview.

"I think this letter is going to hurt them even more, which is fine for us activists, because we want them to fail," activist Ellen Ericksen said.

Ericksen is planning a protest at SeaWorld's San Diego park on Sunday. She says the unexpected letter may help bring 400 protesters to the park.

"I think actually it will bring more protesters out to the protest, and I think people are going to be curious now to see why we're out there," she said.

Though the film has been praised by animal advocates SeaWorld calls its arguments misinformation that could lead to more responses from them in the future.

"The movie does show the truth about what happens at SeaWorld, and they are running scared now because so many people are seeing the movie," Ericksen said.