Yacare with the capybaras together ? I saw both species of yacare here mentioned in breeding groups in the Rio and Sao Paulo zoos. The yacare caimans were quite large there and could easily eat baby capybara. Are all the capybara males ?
I was surprised too, but the mix should work for Temaikén. I only saw one fully grown capybara there, and it didn't seem scared. However, the animal spent all the time on land and the caimans were in the water, so I don't know how they react when they are close to each other. In addition, the caimans weren't very big, I suppose that they were not adults.
I find the mixture a bit dangerous, but Temaiken has a breeding center a few kilometers away from the park. Some species only breed there, so maybe baby capybaras live there.