After I retired from a great career, I saw an ad in The Washington Post asking for volunteers at the National Zoo in Washington, DC. I got accepted and did considerable classroom training for the subject of Invertabrates(creatures without backbones).
I got to do tour guiding at the Invertabrate House and to do various live demonstrations with different critters. My absolute favorite was the Pacific Octopus. She (Caroline)was about 55 pounds and had an armspan of around 8 feet. The feeding demonstration was with shrimp on a long feeding stick and it was so neat to see her grab the shrimp.
Definitely a great volunteer job.