Which animal behavior described below is an example of a learned behavior?

1. Songbirds are born with the ability to sing though they improve their songs by mimicking others and trying new combinations.
2. Prairie dogs in the wilderness hide when a human approaches, but prairie dogs that live near campgrounds are used to humans and do not hide when humans approach.
3. Frog tadpoles are born with the ability to swim.
4. All caterpillars from the same species build identical cocoons in all environments and times of the year.​