How can I make a duplicate of a table row in mysql?

This is my table farm:

+--------+
| animal |
+--------+
| cat    |
| monkey |
| bird   |
| dog    |
| horse  |
+--------+

I want to make an exact duplicate of the row animal. So my table should look like this:

+--------+---------+
| animal | animal2 |
+--------+---------+
| cat    | cat     |
| monkey | monkey  |
| bird   | bird    |
| dog    | dog     |
| horse  | horse   |
+--------+---------+

I tried

INSERT INTO `farm` (`animal2`) SELECT `animal` FROM `animals`

But what happens is this:

+--------+---------+
| animal | animal2 |
+--------+---------+
| cat    |         |
| monkey |         |
| bird   |         |
| dog    |         |
| horse  |         |
|        | cat     |
|        | monkey  |
|        | bird    |
|        | dog     |
|        | horse   |
+--------+---------+