Lenny

Nice shot. He's usually not in clear view to get a shot that clear.

He was far more cooperative than Holly.

He usually is.

How can you tell Lenny and Holly apart?

Lenny (M) is lighter than Holly (F). Lenny also has more white around his face than Holly.

Here's a picture of Holly to compare:
http://www.zoochat.com/532/white-handed-gibbon-366116/

Wow there is quite a difference thanks cypher!

No problem Jake

Cypher is quite right about how to identify them. If you have any questions about IDing any zoo animal this is definitely the group to ask. Many have their own little tips and tricks for telling individuals apart and they are more than willing to share. Some are very easy while others are much harder.