One of the best walks I have ever done was in February in Costa at a wonderful place called Rara Avis. www.rara-avis.com/
One of the residents there was a herpetologist called Don who led a night walk to see what we could see. Not content with walking the paths we were scrambling up streams and down gullies and it was just superb. During this walk I found this snake attacking and eating a frog. They were a Brilliant Forest Frog (Rana warszewitschii) and Northern Cat-eyed Snake (Leptodeira septentrionalis).
You had to feel for the frog, but a snake has to eat too! Cat-Eyed snakes are called that because thier eyes have pupils that resemble a cat.
To scale this the frog was about 4 to 5cm end to end. Snake was 30cm or thereabout long, but very thin.