I by no means claim to be an expert on the series, but I've seen my fair share of episodes. Mostly he's just trying to catch and eat them - usually in a stew. Admittedly, going into his reasons for doing so (immortality serum? philo stone? most delicious morsels on the planet?) is a bit outside the scope of a 10-15 minute children's cartoon, but so far as I can recall, it's not even mentioned obliquely.