I think there was a study done in which scientists didn't feed several species of snake for a year. Even though the animals weren't getting any food, the heads grew. These snakes undoubtedly lost condition and mass, but the point to notice is the increase in head size - which it is theorised, occurred so that the animal in question could increase it's choice of prey.

I'm afraid I can't find the reference right now, but I'll be on the look-out.
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