I have an Eastern (I think) garter about 2 or 3 years old. For the last few months, he hasn't been eating as much as he used to.
He will at first enthusiastically strike and grab a pinkie or goldfish, after which he sometimes eats it, and other times just drops it and moves away.
He will eat no more than one in a sitting now, but he used to eat up to four goldfish in a row before. Is this seasonal perhaps? It's cold here in Chicago now, and so is he whenever I pick him up. He knows where the heat pad is, but doesn't spend much time there. He's still fairly active, just not hungry.