Because they’re abundant and commonly used as a feeder for amphibians, this question sometimes arises among those looking to give their reptiles a wider feeder variety.
The answer is yes, leopard geckos absolutely can eat earthworms, but it’s best if they’re only fed occasionally as they’re high in moisture and low in protein and fat.
Of course, you don’t want too much protein or fat in your gecko’s diet — this can lead to obesity and other health issues. But not enough, combined with an excess of moisture, can result in diarrhea or an underweight gecko.
This is why variety needed. No one feeder comes even close to good enough if they’re being fed exclusively.
What earthworms should I get?
Though they’re large, nightcrawlers are one of the best options. If need be, they can be cut in half to better accommodate your gecko.
Do not buy any worms raised for fishing bait. These are frequently treated with chemicals that can be harmful to reptiles and amphibians.
Another worm to avoid is red wiggler worms. These secrete toxins and are dyed. Fortunately, most leos will just spit these out, but they should be avoided in the first place. (Eisenia hortensis is fine, but red wigglers — Eisenia foetida — are not).
I advise against catching worms from outside for use as feeders, due to the likelihood that they may have come in contact with chemicals such as pesticides and other chemicals. In theory, this is avoidable by capturing them far away from human activity of any kind, but you can never be 100% sure of what other unpleasant things they may have come in contact with.
My leopard gecko isn’t eating earthworms!
As sad as it is, some individuals simply don’t love the taste earthworms. This is more or less normal; don’t force your gecko to eat something it doesn’t want to.
If your gecko isn’t eating any feeders at all, a health issue could be at play. Read more: Why Isn’t My Leopard Gecko Eating?