You know they've made some excellent points. You came here looking for an answer-- And you got several, plus critism due to lack of details. This story IS very disturbing, so yes were wondering how this could ever be managed between two geckos of almost the exact same size. The story really doesn't fit still, but there's nothing we can do about it besides.. Take precaution when housing Leopard Geckos together and make sure that they have everything they need for a stress-free environment. Also, if your putting two geckos in together, don't place them together then walk away. Try to watch how they interact and be sure that they're either male and female or female and female. I don't want help-seekers coming here asking questions then being scolded, but some people here will be firm with you. Also when your seeking tel and getting answers, don't get angry with the results because you were merely asking for them(I know there's difficult individuals to deal with here.. In this situation I was appalled and I let the fur fly.)
I don't like or enjoy belittling others, so don't take it that way, but hopefully from the replies you've gotten you will learn more from this situation and remember to post details, because the way you had stated the cannibalism was very unprofessional for someone of your "expertise".. Good luck next time..
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-Britney
Atlantic Reptiles(In the works)
2.4.1 Leopard Geckos: Ron, Raine, Dream, Tango, Go-Go, Johnneh and Salleh.
0.0.1 Bearded Dragon: Lil' Little.