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It is possible that the kitten could be stressing him, but as long as he is eating and active he should be fine. The moment he abruptly changes his behavior then it would be time to worry, but I will advise that you make sure their is no way the kitten could knock the lid off and get to your FBT. They are toxic and if the kitten was to bite the toad it could not only kill the frog, but could make your kitten sick or worse.