Counting number of times a behavior is repeated with Computer Vision: How hard is this?

I currently work for a lab in neuroscience and we work with small animals. Part of our research is to count the number of times these animal perform certain behaviors like scratching or jumping. We use a fixed camera that records this animal in a cage. Note that these animals are not in fixed positions so in part it might be scratching itself while its back in facing the camera while in another part it is scratching with its front …

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