titanmelon said:
If this is true (the bottom example is currently tagged as interspecies anyway),

Then should there be a specific tag for inter-..species scenes?

Such as [lion x tiger], [dox x fox], [horse x zebra] etc.

I feel searching [interspecies dog fox] would be sufficient enough instead of [dog_on_fox/fox_on_dog (?)]

However, there is always the probability that using such tags would end up with the dog and fox present, but not actually engaging in sexual activity... (Other animals engaging instead)
Thus, having a specific tag can remove the need for searching all three and just go straight to the actual specific interspecies scene, without any chance of lacking the interspecies activity that one wishes to find.

This will need more input from others, other than something like me alone. I tend to make things harder/overly meticulous in my perfectionism. However, it does sound to be of convenient use in my opinion.