Asked by: Carla Redhead, Weymouth
Red and grey squirrels are different species (Sciurus vulgaris and Sciurus carolinensis, respectively) and are not reproductively compatible. Several million years of independent evolution (grey squirrels are native to North America) have resulted in differences in genetics, diet and habitat that would make interbreeding non-viable, whatever outward characteristics they may share. Hedgehogs and porcupines don't interbreed either.
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