Since always. (Well, since post-Crisis, anyway, I'm not sure I've ever seen her do it pre-Crisis, but there's a lot of pre-Crisis I haven't read). The precision of the power varies - Perez-era she just sort of super-empathized with them all Horse Whisperer style, by Rucka-era she could actually intelligently parse concepts like "this bird is fleeing a forest fire" and get mice to search through rubble for disaster survivors - but nevertheless it's there.