Animals easy distinguishing between men and women just by voice of a person, or by their scent. Even if person tries to distort voice - at least dog and cat will recognize it. Around decade ago I saw interesting TV program about this on local channel, there were few different dogs, and were recreating different experiments. One of experiments had those dogs being in a room with a man and a woman in two different corner. Then speaker in center of the room was saying command to them, if voice was male - dogs would look at man in room, if voice saying the very same command was female - they would look at a woman in room. They tried to distort vvoice, by men speaking high pitched voice, or woman speaking very low, tried swapping man and woman corners, put wig on a man and found masculine worker class women - every time dogs were still recognizing correctly. Show was a bit bizzare with many weird experiments in general, but this was fun one.

Few months ago I saw this exactly experiment on youtube (or maybe instagram?), only much simplified version, but can't find it for some reason.