This is a good question! If you have ever been camping or live in a rural area, you may have heard coyotes or even wolves howling too, though probably not in response to sirens. Dogs, coyotes and wolves are all related, and all three groups are social. Coyotes, wolves and wild dogs travel in packs, raise pups in groups and have an organized social structure. Social animals communicate, and because these three groups of animals are related, it is not surprising that they all use a similar form of communication: howling, barking and growling.

Dogs have a wider range of hearing than humans: they hear both higher-pitched and lower-pitched sounds better than we do, and can even hear sounds that we cant. (If you have ever used a dog whistle, you know this.) Like sirens, howls contain high-pitched sounds, and scientists think that a dog howls when he hears a siren because the dog thinks he is hearing a howl from another dog. That is, the dog thinks he is communicating with another dog!

If you are really interested in dogs, a GREAT book to read is The Hidden Life of Dogs by Elizabeth Marshall Thomas. She explains a lot about dog behavior, based on her own observations and on what scientists have discovered about wolves.

The first step in understanding dog behavior is to realize that their ancestors were wolves. Wolves use howling for long-distance communication. Barking may seem loud in the middle of the night when the dog is nearby, but it doesn't carry as far as howling. Wolves usually live in packs of relatives, and they howl together. This probably tells other packs that a certain number of wolves is still healthy, active, and living on a particular territory. They might be communicating other things too. A wolf that is separated from its pack will also howl to find its relatives. I had a dog for almost 17 years and she only howled three times. All were times when we were out in the mountains and I had to leave her with a friend because of an emergency or because I would be crossing boulder fields she couldn't cross.

Other dogs seem to respond to sirens as if they were the howls of dogs. No one (except the dogs) knows whether the dogs really think it's another dog or whether the siren just makes them want to join in. Scientists use tape recorders to find out about howling. Can you think of a way to use a tape recorder to tell whether a dog or wolf can tell who is howling (a pack member, themselves, a stranger)?