Dear Matt A:
When I lived near a canyon in the College Area, there was often a very coarse howl, almost a growl coming from the canyon, often followed by a shrill whistle. Furthermore, it appeared to travel from one end of the canyon to the next very rapidly, by the location of the sound. I've heard it many times, also in a canyon in City Heights. Could it be foxes?
-- Gary, City Heights
We civilians will never get the hang of describing nature well enough to suit a naturalist. Identify a sound from a verbal description? I don't think so. At any rate, you won't get a definitive answer without a high-quality field recording of the growl in question. So when we approached Phil Unitt, curator of birds and mammals at the Natural History Museum, with your query, he said, sorry, no can help. Confronted with weasel words, we badger the expert to ferret out the information until he's cowed. Hey, Phil, take a guess. It's no big professional deal here. "A howl or growl isn't a sound you usually hear discussed in connection with foxes," he says warily. The most commonly heard fox sound is a perfect imitation of a baby crying. Okay, how about a coyote; we don't have coyotes in urban canyons, do we? Heck yes, Phil says. He's seen them walking down the middle of the street late at night in Hillcrest. Yikes! Okay, how about feral dogs; city canyons are full of wild dog packs. Unfortunately, yes, Phil says. Summary of findings: The growl is more likely a dog or a coyote than a fox.
The high-pitched wail is the sound of a dying rabbit. They're not known for their rowdiness until they're grabbed by a predator. Then they make an incredibly loud, piercing cry that grows lower and softer as the bunny expires. This fading may be what you interpret as the sound "moving"; but if the sound actually does move, it's probably just an echo in the canyon. One odd side note -- aggravate a rabbit and he will make a growling sound, not unlike a dog, but it's too soft to be the growl you hear in the canyon.