The whistle frightens them and excites them, causing then to yelp.
Coyotes are similar to wolves in many ways, but not the howl. Wolves have a clear, smooth howl, and coyotes have a whimper-like howl. When coyotes howl, they are barking and then let out a short howl, then keep doing high pitched howls.
no
march
Animals that howl are: Coyotes Dogs Jackals Wolves They all howl for various reasons - to mark their territory, to communicate with their packs, to drive away their prey, and to strengthen family bonds.
Coyotes howl during all hours of the day to give pack mates an idea where they are located. Howling also is a warning or an indication that possible prey has been found.
Primarily, to announce their territory and determine if other coyotes' control territory near their own (e.g. a coyote will howl and then listen for other coyotes to howl back -- if he hears another coyote to the West, than he knows that the land to the West is patrolled and "owned' by a different coyote, and he will respect that coyote's boundaries). They also howl to call their family members back after they split up to hunt. for more info about it go to wikianswers.com/why do coyotes howl :) ;)
It is called Love Train
Coyotes howl to attract a mate. Howling occurs in January and February when they are looking for mates. They also use scent to attract their mate.
They probably think that the sirens are howls of other coyotes.
A dog may howl when an ambulance passes by because the high pitch of the ambulance siren is irritating to the dog on a level greater than it is to humans. Dogs have very sensitive ears and lots of sounds may bother them and cause them to howl.
depending on the temprature or time (either 8:30 pm to 4:00am) coyotes will howl at the times given above. You'll hear them howl at the moon or communicating to each other like "Stay away for this is my territory!".
When they leave the den to run with the pack yes. Not before that because a noisy pup can attract predators. The mother will teach the pups to be quiet while she is gone to look for food.