My boy Sunny would howl on cue. We had a little "howling song" that we would sing, and that set him off. Also, the phrase "you're only a dog and that's all you'll ever be" would result in instant howling! And once started, he would continue. I have a video where I picked him up and held him upside down, and he continued to howl!
Moscow's stray dogs
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This is a very interesting article about the packs of dogs roaming the streets in Moscow. Long but worth reading.
http://www.ft.com/cms/s/2/628a8500-ff1c-11de-a677-00144feab49a.html?a