Okay up front I think we should all go for domestic dog types, great for recon if we pick up a cat or two. Who notices dogs and or cats in an urban environment? 

Also Domestic Dogs are evolutionarily fixed to humans and less likely to go total freak out

I forget if dogs can smell the presence of Yeerks but never fear I shall soon know that answer; I mean they can smell cancers, diabetic, and other ailments on humans.