10 days after people, Some greyhounds have escaped from the more than 40 dog tracks around the United States. Greyhounds are sighthounds and track their prey with their eyes rather than smell. Dogs that cooperate with each other have the best chance to survive in a life after people but greyhounds have been trained to beat their competitors at any cost. They will fight amongst themselves and with other dogs.
Because they were bred to be streamlined greyhounds have thin skins and will be easily injured in fights with other dogs. Greyhounds will not be able to survive long in a life after people. However the ones on remote islands off the coast of Florida could survive longer (possibly for more than 500,000 years) as there is not much competition there.