patches of brown surrounded by dark green grass

by heather
(brantford, ontario, canada)

My lawn has patches of dead grass surrounded by a beautiful green colour grass. The surrounding grass grows taller and faster than the rest of the lawn. We don't have animals and I've sprayed for insects.(didn't know there were alternatives until I read your site).
Help?

Doug says it still sounds like animals. Like wandering dogs to be precise. Not yours but unless you're well fenced - my guess is visits from the neighborhood.