In getting things out of my shed to decorate for Christmas, my son happened upon a rat in which he quickly killed. Further inspection reveals that it was a mamma that had 6 babies. Newborns to be exact! All of which have been killed. Should I be concerned of others? Expect a male? I removed all feed, etc from the shed months ago after discovering something was gnawing on the storage containers that we had initially had feed and scratch in. Now everything is in metal and locked down tight.