Survivors (Erin Hunter). Original series

"In the aftermath of the Big Growl the destroyed his city, a Lone Dog named Lucky must find a way to work with other dogs in order to survive in this frightening new world"--Provided by publisher.

"The Wild Dogs' fierce Alpha reluctantly agrees to let the Leashed Dogs join their pack--but after learning of Lucky's role as a spy, Alpha casts him out of their camp and orders him to never return"--

Lucky and his Pack were able to defeat Terror's dogs. But their new world still holds many dangers. Now the Pack has come to the edge of a strange lake that seems to stretch on forever, and Lucky discovers that there is barely enough food to survive. As winter approaches and the dogs struggle for prey and shelter, Alpha makes it clear that his own needs come before the rest of the Pack. Meanwhile, the Fierce Dogs are determined to destroy Alpha's...