Look at this beautiful labradoodle (labrador retriever / poodle cross):
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1. The first time was because "he became too big". Um, the mix of standard poodle and lab might get big. These breeds might become more than 100 lbs, but of course you can never predict his exact weight. Think about it with people: ever seen two average height people have a tall child? One or more pups in the litter might be smaller than the rest, and one or more might become larger than the rest. It happens with dogs on an even greater scale than in humans. And this dog comes from big-ish dog breeds. That is irresponsible and abusive to the dog's needs. A dog becomes a member of your family, not something to be returned if it's too big, small, or imperfect in the human's eyes.
2. The second time was because the family was moving ... so they just left the dog behind in the laundry room. I cannot fathom such cruelty. It is deplorable, abusive and inhumane. Those humans do not deserve to call themselves human. That's all I have to say about them.
3. The third time was because the household cats could not get used to the dog, so the owners just returned the dog to the humane society. (Socializing pets with new pets can be hard. The owners may not have done the research needed to prepare or put the effort into doing it, but who knows their whole story?)
Isn't that poor dog's history disgusting and angering? This poor dog has done nothing wrong. He's been loyal, beautiful and innocent as human after human abused him in some way or another. Click here for his story.