Not sure what I can do now. The new puppy is way to small to jump over the fence, so I doubt they'll be leashing it to the tree anytime soon, and it has food/water.
It's not like they fed the previous dog ham bones to intentionally kill it or anything. They weren't aware of the danger.
What would I say if I called the police/animal control? "My neighbors had their previous two dogs leashed to a tree for prolonged periods of time, with food and water. One of the dogs was killed by eating ham bones, which the owner didn't know could be deadly for dogs. Not sure what happened to the other one. Oh and they have a new puppy now."
They're not intentionally abusing the dogs and I don't think the level of abuse will be viewed as severe enough for action to be taken.