Lest you think Lava relied a little too much on The Power of Love, note that Uku wasn't extinct, he was dormant. That's when a volcano looks extinct and doesn't erupt, but can still come back to life. Lele's arrival and song sped up/galvanized the process, allowing him to once more break the surface.
Every time one of the volcanoes in "Lava" sings, a rumbling sound is heard just prior to it. This implies that these rumblings are actually the volcano's "language".
In Dug's Special Mission (the short following Up), it has been revealed that the day Russell and Carl met Dug? It was his birthday, and he made a wish. What did he wished for? A new master. While it's a bit more Heartwarming in the events that followed that lead to meet the heroes, but considering how stable Charles Muntz's sanity is, it makes you wonder what the hell he did to Dug.
In relation to the above, it may possibly be due to how Muntz gets more dogs for his little canine army or how he gets rid of the people he kills under suspicion of stealing the bird from him. Mystery Meat dog chow anyone?
More than likely, considering while all the dogs pep up when he offhandedly says 'treat' during the dinner scene, he then gets them all to quiet down and back away fearfully when he says that 'having guests is such a delight.'
Given I have a dog of a breed with a very similar character, I can offer an alternate explanation: he just didn't receive enough attention, and never got to play (drawing from my dog's reaction to leaving his previous master, who didn't give him enough attention: he didn't give a shit. He's otherwise an immensely friendly dog). Add to this the treatment he received from Alfa and the others, and you can realize he just wanted someone capable of appreciating him.
Er... Is nobody else concerned about how the Blue Umbrella blew onto the windscreen of a large truck, in the middle of a busy street?
It has been confirmed that the story of "Lava" takes place over hundreds of millions of years, but there is nothing to suggest that volcanoes experience the flow of time any differently than us. That's a long time to wait for love.
