Most of the dogs I have met have been happy. In fact most of the animals I've seen cats, birds, fish, cows all seem content with their lives. Of course animals do not have bills to pay, so that might be part of the reason they seem happy. Animals are probably happy because their survival depends on it. In fact neuroscience has claimed that survival needs happy creatures. And if animals are happy just by living opportunities are we are also programmed to be happy to.
I heard recently that some elephants in India went on a rampage through a small village. Almost they have discovered when this village brews it beer, and the elephant literally crash the party. The pachyderms after drinking several hundred gallons of brew get rowdy and trash the place. Elephants are pretty intelligent creatures and they probably think something like 'wow this stuff taste great and wow this feels great to, whippy' then there's the crash.
So if animals feel happy and also have the capacity to get drunk it's particularly that they do not always understand the correlation between happiness and survival. Just like we super intelligent humans do not always get it either. The last time I checked the news about some drunken human doing something reckless was a lot more frequent then rampaging, drunken elephants. My point here is simply that we possess the capacity to be happy simply by living, but we do not always understand what promotions happiness.
Happiness is the ability to be satisfied with life. If you're alive then you can be satisfied with your life, but often we place higher conditions on what Promotes our life satisfaction or dissatisfaction. Dissatisfaction with what we do not have in life is often one of the largest culprits to our unhappiness. So an essential ingredient to being happy with everyday life is to find ways to appreciate what we have. Feeling grateful for our lives, our relationships with others, our homes, even the food we eat, are all opportunities to appreciate what we have, and as a result we feel satisfied with life.
Feeling grateful is a great tool to use each day in order to reap the happy benefits of survival. The alternative is to focus your attention on what makes you dissatisfied with your life. If you choose this path you're probably confused about what makes you happy. This confusion usually involves one of two vices, hedonism or materialism. Organisms and fancy cars do not create lasting happiness they are the benefits of living a happy life. Often we confess the two and perceive the high we feel from them as happiness. Happiness really happens after the organism during the spooning, and on the way to work in your new car.