Do animals have empathy?

There are plenty of instances of animals showing traits of empathy, of caring for sick and injured members of their group; wolves, dolphins, elephants, cats, dogs, monkeys, apes, etc. I've read of cases where a researcher followed orangatans in the forest and forgot to bring food. As the orangutans ate above her, one crawled down and offered her some fruit. On the other hand, in a separate story, another researcher claims his water bottle was snatched by an orangutan and soon dumped on his head.