From The Science of Good and Evil:
Examples of pre-moral sentiments among animals abound. Vampire bats share food and follow the principal of reciprocity. They go out at night in hoards seeking large sleeping mammals from which they can suck blood. Not all are successful, yet all need to eat regularly because of their excessively high metabolism. On average, older experienced bats fail one night in ten, younger inexperienced bats fail one night in three. Their solution is that successful hunters regurgitate blood and share it with their less fortunate comrades, fully expecting reciprocity the next time they come home sans bacon. Of course, the bats are not aware they are being cooperative in any conscious sense. All animals, including human animals, are just trying to survive, and it turns out that cooperation is a good strategy.