Cooperation and group living are two interesting adaptations animals have evolved in order to better survive the harsh world. Throughout our time at the field course, we saw three very cool examples of cooperation in several species, namely the Greater Ani, the wood boring bees and the vampire bats!
In the case of the Greater Ani, a beautiful blue-ish black tropical bird commonly seen on Pipeline road, there is cooperation between 2-3 groups of breeding pairs that share a nest and take care of their young together. Within the groups, the pairs are monogamous and remain together for life. All the birds in the group build a nest together and then take turns guarding the eggs and feeding the young. Surprisingly, the adults in the group are not related to one another, and they cannot distinguish between their own or another pair’s young, so all young get treated equally. However, female Anis do seem to know if they have or have not laid eggs, and if they have not yet laid, but come back to a nest full of eggs, they may occasionally eject them from the nest. How scandalous!
Luckily, birding on Pipeline road was successful and we saw a large group of these magnificent birds up in the trees! The blue colour of their feathers glistening in the sunlight… what a stunning sight. Unfortunately, we were much less successful in catching any Greater Ani birds in the mist nets we had set up, so we could only admire their beauty from afar.
The wood boring bees, Megalopta genalis, on the other hand approach cooperative living in a very different way. As their name suggests, they create nests in the hollows of dead twigs and branches. In these colonies, the Queen provides the “societal glue” which gives her the sole reproductive rights and facilitates law enforcement of the division of labour within the colony. This glue seems to be the pheromones of the Queen, which only slightly differ from those of workers. Queens with high reproductive quality are more successful. However, in certain conditions these bees can also live a solitary life… It all comes down to their chemistry!
Not only did we get to see these incredible bees at BCI, but riding at the back of the pick-up truck through the Agua Salud project, bruising our backs the sides and having our internal organs shifted around as the truck hit the holes, we saw another colony! Although seemingly disorganized on the outside, I could only picture the level of organization on the inside. If only we too could smell their pheromones, maybe we’d have a better idea of what it really is like.
Another fascinating species that lives cooperatively are the vampire bats, which feed of the blood of other animals. Feeding exclusively in the night, these furry creatures bite their unsuspecting prey and feed on their blood for up to 30 minutes. By injecting a numbing agent and a blood thinner, the host doesn’t feel the bite and the bat can feed till its tummy is full.They also are the only bat that crawls on the ground, sneaking up to their prey to feed! Not all bats come back successful from their night’s hunt. If they do not feed for two nights in a row, they risk dying of starvation. To avoid certain death, successful roost mates will regurgitate blood and feed their unsuccessful mates. This sharing is seen not only in kin groups, but unrelated bats will also perform this behaviour. Would you give up part of your food to help someone else, someone you don’t even know very well?
Unfortunately, we were unable to catch any vampire bats at bat night as they sneakily avoided the mist nets set up around the lab. We did however, see one already caught bat and got to listen to their echolocation sounds on ultrasonic detectors that convert their ultrasonic sounds into audible sounds we can hear. Mostly unseen by our eyes, they were everywhere in the night sky.