By Nicolas Corea
So many reasons to come to the beautiful islands of Bocas del Toro: surfing, sailing, scuba, snorkeling, salsa-dancing, sloths, Spanish study aaaaannnd…studying bats of course (A for alliteration on that one). Meet Dina Dechmann and Teague O’Mara. They came to Bocas primarily for the latter reason that I mentioned and they represent the Max Plank Institute for Ornithology, University of Konstanz and are affiliated here in Bocas del Toro with the Smithsonian Tropical Research Institute. The three of us sat down one evening and had what I will probably forever consider: the most interesting conversation I’ve ever had about bats.
Not only are bats the only mammal that truly fly (flying squirrels glide, FYI), but they are also mammals whose social behaviors are very much under scientific observation here in the archipelago of Bocas del Toro. Dina and Teague came to Bocas in March to study a species of bat known scientifically as Phyllostomus hastatus or the Greater Spear-Nosed Bat. With their wingspan of almost 1 meter, they are the 2nd largest bat in the Americas. They are known to dwell in the Bastimentos bat caves and La Gruta on Isla Colon (road to Boca del Drago). Dina and Teague specialize in behavioral ecology or as Teague was able to break it down to this very non-scientific layman of a journalist: the study of “why animals are sociable and how animals compensate for ecological unpredictability”.
Greater-Spear Nosed bats have been observed to forage in groups of non-related females. A study out of Trinidad observes this very species forming groups of females from different families, living 16 to 20 years together and even caring for each others’ young. Like many mammals, these bats mate in harems. Every 2 or 3 years, the group chooses a new alpha male bat to mate with and that is the end of the relationship: “It’s not you, it’s us…” and life goes on for the group of Greater Spear-Nosed bat gals.
The group members identify each other with a “screech” call, which is not a sonar or echolocation call, but a distinct vocalization that takes new group members up to 8 months to learn how to do correctly. Dina and Teague claim that when they listen to the recording of the bat calls, they are able to distinguish between different bat groups, but telling apart bats from the same group, who are performing the same call, is impossible. So what is the reason for all this Greater-Spear Nosed bat socialization?
The fact that they forage in groups is up for debate and is the very reason for this particular scientific study. The study out of Trinidad suggests that the bats engage in this social behavior because they are cooperating to defend precious resources. There may be seasons where food is more scarce and their communication and teamwork is essential to their survival. The Greater Spear-Nosed bats in the Bocas del Toro region have been observed to engange in this social behavior only seasonally, which you might think would support the hypothesis from the Trinidad study, however Dina and Teague have their doubts. Some of the females are also pregnant during these group foraging seasons so the behavior might have something to do with nutritional needs during the reproductive stage. Thus, they are probably sharing information about where the flowering trees the bats prefer during those times are, but whether resources are scare or not, no matter what group behavior the bats partake in, they are never really able to protect their food sources from real threats, such as possums, kinkajous and other rodents that eat the same fruits and nectar. Interestingly enough, that’s not all this species of bats eat.
First of all, all bats have a very high metabolism and require a tremendous amount of energy in order to fly. Greater Spear-Nosed bats are rather large and happen to be omnivorous (they eat both plants and animals). These bats are known to eat fruits, nectar, insects, frogs, lizards, mice and even other smaller species of bats. Dina was explaining that a rather interesting phenomenon was discovered during their observations. Sometimes these bats won’t leave the cave for days. They believe this could be similar to when a lion makes a big kill, his tummy is super stuffed and he spends a couple days just relaxing or gorging.
I was interested in the way they study the bats. They catch them in the caves using water coolers with a 30 cm diameter. The bats fall into the bucket and are unable to fly out because the diameter is smaller than their wingspan. The biologists attach a small GPS device on a collar (made of ribbon) and the ribbon is secured by making stitches. They stitches only enter the ribbon, not the skin, and they are they type of stitches that dissolve in 3 weeks. After being exposed to the elements, the GPS devices simply fall off- hopefully in the cave, perhaps somewhere in the jungle. They use the GPS data to study their flying patterns and behavior. They see who flies with who and they study where they forage. They even have microphones on some of these devices and study their group calls. Some groups in past weeks have been tracked foraging all the way in Changinola. The Breeze believes this is the smartest and most bargain-oriented bat because that is where the nearest Romero grocery store is located. There is no scientific foundation for that previous statement. Thank you.
If you find any of these GPS trackers (pictured below), please bring them to Woodstock Lumberyard and you will receive a $50 reward! The best place to look is the Bastimentos Bat Caves or La Gruta (Bat Cave) on Isla Colon. There are still many missing from the study.
Thank you Dina and Teague for the interview and making me so interested the social behavior of the Greater Spear Nosed bat. I hope it was as interesting for my readership as it was for me. Also, I hope I made no factual errors because at the time publication, this journalist was under a deadline and waited too late to get his facts checked by real-life scientific people. Stay tuned for more scientific articles actually written by scientists and edited by editors that pride themselves on prolific, passionate and professional prose.