Recently, our video editors here at NG came across some footage that was flagged for viewing. Submitted by National Geographic Explorer and capuchin monkey specialist Susan Perry, we expected the video to be of monkeys doing something intriguing or goofy.
We were completely wrong.
Susan, a UCLA professor currently based in Bagaces, Costa Rica studying the behavior of white-faced capuchins, happened to stumble on the impromptu dinner party and caught it all on tape. We called up Susan to get the grizzly details:
We understand this was filmed in your backyard- were you shocked?
Susan Perry: We were just doing some yard work when we noticed this. When I first saw it, it had not yet started to swallow the ctenosaur (iguana), and it struck at me. That surprised me, as boas are generally extremely calm even when approached at close range.
How common is a sight like this around your home in Costa Rica?
SP: We commonly encounter boa constrictors, mainly in the forest but occasionally in town as well. It is fairly rare to find them in the act of strangling their prey, however, because they do not need to eat often. This is only the second time I recall seeing a boa eat a ctenosaur.
My graduate student had the highly disturbing experience of coming upon an immense boa swallowing a monkey whom we knew personally. The monkey was already dead when she arrived at the scene, and the rest of the monkey group was mobbing the boa. It took about 2 hours for the snake to swallow the monkey, and then it promptly slid into the river and swam away.
In the only other incident in which my research group saw a juvenile capuchin monkey attacked by a boa, the other monkeys arrived on the scene soon enough to defeat the snake: the monkey’s mother pulled on the snake’s tail and bit it, and the father attacked the other end of the snake, while another monkey helped to pull the juvenile from the coils of the boa. That juvenile who survived is now alpha female of her group, a decade later.
Have you had other surprising animal encounters? Anything as memorable as this?
SP: Yes, we regularly have encounters with interesting animals. Capuchins are omnivores and also extremely feisty, meddlesome animals who take the offensive rather than defensive role when confronting potential predators. So there is no better “tour guide” to the forest than a capuchin monkey.
They are destructive foragers, investigating every hole and crevice they find, and they often wake up sleeping nocturnal animals, pulling them out of their hiding spots to antagonize them. So we get the opportunity to see a lot of animals that we would not otherwise notice: e.g. margays, puma, ocelots, jaguarundis, tayras, tropical porcupines, anteaters, and kinkajous.
One memorable encounter this year was with a crested eagle, a species not normally found at our study site. The monkeys had a conflict with a juvenile crested eagle, which was wounded on the ground.
It is interesting to see the monkeys in the role of predators as well. They routinely hunt coatis, squirrels, small rodents, basilisk lizards, and various birds. Although meat is <1% of their diet, they get really excited about it; everyone begs for a share of the meat. Most of the protein in the capuchin diet comes from insects, such as paper wasp larvae. We get stung quite regularly in wasp breeding season, as the monkeys destroy nests and anger the adult wasps.
Here more from Susan Perry on the National Geographic Radio Show!
We also caught up with Young Explorer and herpetologist Neil Losin who demystified the boa’s dining habits:
Is an iguana standard prey for a boa or is this boa just ambitious?
Neil Losin: Like most snakes, Boa constrictors are “gape-limited predators,” which basically means that they can eat anything they can fit in their mouths. And tackling large prey items definitely has its rewards — after eating a really big meal, a boa might not have to eat again for weeks or months!
Boas usually eat small- to medium-sized birds and mammals, but they have also been observed eating large lizards like this iguana. In Argentina, a boa was recently observed killing (and then attempting to eat) a crab-eating fox! Ultimately, however, it abandoned its attempt to eat the fox, which was much too large to swallow. (See more).
Boas don’t always eat big prey, however. With my fellow biologist Nate Dappen, I recently observed bat-hunting boas in a cave in Puerto Rico. (See more.) The bats that these boas hunt are tiny, but they are also extremely numerous, and on a good night a single Puerto Rican boa might have several small, furry meals.
Can the boa slither away immediately or is it relatively immobile for awhile?
NL: When a snake swallows a big meal, its mobility definitely suffers. Imagine carrying around an extra 30% of your body weight (or more!), and then think about doing that without the aid of arms or legs!
Snakes will move after a big meal if they have to, but they generally just try to find a place where they’re unlikely to be bothered and devote most of their energy to digestion, a process that can take several days.
It’s not just the physical bulk of the meal that hinders a snake’s activity; the digestion process itself takes a lot of energy, and snakes’ body temperature and heart rate often increase dramatically while they’re digesting a big meal.
In the video the boa literally splits its side swallowing the iguana- does that happen often?
NL: It’s not entirely clear from the video just how bad the damage is, but an injury like this can’t be good for the snake’s health. Especially in the wet tropics where these snakes thrive, any wound can easily get infected and cause serious problems.
The nutritional value of a big meal (like this iguana) is huge, but that’s all for naught if the snake suffers a major injury trying to subdue or swallow its prey. Even snakes make mistakes!
Are boas threatening to humans?
NL: Not at all! It’s rare for a wild boa to get much over ten feet long, and at that size a boa certainly wouldn’t consider a human to be a potential meal. That being said, boas – like all wild animals – can be unpredictable, and it’s unwise to approach or handle them if you’re not very experienced with snakes.
Boas are not venomous, but they have large, sharp teeth to hold on to their prey, and they may bite if they feel threatened. Throughout Central and South America, there are also some highly venomous species that live alongside boas and can easily be mistaken for boas by a casual observer. So it’s always best to admire boas and other snakes from a respectful distance!