Birds of Prey: Neotropical monkeys’ most fearsome predators

Check out this blog post featured on the Los Amigos Bird Observatory Blog about our latest publication!

April 5, 2018 | Author: Carla Mere |

Jaguars are without a doubt the top predators in Amazonia, but organisms flying above the canopy certainly have a big advantage and unique predation skills that make them respectable predators when compared to wild cats. Raptors are considered the major predators of new world primates, such as crested eagles (Morphnus guianensis) predation on infant tamarins (Leontocebus mystax & L. fuscicollis) and also squirrel monkeys (Saimiri sciureus); black-hawk eagles are also known to attack howler monkeys; and the largest and powerful harpy eagle (Harpia harpyja) predation on saki, capuchin and night monkeys. Current ecological knowledge of Neotropical raptors is scarce, thus filling in the gaps of information on this particular group of birds will allow us to understand their ecology and general biology, whether it is through anecdotal incidents or observations in the field.

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Photo by Marc Fasol

The black-and-white hawk eagle (Spizaetus melanoleucus) is one of the 55 birds of prey found at Los Amigos. Compared to other well-known raptors such as the mighty harpy eagle or the crested eagle, the black-and-white hawk eagle is a small size bird (body mass: 780-1191 g; wingspan: 110-135 cm), feeding mainly on terrestrial and arboreal birds such as tinamous and guans, and some documents report small mammals and reptiles in their diet. However, successful predation on primates by this species was not described until 2014, when a group of researchers witnessed and described the mortal attack of the Rylands’ bald-faced saki monkey (Pithecia rylandsi) at Los Amigos.

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Ryland’s bald-face saki carcass on the forest floor, and attacked by the black-and-white hawk eagle.         Photo: Adams & Williams, 2017

This fatal event was recorded on 23 July, 2014, during a long-term project assessing the anti-predation behavior and alarm calling of P. rylandsi at Los Amigos. While conducting the usual primate behavior monitoring, one of the research assistants heard a large bird flapping, followed by alarming calls of a group of sakis, which are whistle-like calls emitted when they detect an eagle’s presence. Upon the researcher’s return after a couple of hours, he heard wing’s flapping in the same location. After following the motion event, the researcher found out the black-and-white hawk eagle feeding on an adult saki’s carcass on the ground. The black-and-white hawk quickly flew away after detecting the researcher approaching. Most of the saki’s flesh, muscles and skin were removed, with fur scattered beside and along a 16.4 m path away from the carcass. Several puncture holes were noted on the body and skull, while the stomach lay untouched next to the body despite most of the soft tissue having been removed. Although the observers didn’t visually witness the attack, the described observations together with the physical injuries documented on the saki most likely indicate that it was the black-and-white hawk-eagle as its predator.

Black-and-white hawk eagles utilize the “soar and stoop” hunting tactic, compared to the “perch and wait” strategy used by large raptors, consisting of searching for preys above the canopy and forest edges and, upon prey detection, diving rapidly into the forest to attack them. This report suggested that smaller and lesser-known raptors, like the black-and-white hawk eagle, should also be considered important predators of Neotropical primates, principally those that occupy the mid to upper canopy given their hunting strategy. Identifying and providing evidence of predation events like this is key to learn more about less prominent raptors, so keep your eyes and ears open while walking in the forest!

For more references:

Adams, D., Williams, S. 2017. Fatal attack on a Ryland’s bald-faced saki monkey (Pithecia rylandsi) by a black-and-white hawk eagle (Spizaetus melanoleucus). Primates 58: 361-365.

Robinson, S. 1994. Habitat selection and foraging ecology of raptors in Amazonian Peru. Biotropica 26(4): 443-458.

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Smart Sakis: A Spoonful of Termite Mound helps the Bitter Seeds Go Down

Primatologist Michelle Rodrigues posted a cool write-up of our most recent paper on geophagy in saki monkeys on her blog SpiderMonkeyTales. Check it out below!

Saki monkeys are a Neotropical primate found in Amazonia. They are seed predators, which means that rather than ingesting seeds and passing them whole (like spider monkeys), their teeth and digestive system destroy the seeds they eat. This is a good way to get maximum nutrition from those seeds, but the seeds contain high levels of secondary compounds like tannins. Tannins are the bitter, astringent compounds that give coffee, tea, and wine their unique flavors, but high levels of tannins (much higher than we consume), can be toxic.  Other Amazonian seed predators, like parrots, eat soil with clay and high cation exchange capacity, both of which neutralize the toxic effects. Seeds eaten by parrots in the same region have tannin levels toxic to most verterbrates. If the Sakis are eating the same seeds, how do they cope with those levels of toxins?

Sakis eat termite mounds, which contains soil, clay, and nutrients. Adams and colleagues tested between two hypotheses: 1) Sakis eat the termite mounds because they provide nutritious minerals (like vitamins), or 2) to help counteract the potentially toxic effects of secondary compounds (like a detox supplement). If the soil they ate from termite mounds contained more micronutrients, that would support the vitamin hypothesis. If the soils contained that have more clay and and cation exchange properties, that would support the detox hypothesis.

They observed how long the monkeys ate termite mounds, which age/sex classes at the termite mounds, if there were termites present. They also collected samples from termite mounds that the Saki fed at, and compared to control soil samples and unvisited termite mounds.

About 2/3 of the termite mounds contained termites, and Sakis did eat termites at the active mounds. However, they fed from both active and inactive termite mounds, all age/sex classes fed on the mounds. Termite mounds did have higher levels of some minerals than topsoil, and those levels were similar in the both the Saki-eaten mounds and univisited mounds. The eaten- and uneaten-termite mounds did not differ in in clay content, but the termite mounds that were eaten had twice the cation exchange capacity. Adams and colleagues conclude that the Sakis are eating the termite mounds primarly because it helps counteract the effect of the tannins, supporting the detox hypothesis.

So basically, Sakis are wisely self-medicating with termite mounds to counteract the effects of their potentially toxic diet!

An important caveat: Adams and colleagues do not use terms like the “vitamin” or “detox” hypothesis–I use these terms only to simply the function of termite-mound eating. Also, humans are not seed predators, so we do not have the same need for detoxing. Most talk of “toxins” in human diets is pseudoscience, and unless you’re eating some strange things that are not suitable for human consumption, you should have no need for detoxing!