Testing the Drunken Monkey Hypothesis in Panama


Could alcoholism in humans be an evolutionary hangover? Robert Dudley, professor of Integrative Biology at the University of California, Berkeley believes so. His “Drunken Monkey Hypothesis” suggests that fruit-eating primates —such as BCI’s spider monkeys—may be drawn to naturally occurring ethanol in the fruits they consume. Frugivorous primates have been eating fermented fruit for 40 million years. The health benefits of low-level alcohol consumption are consistent with an ancient and potentially adaptive exposure to this common, psychoactive substance.

Christina Campbell, associate professor of Anthropology at California State University Northridge, who has studied behavior, ecology and reproduction of spider monkeys, Ateles groffroyi, since 1996, is back on BCI with graduate student, Victoria Weaver, to test Dudley’s hypothesis. They will measure the ethanol concentration in the sugary fruits of Spondias mombin, a mango relative extremely important in the monkeys’ diet.

Christina and Victoria will be running through the forest chasing spider monkeys to collect fallen fruits and/or urine samples (which will be tested for an ethanol metabolite) until September 2014.


From Stri.orgImage

On June 1, Karla Aparicio hosted a group of Panamanians on Barro Colorado Island. As she guided them down the trail toward the BCI’s Big Tree, she noticed a rather unusual amount of light up ahead. BCI’s tree was no longer standing. “When we entered the new gap and realized what had happened, it was so impressive. The whole crown of the tree was on the ground and there were tons of bees and ants milling around looking lost!”

Home to epiphytic orchids and cacti, bromeliads and Spanish moss as well as to sloths, monkeys, bats, and birds, the late Big Tree, a kapok (Ceiba pentandra) definitely qualified as an island icon. It was probably the backdrop for more group photos than any other location on the island.

STRI’s staff scientist Joe Wright, who plans to take a core from the main stem to estimate the age of the tree, asked Robert Van Pelt, an adjunct professor at the Institute for Redwood Ecology at Humboldt State University and big tree enthusiast, to comment on BCI’s emblematic tree stature, which held the world record for largest crown:

“The very large base was 13m in one direction, tapering to a 2m cylindrical trunk above the buttressing; ending in a wide crown whose highest leaf reached 47m. What was most remarkable about the BCI tree was the crown spread, which based on 8 crown radii, averaged 60m in diameter. This was by far the largest crown known on the planet for a tree with a single stem. There are several banyans in India and elsewhere larger than this, but none with a single stem. For a self-supporting crown with no cables or other human impacts, I have only ever measured two species to exceed 50m in diameter – Ceiba and Albitzia saman.”

The trunk of the tree is still standing in the center of a huge clearing, a scene of total destruction where no other whole trees are left and the ground is covered in foliage and vines. “This black stuff looks like ash, but it’s rotten wood and termite nest material,” explained Javier Ballesteros as he examined the area of the crown that broke off from the trunk. He and the Fungal Dimensions project team were at the site this week using their Picus Sonic Tomograph to see if individual branches of the tree were rotten as well.

Good-bye Big Tree. You will be missed.

25 years after extreme drought on BCI

from STRI

A new article by Kenneth Feeley from Florida International University, with STRI’s Stuart J. Davies, Rolando Perez and Stephen P. Hubbell and former staff scientist Robin B. Foster (now at the Field Museum, Chicago), was recently published as the cover article of the journal Ecology (April).

The article, entitled “Directional changes in the species composition of a tropical forest”, examines changes in the composition of tree species growing on Barro Colorado Island, Panama, R,P.
Feeley and colleagues show that over the past 25 years there has been a remarkably consistent and directional pattern of increasing abundances of drought-tolerant species at the expense of more drought-insensitive tree species. The cause(s) of this change remains uncertain, but the most likely culprits are either long-term changes in climate leading to reduced water availability (i.e., increasing temperatures and reduced rainfall), or alternatively the compositional changes may be the ongoing legacy of an extreme El Nino drought that occurred in the early 1980’s.

By investigating compositional changes, scientists increase not only their understanding of the ecology of tropical forests and their responses to large-scale disturbances, but also their ability to predict how future global change will impact some of the critical services provided by ecosystems as important as those of the Panama Canal watershed.
You may obtain the article from calderom@si.edu