July 20th, 2012 by

Usually, when we talk about trees and wildlife, we emphasize how important trees are to the animal’s survival. I never knew before working here that the reverse could also be true — that trees would be relying heavily on animals for their survival. New studies are revealing that small rodents known as agoutis are a key to the survival of many trees in Central and South American rainforests.

Colorful seeds of a palm tree in Florida.

Colorful seeds of a palm tree in Florida. Credit: James Albright (greyhound dad)/Flickr

Because plants and trees are fairly stationary, they rely on outside factors for seed dispersal to continue their lines. Some of the methods of transportation include self-projectile mechanisms, wind, water and animals. Some seeds have hooks and burrs to attach to the fur of animals; some hitch a complimentary ride inside the animal, as an enjoyable fruit or snack. The issue with the trees in the American tropics is that the seeds are so large that it is unlikely that animals can swallow them. So how are they being transported from their parent tree and ensuring future generations?

Many years ago, ancient elephant relatives known as gomphotheres roamed these tropical regions, eating the large fruits and passing them as they traveled from place to place. When these mammoth creatures became extinct, the land became inhabited by smaller animals, who have found other ways of spreading the seeds of these trees that rely on seed dispersal for their survival. As scientists recently discovered, the thieving agoutis go around uncovering and stealing each other’s buried seeds and transporting them to areas they would never naturally reach.

An agouti enjoys some fruit in Playa del Carmen.

An agouti enjoys some fruit in Playa del Carmen. Credit: The Sean & Lauren Spectacular/Flickr

In one of the first studies of its kind, researchers from the Smithsonian Tropical Research Institute led by Patrick Jensen studied the black palm on Panama’s Barro Colorado Island by not only radio tracking the potential seed-dispersing animals, but also the seeds themselves. Jensen’s team followed 589 black palm seeds, which had the fruit already scraped off, and 16 agoutis, while also having remote cameras on 154 of the agoutis’ seed supply locations. What they found out was that many of the original seeds were stolen, buried and then stolen again by another thieving rodent. Over the course of a year, one of the palm seeds was hidden 36 times and traveled more than 2,460 feet, eventually being eaten 920 feet from its parent tree.

How beneficial is this for the trees? Without these large rodents, it is likely that certain tropical tree species could become extinct. In the case of the black palm, the agoutis may be carrying the fate of the trees in their paws. Without the wide-spread dispersion of seeds, only a small percentage of the tree’s fruit will become new trees with little chance of survival or future.