Favorite Andean Bear Food: Sapote

Some of these sapote flower buds may develop into food for Andean bears, Sechuran foxes, and other wildlife.

Some of these sapote flower buds may develop into food for Andean bears, Sechuran foxes, and other wildlife.

In conservation research, we’re often interested in measuring variation across space and time, looking for patterns in that variation and deriving explanations for those patterns. However, during my last trip to the field, I found myself pondering changes over time on a much longer scale, across over 1,000 years. As I walked under the hot sun dragging a tape measure through the brush day after day, and I started stepping over ancient stone walls, it was easy to start wondering about the original purpose of the walls, even though that had nothing to do with the task at hand!

What I should have been totally focused on was making sure that we were correctly measuring the distances between trees in the tropical dry forest of northwest Peru. As part of the Andean bear conservation program, I was there working with the Spectacled Bear Conservation Society and with local citizen scientists (see post Citizen Science: Engaging People in Conservation Research). With support from the Disney Worldwide Conservation Fund, Samantha Young and I have been developing several initiatives to engage local people in conservation science and action (see Scientific Concepts for Non-scientists). One focus of my trip was to train citizen scientists in collecting data from woody plants, because we’re interested in knowing more about how plants that are important for Andean bears vary in space and time. In particular, we’re interested in understanding the variation in when and where sapote produces flowers and then fruit, because sapote fruit appears to be the critical food source for Andean bears in the dry forest of northwest Peru (see Andean Bears: A Surprising Discovery).

To get information on the sapote population, we measured little trees...

To get information on the sapote population, we measured little trees…

Although sapote is considered critically endangered, there have not been many studies done on its reproductive ecology, so we can’t simply visit a field site and estimate how much fruit the sapote trees there might produce or how many bears might be supported by those trees. So, our goal is to collect information every month, such as which trees have flowers, which trees have fruit, and the condition and size of those fruit. Because we don’t have any background information on these sapote trees, we’re going to learn something new practically every month. For example, during our first data-collection period we discovered some individual sapote with a few ripe fruit left from this past season and several new flower buds. I had no idea that the same tree might have both flowers and fruit at the same time!

...and we measured big sapote trees.

…and we measured big sapote trees.

Another new observation with more serious implications for bears and other wildlife that feed on sapote fruit is that sapote grows only in a narrow band on the lower slopes of the hills at the edge of the valleys. We knew this generally, but we had never measured the width of this strip; it’s much narrower than we thought, meaning that there’s less area covered by sapote trees than we expected, and, presumably, fewer sapote trees. Over the next several months, we’ll begin to get an idea of how many flowers and fruits those trees produce and how that production varies depending on characteristics of the sapote trees and the places where they’re living.

Although we’ll be looking at variation in flower and fruit production across relatively small-scale changes in space and time, especially in comparison to the scale of the landscape and the scale of human history in this area, these are the data we’ll need to understand variation in sapote and in Andean bear ecology.

Russ Van Horn is a scientist in the Applied Animal Ecology Division of the San Diego Zoo Institute for Conservation Research.