The Birds and the Bees and the Fruits in the Trees
It’s ironic that the California flag shows the California grizzly, since the last of these bears died decades ago in this state. To me this symbolizes not only the wonderful native resources of California, but also what can happen if we don’t understand the consequences of our actions, if we aren’t careful, and if we don’t care. In the Andean bear program we’re working with collaborators in Peru for the conservation of Andean bears so that instead of becoming a tragic symbol, this bear remains a vital component of its forest habitats.
Andean bears are vulnerable to extinction from loss and fragmentation of their habitats, as well as poaching. The cloud forests where most of them still live are rugged and covered with dense vegetation—great places to be a bear, but challenging places to be a human. We’re finding it a little easier to study them in the tropical dry forest. This rare forest is still being converted to agricultural fields at a fast rate and we don’t know much about how bears survive there; the more we learn, the more we think these bears are living on the edge of survival.
Several programs of the San Diego Zoo Institute for Conservation Research use camera traps to collect photos of whatever passes in front of them. From these photos we can extract a lot of data, most of which is valuable for our research, and some of which is interesting only to me.
Like many North Americans, I don’t always remain as active as would be best for me, which I notice when I go from the mesas of San Diego to the mountains of Peru. I can tell whether a camera trap photo was taken just after I arrived from San Diego, or whether it was taken after I’d been walking around the field site for a month. Let me just say that my cheekbones are a lot more prominent after I’ve been walking in the hills! Of much greater importance is that camera trap photos provide valuable data, such as which mammals live in an area, and which individual bears live in an area.
In addition, over the last year we’ve realized that by looking at photos of bears collected over long periods of time we can see changes in the body condition of individual dry forest bears. Instead of seeing individuals vary between good condition and rotund, as black bears and brown bears do, as the California grizzly would have, and as I have, we’ve seen individuals vary between good condition and skeletal. This is shocking to see, but over years of photos we see the same individuals gaining and losing weight. This has led us to reconsider what we think of as “normal” condition for a dry forest bear.
Why are dry forest bears so lean? We think they’re lean because there are now relatively few plants that are nutritionally valuable to dry forest bears, and one of the most important of these, the sapote fruit, is available just a few months per year. It appears that when those fruits are not available the bears are forced to diet and lose weight, but when the fruits are available the bears feast and gain weight. In fact, we suspect that feeding on sapote fruit allows female Andean bears in the dry forest to gain weight and become reproductively active, so sapote reproduction may be necessary for dry forest bear reproduction.
This suggests that sapote conservation is critical for conservation of dry forest bears.
We can’t do anything to conserve the legendary California grizzly, but by learning more about the link between the sapote and the bear, we might be able to conserve these bears.
Russ Van Horn, Ph.D., Scientist, Applied Animal Ecology