This is a camera trap photo of the female Andean bear Magaly on December 7, 2009, when she was thin and in poor condition, before many ripe sapote fruit were available.
It was about 16 months ago when I first saw an Andean bear in the dry forest of Peru during the Southern Hemisphere winter. When I did, I was shocked. As this bear walked down the hillside toward a waterhole I could count her ribs, I could see her backbone, and I could watch her hipbones moving. Her fur was dull, and I could hardly believe how bad she looked. My colleagues had told me that the bears living in the dry forest were thin during the winter because there wasn’t much for them to eat, but I didn’t know the bears became THIN! The only other wild bear I have ever seen so scrawny was an American black bear I encountered many years ago in southwest Montana; that bear had become dependent on food it obtained from people, and it began starving when it no longer had access to the supplemental food.
This is a camera trap photo of the same female Andean bear, Magaly on April 29, 2011, after she’d become plump by feeding on sapote fruit.
When I expressed my concern over the skinniness of the dry forest bear to the field team of the Spectacled Bear Conservation Society (SBC), they told me that they had seen bears in the dry forest that looked even worse than the bear I was watching but that had nevertheless survived. In reality, I was shocked only because I didn’t have much experience in the dry forest; that bear was not unusual. She not only survived, but she mated a few months later and is now raising a young cub. Skinny dry forest bears look shocking to people who don’t have experience in the dry forest, but in fact their weight loss is part of a natural cycle that becomes obvious to anyone who studies dry forest bears for more than a year.
This is a portrait of nearly ripe sapote fruit still on the tree when there were ripe sapote fruits lying on the ground beneath the tree, and when bears were foraging on sapote fruits. We hypothesize that fruits like this one are critical for the survival of individual bears, and the bear population, in the dry forest.
Working with SBC in the dry forest, we’ve accumulated evidence over the last several years that Andean bear movements and body condition are linked to a species of tree, the sapote. Evidence from direct observations, camera traps, and satellite telemetry collars all suggests that bears focus their movements and foraging on sapote fruit when it is available, which is usually only for two to three months just before the annual rainy season.
After ripe sapote fruit become available, usually beginning in late November, the bears’ body condition improves noticeably, so that within a few weeks the bears no longer look like walking skeletons. After a few more weeks of feeding on sapote fruit, the bears start to look a little plump, although they never get as fat as American black bears and brown bears do in autumn. During the rest of the year when sapote fruit is not available, Andean bears in the dry forest gradually lose weight so that they are skinniest just before the sapote fruit is ripe. These observations strongly suggest that healthy populations of sapote trees are critical for the health of individual Andean bears in the dry forest and for the health of the dry forest bear population. The sapote tree is considered critically endangered by the Peruvian government, so we’re promoting conservation of sapote trees as part of the Andean bear conservation program.
A camera trap photo shows male Andean bear Russ on December 5, 2009, when he was thin and in poor condition before many ripe sapote fruits were available.
This is a camera trap photo of the same male Andean bear, Russ, on March 21, 2011, after he’d gained weight by feeding on sapote fruit.
The field team is seeing something unusual right now that may answer a question that’s been puzzling me for over a year. Young cubs and subadult bears often disappear when their mothers are skinniest, shortly before the sapote fruit ripens. We suspect that, unfortunately, when adult bears have a hard time finding food, many young bears do not survive. If that happens year after year, how can the population of bears in the dry forest remain stable? This year some sapote fruits are ripe earlier than normal, and some bears are starting to gain weight earlier than usual. This makes us hopeful that this year more cubs and subadult bears will survive. Of course, the survival of youngsters may depend on what the sapote trees do over the next few months, which reminds me of other questions we have. Why do sapote trees produce fruit when they do? What influences how many sapote fruits are produced? There has been a little research done on these questions, but we’ve still got some work to do to fill in the blanks!
Russ Van Horn is a scientist with the San Diego Zoo Institute for Conservation Research, leading our Andean bear conservation program. Read his previous post, Mountain Lions and Palm Trees.
For more information about the seasonal fluctuations in resources such as sapote and the need to conserve them, see posts Dry Forest Bears of Peru and To See a Bear.
Thanks for the blog Russ. The before and after pictures are unbelieveable. Can anything be done to improve the situation?
As far as we can tell, this cyclical weight change is a natural phenomenon, and it doesn’t appear to be an obvious source of mortality for adult bears. What this cycle suggests is that the sapote fruit is critically important for the bears at our dry forest study site, so the first step will be to try and preserve all of the existing sapote habitat. One possible next step would be to determine where sapote once grew but doesn’t now and assess whether it might be possible to reestablish sapote in those places.
Russ, thanks so much for posting. Would any one be interested in determining where sapote once grew and whether it was possible to reestablish it in those places. The photos are startling, and it’s not the first I’ve heard of such a thing. Again, thanks…keep giving us info. Joyce
At present, none of us involved in the dry forest bear program have the necessary experience in plant husbandry to start a reforestation project. However, in the next year we’re hoping to incorporate additional researchers and projects into our program, including a quantitative evaluation of where sapote once grew and how best to reestablish sapote.
Russ, Curtis and I are always glad to see your posting updates. I got very curios and read all I could about the zapote: Capparis scabrida. 19%protein! I thought it interesting that its climatic requirements are compared to the Prosopis-algarobo blanco and that the flowering and fruiting season is affected by the Nina (ninya).
Tell the bears! Take care, Joy
Fascinating pictures! I have always been intrigued by the ability of many different mammals to go through extreme body mass cycles, but I would have never expected to see this in the Andean bear. I am also struck by how valuable camera traps are in providing key pieces of data such as this. Good luck with the next steps in your conservation efforts, and I hope this will be a good year for the youngsters!