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Big Changes for Little Bears

Xiao Liwu is working on his motor skills.

In recent weeks, a lot has been happening with our bear population at the San Diego Zoo. In particular, some of our smallest bears have been undergoing significant transitions to their daily routine.

Our panda cub is preparing for his debut on exhibit. For him, this is a natural progression as his skill set advances, and he becomes more agile. A month or so ago, Xiao LiWu was a fairly immobile little bear, content to sleep for hours inside the den while his mother stretched her legs in other areas of the facility. Now, his ability to crawl has transformed into good walking skills, and he is ambling around regularly.

Recently, the cub walked, on his own, a good distance toward the north exhibit where he will first meet his admiring public. He got nearly to the door of that exhibit when he encountered a barrier: a slider door in the open position jutted into his travel path about a foot. He investigated the slider and pressed up against it, spending several minutes working the problem this obstacle presented. Ultimately, he couldn’t quite figure out how to go around, as his mother had done on her pass through the tunnel. Deterred, he turned around and headed back to the den for a nap. Before he is regularly on exhibit, he will have figured out how to overcome little adversities like this one.

Our other small bears, the sun bears, have also undergone some transitions in the last few weeks. After unsuccessful pairing attempts for Marcella and Francis earlier this year, we moved Francis to an off-exhibit area where he could receive lots of human attention and training opportunities. The quiet time away from public viewing seemed to serve him well, and he slowly settled into a nice routine. In the fall, we began to acclimate him to a new exhibit near the foot of bear canyon, an area some of our other bears had done very well in. With a slow-moving protocol, we were finally able to get Francis comfortable being on exhibit.

In December, we moved Marcella out of the exhibit on Sun Bear Trail and placed her adjacent to Francis in an exhibit on Center Street. We want her close by the male should she cycle again, but we didn’t want to move Francis away from a place he seems comfortable in. Thankfully, Marcella has been quite adaptable with moves like this, and she is settling in fine. Shortly after her move up the hill, keepers noted that Francis seemed more willing to accept Marcella in his new space. He has even started bringing her gifts, leaving his enrichment objects at the gate that separates him from his potential mate. In time, we hope that this builds into an acceptance of Marcella that promotes successful breeding between our sun bears. It is important for them to try again, as no sun bear cubs have survived more than a few days in the US since the birth of Marcella’s twin cubs nearly five years ago.

As the year winds down, we expect these recent changes will help our bears settle well into the next phases of their lives. We are hopeful that the New Year will be good to our animals, as Xiao Liwu grows into a robust little panda, and our sun bears will (fingers crossed) succeed in breeding. I would also like to extend my warm wishes to you for a happy holiday season and a peaceful transition to a new year.

Suzanne Hall is a senior research technician for the San Diego Zoo Institute for Conservation Research. Read her previous post, Perfectly Panda.

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Sun Bears: Weaning Options

If you are a San Diego Zoo member, you have already received your copy of June’s ZOONOOZ magazine. Our sun bears are highlighted this month, with sun bear dad Dibu on the cover! Flip through the pages, and you will see photos of Marcella and her offspring Palu and Pagi, and watch video of them, too!

Although we miss Pagi, who is reportedly doing well in her new home at the Oakland Zoo, life goes on in our Sun Bear Forest. Marcella and Palu are back out on exhibit, and you can see them daily (see Sun Bears: Up in the Air). Palu, in particular, seems very happy to be able to climb, explore, and stretch his limbs again. He’s still a growing boy, and very active.

We haven’t yet developed a plan for weaning Palu from his mother. Certainly he is of an appropriate age to be weaned, and obviously Pagi has already moved on to a new stage of independence. However, Palu’s situation is different from his sibling in that he is not yet slated to move to another facility. If we separate him now, he would remain at the San Diego Zoo in the near term, and that presents some challenges for us.

Those of you who have visited our Zoo know that we have a very robust population of bears. We are one of the few zoos in the world that has six species of bears exhibited: pandas, polars, brown, Andean, sloth, and sun bears. Bear Canyon is pretty full, and we don’t have any open, unused, bear-friendly exhibits to move Palu to. That means that once he is separated from his mother, he would remain at Sun Bear Forest, where he would need to rotate exhibit time with Marcella.

Rotating animals on exhibit is a common practice. It allows animals to have some time out in the larger open space of the public enclosure, where they get exercise and sunshine. It allows them time in the back, where they get some privacy and closer inspection by their keepers, important for observing changes in their health status or growth pattern. It keeps incompatible animals apart, important for non-social species or aggressive individuals.

Zoo-wide, there are a number of animals that share exhibit time with others via a rotation schedule. Our aged Manchurian brown bear, Blackie, recently began rotating with the younger grizzly bears to allow the youngsters more room to roam when on exhibit and ensure old Blackie gets plenty of peace and quiet behind the scenes (see Brown Bear Changes). Our giant pandas, solitary by nature, have long rotated through our two primary exhibits to allow the public to see all of our individual animals. Not since Hua Mei was dependent upon her mother have we had enough exhibits to house all of our pandas, so rotation has become a fact of life at the panda facility.

In Palu’s case, we have an even better option than rotation: delay weaning. In choosing this option for the time being, both bears get daily exercise during their time on exhibit. They also continue to enjoy each other’s companionship under this option. We are happy to note that, unlike Marcella’s first-born son Danum, Palu is not aggressive and demanding of his mother. The dynamic between them allows us to consider this option, whereas with other individuals it may not be possible to extend this relationship.

Further, at some zoo facilities in Europe, it is common practice not to wean young sun bears from their mothers, especially females, until they are of breeding age. In those cases, the young female is even introduced to a social relationship with her father, as the three bears are housed together when their personalities permit it. Thus, there is precedent for multiple generations of related bears being housed together in this species.

We need not be concerned that Palu will attempt to breed with his mother any time soon. We expect he will not reach sexual maturity for several more years. Long before then, we will have found a new home for him and weaning will take place. Or, a new male will have moved to San Diego to breed with Marcella, necessitating the removal of Palu from the social mix. Weaning will happen some day, but for now, mother and son will continue to remain a pair on exhibit. We hope you find them as interesting to watch as we do!

Suzanne Hall is a senior research technician for the San Diego Zoo’s Institute for Conservation Research.

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Big Little Bears

Siblings Palu, left, and Pagi

I visited with our sun bears this morning (see previous post, Sun Bears: Latest Developments). I am amazed at the size of Palu, our male youngster. He is only 15 months old, but he now weighs in at 88 pounds (40 kilograms), making him slightly heavier than his mother, Marcella. For her part, Marcella is still longer than her cubs, but Palu is a big boy with a broad head belying a solid bone structure. I wonder where he will top out with respect to weight. His father, Dibu, who now resides at the Columbus Zoo, approached 132 pounds (60 kilograms). I think Palu is well on his way to being as large as his daddy.

Palu, Pagi, and Marcella are Bornean sun bears, one of two recognized sun bear subspecies. The Bornean is supposed to be smaller than the other subspecies, the Malayan. However, our Borneans are on the larger side, approaching the weight of some of their Malayan counterparts. This has caused more than one wild sun bear researcher to do a double-take and ask if we are in fact sure that our bears are Bornean!

I have seen some weight data from young, wild-born Bornean bears. Fifteen-month-old bears have been recorded to be between 50 and 64 pounds (23 and 29 kilograms), more than 10 kilos lighter than our boy Palu. Our female cub, Pagi, is also a little bigger than these wild counterparts. What accounts for the size difference we are seeing?

The stresses and strains of living in the wild no doubt contribute to some of the lower weights recorded from wild Bornean bears. As emphasis, all of the weight values I have seen are from orphaned bears, which at various times in their young lives were living without any maternal support before being brought into a captive environment. Without mother’s milk and having experienced some period of famine, their growth was likely to have been impacted to some degree. Fortunately, this type of stress is unknown to Palu and Pagi.

Another factor in the difference in weights is likely to be environment. The Bornean sun bear inhabits a tropical evergreen home range in which food is typically abundant year round. Feeding on fruits and insects, the Bornean bears make adjustments for which trees are fruiting in their areas, but typically don’t have to worry about dramatic seasonal changes to food abundance, as a polar or brown bear might. Despite this fairly stable food source, wild bears simply have to work harder for their meals than do bears in zoos. Pagi and Palu are still nursing a few times each day, and they get additional food supplementation from the keepers. Marcella, too, benefits from regular food rations, allowing her to endure the energy drain of lactation with less stress to her body than a wild female, who must always be looking for her next meal.

What’s more, unlike their wild counterparts, our Borneans don’t have to worry about occasional variations in fruit abundance. In Borneo, the El Nino/Southern Oscillation may be responsible for large, simultaneous fruiting events in which food becomes very abundant. During this time the bears eat well. However, the mass fruitings are often followed by a period of low food abundance, when bears need to work harder to eat. Another factor impacting wild bears is destruction of habitat, which makes finding your next meal that much more difficult. Loss of habitat is a critical threat to the bears of Borneo, as the forests are logged and cleared for the development of palm oil plantations.

Finally, there may be a genetic factor at play here, too; Marcella and Dibu may simply be on the large size for Bornean sun bears. Certainly, I can’t imagine Marcella weighing 10 kilos less than she does currently; she would be skin and bones. She’s a very healthy girl around her current size.

Whatever the reason, our bears are happy and healthy, and the cubs are growing into robust and capable individuals. Which is good news, whatever their size!

Suzanne Hall is a senior research technician for the San Diego Zoo’s Institute for Conservation Research.