My first day observing Chinook and Kalluk came chock-full with several moments of awe. The first was upon getting a good look at Kalluk. He’s a young male, less than half of giant panda Gao Gao’s age, and yet the size difference between them is astonishing. Kalluk, as a representative of the largest bear species on the planet, is a towering hulk. Despite his lean frame, I am told he weighs in excess of 850 pounds, or 380 kilograms (compare that to Gao Gao’s mere 160-pound, or 70-kilogram, weight). Resting on his backside in an erect seated posture, he is taller than I am. And when he stands on his rear legs to get a look at something placed up high…well, even NBA stars would have a run for their money looking big next to Kalluk.

I have spent most of my time over the last few years working with the (not so?) giant panda and the sun bear, the two smallest living bears. What factors might account for the great difference in size that we see in the spectrum from these smallish bears to the massive polar and brown bear species? One major contributing factor is the different environmental niches that these species inhabit.

The largest bears are cold weather animals, living in harsh, extreme climates much of the year. Coping mechanisms to deal with cold and its resultant food shortages include hibernation periods, insulating fat deposits to keep the heat in, and (in the case of the polar bear) translucent hairs which aid in conducting sunlight down to the skin to increase heat absorption. But increased size is also a fundamental way of coping with coldness, as the basic principle of surface-to-volume ratios indicates: the larger the body, the smaller the surface area relative to body volume. This reduced surface area ratio allows for a lower rate of heat loss.

Compared to the harsh, cold climates polar bears inhabit, sun bears enjoy warm, tropical habitats. The steamy rain forests from Borneo to Thailand and India were the birthing grounds of this species, and the bear benefited from a smaller size to aid in rapid dissipation of heat to avoid thermostress. But what about pandas? Don’t they typically inhabit snowy, cold mountain passes more closely resembling the habitat of a larger brown bear? Why aren’t they so large?

One answer to this question lies in the evolutionary history of the panda. Long before man came to be so populous in China, pandas could readily be found in the lowlands of southeastern China, at about 1,600 feet (500 meters) above sea level. The panda populations probably expanded and contracted in range many times as the temperature alternately warmed and cooled, with warm weather allowing expansion due to the increasingly favorable conditions for bamboo growth in warm seasons. Thus, at some points in the panda’s evolutionary history, this ancient bear species enjoyed warmer climates and survived well with a smaller size.

Of course, the question of size differences among bears is more complicated than the surface-to-volume picture I have sketched here, but it does provide a partial answer to the wide variety of sizes achieved across the eight living bear species. It even explains some of the differences seen between subspecies, such as the discrepancy between the warm summering grizzly populations relative to their colder cousins, the big Kodiak brown bear. Next time you have a chance to visit your local zoo and observe the bears housed there, maybe you will see their body sizes in a whole new light!

Suzanne Hall is a senior research technician with the San Diego Zoo’s Giant Panda Unit.

This binational collaboration means there is plenty of news happening on both sides of the international border, and that’s why we’re bringing you a one-stop shop for condor news. Visit www.cacondorconservation.org to find out what is happening in the world of the California condor, from The Peregrine Fund’s World Center of Birds of Prey in Boise, Idaho, south to the Chapultepec Zoo in Mexico City and everywhere in between, including the San Diego Zoo’s Wild Animal Park! There is also a link to condor blogs under “Podcasts and Blogs” on the gold bar on the right side of this page.

The Web site is packed with news, photos, video, and personal accounts from the conservationists themselves. There is a fantastic story, for example, from a U.S. Fish and Wildlife biologist who climbed into this year’s first wild condor nest to check on an egg, only to find himself being pushed around by the protective mother-to-be. Video packages take you behind-the-scenes at various locations so that you can experience what it’s like to be a condor expert.

You’ll find bios not only on some of the condor team members but also on the birds themselves. A map will show you where in the world the California condors can be found and you can even report your condor sightings. Best of all, you can ask questions directly of the people who know condors best! Come join the team and post your comments at www.cacondorconservation.org.

There have been a few changes to the viewing areas. Trimming back branches, installing new tree guards, and some replanting helped make the areas ready. A change of scene is great environmental enrichment for any animal, and with the pandas, there’s the added enrichment of the scent of the previous occupant. This is always stimulating and exciting, at least for the four months that the scent will persist. As an added bonus, the keepers have been recycling to the greater good, using old firehoses from the San Diego Fire Department to craft cozy slings, installed in the trees to provide resting places for our growing cub. (Hose feeders, hammocks, and climbing structures are being used as enrichment in many parts of the Zoo with all kinds of animals, a great way to use what might ordinarily be discarded!)

Watching ZZ explore her new area is a hoot. There’s now a bit of water in the pool and, unlike her older sibs, she’s already plowed right in. And much to my surprise, not only was ZZ rolling in the soil beneath the pine tree but Mom was rolling and tree marking as well. Could it be that Bai is loosening up in her middle years? She actually appeared to be enjoying herself, getting dirty and playing with her cub, at least to me. It’s going to be fun watching them as the months go by. The elm tree will soon leaf out, but the slings are lower down and we can only hope that their allure will remain through the summer months, allowing ZZ to be seen more easily by her many fans.

And Gao Gao?? He, too, has settled readily to his “new home,” in the classroom area but that’s no surprise. He’s always been an adaptable guy, hasn’t he? For now he’ll remain off exhibit—think “Spring Break”—but eventually he’ll be rotated out to give his fans a chance to visit him in the viewing area as well. When this happens will be an animal care decision, but we’ll try to keep you all informed as we get more information.

Ellie Rosenbaum is a panda narrator at the San Diego Zoo.

Now some of you may be wondering how on earth this was even considered in the first place; it was a novel idea tried years ago. Originally ia kiddie pool was placed in the bedrooms and filled with water. I must say that it didn’t last too long. From there it received the usual testing of folding, pouncing, and biting. It wasn’t long before the bears discovered the pool made a good polar bear taco (with your choice of bear inside, of course!) or a nice comfy bed in which to take a nap; Kalluk even tried giving Tatqiq rides on it through the bedrooms. Unfortunately, due to the narrower tunnel, that proved to be a bit challenging. Overall, since the pools seemed to be a hit, we went ahead and allowed the bears to have them on exhibit. Again, they delighted themselves with various and creative uses.

Of course this is a “specialty” item because the pools only come out seasonally, and it’s not something they get often. So I figured I couldn’t miss with this enrichment activity. Well, I won’t say it was a complete dud, but it definitely didn’t make the splash I was hoping for. Kalluk (pictured) and Chinook were first up. They both investigated the pools and, as usual, put them in the water (that’s where everything goes). But Chinook seemed to be having one of her lazy mornings and decided to settle down for a nap. Kalluk did eventually end up in the water and did play some, but not specifically with the pools.

I went ahead and did an afternoon switch and put Kalluk back out but this time with his sister, Tatqiq. I knew she wouldn’t let me down. Kalluk apparently decided to take his cue from Chinook earlier, and he settled down for a nap. Tatqiq was intrigued, though, and it wasn’t long before she decided to go for a swim. But do you think it was all about the kiddie pools? Of course not! She played with her small Boomer balls, especially the pink and red ones. Tatqiq at least entertained the guests, but I was beginning to feel deflated from my earlier enthusiasm. (Maybe if I can find a pink pool it would turn out differently!)

At the end of the day, I did the final switch and it was Chinook’s turn again. Maybe her earlier napping left her with more energy, because after she finished exploring the exhibit she decided to have some fun. Now granted, it wasn’t all about the pools, but she definitely put on a show. She wore one like a hat, swam on her back as if she were a turtle in its shell, and—the favorite—got to a higher vantage point and pounced right in the center. So maybe my reinforcement wasn’t immediate, but Chinook did allow me to leave that day not feeling like a total failure.

Kelly Murphy is a senior keeper at the San Diego Zoo.
Read Kelly’s previous blog, Polar Bear Update.

It appears from droppings left overnight that Bai Yun spent some of her time resting atop the cave-like lair in the exhibit during the evening hours. When staff arrived this morning, she appeared relaxed and was content to begin her morning routine. Little Zhen, or “Z” as many staff members call her, was high in the branches on exhibit. Keepers called Bai Yun into the bedroom area so they could clean and restock the exhibit, and Zhen climbed down and followed momma into the building. What a pro!

This happy adjustment stands a bit in contrast to the last time we moved Bai Yun to this area. In December 2005, we moved her, along with Su Lin, into this space. Bai Yun was less calm then, and for nearly two weeks she displayed some level of restless walking or door-directed behavior. This time, there has been little to none of this undesirable behavior. What accounts for the difference?

It’s hard to say. It could be that Bai Yun spent enough time in that area with Su Lin that she now feels very comfortable in that exhibit, making the transition seem like a move to a very familiar space. Perhaps Zhen’s boisterous personality has left Bai Yun more at ease. Maybe this is another indication of momma’s increased maternal experience, reinforcing the notion that Bai Yun no longer seems to sweat the small stuff. Or maybe the issue is cub age: Zhen is three months older than Su Lin was when she moved to this space, and in Bai Yun’s mind that may make all the difference in the world. Whatever the reason, we are very pleased at how well both mom and cub are doing.

Su Lin (pictured) is being housed in the adjacent exhibit, and she has noticed that there are some new neighbors nearby. She has been seen scaling trees to try to catch a glimpse of the goings on next door. She may well get a chance to see her little sister, who climbs up regularly and is beginning to feel at home in some of Su Lin’s old favorite perches. So far, Bai Yun hasn’t shown any response to Su Lin’s presence next door, and if she did, we would probably expect aggression on momma’s part: she still has a youngun’ to protect, after all. She definitely showed such aggression to other offspring when she encountered them post-weaning. Su Lin, though an important bear to Bai Yun in the past, could be perceived as more of a threat now.

Suzanne Hall is a senior research technician with the San Diego Zoo’s Giant Panda Unit.

While all the bears continue to get along and do well, we seem to have hit a lull in our breeding season. In years past, Kalluk has usually reached a point by now where he’s gone off his food, spends most of his day pining for the female he can’t have, and overall is just very difficult to manage. There’s a part of me that is happy to say we’re not experiencing this just yet. Don’t get me wrong: he does have some moments when he prefers to be with Chinook or is choosy about what’s being offered on the menu, but nowhere near as bad as before.

Of course, we do have to keep in mind that this is the first time he’s actually been allowed to have access to a female during the breeding period. Yes, he’s always been with Tatqiq (pictured above), but we have used contraceptives in order to keep her from experiencing her estrous cycle and therefore not get pregnant. Chinook, too, is not showing all the behavior changes that we associate with this process. It may be possible that the actions of the past year have had some type of effect or maybe we’ll experience a later breeding season this year than usual.

Either way, we still allow Kalluk and Chinook time together every day and will continue to do so until their behavior tells us something different. They still have their boxing matches and sometimes curl up and take naps together. We’re pleased, too, that Tatqiq and Kalluk continue to get along and have some good sibling bonding time.

By no means have we given up on Chinook having a successful pregnancy and are still working toward achieving that goal. Plans for a den have been submitted, and now we are just waiting for a start date for the addition to take place. I’m also pleased to announce that it would appear that the Polar Cam is up and running again (at least I’ve had success when I’ve logged on). So, while we wait patiently for things to progress, please continue to watch the days unfold via the Web cam.

Tune in! As many of you know, we celebrate enrichment here at the Zoo during the second weekend of every month. This Saturday I plan on giving the bears a special surprise that I hope (and anticipate) will get some action going!

Kelly Murphy is a senior keeper at the San Diego Zoo.

Here’s a schedule of enrichment activities for March 8 and 9…