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What to Eat When There’s Nothing to Eat?

Bear ambassador Mi Ton Teiow finds relatively shallow snow, but no food, as the northern winter begins.

Bear ambassador Mi Ton Teiow finds relatively shallow snow, but no food, as the northern winter begins.

The answer? Nothing.

Most of us are familiar with the idea that some bears spend long periods of time in dens, inactive and not consuming significant amounts of food or water. Some bears in some locations survive eating nothing by doing almost nothing. They become inactive, which is sometimes called winter sleep or hibernation. Although you may be familiar with this aspect of bear ecology, have you thought about how incredible it is? These big mammals can go without eating or drinking for months, sometimes while birthing and nursing cubs, yet wake up without bedsores or weakened muscles! This is why the physiology of bears, including that of giant pandas and polar bears, has been a hot field of research.

The only way for a wild American black bear to survive for months without food in the northern U.S. is to save energy by hibernating in a safe, insulated den. The hole to the right of the tree trunk is the only obvious indication that there is an American black bear below the snow.

The only way for a wild American black bear to survive for months without food in the northern US is to save energy by hibernating in a safe, insulated den. The hole to the right of the tree trunk is the only obvious indication that there is an American black bear below the snow.

Although all female bears seclude themselves in dens to give birth to cubs, not all bears enter dens for long periods of time. There’s even variation within species in whether or not individual bears remain in dens or for how long. Researchers have found that in general, bears spend long periods in dens not to avoid cold temperatures, but to reduce their metabolic requirements when there is not enough food to survive environmental conditions. So, in the southern part of their range where their energy balance can remain positive, individual brown bears, Asiatic black bears, and American black bears may not den except to give birth. At last year’s meeting of the International Association for Bear Research and Management (see post, A Whimsical Bear Ambassador Arrives), Lorraine Scotson and Dave Garshelis reported that some sun bears might den for periods of time in the most northern parts of their range, meaning that non-reproductive denning may occur among at least half of the world’s bear species.

The holes melted in the snow are made by the black bear’s respiration.

The holes melted in the snow are made by the black bear’s respiration.

The giant panda is one bear species that has not been known to den in response to a relative lack of food, and perhaps it cannot do so. During the rare times when all the bamboo plants in an area have flowered and then died, the giant pandas have left the area in search of food; they have not entered dens. Perhaps this is because a bamboo die-off is unpredictable from the giant panda’s point of view, or perhaps this is because a giant panda eating bamboo cannot build up sufficient energy reserves to be able to wait out the lean time in a den, or maybe both factors play a role.

Adult polar bears also do not enter dens solely to avoid food shortages. Pregnant polar bears do spend prolonged periods of time in dens, but biologists think other adult polar bears don’t do so. However, polar bears in some populations regularly fast for extended periods when sea ice conditions don’t allow them to hunt. As for other bears, anything that causes a polar bear to expend more energy, whether inside or outside of a den, or to fast for a longer period of time, makes it less likely that the bear will survive. Climate change is doing just that by reducing the amount of sea ice available to polar bears: the bears expend more energy and go without eating for a longer period of time, creating a great challenge for the conservation of this species (see Polar Bears, Climate Change, and Mi Ton Teiow).

Hibernating bears often line their den with leaves, twigs, and grasses, insulating themselves from the cold ground and conserving additional energy.

Hibernating bears often line their den with leaves, twigs, and grasses, insulating themselves from the cold ground and conserving additional energy.

The Bear Specialist Group’s Ambassador Mi Ton Teiow recently made a visit to the northern US, where he found plenty of snow but little food for bears. After a short stay in this area, which receives an average of 45 inches of snow per year, the ambassador returned (fled?) back to sunny San Diego, where the last measurable snow fell on the city in 1967. The odds are good that Ambassador Mi will not be snow camping in San Diego any time soon.

Russ Van Horn is a scientist with the San Diego Zoo Institute for Conservation Research. Read his previous post, Courtship in Front of the Camera.

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Polar Bears, Climate Change, and Mi (Ton Teiow)

Tatqiq's wild counterparts need more snow days.

Tatqiq’s wild counterparts need more snow days.

Mi Ton Teiow, the whimsical “bear” ambassador for the IUCN’s Bear Specialist Group (see post A Whimsical Bear Ambassador Arrives), has continued his travels, along with staff from the San Diego Zoo’s Institute for Conservation Research. With these travels, Mi is gaining experience in the multi-faceted world of bear conservation, which often includes extended periods of sitting and talking! While Mi might be anxious to get outside and do field research, our bear ambassador also understands that bringing people together to discuss the nuts and bolts of bear conservation is an important, and necessary, part of the process.

Recently, Mi traveled to the Toledo Zoo to sit in on the annual meeting of the Polar Bear Species Survival Plan (SSP). The role of the SSP (for polar bears or any other conservation-dependent species) is to bring together experts from zoos around the country to ensure that the members of the zoo community are being as effective as possible in supporting conservation efforts for the species. The focus of this SSP meeting was to enhance the synergy between zoo-based research, field-based research, and effective polar bear conservation. Speakers from the U.S. Geological Survey and researchers from the San Diego Zoo, Cincinnati Zoo, and Memphis Zoo presented overviews on current research and results, as well as ideas for the future.

Mi (center) and Megan (standing second from the right) pose with other members of the Polar Bear SSP.

Mi (center) and Megan (standing second from the right) pose with members of the Polar Bear SSP.

While listening in on discussions regarding conservation research, Mi also learned about the primary threat to polar bears: greenhouse gas emissions resulting from human activities have led to measurable and rapid changes in global climate patterns. The degree and character of these changes is not uniform, and different regions, ecosystems, and species are being impacted in different ways. When it comes to climate warming, scientists have documented the greatest degree of warming at the Earth’s polar regions.

This is bad news for the polar bear, because increases in both air and ocean temperatures in the Arctic have resulted in rapid losses of sea ice over the past several decades. Polar bears depend on the sea ice for their survival. Without the sea ice, polar bears cannot feed themselves or reproduce successful. This dependence on sea ice has left polar bears vulnerable to extinction in the face of climate change.

While the situation is critical for polar bears, it is not hopeless. Each and every one of us has the ability to help save polar bears by making small changes in our daily lives, such as turning off unneeded lights and riding our bikes more, to reduce our carbon footprint along the way. Because zoos have tremendous access to a large number and wide range of people, we play a critical role in polar bear conservation. As a conservation organization, we are responsible to get the word out, and we are happy that we were able to share our work with ambassador Mi Ton Teiow.

Megan Owen is an associate director for the San Diego Zoo Institute for Conservation Research.
Read about Ambassador Mi Ton Teiow’s previous adventure in Black Bears: A Conservation Success.

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Black Bears: A Conservation Success

There are American black bears in Zion National Park. Ambassador Mi Ton Teiow, the special traveling “ambassador” of the Bear Specialist Group, paused for a photo here.

There are American black bears in Zion National Park. Ambassador Mi Ton Teiow, the special traveling “ambassador” of the Bear Specialist Group, paused for a photo here.

After the recent meeting of the IUCN’s Bear Specialist Group and the International Association for Bear Research and Management in Provo, Utah, I explored some bear habitat between Provo and San Diego and was reminded that one bear species in North America is an example of great conservation success: the American black bear. The IUCN (International Union for Conservation of Nature) maintains the Red List of Threatened Species, which is a global list of species and their conservation status. The American black bear Ursus americanus is listed as a species of Least Concern, primarily for two reasons. First, overall there are a lot of black bears. There may be twice as many American black bears as all the other bears in the world combined! Second, most populations of American black bears are stable or increasing, making this a great story of how a species can recover through conservation action and human tolerance. Some local black bear populations are not doing very well, but overall the prognosis for the species looks fantastically better than it did 100 years ago.

When European settlers reached North America, black bears were found throughout much of Canada, the US, and northern Mexico. There are once again black bears in most of those areas. However, there was a great decline in the number and range of black bears until the early to mid-20th century. In fact, I think that if the IUCN Red List had existed 100 years ago, the reduction in numbers and range of the American black bear would have led it to be listed as Endangered, which is the same category of conservation concern as the giant panda is now!

What led to such a dramatic decline in American black bears? The main causes were habitat loss, habitat fragmentation, overhunting, and conflict between humans and bears. These are the same issues that still threaten most of the other bear species. It’s taken decades and a lot of effort by many national, state, and provincial governments, conservation organizations, scientists, educators, and citizens, but the recovery of the American black bear illustrates that conservation of bears can succeed.

How did the recovery happen? A wide variety of actions were taken in support of American black bear conservation, including habitat protection, changes in bounties and hunting laws, changes in programs mitigating human-wildlife conflict, and more intensive efforts such as translocations and reintroductions. It’s also helped that this bear is an omnivorous habitat generalist, so although it is restricted to forested habitats, it can and will learn to eat a wide variety of foods, and it can live in fairly dense populations. That means that a population of American black bears can survive in an area that would be too small to support a population of brown bears.

Researchers with San Diego Zoo Global have collaborated with others to investigate various aspects of the physiology and behavior of American black bears, both to understand this species better and as a means to better understand other bear species. Doctors Barbara Durrant and Tom Spady have described the seasonally polyestrus, promiscuous mating system of the American black bear, showing that ovulation and conception occurs in each of a black bear female’s estruses during a breeding season. DNA analysis of preimplantation embryos proved that if a female mates with more than one male during the same mating season, the cubs born in her litter may be maternal half-siblings and not full siblings. Barbara and Tom also investigated the potential use of the hormone leptin as a wildlife management tool to monitor the adiposity (fatness) of American black bears and found that serum leptin measurements markedly improved the resolution and accuracy of common field estimates of body condition in this species.

A sign in the Olympic Peninsula of Washington reminds people hiking and camping in the forest that their behavior can have negative consequences for bears.

A sign in the Olympic Peninsula of Washington reminds people hiking and camping in the forest that their behavior can have negative consequences for bears.

Did you know that bears hum? Megan Owen has worked with others to study humming by bears, which occurs in all bear species but the giant panda. Most humming is done by cubs and is generally associated with suckling; however, the exact function of this behavior is still unknown. The relative loudness and very persistent nature of humming are puzzling! Further, we still don’t know whether the hum is an acoustic signal or whether its associated vibration physically stimulates the mother, perhaps enhancing milk production. Megan has also researched the interactions between mothers and their young cubs, in hopes of developing a better understanding of maternal care behavior and the range of variation associated with maternal care and cub behavior. Understanding this process in black bears may help us better understand the process in other bear species as well, including brown and polar bears.

Although the overall picture looks good for American black bears, as populations of both bears and humans have grown, new conservation challenges have developed. Because American black bears are fairly quick to learn to feed on new food sources, whether or not those food sources are “natural,” black bears learn to feed on foods they get from humans, whether the humans want them to or not. This leads to new conflicts as the bears use their intelligence and strength to seek the most profitable food source available. If you are fortunate enough to live or recreate in bear country, you can help bears and bear conservation, and avoid damage and risk from food-habituated bears, by ensuring that bears don’t get access to any human sources of food. That includes foods like pet foods, seed in bird feeders, greasy barbecue grills, garbage, etc. With your help, the support of citizens like you, and effective conservation actions, the American black bear can continue to be a great conservation success story.

Russ Van Horn is a scientist with the San Diego Zoo Institute for Conservation Research. Read his previous post, Whimsical Bear Ambassador Arrives.

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Whimsical Bear Ambassador Arrives

Ambassador Mi travels the world in an effort to aid in the conservation of bears.

Ambassador Mi travels the world in an effort to aid in the conservation of bears.

There are eight bear species living today, and, until recently, the San Diego Zoo hosted ambassadors for five of them. We’re happy to announce the arrival at San Diego Zoo Global of another bear ambassador: Ambassador Mi Ton Teiow, also known as Traveling Bear. Ambassador Mi represents all eight living bear species as the special traveling ambassador of the International Union for the Conservation of Nature’s (IUCN) Bear Specialist Group (BSG). As such, Mi travels “to gain worldly experience and aid in bear conservation endeavors” and to promote the conservation of bears.

Ambassador Mi was “born” in the Lao People’s Democratic Republic and has since traveled to Canada, South Korea, India, Venezuela, and the US (Minnesota). Mi was officially posted to the San Diego Zoo Institute for Conservation Research (ICR) at the recent conference of the International Association for Bear Research and Management in Utah, and plans are underway for Mi to travel with our staff both internationally (China, India, and Peru) and within the US before traveling to Greece in October 2014. This bear gets around!

Although you may never have heard of the IUCN or the BSG, these are among the most credible international groups for the conservation of wildlife, and bears. The IUCN is the world’s oldest and largest global environmental organization, composed of more than 1,200 member organizations, including more than 200 governmental and 900 nongovernmental organizations. The BSG is one part of the IUCN, and it is made up entirely of more than 200 volunteer scientists from around the world. Several of our scientists are part of the BSG in various Expert Teams, including Ron Swaisgood (co-chair, Giant Panda Expert Team), Megan Owen (member, Captive Bear Expert Team), and Russ Van Horn (member, Andean Bear Expert Team). Many Institute staff members belong to other Specialist Groups within the IUCN (e.g., the Iguana Specialist Group, the Tapir Specialist Group), providing technical advice and mobilizing action for the IUCN as it works to “find pragmatic solutions to our most pressing environment and development challenges.”

Ambassador Mi Ton Teiow of the BSG was officially posted to the delegation from the San Diego Zoo Institute for Conservation Research on 17 September, 2013. From left to right: Megan Owen (ICR, BSG), Lorraine Scotson (BSG), the author, Ron Swaisgood (ICR, BSG), Barbara Durrant (ICR), Dave Garshelis (BSG), and Emre Can (BSG). Photo credit: Dr. Mei-hsiu Hwang, National Pingtung University of Science & Technology and the Taiwan Black Bear Conservation Association

Ambassador Mi Ton Teiow of the BSG was officially posted to the delegation from the San Diego Zoo Institute for Conservation Research on September 17, 2013. From left to right: Megan Owen (ICR, BSG), Lorraine Scotson (BSG), the author, Ron Swaisgood (ICR, BSG), Barbara Durrant (ICR), Dave Garshelis (BSG), and Emre Can (BSG).
Photo credit: Dr. Mei-hsiu Hwang, National Pingtung University of Science & Technology and the Taiwan Black Bear Conservation Association

Now, all of this probably sounds pretty bureaucratic, dry, and abstract, which might be part of why you can’t remember ever hearing of the BSG or the IUCN in spite of their conservation significance. However, given Mi’s colorful personality, willingness to put up with inconvenient travel without complaining, and hardiness in the face of harsh field conditions, we hope you’ll find Mi’s adventures to be enjoyable, memorable, and educational about bear conservation. Mi’s earlier travels have included a visit to the den of an American black bear, participation in technical scientific conferences, representing the BSG at the World Conservation Congress during a debate on curtailing bear farming, hiking to the highest point in South Korea, and waterskiing. Welcome to San Diego Zoo Global, Ambassador Mi Ton Teiow!

Russ Van Horn is a scientist with the San Diego Zoo Institute for Conservation Research. Read his previous post, Andean Bears and Their Favorite Food: Sapote.