Summer is finally here in San Diego, and the polar bears are ecstatic. With the grand opening of the new Polar Bear Plunge exhibit at the San Diego Zoo, these great white bears of the North are lounging in style by the side of their Olympic sized pool. Their relatives up North however aren't faring so well. With global climate change melting polar ice caps at an alarming rate, polar bear habitats are rapidly disappearing and the fate of this Arctic icon is slipping away.  

The San Diego Zoo's Institute for Conservation has been tracking polar bear populations for decades, examining the impact of human activity on their health and behavior. Their discoveries have guided conservation efforts around the globe and continue to shape the future for these snowy behemoths. Showcasing these findings, the new Polar Bear Plunge exhibit updates the public on a rapidly deteriorating situation.

“In 1996, when we first built Polar Bear Plunge, there was no concern for loss of habitat because we didn't know it was happening... it wasn't even on the radar. We thought polar bears were fine,” says Rick Schwartz, a keeper and ambassador for the San Diego Zoo. “With years of doing studies up in the Arctic on polar bears our scientists and our researchers have come back showing us that the habitat is changing drastically. As a research and conservation organization, it is our responsibility to tell people what is going on with these animals in the wild, not just exhibit them.” Revamping the guest experience into a family friendly, interactive and engaging adventure, the new Polar Bear Plunge familiarizes the public with the plight of the polar bear and motivates action to save these charismatic creatures.

The Plight

The shrinking of polar ice caps over the last 30 years has exceeded even the most dire predictions by climate scientists. In 2007 alone, 1 million square miles of ice were lost and some predict that the Arctic will be ice-free during summer months by the year 2030. For polar bears, this is practically a death sentence.

Multi-year ice is particularly important, providing a year round stable platform that polar bears depend on for hunting. Waiting patiently for hours until a Ringed Seal emerges for a breath of fresh air, the polar bear strikes swiftly to snatch a meal. During the winter months, when ice is plentiful, the bears chow down as much as possible in hopes of packing on enough blubber to sustain them through the summer fast. After the spring thaw they will lose two pounds a day until the autumn freeze brings back their hunting grounds.

Global climate change has affected these seasonal transitions, cutting short the feeding season and prolonging the fast, making it more difficult for bears to weather the times of scarcity. The earlier spring thaw and loss of multi-year ice also interfere with food availability. Mother seals and their pups sunbathe on stable multi-year ice, providing bears with easy grab and go snacking opportunities. These vulnerable tidbits can escape more easily from fragmented seasonal ice flows, and even tend to avoid these precarious perches all together, as they are prone to the dangers of breakage and capsizing. For polar bears, this means slim pickings during the most plentiful time of the year.

Changes in Arctic ice patterns also impact polar bear behavior. Secreting scent signals through the pads of their paws, bears leave trails of information across the ice. “These are ways in this vast vast territory bears can keep tabs on each other,” explains Schwartz. As solitary animals, these lines of communication are essential to coordinate mating. Using an acute sense of smell, a male can track a fertile female for miles by following the path of her unique perfume. Illustrating the point, the Plunge's studly male Kalluk bobs his head side to side sniffing out the sweet smell of his girlfriend Chinook's pheromones from across the enclosure, pacing in anticipation of a conjugal visit.  

 These crucial scent trails are disrupted by ice fragmentation. “The path gets lost, it breaks up, it shifts, and the bears lose track of each other,” says Schwartz. Earlier spring thaws interfere with the critical mating season, leading males on dead end journeys. Alternatively, unexpected encounters may lead to aggression rather than affection, as male mating behavior is triggered by exposure to female estrous hormones, and takes nearly a week to kick in. Mixed signals and extreme hunger have led to instances of cannibalism among bears.

Conservation Research

To add insult to injury, human activity in what little habitat remains may be further disrupting polar bear wellbeing. Researchers at the San Diego Zoo's Institute for Conservation are studying these effects in hopes of guiding future conservation efforts.

In collaboration with Polar Bears International, Sea World's Hubb Research Institute and 11 zoos across the country, Megan Owen and her colleagues are investigating how petroleum extraction impacts polar bear denning behavior. Owen believes that noise pollution may impede effective mothering, as cub vocalization plays an important role in maternal care. Playing mother bear up in Alaska, Owen digs her own snow dens for 3 weeks every year to test acoustic measurements from nearby industrial sites. Meanwhile, 'Big brother' cams and microphones placed in dens in zoos across the country and in the wild reveal maternal responses to cubs' incessant whining and how industrial noise may affect this relationship. Current regulations require a 1 mile buffer zone between known dens and industrial activity, but this is an arbitrary guideline without any scientific basis. Owen and her colleagues hope to protect polar bear rearing by providing sound science to back these regulations.

Less obvious threats to polar bears are posed by invisible chemical pollutants. “Polar bears are the poster species for environmental contaminants,” explains Matt Milnes, an environmental toxicology scientist at the zoo's Institute for Conservation. At the top of the food chain, polar bears are particularly susceptible to toxin build up. Each tasty morsel of seal blubber contains deposits of chemicals that have accumulated over the seal's entire lifetime, concentrated from all of the fish it ever ate, and in turn, all of the smaller fish they ate, and on down the line. Eating an average of 45 seals per year over a lifespan of 18 years, polar bears accumulate some of the highest concentrations of contaminants ever measured in animal tissues.

Offenders such as DDT and PCBs have been banned, but will exist in the environment for years to come. New dangers are posed by brominated flame retardants found in everything from clothing to mattresses to housing insulation. These compounds interfere with hormonal signaling in mice, rats and humans by mimicking estrogens, androgens and thyroid hormones. No one has studied the effects of these substances in polar bears, but many believe their widespread distribution may be responsible for documented decreases in bone mineral density and lesions found in kidneys and liver.

Matt Milnes collaborates with researchers from Japan, Norway and Canada to determine how these substances might be impacting polar bear health. Milnes suspects that interference with thyroid signaling may have profound consequences. “There have been a lot of reports of disrupted thyroid homeostasis,” he explains. “The thyroid has a really important role in metabolism. In a species that fasts for months, any disruption could really affect survival, especially of cubs... whether or not the pregnancy is going to be successful, whether the mother is going to produce enough milk for those cubs to survive.” Mothers pass these toxins on to newborns through breast milk, which is generated from toxin-laden fat tissue. At this age of rapid growth and development, cubs are under great metabolic strain and extremely susceptible to metabolic interference by these chemicals. While supplying her cubs with this elixir of life, mama bear may inadvertently be delivering a cocktail of death.  

These toxicology studies will guide policy decisions made by regulatory agencies like the Environmental Protection Agency. But Milnes also foresees the project growing into something bigger. “We would like it to be responsive to environmental issues but also be proactive. It would be nice to understand if a contaminant is a threat before a species becomes endangered.”

The Message

The San Diego Zoo is thoroughly vested in defending the polar bear and its habitat, employing public education as a powerful tool. “Public interest in a species is very helpful for conservation in action, as we live in a consumer driven world,” says Owen. Watching children run from one learning module to the next, crawling into a life sized polar bear den and under the towering statue of a 1500 pound bear, peering out the windshield of an Alaskan research helicopter and feeling the polar ice-caps of a 4-D satellite imagery relief map, it is clear that the San Diego Zoo has brought the Arctic to life for its patrons. Excitement is in the air when keeper Joanne Simmons pulls back the glass barrier, exposing an open mesh gate into the bear enclosure. The crowd gathers, buzzing with anticipation, as Tatqiq lumbers over and belly flops down in front of her audience, legs splayed out out behind her. Happily munching on her favorite treats, a healthy selection of grapes, carrots, yams and cantaloupe, it's hard not to fall in love.

Schwartz gazes into the icy pools of Tatqiq's Arctic eyes. “Polar bears are our flagship species. They are the ones who are going to carry that torch for their habitat... put in the spotlight to save everything else that lives there too.”

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                                  Written by Shannon Weiman, PhD