Audubon Images

From 4-D exhibits to state-of-the-art veterinary care, zoos across the U.S. continue to change, modernize and grow for the benefit of both humans and non-human animals.

Female Asian elephants Panya and Jean are getting ready for a new state-of-the-art elephant exhibit at New Orleans' Audubon Zoo. Set to open in late summer 2014, the 42,000-square-foot exhibit will include an elephant barn with heated, padded floors. The outdoor area will be contoured, with gentle inclines to feature shade trees, pools, and a replica of a fallen tree trunk, where keepers plan to hide tasty treats -- like pumpkins -- for the elephants to dig out.

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Oakland Zoo

Quality health care is essential for zoos, and is exemplified by the new 17,000-square-foot Veterinary Medical Hospital at the Oakland Zoo in California. "Our goal is to provide an optimal, comfortable respite for zoo animals in order to speed recovery from illness or injury," said Joel Parrott, president & CEO of Oakland Zoo. Here, a tortoise is readied for a procedure. The facility includes a radiology suite, aquatic animal area with pool, a quarantined section with its own airflow system, several climate-controlled rooms and other high-tech additions.

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Ken Bohn, San Diego Zoo

What's better than a 3-D movie? A 4-D movie! The San Diego Zoo is now showing "Rio Rainforest Adventure in 4-D" in its special theater that combines high-definition 3-D footage with sensory effects, such as wind and mist. This particular movie takes zoo guests on a journey through Rio de Janeiro while sharing the challenges facing rainforest wildlife.

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quadell, Wikimedia Commons

Whenever possible, many zoos are installing solar panels for fuel efficiency. The Cincinnati Zoo, for example, has cleverly placed numerous solar panels over part of its parking lot. They help to shade cars while tapping into Sun energy. Some rides are also incorporating solar panels. The Speedwell Foundation Conservation Carousel at the Smithsonian's National Zoo, for example, is one of the few all solar-powered carousels in the world.

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Saint Louis Zoo

The Saint Louis Zoo recently announced plans for a 40,000-square-foot polar bear exhibit, scheduled to open in 2015. "It is critical that zoos protect polar bears, which are declining in the wild and are highly vulnerable," explained Jeffrey P. Bonner, president and CEO of the Saint Louis Zoo. "By working to not only conserve polar bears in the wild but to offer a wonderful habitat for breeding and protecting bears in our care, we can help save these iconic animals."

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Tim Evanson, Flickr

Smaller zoos often look to larger, well-funded ones for ideas and inspiration. Alan Sironen, a board member of the Zoological Association of America, told Discovery News that zoos now at the forefront include the San Diego Zoo, the Fort Worth Zoo, the Bronx Zoo and the Cincinnati Zoo. The San Diego Zoo, at the top of many such lists, pioneered the concept of open-air, cageless exhibits that recreate natural animal habitats. Here, an orangutan at the San Diego Zoo hangs out in an open, grassy area.

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Flying Puffin, Wikimedia Commons

Movies like "Jurassic Park" envision zoos housing once extinct animals brought back to life. Woolly mammoths are a possibility, since remains are sometimes found in relatively good condition. Just this past summer, the most complete woolly mammoth carcass ever recovered from Russia was unveiled at an exhibit in Japan. While viable cells for cloning have yet to be isolated, scientists continue to look for them.

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Dkroetsch, Wikimedia Commons

Critter cams and other devices already allow for non-invasive, virtual viewing of animals. Sironen speculated that such technologies could expand even more in future. "Drones, for example, might fly over large park-like exhibits," he said. It's hard to imagine, however, that any virtual experience could ever fully take the place of an in-person zoo visit.

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Bjørn Christian Tørrissen, Wikimedia Commons

"In an ideal world, there would be no need for zoos," Sironen said, explaining that such a world would have humans and non-human animals co-existing freely and in peace. "I doubt that will ever happen. Too many things would need to change." Not many places, for example, could support a large population of wildebeest, seen here during a migration in Africa.

Sironen concluded, "Hopefully zoos will continue to blur the line between captivity and the wild, with zoos providing larger, more natural spaces for animals."