• Gorgeous portraits of endangered species draw attention to their plight

    By Mish Whalen

    A waxy monkey frog, a chameleon and an elephant are some of the world's rarest and most stunning species. Photographer Joel Sartore captures these beautiful zoo animals in striking portraits. 

    Joel Sartore/Nat Geo Stock/Caters News

    A veiled chameleon.

    Joel Sartore/Nat Geo Stock/Caters News

    A female African elephant.

    Joel Sartore/Nat Geo Stock/Caters News

    Black-footed ferret.

    Joel Sartore/Nat Geo Stock/Caters News

    A waxy monkey frog.

    Joel Sartore/Nat Geo Stock/Caters News

    A gray wolf.

    Joel Sartore/Nat Geo Stock/Caters News

    A grizzly bear.

    Joel Sartore/Nat Geo Stock/Caters News

    A hippopotamus.

    Joel Sartore/Nat Geo Stock/Caters News

    A captive, five-month-old mandrill.

    Joel Sartore/Nat Geo Stock/Caters News

    California tiger salamander.

    Joel Sartore/Nat Geo Stock/Caters News

    Joel Sartore photographs an American crocodile at the Omaha Zoo.

    Sartore, a National Geographic photographer from Nebraska, created the "Biodiversity Project" to highlight the importance of the animals and encourage people to pay closer attention to endangered species.

    Though he started with amphibians, today he photographs "anything that will hold still on a background long enough for me to take a picture," he said on his website.

    These photos were all taken between 2006 to 2010, a lengthy project due to the extensive travelling to remote parts of the world to find and photograph the rare species. The photos are featured in a recently released book entitled "Rare."

  • Keeping cool at the Belgrade zoo

    Ivan Milutinovic / Reuters

    A zookeeper sprays water on a polar bear to help it cool down at Belgrade's zoo July 13.

    Ivan Milutinovic / Reuters

    Children watch as water is sprayed on an Asian elephant to help it cool down at Belgrade's zoo July 13.

    Ivan Milutinovic / Reuters

    A zookeeper sprays water on a hippopotamus to help it cool down at Belgrade's zoo July 13, 2011 as an intense heat wave sweeps Serbia with temperature reaching 104 degree Fahrenheit (40 degrees Celsius).

    By Phaedra Singelis, NBC News

    It must be hot for a polar bear in that kind of heat. I'm guessing zoos across the Midwest and Northeast United States will be doing the same thing today as a heat wave continues there.

    See more animals in our new Animal Tracks blog.

  • A baby pygmy hippopotamus named Oliver

    Parken Zoo / Reuters

    A baby pygmy hippopotamus named Oliver sits next to his mother, Krakunia, after he was born at Parken Zoo in Eskilstuna, Sweden in this handout photo taken Feb. 15, and released Thursday, Mar. 3.

    By Jonathan Woods, msnbc.com

    If you have a soft spot in your heart for animals, take a look at our editors' picks for the cutest thing ever.

    Sweden's Parken Zoo is celebrating their baby hippo, Oliver, after zoo keepers managed to milk the mother hippo to save Oliver's life.

  • Reuters

    A keeper brushes a hippo's teeth at the Shanghai Zoo on Nov. 3. The hippo has its teeth cleaned three times a week to reduce the chance of mouth diseases.

    The Year in Pictures: Outtakes

    By Meredith Birkett

    I voted for this hippo image to be included in the Year in Pictures. Yes it's a zoo picture, yes, it's an animal -- so some would say it's not "serious" photojournalism and doesn't stand up against all of the important news of the year. Yes, all that is true, but also, it's nice to take a moment to appreciate the lighter moments that were captured. This picture makes me smile, in part because the hippo seems a little happy about the attention and the carrot is a fun, whimsical detail. See the images that did make the cut here.

  • Two-ton hippo leaves zoo to swim through flooded village in Montenegro

    By Carissa Ray

    I think it would be a little alarming to return to your flooded home to find a hippo swimming through the yard. The house cat in the bottom photo might agree

    Stevo Vasiljevic / Reuters

    Nikica, the hippopotamus walks partially submerged in a flooded yard at a village in Berislavci, about 15 miles south of the Montenegrin capital of Podgorica, on Dec. 6. Nikola Pejovic, owner of a private zoo, says that the 12-year-old, 2-ton hippopotamus was released from her cage after the flood. The only hippopotamus from Montenegro regularly escapes from the mountainous Adriatic nation's zoo during seasonal floods.

    Stevo Vasiljevic / Reuters

    Nikica the hippopotamus walks partially submerged in a flooded yard at a village in Berislavci, about 15 miles south of the Montenegrin capital of Podgorica, on Dec. 6. Nikola Pejovic, owner of a private zoo, says that the 12-year-old, 2-ton hippopotamus was released from her cage after the flood. The only hippopotamus from Montenegro regularly escapes from the mountainous Adriatic nation's zoo during seasonal floods.

    Savo Prelevic / AFP - Getty Images

    Nikica, a two-ton hippopotamus, swims on Dec. 6, through flood waters, four kilometers from her flooded pen, in Plavnica, south of the capital Podgorica. The hippopotamus had to leave her flooded pen in a private zoo after a similar evacuation in January floods. In Montenegro, the situation was still serious on Dec. 5 in the Lake Skadar region, at the border with Albania, and around Podgorica. More than 1,000 soldiers were called to help the population.

    To see more animal photos, check out the latest edition of Animal Tracks.