A sixteen days old elephant calf rests beneath her mother inside their enclosure at the Bannerghatta National Park, 25 kilometers (16 miles) south of Bangalore, India, Wednesday, July 1, 2015. (Photo by Aijaz Rahi/AP Photo)

A squirrel relaxes on a branch of a tree during warm weather in Mainz, Germany, Tuesday, June 30, 2015. (Photo by /Fredrik von Erichsen/dpa via AP Photo)

Ruben, a 3-year-old chimpanzee, plays at the Oklahoma City Zoo in Oklahoma City, Thursday, July 2, 2015. (Photo by Sue Ogrocki/AP Photo)

A crab crawls on the beach in El-Mansouri near Tyre, south Lebanon, June 29, 2015. (Photo by Jamal Saidi/Reuters)

Tourists take pictures of Aling at a zoo in Changchun, Jilin province, China, July 1, 2015. Aling is one of two giant pandas that have been recently moved from their original habitat in China's Southwest Sichuan Province to the northeastern Jilin. According to the local media, this is China's first attempt at raising Giant Pandas in a high latitude area. This is considered by them to be valuable for scientific research. (Photo by Reuters/China Daily)

Kaveri, eight-year-old hippopotamus, right, plays with her yet to be named three-day-old baby hippo inside their enclosure at the Bannerghatta National Park, 25 kilometers (16 miles) south of Bangalore, India, Wednesday, July 1, 2015. (Photo by Aijaz Rahi/AP Photo)

A hippopotamus calf walks next to its eight-year-old mother Kaveri inside their enclosure at the zoo within the Bannerghatta Biological Park, on the outskirts of Bengaluru, India, July 1, 2015. The yet unnamed calf was born in the zoo on June 29, 2015. (Photo by Abhishek N. Chinnappa/Reuters)

Female walrus Polosa and her 4-weeks old cub, nameless until now, are pictured in Hagenbecks zoo in Hamburg, Germany, July 2, 2015. (Photo by Fabian Bimmer/Reuters)

Female walrus Polosa and her 4-weeks old cub, nameless until now, are pictured in Hagenbecks zoo in Hamburg, Germany, July 2, 2015. (Photo by Fabian Bimmer/Reuters)

Female walrus Polosa (L) and her 4-weeks old cub, nameless until now, are pictured in Hagenbecks zoo in Hamburg, Germany, July 2, 2015. (Photo by Fabian Bimmer/Reuters)

Female walrus Polosa and her 4-weeks old cub, nameless until now, are pictured in Hagenbecks zoo in Hamburg, Germany, July 2, 2015. (Photo by Fabian Bimmer/Reuters)

A brown bear eats frozen vegetables and fruits during a hot summer day at the zoo in Madrid, Spain, July 2, 2015. (Photo by Andrea Comas/Reuters)

A brown bear tries to catch frozen vegetables and fruits during a hot summer day at the zoo in Madrid, Spain, July 2, 2015. (Photo by Andrea Comas/Reuters)

An orangutan eats frozen fruits during a hot day at Biopark Zoo in Rome, Italy, July 2, 2015. (Photo by Alessandro Bianchi/Reuters)

An orangutan eats popsicles as zoo-keepers gave animals iced food to keep them cool as temperatures soar, at Rome's zoo, Thursday, July 2, 2015. The European weather forecast is predicting high temperatures for the next few days. (Photo by Andrew Medichini/AP Photo)

An orangutan eats a popsicle as zoo-keepers gave animals iced food to keep them cool as temperatures soar, at Rome's zoo, Thursday, July 2, 2015. (Photo by Andrew Medichini/AP Photo)

A brown bear eats fruits during a hot day at Biopark Zoo in Rome, Italy, July 2, 2015. (Photo by Alessandro Bianchi/Reuters)

A brown bear eats frozen vegetables and fruits during a hot summer day at the zoo in Madrid, Spain, July 2, 2015. (Photo by Andrea Comas/Reuters)

A brown bear takes fruits to eat during a hot day at Biopark Zoo in Rome, Italy, July 2, 2015. (Photo by Alessandro Bianchi/Reuters)

Female polar bear Anori looks out through a toy as she cools off during a hot summer day at the zoo of Wuppertal, Germany, Jul 2, 2015. A widespread, long-lasting heat wave will spread across much of France, U.K., Belgium, the Netherlands and western Germany with forecast highs on Wednesday reaching 35 degrees Celsius (95 degrees Fahrenheit). (Photo by Wolfgang Rattay/Reuters)

Female polar bear Anori she cools off during a hot summer day at the zoo of Wuppertal, Germany, Jul 2, 2015. (Photo by Wolfgang Rattay/Reuters)

Male polar bear Luka swims during a hot summer day at the zoo of Wuppertal, Germany, Jul 2, 2015. (Photo by Wolfgang Rattay/Reuters)

Female polar bear Anori swims during a hot summer day at the zoo of Wuppertal, Germany, Jul 2, 2015. (Photo by Wolfgang Rattay/Reuters)

A pink flamingo is pictured during a hot summer day at the zoo of Wuppertal, Germany, July 2, 2015. (Photo by Wolfgang Rattay/Reuters)

A pink flamingo is pictured during a hot summer day at the zoo of Wuppertal, Germany, July 2, 2015. (Photo by Wolfgang Rattay/Reuters)

Black-capped squirrel monkeys eat blocks of ice at the zoo on a hot summer day in Antwerp, Belgium, July 2, 2015. The United Nations warned on Wednesday of the dangers posed by hot weather, especially to children and the elderly, as much of Europe sweltered in a heatwave whose intensity it blamed on climate change. (Photo by Yves Herman/Reuters)

Two keepers at the Australian Reptile Park in New South Wales struggle with Leonardo, an alligator snapping turtle weighing 45 kilos at the park in Gosford, NSW 2 July 2015. The 50cm long Leonardo – who was smuggled illegally into Australia and found in a Sydney sewer in November 2000 – was removed from his tank for an annual health check. And as a gesture to onlooking press photographers demonstrated his strength by snapping a piece of bamboo in half. (Photo by EPA/HO)

Leonardo, an alligator snapping turtle weighing 45 kilos, demonstrated his jaw-dropping strength by snapping a piece of bamboo at the Australian Reptile Park in Gosford, NSW 2 July 2015. (Photo by EPA/HO)

A giraffe gets a cold shower in Ouwehands Dierenpark (Ouwehands Zoo) in Rhenen, Netherlands, 30 June 2015. The animals in the zoo get some refereshments to cool them down, with temperatures reaching 28 degrees Celsius. (Photo by Piroschka van de Wouw/EPA)

Snow leopard Twins will in Zoo Magdeburg baptized on the Name Maleo and Askari photographed at June 28, 2015. (Photo by Imago/ZUMA Wire)

In this undated handout photo released by Zoos South Australia on June 30, 2015 a baby Goodfellows tree kangaroo known as a joey rest in a blanket at Adelaide Zoo. In a world first for conservation, Adelaide zoo keepers and veterinarians saved the life of the orphaned Goodfellows tree kangaroo through utilising a surrogate female yellow-foot rock wallaby mother a technique never attempted before with a tree kangaroo after its mother was killed in an accident. (Photo by Kate Fielder/AFP Photo)

Two Siberian tiger cubs play during their first outing at the zoo of Olomouc, Czech Republic, on June 30, 2015. The tiger twins were born at the zoo in May 2015. (Photo by Radek Mica/AFP Photo)

A seal swims in its enclosure in the zoo in frankfurt am Main, central Germany, on July 1, 2015. (Photo by Christoph Schmidt/AFP Photo/DPA)

A baby snow leopard and his mother are presented to the public in Servion, Switzerland, Thursday, July 2, 2015. Two baby snow leopards where born on May 20, 2015, in the zoo. (Photo by Christian Brun/Keystone via AP Photo)

Jaxson, left, and Hendrix, right, reach for a fish at the Oklahoma City Zoo in Oklahoma City, Thursday, July 2, 2015. The two male California sea lions came to the zoo from The Marine Mammal Center in Sausalito, Calif., after being found stranded and malnourished multiple times. The were deemed non-releasable by the National Marine Fisheries Service and the zoo was determined to be a suitable home for them. (Photo by Sue Ogrocki/AP Photo)

A week-old panda cub sleeps in an incubator at the Chengdu Research Base of Giant Panda Breeding on June 30, 2015 in Chengdu, China. The twin female cubs were born by artificial insemination to seven-year-old Kelin on June 22. China's Sichuan province is home to the majority of the the world's nearly 1,900 endangered giant pandas. (Photo by John Moore/Getty Images)

A giant panda eats bamboo at a panda research base on June 29, 2015 in Ya'an, China. China's Sichuan province is home to the majority of the the world's nearly 1,900 endangered giant pandas. (Photo by John Moore/Getty Images)

A young visitor tries to caress one of two Siberian tiger cubs being held behind a glass window during their first outing at the zoo of Olomouc, Czech Republic, on June 30, 2015. Siberian tiger twins were born at the zoo in May 2015. (Photo by Radek Mica/AFP Photo)