A deer jumps over a meadow with blooming dandelions near Bodneg, southern Germany, Monday, May 4, 2015. (Photo by Felix Kaestle/AP Photo/DPA)

Employees at the Hagenbeck Zoo measure a walrus in its enclosure in†Hamburg, Germany, May 7, 2015. The zoo has begun its annual inventory of all the animals. (Photo by Axel Heimken/EPA)

A handout by Denver Zoo shows Bertie, a 58-year-old male hippopotamus, the Zoo's longest resident, in this image released on May 4, 2015. Denver Zoo was mourning the death on Monday of Bertie, a 58-year-old male hippopotamus who was its longest resident and the oldest hippo accredited to a North American zoo, officials said. Bertie was humanely euthanized after his keepers saw “a significant decline in his quality of life due to his advanced age”, the zoo said in a statement. Most hippos live about 30 to 40 years in the wild, and up to 50 in zoos. (Photo by Reuters/Denver Zoo)

A 34-year-old Malayan sun bear named Dresena is shown in this undated photo released on May 6, 2015. Dresena has been euthanized at a southern Arizona zoo, officials said on Wednesday. (Photo by Reuters/Reid Park Zoo)

A 34-year-old Malayan sun bear named Dresena is shown in this undated photo released on May 6, 2015. (Photo by Reuters/Reid Park Zoo)

Keeva, a two-month-old chimpanzee, born in Maryland and rejected by her mother, is shown in this undated handout photo provided by Tampa's Lowry Park Zoo in Tampa, Florida, May 7, 2015. Keeva has found a new home at the central Florida zoo, where she is beginning to teeth and hold up her head and soon will be paired with with a surrogate mother. (Photo by Dave Parkinson/Reuters/Tampa's Lowry Park Zoo)

Keeva, a two-month-old chimpanzee, born in Maryland and rejected by her mother, is shown in this undated handout photo provided by Tampa's Lowry Park Zoo in Tampa, Florida, May 7, 2015. (Photo by Dave Parkinson/Reuters/Tampa's Lowry Park Zoo)

A baby Alpaca is seen at an exhibition outside Parliament House in Canberra, Australia, 30 April 2015. (Photo by Lukas Coch/EPA)

A baby Alpaca is seen at an exhibition outside Parliament House in Canberra, Australia, 30 April 2015. (Photo by Lukas Coch/EPA)

The New World porcupine, family Erethizontidae, 1280 Gram born at 11 April 2015 Inventory in Zoo. Counting trade Fairs Weighing the Zoo is at 7 May 2015 too the 108 Birthday Zoo Hagenbeck Hamburg, Germany. (Photo by Imago/ZUMA Wire)

A Siamang Gibbon (Symphalangus syndactylus) mother Jambi, 8, carries her baby at the safari park and zoo on May 4, 2015 in Ramat Gan near Tel Aviv. The baby is reported to have been born about a month and a half ago, unkown to the zookeepers as the monkeys live in thick brush and the newborn was ensconced in his mother's fur. (Photo by Jack Guez/AFP Photo)

Two Canada goose goslings are pictured on a daisy meadow at the Volksgarten park in Duesseldorf, western Germany, on May 5, 2015. (Photo by Maja Hitij/AFP Photo/DPA)

Black-Naped Monarch hatchlings are seen at the Hlawga National Park, in Mingaladon, some 22 miles (35 km) north of Yangon on May 8, 2015. The 1540-acre (623-hectare) facility, with over 70 kinds of herbivorous animals and 90 species of birds, has a wildlife section as well as a mini-zoo and is a popular day-trip destination from Yangon. (Photo by Ye Aung Thu/AFP Photo)

A squirrel runs through freshly fallen snow along Mt. Baldy Rd., in the Southern California mountains, Friday, May 8, 2015 in Mt. Baldy, Calif. Approximately 2-3 inches fell overnight near the Mt. Baldy ski lifts. (Photo by Will Lester/AP Photo/The Inland Valley Daily Bulletin)

Two young sloth bears play in the zoo in Leipzig, Germany, May 5, 2015. In the past year, 912 animals were born in the zoo. (Photo by Lukas Schulze/EPA)

Two young sloth bears play with their mother Lina on May 5, 2015 at the zoo in Leipzig, eastern Germany. (Photo by Lukas Schulze/AFP Photo/DPA)

A swan swims on May 7, 2015 in Landsberg am Lech, Germany. (Photo by Karl-Josef Hildenbrand/AFP Photo/DPA)

A deer runs across the road, Wednesday, May 6, 2015 in Kinross Charter Township, Mich. Harsh winters the past few years have decimated deer herds across the Upper Midwest. In Michigan's Upper Peninsula, where the annual fall deer hunt is a way of life, the population has dropped as much as 40 percent after two bitterly cold and snowy winters. The state's Natural Resources Commission will discuss the situation Thursday during its monthly meeting in Lansing. A memo prepared by the Department of Natural Resources lists six options, including canceling this year's U.P. deer hunting season. (Photo by Carlos Osorio/AP Photo)

Seagulls take off Kalk Bay harbour wall at dawn in Cape Town, South Africa, 06 May 2015. Seagulls are scavengers with large numbers congregating in the commercial fishing harbour of Kalk Bay which provides numerous sources of food ranging from scraps off the fishing boats to the waste generated around a fish and chip restaurant. (Photo by Nic Bothma/EPA)

Sparrows fly in and out of the muzzle of a former Soviet tank in Berlin, Germany, Monday, May 4, 2015. The former tank is part of a memorial for dead Red Army soldiers at the Berlin central district Tiergarten and is used by a group of sparrows to build their nests inside. (Photo by Markus Schreiber/AP Photo)

In this Wednesday, May 6, 2015 photo released by the Takasakiyama Natural Zoological Garden, a newborn baby monkey named Charlotte clings to her mother at the zoo in Oita, southern Japan. The Japanese zoo has apologized for naming the baby monkey Charlotte after the newborn British princess following complaints at home. The Takasakiyama Natural Zoological Garden said Thursday, May 7 it was considering renaming the macaque. It was flooded with angry calls and emails Wednesday hours after announcing the name for its first born monkey of the year, a tradition at the city-run zoo. (Photo by The Takasakiyama Natural Zoological Garden via AP Photo)

A Siamang Gibbon (Symphalangus syndactylus) mother Jambi, 8, nurses her baby at the safari park and zoo on May 4, 2015 in Ramat Gan near Tel Aviv. The baby is reported to have been born about a month and a half ago, unkown to the zookeepers as the monkeys live in thick brush and the newborn was ensconced in his mother's fur. (Photo by Jack Guez/AFP Photo)

Raccoons washing clothes in a zoo on May 5, 2015. Keepers at this zoo who decided to put to the test a claim that raccoons like washing clothes found it to be 100 per cent true. As soon as the clothing and the bowl of water was placed in the cage, the raccoons grabbed it and started washing away to the delight of zoo visitors. Staff at the Yunnan Wild Animal Park in Kunming City, capital of south-west China's Yunnan Province, had been looking around for a stunt to entertain visitors over the Labour Day holiday. (Photo by Europics)