A polar bear fast asleep at London Zoo. (Photo by Fox Photos/Getty Images). 1961

A cool drink during the hot weather is welcomed by Joan the hippo at the London Zoo. (Photo by Fox Photos/Getty Images). 6th June 1939

A group of emus at Whipsnade Zoo flock around their keeper in order to be sprayed with cold water on a hot day. (Photo by Fox Photos/Getty Images). 1st July 1938

Anna, a ten year old Indian elephant, cools off at London Zoo. (Photo by Evening Standard/Getty Images). 5th June 1980

A zoo keeper gives a penguin a shower from a watering can. (Photo by Fox Photos/Getty Images). 28th August 1930

A horse getting a drink on a hot day in London. (Photo by Topical Press Agency/Getty Images). 14th July 1926

A golden retriever named Hercules sits next to a sprinkler during a break from playing fetch August 25, 2003 at Golden Gate Park in San Francisco, California. (Photo by Justin Sullivan/Getty Images)

A golden retriever named Hercules cools off during break from playing fetch August 25, 2003 at Golden Gate Park in San Francisco, California. (Photo by Justin Sullivan/Getty Images)

Pugli the bearded pig gets a shower in London Zoo July 14, 2003 in London. Tempratures over much of Great Britain have reached 30C, as the country enjoys a mini heat wave. (Photo By Steve Finn/Getty Images)

Nicola the hippopotamus is hosed down by London Zoo worker Greta John in London Zoo July 14, 2003 in London. (Photo By Steve Finn/Getty Images)

Syrian brown bears get an iced treat of frozen fruit and vegetables as temperatures soar to the high 30's during a heat wave April 12, 2005 at the Safari Park in Ramat Gan near Tel Aviv, Israel. (Photo by Uriel Sinai/Getty Images)

London Zoo Keeper Tim Savage cools down its resident penguins as the British heatwave peaks at the Regent's Park Zoo on June 8, 2004 in London. (Photo by Steve Finn/Getty Images)

A polar bear enjoys a ice bomb with frozen fruit and fish on July 21, 2006 at the zoo in Berlin, Germany. (Photo by Andreas Rentz/Getty Images)

England bowler Matthew Hoggard gets a shower off an elephant during a visit to the Elephant centre in Pinwella near Kandy on November 28, 2007 in Kandy, Sri Lanka. (Photo by Stu Forster/Getty Images)

A racing horse get a shower after the Friday's Race Day at Iffezheim Race Track on September 5, 2008 in Baden-Baden, Germany. (Photo by Patrik Stollarz/Bongarts/Getty Images)

Keepers at ZSL London Zoo hose down the Bearded Pigs in their enclosure to keep them cool in the hot weather on July 2, 2009 in London, England. (Photo by Oli Scarff/Getty Images)