New York Police Department tactical police officers stand guard near the New York Stock Exchange on September 9, 2011 in New York City. Officials are stepping up security in New York and Washington D.C. a day after U.S. officials received a credible but unconfirmed terror threat to utilize car bombs on bridges or tunnels in New York or Washington. (Photo by Justin Sullivan/Getty Images)

One-year-old female giant panda cub Nuan Nuan reacts inside her enclosure during joint birthday celebrations for the panda and its ten-year-old mother Liang Liang at the National Zoo in Kuala Lumpur on August 23, 2016. Giant pandas Liang Liang, aged 10, and her Malaysian-born cub Nuan Nuan, 1, were born on August 23, 2006 and August 18, 2015 respectivetly. (Photo by Mohd Rasfan/AFP Photo)

A staff member sets up a ROBOTLEO robot at the Global Mobile Internet Conference (GMIC) 2017 in Beijing, China April 28, 2017. (Photo by Jason Lee/Reuters)

Merit: A Night at Deadvlei. The night before returning to Windhoek, we spent several hours at Deadveli. The moon was bright enough to illuminate the sand dunes in the distance, but the skies were still dark enough to clearly see the milky way and magellanic clouds. Deadveli means “dead marsh. The camelthorn trees are believed to be about 900 years old, but have not decomposed because the environment is so dry. (Photo and caption by Beth McCarley/National Geographic Traveler Photo Contest)

The British Wildlife Photography Awards winners have been revealed, with Lee Acaster from Suffolk taking home the top prize for his shot of a Graylag Goose in London. Acaster, who received £5,000, photographed the animal against an ominous London skyline, with The Shard clearly visible in the background. Here: “Urban Tourist (Graylag Goose)”. Urban category and overall winner. (Photo by Lee Acaster/British Wildlife Photography Awards 2014)

Dancers of the Czech National Ballet warm up backstage during a performance of “The Nutcracker – A Christmas Carol” at the National Theatre in Prague, Czech Republic, late 16 December 2017. Peter I. Tchaikovsky's “The Nutcracker”, one of his most famous compositions and seasonal ballets, premiered in St. Petersburg, Russia, on 18 December 1872, celebrates its 125th anniversary this year. (Photo by Martin Divisek/EPA/EFE)

A river otter (lontra longicaudis) of 6-weeks-old looks in the mirror during a bath in the Animal Welfare Unit of the Zoo in Cali, Colombia, on October 22, 2019. The baby otter was found abandoned brought to the Cali Zoo for breeding, for its extensive experience in raising these species. According to the International Union for Conservation of Nature the river otter (lontra longicaudis) are in danger of extinction, because of mining, agriculture, pollution of rivers and housing construction in their habitat. (Photo by Luis Robayo/AFP Photo)