German troops in Stalingrad, USSR. September 10, 1942. (Photo by TASS)

A woman from the Hui Muslim community carries food that will be eaten by her and others to break their fast during the holy fasting month of Ramadan at the Nanxiapo Mosque on June 8, 2018 in Beijing, China. (Photo by Kevin Frayer/Getty Images)

A green rosella and a wallaby, known as a Pademelon, eye off as they drink from a water bowl put out for thirsty wild animals at a back-yard in Kayena, in northern Tasmania, 01 February 2019. Australia recorded its hottest month on record in January; it was also the hottest and driest month on record for the Australian island state of Tasmania. (Photo by Barbara Walton/EPA/EFE)

In this January 27, 2019, photo, Hindu holy men of monastic order Juna Akhara participate in a ritual before becoming Naga Sadhus or naked holy men at Sangam, the confluence of three holy rivers during the Kumbh Mela or pitcher festival in Prayagraj Uttar Pradesh state, India. At every Kumbh, including this year's, thousands of devotees were initiated into the reclusive sect of the Naga Sadhus, naked, ash-smeared cannabis-smoking Hindu warriors and onetime-armed defenders of the faith who for centuries have lived as ascetics in jungles and caves. (Photo by Rajesh Kumar Singh/AP Photo)

An annual fire festival is held in Nachikatsuura, Wakayama Prefecture, western Japan, on July 14, 2019. (Photo by Kyodo News via Getty Images)

A Monster Jam truck performs a back flip during the first-ever monster truck event in Beijing's iconic “Bird's Nest” National Stadium on Saturday, July 29, 2017. (Photo by Ng Han Guan/AP Photo)

Behaviour: Mammals category. Giant Gathering by Tony Wu, USA. Dozens of sperm whales mingled noisily off Sri Lanka’s northeast coast, stacked as far down as Tony could see. This was a congregation of dozens of social units, like a gathering of the clans. Aggregations like this could be a critical part of the whales’ rich social lives but are rarely reported. Some two thirds of the population was wiped out before commercial whaling was banned in 1986. This kind of major gathering could be “a sign that populations are recovering”, says Tony. (Photo by Tony Wu/Wildlife Photographer of the Year 2017)

Rescuers attempt attempt to push stranded whales back into the ocean at Ujong Kareng beach in Aceh province, Indonesia, Monday, November 13, 2017. An official said a small pod of whales was stranded at the beach and attracted hundreds of onlookers who posed for pictures with them. (Photo by AP Photo/Zulkarnaini)