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)

A mahout guards the elephants during the annual Vrischikolsavam festival, which features a colourful procession of decorated elephants along with drum concerts, at a temple in Kochi, India, November 18, 2017. (Photo by Sivaram V/Reuters)

A sadhu, or a Hindu holy man, blesses a devotee as he smokes marijuana at a transit camp on the way to Gangasagar, in Kolkata, India, Sunday, January 7, 2018. Thousands of Hindu pilgrims are expected to take the annual holy dip at Gangasagar, where the Ganges River reaches the Bay of Bengal, on the auspicious Makar Sankranti festival day that falls on Jan. 14. (Photo by Bikas Das/AP Photo)

Cardi B looking stylish as she leaves the Warner Music Grammy party in NYC on January 26, 2018. (Photo by Splash News and Pictures)

In this April 16, 2019 photo, people wait to be given empty water containers and water purification pills during the first aid shipment from the Red Cross in Caracas, Venezuela. In late March, the Red Cross federation announced it would soon begin delivering assistance to an estimated 650,000 people and vowed that it would not accept interference from either side of the polarized country. (Photo by Ariana Cubillos/AP Photo)

Mil Mi-8 combat helicopter flies over Moscow, Russia on May 7, 2019 during the dress rehearsal of a Victory Day air show marking the 74th anniversary of the victory over Nazi Germany in the 1941-1945 Great Patriotic War, the Eastern Front of World War II. (Photo by Sergei Savostyanov/TASS)

A woman carries her son in a bucket after collecting water from a municipal water tanker on the outskirts of Chennai, India, July 4, 2019. (Photo by P. Ravikumar/Reuters)

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