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)

These sand-swept images show the ghostly remains of what was once a mineral-rich mining community. In its heyday, the town of Kolmanskop, Namibia, was home to about 700 families. Now all that remains are empty homes filled with sand, while cast-off items such as bathtubs are scattered about the surrounding area. Over time, the sand of the stunning dunes that encircle the town of Kolmanskop has been blown towards the abandoned residences, coating everything from streets to the interiors of houses and workshops. Here: Kolmankop, an abandoned mining town in Namibia. (Photo by David Ogden/Caters News)

An open house known as “The Doll Asylum” in Portland, Oregon on October 23, 2016. Mark Williams and his wife Heidi Loutzenhiser love halloween so much they fill their home with over 1,000 creepy dolls before opening it up for the public to enjoy over the halloween season. (Photo by ddp USA/Rex Features/Shutterstock)

An army dog stands up as retiring soldiers salute their guard post before retirement in Suqian, Jiangsu province, China on November 29, 2017. (Photo by Reuters/China Stringer Network)

A retired man (L) looks toward two girls wearing miniskirts, July 13, 1969 in Nice, France. (Photo by AFP Photo)

A cat sits in front of a retro car owned by retired mechanic Mikhail Krasinets at an open-air museum of Soviet-era vehicles in the village of Chernousovo, Tula region, Russia on September 27, 2018. In the remote village of Chernousovo, retired mechanic Mikhail Krasinets tends to more than 300 ramshackle, Soviet-era cars, remnants of a once vibrant auto industry that crumbled with the fall of the Soviet Union. (Photo by Maxim Shemetov/Reuters)

Moonlight illuminates sandstone buttes in the Valley of the Gods in the proposed Bear Ears National Monument near Mexican Hat, Utah, USA, 12 November 2016. In October 2015, a coalition of five Indian nations, including the Hopi, Ute, and Navajo, formally proposed the monument, attempting to preserve the parcel's 100,000 archeological sites from ongoing looting and grave robbing. Less than two months before handing over the White House to President Elect Trump, President Obama must decide if it's worth the political capital to designate Bear Ears a national monument. (Photo by Jim Lo Scalzo/EPA)