Geese fight during the annual Geese Fight Day in the northern Serbian village of Mokrin, some 160km (100 miles) from Belgrade February 22, 2015. Every year in the last week of February, goose fights are held in the northern Serbian village of Mokrin. Left alone, male geese, or ganders, are unlikely to fight each other, hence why females are brought along for whose affections the ganders then fight until one or the other gives up. (Photo by Marko Djurica/Reuters)

The blue-footed booby (Sula nebouxii) is a marine bird in the family Sulidae, which includes ten species of long-winged seabirds. Blue-footed boobies belong to the genus Sula, which comprises six species of boobies. It is easily recognizable by its distinctive bright blue feet, which is a sexually selected trait. Males display their feet in an elaborate mating ritual by lifting their feet up and down while strutting before the female.

Bodybuilders pose on stage during the Mr.001 bodybuilding competition in Mombasa, Kenya, on December 11, 2021. This bodybuilding competition was created by a former bodybuilder and its the first one to happen in the coastal city since 2015. The name comes from Mombasa's county code and currently is considered one of the biggest in East and Central Africa. The first edition brought over 200 participants from Kenya, Uganda, Tanzania, Nigeria, South Africa and Pakistan who competed in different categories including physique, bikini and figure. (Photo by Patrick Meinhardt/AFP Photo)

Lily Winter (top) and Lana Austin (back) match up during the “Atomic 6 – Atomic Fighter” wrestling show at the Azvex Brewery in Liverpool, Britain, 21 February 2024. Atomic Pro Wrestling was started in 2023 by wrestling enthusiasts and former training mates Matt Davies, Declan McCarthy (stage name Declan Sands) and Chris Welsh as a way to showcase emerging male and female wrestling talent from England’s North and North West regions, which they felt were being overlooked and under-represented. In contrast to the highly polished world of televised WWE (World Wrestling Entertainment), Atomic takes a DIY approach, holding shows at a local brewery large enough to make way for the ring, and where customers can enjoy craft beer as they watch the wrestling matches from up close. (Photo by Adam Vaughan/EPA/EFE)

A family of baby brown bears appear to be dancing to Ring a Ring o' Roses as their mother relaxes behind a tree nearby. At just a few months old, two young males and one female gather in a circle, clutch each others' hands and begin to dance to the popular nursery rhyme. It's almost like a scene from a school playground as the bears joyfully play together, tapping their feet and moving around in a circle. (Photo by Valtteri Mulkahainen/Solent News & Photo Agency)

A female Kurdistan Workers Party (PKK) fighter stands near a security position in Sinjar, March 13, 2015. Women fighters at a Kurdistan Workers Party (PKK) base on Mount Sinjar in northwest Iraq, just like their male counterparts, have to be ready for action at any time. Smoke from the front line, marking their battle against Islamic State, which launched an assault on northern Iraq last summer, is visible from the base. Many of the women have cut links with their families back home; the fighters come from all corners of the Kurdish region. (Photo by Asmaa Waguih /Reuters)

A female Kurdistan Workers Party (PKK) fighter works on her laptop while watching a Kurdish TV station at a base in the Sinjar mountains, March 11, 2015. Women fighters at a Kurdistan Workers Party (PKK) base on Mount Sinjar in northwest Iraq, just like their male counterparts, have to be ready for action at any time. Smoke from the front line, marking their battle against Islamic State, which launched an assault on northern Iraq last summer, is visible from the base. Many of the women have cut links with their families back home; the fighters come from all corners of the Kurdish region. (Photo by Asmaa Waguih/Reuters)

Iranian bodybuilder Sharareh Nobahari, 30, assists her fitness trainees at a gym in Tehran, Iran on September 20, 2019. (Photo by Nazanin Tabatabaee/Reuters)