Japanese macaque monkeys enjoy sitting in the hot springs at Jigokudani-Onsen (Hell Valley) on January 23, 2005 in Jigokudani, Nagano-Prefecture, Japan. Japanese Macaques, also known as snow monkeys are the most northerly nonhuman primate in the world. In 1963 a female Macaque ventured into the hot springs to retrieve some soybeans. This behaviour was adopted by other monkeys, and eventually by the entire troop. This Macaque troop regularly visits the Jigokudani-Onsen springs to escape the cold. The hot springs are said to help relieve nerve pain and fatigue. (Photo by Koichi Kamoshida/Getty Images)

The Greater Sage-Grouse is certainly a formidable-looking bird. Being the largest grouse in North America and having tail feathers, which look like giant spikes, make for a ferocious sight. These birds are well known for their complicated courtship rituals, in which the males perform a special “strutting display” to attract the females. Another distinct feature of the Greater Sage-Grouse is two large yellow throat sacs (gular sacs), which are inflated by the males during the courtship display. Unlike pelicans, whose gular sacs are used to store fish while hunting, the throat sacks of the Greater Sage-Grouse are merely for display.

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.

Iraqi army soldiers warm themselves next to a fire near the Qayara air base, south of Mosul, Iraq, Tuesday, November 1, 2016. The U.N. human rights office is lauding efforts by the U.S.-led coalition in the battle against the Islamic State group in Mosul. The office in Geneva says coalition flights over Iraq have largely succeeded in preventing IS from bringing in 25,000 more civilians to the city center, where the militant group has been using people as human shields as Iraqi forces advance on Mosul. (Photo by Felipe Dana/AP Photo)

Factory landlord Lawrence Taylor (L), portraying a Colour Sergeant from the King's Royal Rifle Corps, part of the Rifles Living History Society, performs a drill with Connor Young (R) of the Queen's Own Royal West Kent Regiment Living History Group as they recreate the life of a First World War soldier at the Eden Valley Museum in Edenbridge in southeast England May 10, 2014. Lawrence has always had an interest in military history and specifically “The Rifles” – his veteran father's WWII regiment. When he became a re-enactor he chose not to re-enact WWII as many of the veterans are still alive, and he felt uncomfortable as he remembers his father would have flashbacks and nightmares about the war. United by a fascination with military history and a fondness for dressing up, groups such as the Rifles Living History Society and the Queen's Own Royal West Kent Regiment Living History Group get together to recreate aspects of life during the First World War. Reuters photographer Luke MacGregor photographed members of the groups, both as they took part in living history events and at their day jobs. (Photo by Luke MacGregor/Reuters)

With their affinity for hunting, sneaking, and hidden blade-like retractable claw, cats are really the assassins of the animal world. They're not as intimidating when they're kittens dressed up as assassins from the upcoming Assassin's Creed Unity, but what they lack in deadliness they more than make up for in cuteness. YouTube user Mr.TVCow posted the video, in which four hooded kittens hunt down a french soldier, much like like in a number of trailers for Assassin's Creed Unity. They use their eagle vision ability, parkour after their target, and perform lethal aerial assassinations, and yes, it's as unbearably adorable as it sounds.

Penitents wearing masks, known locally as “Morions” take a selfie during the start of Holy Week celebrations in Mogpog, Marinduque in central Philippines March 21, 2016. The Moriones is an annual festival held on Holy Week on the island of Marinduque, Philippines. The “Moriones” are men and women in costumes and masks replicating the garb of biblical Roman soldiers as interpreted by local folks. (Photo by Erik De Castro/Reuters)

A bodypainter uses UV paint to create electrifying masterpieces of stunning landscapes on models. John Poppletons vibrant Bodyscapes feature bright savannahs, lightning storms and vivid galaxies leaping from the bodies of his subjects. The artist, who lives in Wellsville in Utah, USA, uses a black light on his paintings to make them look as close to real life as possible. He predominantly uses female models and often paints across their backs to give him the largest surface area to work with. Here: “Bamboo Mist”. (Photo by John Poppleton/Caters News)