Two Red Deer stags stand in the early morning mist in Richmond Park on October 15, 2011 in London, England. Autumn sees the start of the “Rutting” season where the large Red Deer stags can be heard roaring and barking in an attempt to attract females known as bucks. The larger males can also be seen clashing antlers with rival males. (Photo by Dan Kitwood/Getty Images)

An undated handout picture released on January 10, 2017 by the Issekinicho publishing house shows an inter- species sexual behaviour between a male Japanese macaque and female sika deer, in Yakushima Scientists revealed on January 10, 2017 the “highly unusual” behaviour of a male monkey filmed trying to have sеx with female deer in Japan – a rare case of inter- species nookie. (Photo by Editions Issekinicho/AFP Photo)

This huge male orangutan is having a right old laugh as he squints his eyes and shows his huge teeth. The orangutan, called Bimbo, was relaxing on a platform around 5m high in his enclosure when he broke out into a laugh. But his happy smile soon disappeared when another orangutan came over to see what was going on. Bimbo – the only male in the group of five apes at Leipzig Zoo, in Germany - appears to be laughing in much the same way as a human would. (Photo by Martina Radtke/Solent News)

Almost two years old male baby orang-utan Dalai looks on in the zoo in Dresden, Germany, 30 March 2017. Dalai was born to mother Daisy in June 2016. (Photo by Filip Singer/EPA)

A male green anole lizard flares his throat fan in a backyard in Cary, North Carolina on April 27, 2021. This pink section is actually a thin flap of skin that hangs down below the green anole's throat. Anoles are renowned for their displays in which they do pushups, bob their heads up and down, and unfurl their colorful dewlaps. The male anole uses it for two primary purposes: to protect his territory and attract a mate. (Photo by Bob Karp/ZUMA Press Wire/Alamy Live News)

Eugloss dilemma, male, Florida, Biscayne National Monument. (Photo and caption by Sam Droege/USGS Bee Inventory and Monitoring Lab)

The double compound eyes of a male St. Mark's fly (Bibio marci), submitted by Dr. David Maitland from Feltwell, UK. (Dr. David Maitland)

A male deer barks at dawn during the annual deer rutting season at Richmond Park in London, Britain, October 9, 2016. (Photo by Toby Melville/Reuters)