Combat between two male stag beetles, Italy, 2022. During the mating season, male stag beetles (Lucanus cervus) go into a frenzy, with lively but harmless clashes, in which bigger males often have the advantage over smaller ones due to their impressive mandibles. Longer larval development and genetic traits can increase the size of some individuals, but all saproxylic beetles are threatened by poor forest management, logging and dead wood removal to “clean” the forest. (Photo by Iacopo Nerozzi)

A young male fiddler crab is dwarfed by an older male of the same species, looming behind it at Morua estuary, in the Gulf of California, Mexico on January 4, 2022. Whereas female fiddler crabs have small claws of equal sizes, the males’ pincers can vary in size, with the small one used to pick up food and the larger to impress females. (Photo by Claudio Contreras/Solent News)

1st Place in Wildlife: A male orangutan peers from behind a tree while crossing a river in Borneo, Indonesia. (Photo by Jayaprakash Joghee Bojan/National Geographic Nature Photographer of the Year contest 2017)

Two male African mantis Pseudempusa pinnapavonis (Peacock Mantis) show their colours in Igor's home studio in Munich, Germany. (Photo by Igor Siwanowicz/Barcroft Media)

It looks like a kiss but this male and female blackbird were fighting in flight in Charlton Adam, Somerset, South West England in July 2022. (Photo by Ben Pulletz/Solent News)

A volunteer approaches a male toad to pick him up from a road near Berlin on March 18, 2012 in Gueterfelde, Germany. (Photo by Sean Gallup/Getty Images)

“This grey adult male seal enjoys a good grin while lying on the beach”. (Photo by Michael Hutch/SplashdownDirect via Rex USA)

Five micropigs born to mother, “Truffel”, are seen in Zoo Wuppertal on August 11, 2014 in Wuppertal, Germany. The five micropigs are the major attraction of Zoo Wuppertal. Pigedy, Fiete, Frederik, Smartie are 4 males and is Keks is a female micropig. (Photo by Animal Press/Barcroft Media)