Today seems appropriate to share a portrait of a chimpanzee.

Black crested macaque, famous for its winning smile. It uses this facial expression, among others, to invite another troop member to play, groom or mate. And just to show friendly intentions in general. From Tangkoko Nature Reserve on Sulawesi, the hotspot for this threatened species.

Red eyeliner, blue eyeshadow, a heart-shaped coiffure. The pig-tailed macaque males go all in to look their best. Khao Yai National Park, Thailand.

Eye contact with black crested macaque in the monsoon forest of Sulawesi.

MEDITATION / Golden snub-nosed monkey from the Qinling Mountains, Shaanxi, China.

Gelada male from the high mountains of Ethiopia.

Chimpanzee male with a scar on his lip from a colobus hunt. Kibale National Park, Uganda.

Black-and-white snubnosed monkey from Yunnan, China eating its favourite - or at least dominant - food, lichens. A male with big pink lips.

Wild blue-eyed black lemur from north-western Madagascar.

Japanese macaque mother cradling her young in the Jigokudani hot spring in the winter mountains of central Japan.

MOHAWK / Black crested macaque alpha male from the monsoon forest of Sulawesi, Indonesia.

Golden snub-nosed monkey from the winter landscape of the Qinling Mountains of China. Thick fur and a habit a hugging each other at night allows it to survive night temperatures down to -30 degrees Celsius.

Close-up portraits of the drill (Mandrillus leucophaeus), the lesser-known cousin of the mandrill. The black mask of the big males is almost orangutan-like. Pandrillus Afi Mountain, Cross River, Nigeria.

A female Bornean orangutan from the wild.

Female Japanese macaque, aka snow monkey, relaxing in a hot spa on a cold winter day, looking lazily over her shoulder to send me a glance with her expressive amber eyes. The face of the females gets redder during the mating season. Jigokudani, Japan.

Eye contact with a proboscis monkey youngster from the mangrove of Borneo.

Mandrill youngster from the wild. Gabon.

Wild Golden Langur from Assam, India.

Gelada youngster, Ethiopia.

Drill male making flirtation face, making eye contact with a female. Afi Mountains Pandrillus site, Cross River, Nigeria.

Snow monkey cannot believe its own eyes. Japan.

Black crested macaque alpha male from Tangkoko Nature Reserve, Sulawesi.

Gelada male from the Simian Mountains of Ethiopia. The larger a harem a male has, the darker and more intensely red his chest mark gets.

Lion-tailed macaque female from the jungle of the Western Ghats mountains in southern India.

Snow monkey mother and youngster in snowy weather in the winter mountains of Japan.

Big drill male from Nigeria. Pandrillus Afi Mountain field site, Cross River, Nigeria.

Wild orangutan infant from the rainforest of Borneo.

Golden snub-nosed monkey with a youngster. Qinling Mountains, Sichuan, China.

Black-crested macaque baby from the Tangkoko Nature Reserve, Sulawesi.

Black-and-white snub-nosed monkey male. The dominant males have the most pink lips and during the mating season turn up the "pinkness" of their lips even more. It's a way to signal masculinity. Yunnan, China.

Hanuman langur youngster from Ranthambore National Park, India.

Golden snub-nosed monkey infant from the Qinling Mountains of China, warmly dressed to survive winter temperatures down to -30 degrees Celsius.

Drill male in a quiet moment. Pandrillus Afi Mountain site, Cross River, Nigeria.

Gelada male with a stern look on his face. Ethiopia.

Red-shanked douc from Vietnam, one of the world's most colourful primates.

Blue-eyed black lemur from the wild of Madagascar.

SCARFACE / A drill male with a scarred nose, very likely from a fight over power with another male. Pandrillus Afi Mountains site, Cross River, Nigeria.

Mandrill male from the jungle of Gabon communicating to an approaching female that he is in a friendly mood.

Wrinkle-faced gelada youngster. Simian Mountains National Park, Ethiopia.

A very patient orangutan mother allowing her offspring to pick food out of her mouth. This is a way for youngsters to learn what is good orangutan food. Tanjung Puting National Park, Borneo.

Black crested macaque smiling. Tangkoko Nature Reserve, Sulawesi, Indonesia.

Wild chimpanzee male in profile. Kibale National Park, Uganda.

Portrait of a female bear macaque (aka stump-tailed macaque) from Thailand, one of only two species where both sexes have red faces.

Long-tailed macaque female enjoying a mussel. She belongs to the tribe of stone-tool-using "stone-age monkeys" that I photographed on an uninhabited island in Thailand last year.

Tibetan macaque mother in thick winter fur cradling her young to keep it warm and safe. The species is mostly terrestrial and said to prefer sleeping in caves. From the mountains of Labahe Naure Reserve, Sichuan, China.

Observant pig-tailed macaque female from Khao Yai National Park, Thailand.

Japanese macaque female in thick winter coat looking to the sky. Jigokudani, Japan.

Black crested macaque males have some of the longest canine teeth of all primates. The species is mostly a fruit-eater so these weapons are used for intimidation and fights. Tangkoko, Sulawesi.

Portrait of a wild chimpanzee male from Kibale National PArk, Uganda.

Coquerel's sifakas can jump 10-12 meters between trees using their powerful hindlegs. Ankarafantsika National Park, NW Madagascar.