Gunung Leuser National Park is a national park covering 7,927 km² in northern Sumatra, Indonesia, straddling the border of North Sumatra and Aceh provinces. The national park, named after Mount Leuser (3,381 m), protects a wide range of ecosystems. An orangutan sanctuary of Bukit Lawang is located inside the park. Together with Bukit Barisan Selatan and Kerinci Seblat national parks it forms a World Heritage Site, Tropical Rainforest Heritage of Sumatra.

A woman smokes a cigarette next to man wearing a mask during lunch hour at the central business district in Singapore September 29, 2015. The 3-hour haze Pollutant Standards Index (PSI) reached a high of 173 at 8am on Tuesday, according to the National Environment Agency. Slash-and-burn agriculture in neighboring Indonesia has blanketed Singapore in a choking haze for weeks. (Photo by Edgar Su/Reuters)

Malabon Zoo owner Manny Tangco holds a full-grown but very small rooster named “Small But Terrible” from Malaysia to compare it with the giant red rooster from France named “Mr. Universe” as they are shown to the media as part of the “Roosters of the World” exhibition to celebrate the “Red Fire Rooster” in the Chinese lunar calendar Friday, January 27, 2017 in suburban Malabon city north of Manila, Philippines. The Roosters of the World exhibition features roosters from countries as the United States, Japan, United Kingdom, France, China, Malaysia, Indonesia and Poland. (Photo by Bullit Marquez/AP Photo)

Indonesian residents look at the Mount Sinabung volcano as it spews volcanic ash near the Tiga Pancur village in Karo, North Sumatra on August 3, 2016. Volcanic eruptions in Indonesia in recent days have forced the closure of two airports and disrupted some flights to the holiday island of Bali, officials said August 3. Mount Sinabung, a volcano on the western island of Sumatra which has been rumbling for some time, also erupted violently on August 2, although its ash clouds did not disrupt any flights. (Photo by Y.T. Haryono/AFP Photo)

A handout photo made available by Borneo Orangutan Survival Foundation (BOSF) shows veterinarian wearing protective masks and suit, conducting anesthesia procedure on Nenuah, a nine year old Bornean Orangutan before being transported and released to the Bukit Batikap protection forest, at the Nyaru Menteng Orangutan Rehabilitation Center in Palangkaraya, Central Kalimantan, Indonesia, 15 February 2021. BOSF and the national nature conservation agency (BKSDA) released 10 orangutans back to the wild in Bukit Batikap Protection Forest in Central Kalimantan and the Kehje Sewen Forest in East Kalimantan amid the pandemic according to BOSF. (Photo by BOSF Handout/EPA/EFE)

A devotee of the Chinese shrine of Samkong, pierces his cheeks with toy guns during a procession of Vegetarian Festival on October 11, 2010 in Phuket, Thailand. Ritual Vegetarianism in Phuket Island traces it roots back to the early 1800's. The festival begins on the first evening of the ninth lunar month and lasts for nine days. Participants in the festival perform acts of body piercing as a means of shifting evil spirits from individuals onto themselves and bring the community good luck. (Photo by Athit Perawongmetha/Getty Images)

Casket of Leibby Kletzky, a murdered eight-year-old boy who went missing from the Hasidic neighborhood of Borough Park, Brooklyn is carried during a procession on July 13, 2011 in New York City. After a two day search Kletzky's dismembered body was found partially in a suitcase inside a dumpster and partially in a refrigerator in a nearby apartment. Police detectives have taken Levi Aron, 35, into custody in connection to the killing. (Photo by Ramin Talaie/Getty Images)

Participants prepare backstage before the 5th “Strongo Cup” open amateur bodybuilding tournament at the State Opera and Ballet Theatre in Russia's Siberian city of Krasnoyarsk, November 1, 2014. Participants from all over Russia took part in the tournament competing in bodybuilding, body fitness and bikini fitness disciplines. (Photo by Ilya Naymushin/Reuters)