Hainan crested gibbon
| Hainan crested gibbon | ||||||||||||
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Hainan crested gibbon |
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| Nomascus hainanus | ||||||||||||
| ( Thomas , 1892) |
The Hainan black crested gibbon ( Nomascus hainanus ) is a primate of the family of gibbons (Hylobatidae). Until recently it was grouped into one species with the Eastern Black Crested Gibbon .
features
The Hainan crested gibbon reaches a head-trunk length of up to 49 cm (males) or 48 cm (females) and a weight of 5 to 10 kg. Like all other species of its genus, this species has a sexual dimorphism . Males are completely black in color, while females have a brownish-yellow-brown fur, a black vertex and a thin, white ring around the face. Infants are born yellow-brown in color. At 5 to 6 months, the young turn black. While the males keep this coat color for their entire life, the females get a brownish-yellow-brown coat with sexual maturity.
distribution and habitat
The Hainan crested gibbon was once widespread all over Hainan . Today the distribution area of the only known population is limited to the Bawangling nature reserve in the west of the island.
Preferred habitat was lowland forests, which are now largely disappeared, so that the animals now only in mountain forests in 700- 1200 m occur height.
Way of life and reproduction
The Hainan crested gibbon is a diurnal tree dweller. The activity starts just before dusk with loud chants. Adult males lead the group on the walks through the area . The number of members of a group in Hainan Crested Gibbons is high. Observations of the last two groups in 2008 showed that they contain nine to six individuals. The districts are also very large with 548 hectares and 987 hectares, respectively. It is not known whether the large territories are typical for this species, related to the lack of preferred habitats or the lack of competition from neighboring groups. Observations over 30 years have shown that the two groups have polygamous mating strategies with two females and one male. However, mating chances are limited, which is believed to reflect abnormal behavior - a point of contention for many years. Subadult animals leave the groups or are driven away when they are around 5.5 years old. Leaving the group carries a high risk of mortality and few animals formed new groups.
So far, 119 species of plants are known to be eaten in parts by Hainan crested gibbons. Food availability is believed to be limited from February to April. During this time they feed on less preferred plant species. The displacement into actually avoided mountain forests also had consequences on their diet, as there are fewer different plant species in these regions and only a few preferred tree species are found here.
The gestation period for the Hainan crested gibbons is 136–173 days and the interval between births is over two years. Births do not depend on the season and the young are suckled for about 1 year. The chances of survival of infants can be up to 92%. Between 1982 and 1989, nine of the twelve young animals born were males, which distorted the gender ratio and led to disputes over the choice of mate. Polygamous groups are quite common. Females initiate sexual meeting places with multiple males while they are ready to conceive and are receptive even after this time.
One hybrid is known to be a Northern white-cheeked gibbon from the Twycross Zoo in 1987.
threat
The Hainan crested gibbon is classified by the IUCN as "critically endangered" (critically endangered). It is protected in China and only occurs in a single nature reserve, the Bawangling Nature Reserve. Three hundred years ago the species lived almost all of Hainan Island, covering nearly 27,784 km 2 , but several waves of habitat destruction have reduced the suitable habitat to only 66 km 2 . The animals are now limited to a mere 14–16 km 2 . The population has shrunk from over 2000 animals in the 1950s to a low of 7 to 8 known animals in the 1970s. A discovery of further animals in the 1980s increased the value to 21. In 2008 the population consisted of 22 individuals, two groups with seven or eleven animals and four individually living specimens, in 2015 25 individuals were counted. Although the number has increased in recent years, no new groups have been formed since 2000. The small population is prone to inbreeding, disease outbreaks, and natural disasters.
Another threat is habitat degradation, which has increased on a large scale in recent decades due to infrastructure development and agriculture. Between 1991 and 2008, 35% of the island's forest area and 7% of the only area inhabited by Hainan crested gibbons disappeared (in the Bawangling National Nature Reserve). Not only did the total forest area become smaller, the number of suitable forest areas (at least 1 km 2 of contiguous forest area) also fell from 92 to 64 in the 17 years. In relation to such areas, the shrinkage was particularly pronounced with a decrease from 754 km 2 to 316 km 2 . The continued demand for Hainan crested gibbons as a traditional Asian medicine is also a threat, although there has been no known hunt for these animals in recent years. Stopping these threats is an important goal for the conservation of the species, as is the planting of new forests, which has already begun in some regions.
literature
- Russell A. Mittermeier, Anthony B. Rylands, Don E. Wilson: Handbook of the Mammals of the World. Volume 3: Primates. Lynx Edition, Barcelona 2013, ISBN 978-84-96553-89-7 , p. 788.
Web links
Individual evidence
- ↑ Van Ngoc Thinh, Alan R. Mootnick, Vu Ngoc Thanh, Tilo Nadler, Christian Roos: A new species of crested gibbon, from the central Annamite mountain range. (PDF) In: Vietnamese Journal of Primatology 4, 2010, pp. 1–12.
- ↑ Jiang Zhou, Fuwen Wei, Ming Li, Chan Bosco Pui Lok, Deli Wang: Reproductive characters and mating behavior of wild Nomascus hainanus. In: International Journal of Primatology 29, No. 4, 2008, pp. 1037-1046, doi: 10.1007 / s10764-008-9272-7 .
- ↑ Zhenhe Liu, Chaofeng Tan: An analysis on habitat structure of the Hainan gibbon. In: Acta Theriologica Sinica 10, No. 3, 1990, pp. 163-169.
- ↑ International Zoo Yearbook. 1989, p. 320.
- ↑ Thomas Geissmann: Status reassessment of the gibbons: results of the Asian primate red list workshop 2006. (PDF) In: Gibbon Journal 3, No. 2007, 2007, pp. 5-15.
- ↑ John R. Fellowes, Chan Bosco Pui Lok, Zhou Jiang, Chen Shenghua, Yang Shibin, Ng Sai Chit: Current status of the Hainan gibbon (Nomascus hainanus): progress of population monitoring and other priority actions. (PDF) In: Asian Primates Journal 1, No. 1, 2008, pp. 2–11.
- ↑ New action plan to save world's rarest primate. On: eurekalert.org from May 19, 2015.
- ^ Mingxia Zhang, John R. Fellowes, Xuelong Jiang, Wei Wang, Bosco PL Chan, Guopeng Ren, Jianguo Zhu: Degradation of tropical forest in Hainan, China, 1991-2008: Conservation implications for Hainan Gibbon (Nomascus hainanus). In: Biological Conservation 143, No. 6, 2010, pp. 1397–1404, doi: 10.1016 / j.biocon.2010.03.014 .