Trachypithecus francoisi (de Pousargues, 1898)

Russell A. Mittermeier, Anthony B. Rylands & Don E. Wilson, 2013, Cercopithecidae, Handbook of the Mammals of the World – Volume 3 Primates, Barcelona: Lynx Edicions, pp. 550-755 : 751

156.

Francois’s Langur

Trachypithecus francoisi

French: Langur de Francois / German: Tonkin-Langur / Spanish: Langur de Francois

Other common names: Black Leaf Monkey, Francois’s Leaf Monkey, Tonkin Leaf Monkey, White Side-burned Black Langur

Taxonomy. Semnopithecus francoisi de Pousarges, 1898 ,

LLongzhou, China.

1. francoisi is a member of the francois species group, also known as the karst or limestone langurs. Monotypic.

Distribution. SC China (Chongqing Municipality and Guizhou and Guangxi provinces) and N Vietnam (Ha Giang, Cao Bang, Tuyen Quang, Bac Kan, and Thai Nguyen provinces). Francois’s Langur has the northernmost distribution of the langurs.

Descriptive notes. Head-body 51-63 cm (males) and 50-60 cm (females), tail 80-90 cm (males) and 74-90 cm (females); weight 6.4-7.9 kg (males) and 5.5-7.9 kg (females). Pelage of Francois’s Langur is glossy-black, with only a narrow tract ofslightly elongated white hairs running from corners of mouth along sides of face to upper edges of ears, in a sort of exaggerated handlebar moustache. They have a tall, pointed crest on their crowns. Face is jet black. There are no differences in coloration between males and females, except that females have a pubic patch with unpigmented skin and whitish or yellowish hairs in front of callosities. Pubic patch has an individually different irregular shape. Infants are born with a yellow-orange pelage but with individually variable blackish shades on back, hips, and tail. Facial skin is yellowish-brown. Color of hair starts to change to black at c.3 weeks of age, and the infant is entirely black by six months of age.

Habitat. Evergreen broadleaf, mostly limestone, forest. Steep limestone outcrops are the typical habitat, predominantly at elevations up to 600 m. Francois’s Langurs use caves and crevices on steep slopes and cliffs as shelters and sleeping sites. Minimum and maximum temperatures in the northern part of its distribution are 5°C and 40°C.

Food and Feeding. Francois’s Langurs are primarily folivorous, but fruits and seeds also make up a large part of their diet. Diets are variable among the populations. Ninety plant species provided food items for the population in Nonggang Nature Reserve, Guangxi, China. Ten species accounted for 60% of the diet. In Fusui Nature Reserve, Guangxi, China, 37 plant species were recorded, and ten species accounted for 90% of the diet. In Fusui, the diet was 94% leaves and 6% fruits, flowers, and stems, and in Nonggang, it was 53% leaves (39% young leaves, 14% mature leaves), 17% fruits, 14% seeds, 8:5% flowers, and 7% stems, roots, and bark. Francois’s Langurs lick rock surfaces and put pieces in their mouths, possibly for minerals.

Breeding. Male Francois’s Langurs reach sexual maturity at ¢.5 years old, females at 3:5—4-5 years. The menstrual cycle is 22-5 (+ 7-9) days. The gestation period is 184 (+ 15) days, and the interbirth interval is 19-1 (+ 2:2) months. Females give birth to a single offspring.

Activity patterns. Francois’s Langurs are diurnal, crepuscular, arboreal, and terrestrial. Caves and crevices are normal sleeping places. In the evening, they enter their sleeping cave, depending on the season, at 18:30-20:00 h and move out in the morning before dawn. There are two feeding peaks: 09:00-11:00 h and 16:00-18:00 h. Francois’s Langurs spend c.43-52% of the daytime resting, 23-25% feeding, 14-17% moving, 6-9% playing, and 6-8% grooming. Some activities change seasonally. In spring, when availabilities of young leaves are greater, they spend less time feeding and more time playing; in winter, more time is spent resting. In a small isolated population in Fusui Nature Reserve, Francois’s Langurs spend only 10% of their day feeding in summer compared to 21% in winter, because the abundance of leaves in the rainy season reduces feeding time. Juveniles play much more than adults: 15% for juveniles compared to 3% for adults.

Movements, Home range and Social organization. In summer, Francois’s Langurs spend c.60% of their day in trees and 40% on rocks; in winter, less time is spent on rocks. Leaping, quadrupedal walking, and climbing account for 92:8% of locomotory behavioral records, dropping or free-falling to lower levels of the canopy for 7-9%, and brachiating for 2-1%. During walking, running, and leaping, a concave downward arch of the tail is exhibited, as in other northern species of the “limestone langurs,” the Cat Ba Langur (71. poliocephalus ), the White-headed Langur (7. leucocephalus ), and Delacour’s Langur (71. delacouri ). This posture differs from the southern species, the Hatinh Langur (7 hatinhensis ), the Laos Langur (7. laotum ), and the Black Langur (1 ebenus ). There are no detailed studies on the home ranges of Francois’s Langurs, but some groups use less than 50 ha. The normal social unit is a unimale-multifemale group, with their offspring. The average group sizes were 5-7-7-5 individuals for several larger subpopulations with 18-75 total individuals in Guangxi. Average group size for all populations is 7-2 individuals.

Status and Conservation. CITES Appendix II. Classified as Endangered on The IUCN Red List. Francois’s Langur is protected by law in China and Vietnam. The population has decreased because of hunting for use in traditional medicine and is now highly fragmented. The total population declined in China during the last decade of the 20" century by ¢.70% from an estimated 6000-7000 individuals to ¢.1600. The population decline in Guangxi has been ¢.85%, to ¢.300 individuals in 14 isolated populations. There are an estimated ten populations with 900-1000 individuals in Guizhou and four populations with ¢.150-200 individuals in Chongqing. The largest population occurs in Mayanghe Nature Reserve, Guizhou, with ¢.400-450 individuals. In Vietnam, Francois’s Langurs have been almost extirpated from their historical distribution; scattered populations exist in the northern provinces of Ha Giang, Cao Bang, Tuyen Quang, and Bac Kan. Populations in the provinces of Lang Son, Vinh Phuc, Lao Cai, and Yen Bai have already been extirpated. In Vietnam, there are only a few sightings of Francois’s Langurs that have been recorded in the last few decades. Based on interview surveys of local people, the total population in Vietnam is estimated to be less than 250 individuals, divided into at least ten subpopulations. Francois’s Langurs do not overlap with other “limestone langurs.” The population in Guangxi, China, is separated by the Zuojiang River from the White-headed Langur, which occurs to south. Some individual Francois’s Langurs have been released in the distribution of the White-headed Langur, which has resulted in some hybrids. First generation hybrids and their descendants have features most similar to Francois’s Langur.

Bibliography. Brandon-Jones (1995b), Fooden (1996), Gibson & Chu (1992), Huang Chengming, Wu Hua et al. (2008), Huang Chengming, Zhou Qihai et al. (2006), Li Youbang et al. (2007), Li Zhaoyuan (2006), Mai Qunian (1998), Mai Qunian & Lai Maoging (1998), Mai Qunian et al. (1998), Nadler (1994, 1996¢, 2006), Nadler et al. (2003), Que Tengcheng et al. (2006), Stevens et al. (2008), Zhou Qihai (2005), Zhou Qihai, Huang Chengming et al. (2006), Zhou Qihai, Wei Fuwen et al. (2006).

Figures

149. Tenasserim Langur (Trachypithecus barber), 150. Dusky Langur (Trachypithecus obscurus), 151. Phayre’s Langur (Trachypithecus phayrei), 152. Indochinese Gray Langur (Trachypithecus crepusculus), 153. Cat Ba Langur (Trachypithecus poliocephalus), 154. White-headed Langur (Trachypithecus leucocephalus), 155. Delacour’s Langur (Trachypithecus delacouri), 156. Francois’s Langur (Trachypithecus francoisi), 157. Black Langur (Trachypithecus ebenus), 158. Laos Langur (Trachypithecus laotum), 159. Hatunh Langur (Trachypithecus hatinhensis)

Distribution. SC China (Chongqing Municipality and Guizhou and Guangxi provinces) and N Vietnam (Ha Giang, Cao Bang, Tuyen Quang, Bac Kan, and Thai Nguyen provinces). Francois’s Langur has the northernmost distribution of the langurs.