Lipotes vexillifer, Miller, 1918

Russell A. Mittermeier & Don E. Wilson, 2014, Lipotidae, Handbook of the Mammals of the World – Volume 4 Sea Mammals, Barcelona: Lynx Edicions, pp. 380-385 : 385

Baiji

Lipotes vexillifer

French: Baiji / German: Jangtse-Delfin / Spanish: Delfin del Yangtsé

Other common names: Changjiang Dolphin, Chinese Lake Dolphin, Chinese River Dolphin, White Flag Dolphin, Whitefin Dolphin, Yangtze River Dolphin

Taxonomy. Lipotes vexillifer Miller, 1918 ,

Tung Ting Lake, about 600 miles up the Yangtze River, Hunan Province, China.

This species is monotypic.

Distribution. Endemic to the middle and lower reaches of the Yangtze River, China, including Dongting and Poyang lakes, but now probably extinct.

Descriptive notes. Total length 180- 999 cm (males) and 200-253 cm (females); maximum weight 167 kg. Sexual size dimorphism is apparent, with females 8% larger than males. Body length at birth for both males and females is 91-5 cm. The Baiji is spindle-shaped but with a slightly clunky appearance compared with more streamlined shapes of most marine dolphins. Snoutis elongated (13-19% of the total body length in adults) and slightly upturned; it starts from a low, rounded melon. Body is moderately robust forward of a low, triangular dorsal fin, with a height of 4-6% of the body length and a wide base;it is located ¢.66% of the body length behind the tip of the snout. Body attenuates are more abruptly posterior of the dorsal fin to a narrow tailstock. Flukes are broad and triangular, with a breadth of ¢.18-37% ofthe total body length, slightly concave trailing edges, and a distinct median notch. Flippers are broad, with rounded leading and flat, crenellated trailing edges formed by the underlying phalanges. Baijis have a countershaded color pattern. Posterior and lateral surfaces of the body are dark gray, and belly, chin, and lower snout are pinkish-white, coming up slightly higher in a wavy boundary onto the facial region and in two ill-defined stripes from the tail region.

Habitat. Generally in countercurrents induced by complex geomorphic features, including channel confluences, mid-channel islands, and sharp meanders. These nodes of hydraulic complexity concentrate prey and provide refuge from energy-draining downstream currents. Baijis also inhabited Dongting and Poyang lakes, appended to the Yangtze River. Before 1960, a few individuals were reported in the Qiantang River, just south of the mouth of the Yangtze River.

Food and Feeding. The Baiji normally feeds on bottom fish but opportunistically preys on any small fish that can fit down its throat.

Breeding. Baiji generally breed and give birth in January-June when water levels are low, with peak births occurring in February-April. Maturity is reached at 4-6 years of age, and gestation lasts 10-11 months. Oldest recorded individual was 24 years old.

Activity patterns. Mean respiration rate of three Baijis recorded for c.10 hours while traveling upstream and crossing from one bank to the other to minimize swimming resistance was 1-2 breaths/minute, an interval close to that recorded for a captive Baiji during its daytime, non-feeding behavior. The three Baijis traveled together, generally within 5-15 m of each other. During the same sighting, groups of 2-5 “Yangtze Finless Porpoises” ( Neophocaena asiaeorientalis asiaeorientalis ) joined the Baijis for 2-25 minutes, with no obvious indication of aggressive or competitive interactions. More interactive interactions between the two species have been described, with Yangtze Finless Porpoises surfacing over the top of Baijis, which was interpreted by some local researchers as play and by others as possible aggression.

Movements, Home range and Social organization. The largest recorded group sizes of Baijis are 3—4 animals, but up to 16 individuals have been observed together. Baiji groups have been recorded moving between countercurrents induced by confluences and meanders within a relatively small stretch of river (about 10 km) for between 20 days and 30 days. Long-range movements of more than 200 km also have been documented. Their range apparently expands upstream when water levels are high, perhaps to take advantage of prey in smaller tributaries and appended lakes before they were dammed, and then contracts downstream when water levels are low.

Status and Conservation. CITES Appendix I. Classified as Critically Endangered on The IUCN Red List (probably now extinct). The historical abundance of the Baiji is little known due to the relatively late attention the species received from conservation science and difficulties in applying standardized population assessment techniques in large floodplain rivers. In the late 1970s and early 1980s, based on sighting surveys, local scientists made educated guesses that only 300-400 Baijis remained in the Yangtze River. By the late 1980s and early 1990s, surveys suggested a population of ¢.100 individuals, declining to a maximal count of 13 dolphins recorded during a rangewide survey in 1997. Even though no time series of rigorous abundance estimates is available, the Baiji undoubtedly underwent a rapid decline from when surveys began in the late 1970s, and it almost certainly went extinct less than 100 years after the species was described scientifically. An exhaustive visual and acoustic survey for the Baiji in 2006 and an extensive interview survey in 2008 failed to find evidence of its continued existence. Pernicious fishery interactions were probably the primary cause of the species’ precipitous decline (particularly snagging on illegal bottom-set long lines with multiple hooks in the 1980s and possibly electrocution from illegal electrofishing starting in the 1990s); however, construction of extensive hydropower, flood control, and irrigation projects, resulting in extensive habitat loss in the Yangtze River system, were almost certainly contributing factors. Efforts to prevent extinction of the Baiji were hampered by a lack of consensus on whether or not it should be protected within a degraded Yangtze ecosystem or if an ex situ population should be established in one or more “semi-natural” reserves. Ultimately, an insufficient commitment was made to implement either approach, and the Baiji is presumed to be extinct. This represents a disproportionately large loss of evolutionary history because the Baija belongs to a monotypic family with no living sister taxon.

Bibliography. Akamatsu et al. (1998), Barnes (1985a), Braulik et al. (2005), Brownell & Herald (1972), Cassens et al. (2000), Chen Peixun (1989), Chen Peixun & Hua Yuanyu (1989), Chen Peixun, Lin Kejie & Hua Yuanyu (1985), Chen Peixun, Liu Peilin et al. (1980), Diamond (1987), Hamilton et al. (2001), Hoy (1923), Hua Yuanyu et al. (1989), IWC (2001a), Kasuya (1973), Lin Kejie et al. (1986), Liu Renjun et al. (2000), Liu Renjun, Yang Jian et al. (1998), Mead & Brownell (2005), Miller (1918, 1923), de Muizon (2009), Nikaido et al. (2001), Pyenson (2009), Rice (2009c), Scheffers et al. (2011), Smith, A.M. & Smith (1998), Smith, B.D. & Reeves (2012), Smith, B.D. et al. (2008), Turvey (2008), Turvey, Barrett, Hao Yujiang et al. (2010), Turvey, Barrett, Hart et al. (2010), Turvey, Pitman et al. (2007), Wang Ding, Lu Wenxiang & Wang Zhifan (1989), Wang Ding, Zhang Xianfeng etal. (2006), Wang Kexiong et al. (20006), Wiirsig et al. (2000), Xiao Youfu & Jing Rongcai (1989), Yan Jie et al. (2005), Yang Guang, Zhou Kaiya et al. (2002), Zhang Xianfeng et al. (2003), Zhou Kaiya (1982, 1989, 2009), Zhou Kaiya & Li Yuemin (1989), Zhou Kaiya & Zhang Xingduan (1991), Zhou Kaiya, Qian Weijuan & LiYuemin (1978, 1979), Zhou Kaiya, Sun Jiang et al. (1998).

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Distribution. Endemic to the middle and lower reaches of the Yangtze River, China, including Dongting and Poyang lakes, but now probably extinct.