Pseudois schaeferi [Haltenorth, 1963].
- Citation: Handb. Zool., 8(32):126.
- Type locality: China, upper Yangtze Gorge (Drupalong, south of Batang).
- Citation: Handb. Zool., 8(32):126.
The above taxonomic record is from Wilson and Reeder (1993). Pseudois schaeferi was initially "discovered" by Dolan and Schäfer during their 1934-1936 expedition to the Tibetan plateau (Groves, 1978; Wang and Hoffmann, 1987). While transcribing Schäfer's field notes the following year, Engelmann (1938) attributed subspecific status to this new blue sheep, but failed to name it (Wang and Hoffmann, 1987). Allen (1940) considered these "new" specimens to be either immature or stunted due to insufficient food, and attributed them to Pseudois nayaur szechuanensis (Wang and Hoffmann, 1987). It was not until 1963 that Haltenorth first assigned a name to the dwarf blue sheep, designated as the subspecies P. nayaur schaeferi. Groves (1978) found sufficient morphological evidence to place P. schaeferi as a separate species.
Recently, genetic techniques have been used to try and resolve the taxonomic status of the genus Pseudois, with results that challenge the multiple-species classification presented here. Feng et al. (2001) found an average 12.21% sequence divergence in mitochondrial DNA between P. schaeferi and P. nayaur, supporting at least a subspecific ranking for the dwarf blue sheep. However, there was weak differentiation between the two species based on nuclear Y-linked genes, leading the study to conclude that P. schaeferi should not be a separate species, but considered to be a subspecies of P. nayaur. Other recent studies, using the mitochondrial cytochrome b gene (Zhou et al., 2003), D-loop, and ZP3 gene (Zeng et al., 2008), have concluded that even subspecific rank may not be merited for the individuals recognized as P. schaeferi; Zeng et al. (2008) concluded that the dwarf blue sheep is simply a "morphologically different population of P. n. szechuanensis, and the rank of a full species or subspecies is not appropriate".
Much speculation has been given to what maintains the reproductive isolation between the two 'species' of Pseudois, as they are geographically separated by a forest zone only 1,000 meters in altitudinal height (Wang and Hoffmann, 1987). Zeng et al. (2008) propose that a single genetic mutation may be responsible for the phenotypic dwarfism of the dwarf blue sheep. Wang and Hoffmann (1987) suggest that the dwarf blue sheep may be a peripheral, isolated population undergoing speciation. Despite the controversy and recent leanings towards there being a single species within Pseudois, many authors still tentatively recognize P. schaeferi as a unique entity; as a result, it is treated as a full species in this account.
The dwarf blue sheep is monotypic (Wang and Hoffmann, 1987). Few studies have been conducted on P. schaeferi, and much of the available data merely compares this species with P. nayaur.
|Reported measurements for dwarf blue sheep (Pseudois schaeferi)|
|Source||Adult Weight||Head & Body Length||Shoulder Height||Tail Length|
and Allen (1940).
in Groves, 1978
Wang and Hoffmann, 1987
|Smith and Xie, 2008||28-39 kg
(up to 65 kg)
|109-160 cm||50-80 cm||7-12 cm|
|Wang et al., 2000||est. 34-44 kg
(up to 65 kg)
|Wu et al., 1990
in Wang et al., 2000
|35 kg (one )||106-107 cm (n=2)||64 cm (one )||15-17 cm (n=2)|
Groves (1978) provides several comparative features between the two species of Pseudois. Compared to P. nayaur, P. schaeferi is generally darker but the black markings of the bharal (on the head, neck, legs, and a lateral flank stripe) are only weakly expressed (except in old males). There is less white on the underbelly in the dwarf blue sheep than the bharal. The pelage is shorter and has a sparser undercoat compared to P. nayaur.
Apart from body weight, the horns of males are the best diagnostic feature for differentiating P. schaeferi from P. nayaur. Compared to the Himalayan blue sheep, male dwarf blue sheep have smaller, thinner, and more upright horns which have no inward curve (Groves, 1978). The laterally-spreading horns of P. schaeferi males never form the sweeping semicircles of P. nayaur and the straight tips point up and out rather than backwards (Groves, 1978). The horn span - always greatest at the tips - averaged 54.3 cm among seven males measured by Groves (1978). The horns of one male (estimated to be 4.5 years old) measured by Wang et al. (2000) were 41 cm long, with a basal circumference of 23 cm. The horns of females are very similar to those of female Himalayan blue sheep, being short and curving slightly upward then outward (Wang and Hoffmann, 1987).
Population densities range between 0.5-1.0 individuals per square kilometer (Wu et al., 1990), a figure corroborated by the density of 0.705 animals per square kilometer reported by Wang and Wang (2003).
Dwarf blue sheep are known to eat more than twenty species of plants (Wu et al., 1990). According to the observations made by Wang et al. (2000), P. schaeferi feeds primarily on grasses (for instance Pennisetum flaccidum and Setarica glauca), although other plants such as clubmoss (Selaginella sanguinolenta) are also eaten. Dwarf blue sheep are hunted by wolf (Canis lupus), dhole (Cuon alpinus), leopard (Panthera pardus), and large raptors (Wang et al., 2000).
Dwarf blue sheep have been described as "timid and wary" (Wang and Wang, 2003). This species appears to be most active in the early to mid morning and in the late afternoon; animals typically bed down between 11h00 and 15h00 (Long et al., 2009). Prior to resting, dwarf blue sheep will scrape and dig at the ground with their forelimbs (Wang and Wang, 2003). Foraging accounts for 30% of the summer daylight time budget, with bedding (resting), standing, and moving accounting for the majority of the rest of the time (26, 25, and 16%, respectively) (Long et al., 2009).
Countries: China (Harris, 2008).
- Local names
Rong-na [Tibetan] (Wang et al., 2000)
- Ai Yanyang [Chinese] (Smith and Xie, 2008)
- das Zwergblauschaf (Schäfer, 1937 in Groves, 1978)