Pseudois schaeferi [Haltenorth, 1963].

Citation: Handb. Zool., 8(32):126.

Type locality: China, upper Yangtze Gorge (Drupalong, south of Batang).

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.

P. schaeferi is differentiated from the closely-related blue sheep or bharal (P. nayaur) primarily by size (Groves, 1978). Adult male dwarf blue sheep weigh half as much as similar specimens of P. nayaur, averaging 35 kg. Other body measurements are apparently much less different (Groves, 1978), but are not reported. There is considerably less sexual dimorphism in the dwarf blue sheep than in the bharal, and females of the two species are very similar (Groves, 1978). P. schaeferi does not maintain body condition well during the winter, becoming noticeable thin (Schäfer, 1937 in Groves, 1978).

The overall color of the dwarf blue sheep is a steely or silvery gray with whitish underparts (Schäfer, 1937 in Groves, 1978). In summer, the main body color tends to be a brownish-gray with a yellowish tinge, becoming "rather drab" in winter (Groves, 1978; Wu et al., 1990). The tips of newly-grown hairs are darker than the rest of the hair shaft, but these dark bands are short and wear off quickly (Groves, 1978). The limbs are dark but do not have clear black markings (Groves, 1978). Skull measurements are presented by Groves (1978).

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).

Little is known on the reproduction of the dwarf blue sheep. According to local reports, the breeding season (rut) occurs between mid-November and mid-December (Wang et al., 2000). Females typically give birth to a single young between late May and late June (Wang et al., 2000), although twins may occur (Smith and Xie, 2008). The gestation period is about 6 months, specified to 160 days by Smith and Xie (2008). Weaning occurs around six months of age, and sexual maturity is reached at 1.5 years, although males may not reach their full size until their seventh year (Smith and Xie, 2008).

Dwarf blue sheep inhabit rugged terrain along the Yangtze river valley. They are found at altitudes between 2,600 and 3,200 meters, and are usually observed on very steep rocky slopes with an incline of 70 to 80 degrees (Wu et al., 1990; Wang et al., 2000). This valley habitat is dry with sparse vegetation cover; common plant species include grasses (Cymbopogon distans and Themeda hooderi), low shrubs (Berberis sp., Rosa sp., Cotoneaster sp., Cladrastis sp., Ephedra sp., and Rhododendron sp.), and clubmoss (Selaginella sanguinolenta) (Wang et al., 2000). This species is occasionally seen in coniferous forests and clearings (Smith and Xie, 2008). The area occupied by P. schaeferi is isolated from the alpine habitat of P. nayaur by a belt of oak forest in which neither species is observed (Groves, 1978; Wang et al., 2000).

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).

The initial records of Schäfer (1937 in Groves, 1978) report herds of three to ten animals, with lone individuals being common. Modern reports confirm that dwarf blue sheep live in small groups - the largest herd observed by Wang et al. (2000) contained 15 animals. However, contrary to Schäfer's original reports (1937), neither Wu et al. (1990) nor Wang et al. (2000) ever observed solitary individuals. Recent observations have shown a reduction in average group size: the majority of herds (80%) observed by Wang et al. (2000) contained fewer than eight individuals, and more than one-fifth of group sightings were of pairs. Reported average group sizes range from 3.85 (± 1.99 standard error; Wang and Wang, 2003) to 6.2 (± 0.78; Wang et al., 2000), and all group types, including all-male groups, maternal herds (females and young), and mixed herds, have been observed (Wang et al., 2000). The largest herd reported by locals was 25 animals, although this was seen in the 1950's (Wang et al., 2000). These same locals also stated that herd size has been declining since then, as a result of heavy hunting and habitat loss.

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).

Dwarf blue sheep inhabit low, arid grassy slopes of the upper Yangtze gorge in Batang County of Sichuan Province and a small area in Mukang County in the Tibetan Autonomous Region of China (Groves, 1978; Wang et al., 2000). Most of the population appears to be concentrated in an area of 295 square kilometers, principally between the villages of Suwalong and Zhubalong (=Drupalong) (Wang et al., 2000). Cai et al. (1990, in Wang et al., 2000) suggested that this species might occur in Beiyu Province (north of Batang), but Wang et al. (2000) found no evidence of occurrence north of the city of Batang.

Countries: China (Harris, 2008).

The total number of the existing dwarf blue sheep in Batang Province was estimated by Wu et al. (1990) between 70 and 150 animals, and just over 200 individuals by Wang et al. (2000). Human pressures are pervasive; nowhere in their limited range can the sheep escape from humans and livestock (Wang et al., 2000). P. schaeferi is classified as endangered (Criteria A2cd) by the IUCN (Harris, 2008), but is not listed by CITES (2011). They are threatened by over-hunting - it is projected that the population will be reduced by at least 50% within the next ten years based on potential levels of exploitation. A prefectural reserve, covering 142.4 square kilometers around Zhubalong was created in 1995 to protect the dwarf blue sheep (Wang et al., 2000). However, as with many protected areas around the world, the protection is only on paper, and human activities - including mushroom gathering, livestock grazing, and illegal hunting - continue to occur in the "safe" zone (Wang et al., 2000).

The genus name Pseudois is derived from the Greek words pseudes, meaning false, and ois, a sheep. In form, blue sheep appear sheep-like, while the absence of facial glands and the character of the tail are distinctly goat-like characteristics. Indeed, it appears that Pseudois is actually more goat-like than sheep-like. E. Schäfer first described this species after his 1930's expedition to Tibet (Groves, 1978).

Local names

Rong-na [Tibetan] (Wang et al., 2000)

Ai Yanyang [Chinese] (Smith and Xie, 2008)

 

German

das Zwergblauschaf (Schäfer, 1937 in Groves, 1978)