 Pseudois
schaeferi
Dwarf blue sheep |
Taxonomy | Description
| Reproduction | Ecology
| Behavior | Distribution
| Conservation | Remarks
| Literature |
| Taxonomy
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Pseudois schaeferi [Haltenorth, 1963].
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Citation: Handb. Zool., 8(32):126.
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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: P. nayaur schaeferi. Groves
(1978) found sufficient morphological evidence to place P. schaeferi
as a separate species. In a recent study, Feng et al. (2001)
found an average 12.21% sequence divergence in mitochondrial DNA between
P. schaeferi and P. nayaur - disproving Allen's 1940 suggestion
that the observed difference between the two species of the genus
Pseudois was an environmental effect, and supporting at least a
subspecific ranking for the dwarf blue sheep. However, there was weak
differentiation between the two species based on ZFY introns (nuclear Y-linked
genes), leading the study to conclude that Pseudois schaeferi should
not be a separate species, but considered to be a subspecies of Pseudois
nayaur. 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). Wang and Hoffmann (1987) also suggest
that the dwarf blue sheep may be a peripheral, isolated population undergoing
speciation. 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. shaeferi, and much of the available
data merely compares this species with P. nayaur.
General Characteristics
Pseudois schaeferi is differentiated from 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 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).
Reported measurements fordwarf blue sheep (Pseudois schaeferi) |
| Source |
Adult Weight |
Head & Body Length |
Shoulder Height
|
Tail Length |
Schäfer (1937),
Englemann (1938),
and Allen (1940).
in Groves, 1978
Wang and Hoffmann, 1987 |
28-39 kg 
25 kg  |
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70-80 cm |
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| Wang et al., 2000 |
est. 34-44 kg
(max. 65 kg) |
- |
- |
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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) |
The overall color of the dwarf blue sheep is a steely grey with a silvery
sheen (Schäfer , 1937 in Groves, 1978). The summer coat is brown-grey,
with a slightly yellowish tinge to the upperparts (Wu et al., 1990).
The winter coat is rather drab (Groves, 1978). The general coloration
is darker than that of P. nayaur, but the black markings of the bharal
(on the head, neck, and a lateral flank stripe) are only weakly expressed,
except in old males (Groves, 1978). Overall, the limbs are dark, with
the bharal's distinct black stripes on the front side of both the forelegs
and hind legs being short or obselete (Groves, 1978). The fur
is shorter than P. nayaur, and has less underwool (Groves, 1978).
New hairs bear dark terminal bands, but these are short and typically
wear off quickly, at least in the winter pelage (Groves, 1978). There
is less white on the underbelly in the dwarf blue sheep than the bharal (Groves,
1978). Skull measurements are presented by Groves (1978).
Apart from body weight, the horns of males are one of the best diagnostic
features 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 from 7 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 slightly curved first upward then outward, and
with a suboval cross-section (Wang and Hoffmann, 1987).
Ontogeny and Reproduction
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),
indicating a gestation period of about 6 months.
Ecology and Behavior
Dwarf blue sheep inhabit rugged valley terrain along the Yangtze river valley.
They are found at altitudes between 2,600 and 3,200 metres, and
are usually observed on very steep - between 70 and 80o -
rocky slopes (Wu et al., 1990; Wang et al., 2000). This
valley habitat is dry with sparse vegetation cover; common species include
grasses (Cymbopogon distans and Themeda hooderi), low shrubs
(Berberis spp., Rosa spp., Cotoneaster spp.,
Cladrastis spp., Ephedra spp., and Rhododendron spp.),
and clubmoss (Selaginella sanguinolenta) (Wang et al., 2000).
P. schaeferi is isolated from the alpine habitat of P.
nayaur by a belt of oak forest, in which they are never present
(Groves, 1978; Wang et al., 2000).
The initial records of Schäfer (1937 in Groves, 1978) reported 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,
the majority of groups (80%) contained fewer than eight individuals, and
more than one-fifth of the observations were of pairs. The average
group size is 6.2 sheep (± 0.78 standard error), and all group types,
including all-male groups, maternal herds (females and young), and mixed
herds, have all 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 - due primarily to hunting,
but also due to habitat loss. Contrary to Schäfer's original reports
(1937), neither Wu et al. (1990) nor Wang et al. (2000) ever
observed solitary individuals. Population densities range between 0.5-1.0
individuals per square kilometer (Wu et al., 1990).
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. In
turn, dwarf blue sheep are depredated by wolf (Canis lupus), dhole
(Cuon alpinus), leopard (Panthera pardus), and large raptors
(Wang et al., 2000).
Distribution
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 (IUCN, 2004).
Range Map (Redrawn from Wang et al., 2000)
Conservation Status
The total number of the existing dwarf blue sheep in Batang Province was
estimated by Wu et al. (1990) at 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 A2d, B1+2e) by the IUCN (2004), but
is not listed by CITES. 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).
Remarks
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 Psudois is actually more goat-like than sheep-like. E.
Schäfer first described this species after his 1930's expedition
to Tibet.
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Local names
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Rong-na [Tibetan] (Wang et al., 2000)
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German
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Zwergblauschaf (Schäfer, 1937)
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Literature
Cited
Feng, J., C. Lajia, D. J. Taylor, and M. S. Webster. 2001. Genetic
distinctiveness of endangered dwarf blue sheep (Pseudois nayaur schaeferi):
Evidence from mitochondrial control region and Y-linked ZFY intron sequences.
Journal of Heredity; 92(1); 9-15.
Groves, C. P. 1978. The taxonomic status of the Dwarf Blue Sheep
(Artiodactyla: Bovidae). Saugetierkundliche Mitteilungen; 26:177-183.
IUCN (International Union for Conservation of Nature and Natural Resources).
2004. 2004 IUCN Red List of Threatened Species. Available
online at http://www.redlist.org/
Wang, X., and R. S. Hoffmann. 1987. Pseudois nayaur
and Pseudois schaeferi. Mammalian Species (278): 1-6.
Wang, X. M., J. T. Peng, and H. M. Zhou. 2000. Preliminary
observations on the distribution and status of dwarf blue sheep Pseudois
schaeferi. Oryx; 34(1): 21-26.
Wilson, D. E., and D. M. Reeder [editors]. 1993. Mammal Species of the World
(Second Edition). Washington: Smithsonian Institution Press.
Available online at
http://nmnhwww.si.edu/msw/
Wu, Y., C. Yuan, J. Hu, J. T. Peng, and P. L. Tao. 1990. A biological
study of dwarf blue sheep [in Chinese]. Acta Theriologica Sinica; 10(3):
185-188.
Additional Resources
Cai, C. P., J. C. Hu, and J. T. Peng. 1990. The dwarf blue sheep
of western Sichuan [in Chinese]. Journal of East China Normal University
(Mammalian Ecology Supplement) 90-95.
*Cao Li-Rong, Wang Xiao-Ming, Fang Sheng-guo. 2003. A molecular
phylogeny of Bharal and dwarf blue sheep based on mitochondrial cytochrome
b gene sequences. Acta Zoologica Sinica; 49(2): 198-204.
Englemann, C. 1938. Über die Großsauger Szetschwans,
Sikongs, und Osttibets. Zeitschrift fur Saugetierekunde (Berlin) 13:
1-76.
Shackleton, D.M. 1997. Wild Sheep and Goats and Their Relatives - Status
Survey and Conservation Action Plan for Caprinae. IUCN.
Schäfer, E. 1937. Über das Zwergblauschaf
(Pseudois spec. nov.) und das Großblauschaf (Pseudois
nahoor Hdgs.) in Tibet. Zool Garten (N.F.), Leipzig 9: 263–278.
Tan, B.J. 1996. Into the Wild - The Rare and Endangered Species
of China. New World Press, Beijing, China.
*Zhou Cai-Quan, Zhou Kai-Ya, and Hu Jin-Chu. 2003. The validity
of the dwarf bharal (Pseudois schaeferi) (Bovidae, Artiodactyla) species
status: inferred from mitochondial Cytb gene. Acta Zoologica Sinica;
49(5): 578-584.
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