Species of zebra
Grevy's zebra
(
Equus grevyi
), also known as the
imperial zebra
, is the largest living wild
equid
and the most threatened of the three species of
zebra
, the other two being the
plains zebra
and the
mountain zebra
. Named after
Jules Grevy
, it is found in parts of
Kenya
and
Ethiopia
. Superficially, Grevy's zebras' physical features can help to identify it from the other zebra species; their overall appearance is slightly closer to that of a
mule
, compared to the more "equine" (horse) appearance of the plains and mountain zebras. Compared to other zebra species, Grevy's are the tallest; they have mule-like, larger ears, and have the tightest stripes of all zebras. They have distinctively erect manes, and more slender snouts.
The Grevy's zebra live in semi-arid savanna, where they feed on grasses,
legumes
, and
browse
, such as
acacia
; they can survive up to five days without water. They differ from the other zebra species in that they do not live in a
harem
, and they maintain few long-lasting social bonds. Stallion territoriality and mother?foal relationships form the basis of the social system of the Grevy's zebra. Despite a handful of zoos and animal parks around the world having had successful captive-breeding programs, in its native home this zebra is listed by the
IUCN
as
endangered
. Its population has declined from 15,000 to 2,000 since the 1970s. In 2016, the population was reported to be "stable"; however, as of 2020, the wild numbers are still estimated at only around 2,250 animals, in part due to anthrax outbreaks in eastern Africa.
[6]
Taxonomy and naming
[
edit
]
The Grevy's zebra was first described by French naturalist
Emile Oustalet
in 1882. He named it after
Jules Grevy
, then
president of France
, who, in the 1880s, was given one by the government of
Abyssinia
. Traditionally, this species was classified in the subgenus
Dolichohippus
with
plains zebra
and
mountain zebra
in
Hippotigris
.
[7]
Groves and Bell (2004) place all three species in the subgenus
Hippotigris
.
[8]
Fossils of zebra-like equids have been found throughout Africa and Asia in the
Pliocene
and
Pleistocene
deposits.
[7]
Notable examples include
E. sanmeniensis
from China,
E. cautleyi
from India,
E. valeriani
from central Asia and
E. oldowayensis
from East Africa.
[7]
The latter, in particular is very similar to the Grevy's zebra and may have been its ancestor.
[7]
The modern Grevy's zebra arose in the Middle Pleistocene.
[9]
Zebras appear to be a
monophyletic
lineage
[10]
[11]
[12]
and recent (2013) phylogenies have placed Grevy's zebra in a
sister taxon
with the plains zebra.
[10]
In areas where Grevy's zebras are
sympatric
with plains zebras, the two may gather in same herds
[13]
and fertile hybrids do occur.
[14]
Description
[
edit
]
From left to right: a cranium, a complete skeleton, a left forefoot frontal, and a left forefoot lateral from a Grevy's zebra
The Grevy's zebra is the largest of all wild equines. It is 2.5?2.75 m (8.2?9.0 ft) in head-body with a 55?75 cm (22?30 in) tail, and stands 1.45?1.6 m (4.8?5.2 ft) high at the withers. These zebras weigh 350?450 kg (770?990 lb).
[15]
Grevy's zebra differs from the other two zebras in its more primitive characteristics.
[16]
: 147
It is particularly
mule
-like in appearance; the head is large, long, and narrow with elongated nostril openings;
[16]
: 147
the ears are very large, rounded, and conical and the neck is short but thick.
[17]
The zebra's muzzle is ash-grey to black in colour with the lips having
whiskers
. The
mane
is tall and erect; juveniles have a mane that extends to the length of the back and shortens as they reach adulthood.
[17]
As with all zebra species, the Grevy's zebra's pelage has a black and white striping pattern. The stripes are narrow and close-set, being broader on the neck, and they extend to the hooves.
[17]
The belly and the area around the base of the tail lack stripes and are just white in color, which is unique to the Grevy's zebra. Foals are born with brown and white striping, with the brown stripes darkening as they grow older.
[17]
Range and ecology
[
edit
]
Zebra in dense brush
The Grevy's zebra largely inhabits northern
Kenya
, with some isolated populations in
Ethiopia
.
[16]
: 147
[17]
It was
extirpated
from
Somalia
and
Djibouti
and its status in
South Sudan
is uncertain.
[3]
It lives in
Acacia
-
Commiphora
bushlands and barren plains.
[13]
Ecologically, this species is intermediate between the arid-living
African wild ass
and the water-dependent plains zebra.
[13]
[16]
: 147
Lactating
mares and non-territorial stallions use areas with green, short grass and medium, dense bush more often than non-lactating mares and territorial stallions.
[18]
Grevy's zebras rely on
grasses
,
legumes
, and
browse
for nutrition.
[17]
They commonly browse when grasses are not plentiful.
[13]
[19]
Their
hindgut fermentation
digestive system allows them to subsist on diets of lower nutritional quality than that necessary for
ruminant
herbivores. Grevy's zebras can survive up to a week without water, but will drink daily when it is plentiful.
[20]
They often migrate to better watered highlands during the dry season.
[13]
Mares require significantly more water when they are
lactating
.
[21]
During droughts, the zebras will dig water holes and defend them.
[13]
The Grevy's zebra's main predator is the
lion
, but adults can be hunted by
spotted hyenas
.
African hunting dogs
,
cheetahs
and
leopards
almost never attack adults, even in desperate times, but sometimes prey on young animals, although mares are fiercely protective of their young.
[17]
In addition, they are susceptible to various gastro-intestinal parasites, notably of the genus
Trichostrongylus
.
[22]
Behaviour and life history
[
edit
]
Herd of zebras
Adult stallions mostly live in territories during the wet seasons but some may stay in them year round if there's enough water left.
[13]
Stallions that are unable to establish territories are free-ranging
[16]
: 151
and are known as bachelors. Mares, young and non-territorial stallions wander through large home ranges. The mares will wander from territory to territory preferring the ones with the highest-quality food and water sources.
[23]
Up to nine stallions may compete for a mare outside of a territory.
[17]
Territorial stallions will tolerate other stallions who wander in their territory. However, when an oestrous mare is present the territorial stallion keeps other stallions at bay.
[13]
[16]
: 151
Non-territorial stallions might avoid territorial ones because of harassment.
[18]
When mares are not around, a territorial stallion will seek the company of other stallions. The stallion shows his dominance with an arched neck and a high-stepping gait and the least dominant stallions submit by extending their tail, lowering their heads and nuzzling their superior's chest or groin.
[16]
: 151
Zebras produce numerous sounds and vocalisations. When alarmed, they produce deep, hoarse grunts. Whistles and squeals are also made when alarmed, during fights, when scared or in pain. Snorts may be produced when scared or as a warning. A stallion will bray in defense of his territory, when driving mares, or keeping other stallions at bay. Barks may be made during copulation and distressed foals will squeal.
[17]
The call of the Grevy's zebra has been described as "something like a
hippo
's grunt combined with a
donkey
's wheeze".
[13]
To get rid of flies or parasites, they roll in dust, water or mud or, in the case of flies, they twitch their skin. They also rub against trees, rocks and other objects to get rid of irritations such as itchy skin, hair or parasites.
[17]
Although Grevy's zebras do not perform
mutual grooming
, they do sometimes rub against a conspecific.
[17]
Reproduction
[
edit
]
Zebra foal resting
Grevy's zebras can mate and give birth year round, but most mating takes place in the early rainy seasons and births mostly take place in August or September after the long rains.
[17]
An
oestrous
mare may visit as many as four territories a day
[23]
and will mate with the stallions in them. Among territorial stallions, the most dominant ones control territories near water sources, which mostly attract mares with dependant foals,
[24]
while more subordinate stallions control territories away from water with greater amounts of vegetation, which mostly attract mares without dependant foals.
[24]
Zebra mare near younger zebras
The resident stallions of territories will try to subdue the entering mares with dominance rituals and then continue with courtship and copulation.
[13]
Grevy's zebra stallions have large
testicles
and can ejaculate a large amount of
semen
to
replace the sperm of other males
.
[23]
This is a useful adaptation for a species whose mares mate
polyandrously
. Bachelors or outside territorial stallions sometimes "sneak" copulation of mares in another stallion's territory.
[23]
While mare associations with individual stallions are brief and mating is
promiscuous
, mares who have just given birth will reside with one stallion for long periods and mate exclusively with that stallion.
[23]
Lactating females are harassed by stallions more often than non-lactating ones and thus associating with one male and his territory provides an advantage as he will guard against other males.
[25]
Gestation of the Grevy's zebra normally lasts 390 days,
[17]
with a single foal being born. A newborn zebra will follow anything that moves, so new mothers prevent other mares from approaching their foals while imprinting their own striping pattern, scent and vocalisation on them.
[17]
Mares with young foals may gather into small groups.
[21]
Mares may leave their foals in "kindergartens" while searching for water.
[21]
The foals will not hide, so they can be vulnerable to predators.
[13]
However, kindergartens tend to be protected by an adult, usually a territorial stallion.
[21]
A mare with a foal stays with one dominant territorial stallion who has exclusive mating rights to her. While the foal may not be his, the stallion will look after it to ensure that the mare stays in his territory.
[26]
To adapt to a semi-arid environment, Grevy's zebra foals have longer nursing intervals and wait until they are three months old before they start drinking water.
[21]
Although offspring become less dependent on their mothers after half a year, associations with them continue for up to three years.
[13]
Relationship with humans
[
edit
]
An engraving of the zebra given to Jules Grevy and kept at the
Menagerie du Jardin des Plantes
in 1882
The Grevy's zebra was known to the Europeans in
antiquity
and was used by the
Romans
in
circuses
.
[7]
It was subsequently forgotten in the Western world for a thousand years.
[7]
In the seventeenth century, the king of
Shoa
(now central Ethiopia) exported two zebras; one to the Sultan of Turkey and another to the Dutch governor of
Jakarta
.
[7]
A century later, in 1882, the government of
Abyssinia
sent one to French president
Jules Grevy
. It was at that time that the animal was recognised as its own species and named in Grevy's honour.
[7]
Grevy's zebra appears on the
Eritrean 25-cent coin
.
[27]
Status and conservation
[
edit
]
Grevy's zebras in
Samburu National Reserve
The Grevy's zebra is considered
endangered
.
[3]
Its population was estimated to be 15,000 in the 1970s and by the early 21st century the population was lower than 3,500, a 75% decline.
[28]
: 11
In 2008 it was estimated that there are less than 2,500 Grevy's zebras still living in the wild, further declining to fewer than 2,000 mature individuals in 2016. Nonetheless, the Grevy's zebra population trend was considered stable as of 2016.
[3]
There are also an estimated 600 Grevy's zebras in captivity.
[28]
: 20
Captive herds have been known to thrive, like at
White Oak Conservation
in
Yulee, Florida
, United States, where more than 70 foals have been born. There, research is underway in partnership with the Conservation Centers for Species Survival on semen collection and freezing and on artificial insemination.
[29]
The Grevy's zebra is legally protected in Ethiopia. In Kenya, it is protected by the hunting ban of 1977. In the past, Grevy's zebras were threatened mainly by hunting for their skins which fetched a high price on the world market. However, hunting has declined and the main threat to the zebra is habitat loss and competition with livestock. Cattle gather around watering holes and the Grevy's zebras are fenced from those areas.
[28]
: 17
Community-based conservation efforts have shown to be the most effective in preserving Grevy's zebras and their habitat. Less than 0.5% of the range of the Grevy's zebra is in protected areas. In Ethiopia, the protected areas include Aledeghi Wildlife Reserve,
Yabelo Wildlife Sanctuary
,
Borana National Park
, and
Chelbi Sanctuary
. In Kenya, important protected areas include the
Buffalo Springs
,
Samburu
and
Shaba
National Reserves and the private and community land wildlife conservancies in
Isiolo
,
Samburu
and the
Laikipia Plateau
.
[3]
The
mesquite
plant was introduced into Ethiopia around 1997 and is endangering the zebra's food supply. An invasive species, it is replacing the two grass species,
Cenchrus ciliaris
and
Chrysopogon plumulosus
,
which the zebras eat for most of their food.
[30]
[31]
References
[
edit
]
- ^
Grubb, P.
(2005).
"Order Perissodactyla"
. In
Wilson, D.E.
; Reeder, D.M (eds.).
Mammal Species of the World: A Taxonomic and Geographic Reference
(3rd ed.). Johns Hopkins University Press. p. 631?632.
ISBN
978-0-8018-8221-0
.
OCLC
62265494
.
- ^
O'Brien, Kaedan; Tryon, Christian A.; Blegen, Nick; Kimeu, Boniface; Rowan, John; Faith, J. Tyler (15 March 2021). "First appearance of Grevy's zebra (Equus grevyi), from the Middle Pleistocene Kapthurin Formation, Kenya, sheds light on the evolution and paleoecology of large zebras".
Quaternary Science Reviews
.
256
: 106835.
Bibcode
:
2021QSRv..25606835O
.
doi
:
10.1016/j.quascirev.2021.106835
.
S2CID
233638447
.
- ^
a
b
c
d
e
Rubenstein, D.; Low Mackey, B.; Davidson, Z.D.; Kebede, F.; King, S.R.B. (2016).
"
Equus grevyi
"
.
IUCN Red List of Threatened Species
.
2016
: e.T7950A89624491.
doi
:
10.2305/IUCN.UK.2016-3.RLTS.T7950A89624491.en
. Retrieved
12 November
2021
.
Database entry includes a brief justification of why this species is endangered.
- ^
"Appendices"
.
CITES
. Retrieved
14 January
2022
.
- ^
Oustalet, E. (1882).
"Une nouvelle espece de Zebre. Le Zebre de Grevy (
Equus revyi
)"
.
La Nature
.
10
(470): 12?14.
- ^
"Six endangered Grevy's Zebra foals make their debut at the San Diego Zoo Safari Park"
. San Diego Zoo Global. 30 September 2020
. Retrieved
29 September
2022
.
- ^
a
b
c
d
e
f
g
h
Prothero D.R.; Schoch R. M. (2003).
Horns, Tusks, and Flippers: The Evolution of Hoofed Mammals'
. Johns Hopkins University Press. pp. 216?18.
ISBN
978-0-801-87135-1
.
- ^
Groves, C. P.; Bell, C. H. (2004). "New investigations on the taxonomy of the zebras genus
Equus
, subgenus
Hippotigris
".
Mammalian Biology
.
69
(3): 182?196.
doi
:
10.1078/1616-5047-00133
.
- ^
O'Brien, Kaedan; Tryon, Christian A.; Blegen, Nick; Kimeu, Boniface; Rowan, John; Faith, J. Tyler (15 March 2021). "First appearance of Grevy's zebra (Equus grevyi), from the Middle Pleistocene Kapthurin Formation, Kenya, sheds light on the evolution and paleoecology of large zebras".
Quaternary Science Reviews
.
256
: 106835.
Bibcode
:
2021QSRv..25606835O
.
doi
:
10.1016/j.quascirev.2021.106835
.
S2CID
233638447
.
- ^
a
b
Vilstrup, Julia T.; et al. (2013).
"Mitochondrial Phylogenomics of Modern and Ancient Equids"
.
PLOS ONE
.
8
(2): e55950.
Bibcode
:
2013PLoSO...855950V
.
doi
:
10.1371/journal.pone.0055950
.
PMC
3577844
.
PMID
23437078
.
- ^
Forsten, Ann (1992).
"Mitochondrial?DNA timetable and the evolution of
Equus
: of molecular and paleontological evidence"
(PDF)
.
Annales Zoologici Fennici
.
28
: 301?309.
- ^
Ryder, O. A.; George, M. (1986).
"Mitochondrial DNA evolution in the genus
Equus
"
.
Molecular Biology and Evolution
.
3
(6): 535?546.
doi
:
10.1093/oxfordjournals.molbev.a040414
.
PMID
2832696
.
- ^
a
b
c
d
e
f
g
h
i
j
k
l
Estes, R. (1991).
The Behavior Guide to African Mammals
. University of California Press. pp.
240?242
.
ISBN
978-0-520-08085-0
.
- ^
J. E. Cordingley; S. R. Sundaresan; I. R. Fischhoff;
B. Shapiro
; J. Ruskey; D. I. Rubenstein (2009).
"Is the endangered Grevy's zebra threatened by hybridization?"
(PDF)
.
Animal Conservation
.
12
(6): 505?13.
doi
:
10.1111/j.1469-1795.2009.00294.x
.
S2CID
18388598
.
- ^
Huffman, B.
"Grevy's zebra"
. Ultimate Ungulate.
- ^
a
b
c
d
e
f
g
Kingdon, J. (1988).
East African Mammals: An Atlas of Evolution in Africa, Volume 3, Part B: Large Mammals
. University of Chicago Press. pp. 147?61.
ISBN
9780226437224
.
- ^
a
b
c
d
e
f
g
h
i
j
k
l
m
n
Churcher C.S. (1993).
"Equus grevyi"
(PDF)
.
Mammalian Species
(453): 1?9.
doi
:
10.2307/3504222
.
JSTOR
3504222
.
- ^
a
b
Sundaresan, Siva R.; Fischhoff, Ilya R.; Hartung, Helen M.; Akilong, Patrick; Rubenstein, Daniel I. (2008). "Habitat choice of Grevy's zebras (
Equus grevyi
) in Laikipia, Kenya".
African Journal of Ecology
.
46
(3): 359?364.
CiteSeerX
10.1.1.584.7037
.
doi
:
10.1111/j.1365-2028.2007.00848.x
.
S2CID
12625704
.
- ^
Bauer, I. E.; McMorrow, J.; Yalden, D. W. (1994). "The historic ranges of three equid species in North-East Africa: a quantitative comparison of environmental tolerances".
Journal of Biogeography
.
21
(2): 169?182.
doi
:
10.2307/2845470
.
JSTOR
2845470
.
- ^
Youth, H. (2004).
"Thin Stripes on a Thin Line"
.
Zoogoer
.
33
(November/December 2004). Archived from
the original
on 26 October 2005.
- ^
a
b
c
d
e
Becker, C. D.; Ginsberg, J. R. (1990). "Mother-infant behaviour of wild Grevy's zebra".
Animal Behaviour
.
40
(6): 1111?1118.
doi
:
10.1016/S0003-3472(05)80177-0
.
S2CID
54252836
.
- ^
Muoria. P. K.; Muruthi. P.; Rubenstein. D.; Oguge N. O.; Munene E. (2005).
"Cross-sectional survey of gastro-intestinal parasites of Grevy's zebras in southern Samburu, Kenya"
(PDF)
.
African Journal of Ecology
.
43
(4): 392?95.
doi
:
10.1111/j.1365-2028.2005.00588.x
.
- ^
a
b
c
d
e
Ginsberg, J.R.; Rubenstein, D.I. (1990). "Sperm competition and variation in zebra mating behavior".
Behavioral Ecology and Sociobiology
.
26
(6): 427?34.
CiteSeerX
10.1.1.512.1394
.
doi
:
10.1007/BF00170901
.
S2CID
206771095
.
- ^
a
b
Rubenstein, D. I. (2010)
"Ecology, social behavior, and conservation in zebras"
. pp. 231?58. In:
Advances in the Study Behavior: Behavioral Ecology of Tropical Animals
, Vol. 42. R. Macedo, ed. Elsevier Press.
ISBN
0123808944
- ^
Sundaresan, S. R.; Fischhoff, I. R.; Rubenstein, D. (2007).
"Male harassment influences female movements and associations in Grevy's zebra (
Equus grevyi
)"
(PDF)
.
Behavioral Ecology
.
18
(5): 860?65.
doi
:
10.1093/beheco/arm055
.
- ^
Rubenstein, D.I. (1986).
"Ecology and sociality in horses and zebras"
(PDF)
. In D. I. Rubenstein; R. W. Wrangham (eds.).
Ecological Aspects of Social Evolution
. Princeton University Press. pp. 282?302.
ISBN
978-0691084398
.
JSTOR
j.ctt7zvwgq
.
- ^
"25 Cents, Eritrea"
.
en.numista.com
.
- ^
a
b
c
Moelman, P.D. (2002). "Status and Action Plan for the Grevy's Zebra (
Equus grevyi
) by Stuart D. Williams".
Equids. Zebras, Asses and Horses. Status Survey and Conservation Action Plan'
. IUCN/SSC Equid Specialist Group. pp. 11?27.
ISBN
978-2-831-70647-4
.
- ^
"Grevy's Zebra"
. Retrieved
21 June
2013
.
- ^
Platt, John R.
"Devil Tree Threatens the World's Rarest Zebras"
. Retrieved
7 August
2015
.
- ^
Kebede, Almaz T.; Layne Coppock, D. (September 2015). "Livestock-Mediated Dispersal of Prosopis juliflora Imperils Grasslands and the Endangered Grevy's Zebra in Northeastern Ethiopia".
Rangeland Ecology & Management
.
68
(5): 402?407.
doi
:
10.1016/j.rama.2015.07.002
.
S2CID
83558974
.
External links
[
edit
]