Plains zebra
The Plains zebra (Equus quagga), also known as the common zebra, consists of several subspecies and is the most widespread and numerous species of zebra, native to Africa and renowned for its striking black-and-white striped coat that provides camouflage from predators and helps regulate body temperature.[1] Adults typically stand 1.1 to 1.45 meters at the shoulder, with males weighing 220 to 430 kilograms and females 175 to 300 kilograms, and head-body lengths ranging from 2.17 to 2.5 meters.[2] The unique stripe pattern varies by individual and subspecies, featuring broad bands on the neck and head that narrow toward the hindquarters, often with faint "shadow stripes" between them, and a distinctive dewlap on the throat.[3] This herbivorous equid inhabits a broad range of open landscapes across eastern and southern Africa, from Ethiopia and Kenya in the north to South Africa in the south, favoring grasslands, savannas, and acacia woodlands while avoiding dense rainforests and arid deserts.[1] As a habitat generalist, it thrives in areas with access to water sources and short to medium grasses, migrating seasonally in some regions to follow rainfall and fresh forage.[3] Plains zebras primarily graze on over 50 species of grasses, and their hindgut fermentation allows them to process tough, low-quality vegetation that other herbivores cannot.[3] Socially, Plains zebras form stable family units or "harems" led by a dominant stallion, several mares, and their foals, with groups ranging from 5 to 20 individuals; these may coalesce into massive herds of thousands during migrations, while young or subordinate males join bachelor groups.[1] Communication occurs through vocalizations like barks and whinnies, as well as visual cues from tail swishing and ear positioning, and the stallion fiercely defends the group from threats such as lions, hyenas, and crocodiles.[2] Females reach sexual maturity at 2–3 years and give birth to a single foal after a 12–13 month gestation, with offspring able to stand and follow the herd within minutes; wild lifespan averages 20–25 years, though up to 40 in protected areas.[3] Despite its abundance, the Plains zebra is classified as Near Threatened on the IUCN Red List, with a global population estimated at 500,000–750,000 mature individuals as of the 2020 assessment, showing an overall declining trend with approximately 25% reduction since the early 2000s.[4] Major threats include habitat fragmentation from agricultural expansion, poaching for meat and hides, competition with livestock for resources, and diseases like anthrax and trypanosomiasis, though conservation efforts in protected areas like Serengeti National Park and community-based initiatives have stabilized some populations.[5]Taxonomy and phylogeny
Classification and etymology
The plains zebra (Equus quagga) is classified within the genus Equus of the family Equidae, order Perissodactyla, suborder Hippomorpha.[6] The genus Equus, encompassing horses, asses, and zebras, was established by Carl Linnaeus in his Systema Naturae (1758), with the name derived from the Latin equus meaning "horse."[7] The species E. quagga itself was formally described by Dutch naturalist Pieter Boddaert in 1785, based on a specimen collected near the Cape of Good Hope and illustrated by Peter Simon Pallas; it was initially placed in the subgenus Hippotigris, reflecting its striped pattern akin to a "tiger-horse" from Greek roots hippos (horse) and tigris (tiger).[8][7] The specific epithet quagga originates from the Khoikhoi (also known as Khoekhoe) language spoken by indigenous pastoralists of southern Africa, where it served as an onomatopoeic term imitating the animal's distinctive bark-like vocalization or denoting a striped equine.[9][10] European colonizers, including Dutch settlers at the Cape, adopted the term in the 18th century to refer broadly to plains zebras encountered in the region, without distinguishing subspecies.[11] This usage led to the name being retained for the species level in modern taxonomy, distinguishing it from related equids like the mountain zebra (Equus zebra, described by Linnaeus in 1758) and Grévy's zebra (Equus grevyi, named in 1884 after Jules Grévy).[7] Historical nomenclature for the plains zebra has been marked by confusion, particularly in the 19th century when explorers and naturalists applied regional names interchangeably. For instance, the southern form was commonly called "quagga," while central and eastern populations received names like "Burchell's zebra" after explorer William John Burchell, leading to the junior synonym Equus burchellii (1829) that persisted until taxonomic revisions in the late 20th century synonymized it under E. quagga.[8] Early accounts sometimes conflated plains zebras with mountain zebras, using variants like "couagga" for the latter, and the discovery of Grévy's zebra in the Horn of Africa further complicated identifications until genetic and morphological studies clarified the three extant zebra species.[12] Today, E. quagga is recognized as comprising several subspecies, with the extinct Cape quagga (E. q. quagga) representing the original type locality of the name.[13]Evolutionary history
The genus Equus, ancestral to the plains zebra (Equus quagga), originated in North America during the late Miocene to early Pliocene epochs, approximately 5 to 4 million years ago, with Equus simplicidens representing a key early species in this lineage.[14] From North America, ancestral Equus populations migrated to Eurasia across the Bering land bridge around 2.6 million years ago, marking the onset of Old World diversification.[15] Subsequent dispersal into Africa facilitated the establishment of the zebra-ass clade, where environmental pressures in expanding grasslands drove further adaptations in the Equus lineage leading to modern zebras.[14] The plains zebra descends from early Equus ancestors that evolved in North American and Eurasian grasslands, sharing ecological traits with Miocene hipparion-like equids such as high-crowned teeth for grazing and adaptations to open habitats, though modern zebras represent a distinct one-toed branch.[16] The iconic stripes of the plains zebra likely developed as an antipredator adaptation, providing visual camouflage and disruption in tall grass or against moving herds to confuse predators like lions and hyenas.[17] The genus Equus originated around 4.0–4.5 million years ago in the Pliocene. Within Equus, the zebra lineage diverged from horses approximately 2.1–3.4 million years ago and from asses around 1.7–2.0 million years ago, coinciding with the radiation of the genus.[18] This split preceded the Pleistocene epoch (2.58 million to 11,700 years ago), during which the three extant zebra species underwent significant radiation, influenced by glacial-interglacial cycles that altered African savanna ecosystems and promoted speciation.[19] Mitochondrial DNA and multi-locus genetic analyses from the 2010s have elucidated the phylogeny of zebras, confirming their monophyly within Equus and revealing that the plains zebra shares a closer evolutionary relationship with the mountain zebra (Equus zebra) than with Grevy's zebra (Equus grevyi).[20] For instance, a 2012 study sequencing 22 nuclear genes positioned the mountain zebra as the sister taxon to the plains zebra, with Grevy's zebra as the outgroup, supporting a divergence timeline where the mountain and plains lineages split around 1.6 million years ago.[21]Subspecies
The plains zebra (Equus quagga) is divided into six recognized subspecies based primarily on morphological variations, particularly in stripe patterns, body size, and mane characteristics, though taxonomic classification remains debated due to evidence of clinal variation across its range. These subspecies were formalized in a comprehensive taxonomic revision that emphasized cranial measurements, stripe density, and geographic distribution. A seventh subspecies, the quagga (E. q. quagga), is extinct, having been hunted to disappearance in the late 19th century, and is notable for its minimal striping confined mostly to the head, neck, and forequarters, with a brownish rear resembling a horse. The recognized extant subspecies include:| Subspecies | Common Name | Key Morphological Features |
|---|---|---|
| E. q. boehmi | Grant's zebra | Bold, wide black stripes with minimal shadow stripes; full striping on legs and underbelly; prominent mane. Found in eastern Africa, this subspecies exhibits the most uniform bold patterning among plains zebras.[7] |
| E. q. borensis | Maneless zebra | Reduced or absent mane; extensive striping similar to boehmi but with a shorter, upright mane in some individuals; bold stripes overall. This northern form shows variation in mane development as a distinguishing trait.[7] |
| E. q. burchellii | Burchell's zebra (includes Damara zebra form) | Narrower stripes with prominent shadow (brownish) stripes between blacks; less striping on legs and hindquarters; smaller body size. Southern populations display increased white areas and finer patterning compared to northern forms.[7] |
| E. q. chapmani | Chapman's zebra | Intermediate stripe width between boehmi and burchellii; some shadow stripes present; full leg striping but with more variation in belly patterns. This subspecies bridges northern and southern morphological clines.[7] |
| E. q. crawshayi | Crawshay's zebra | Very bold, wide stripes extending to hind legs and tail; minimal shadow stripes; larger cranial measurements. Northernmost subspecies with the densest striping coverage.[7] |
| E. q. selousi | Selous' zebra | Broad stripes with some shadow elements; heavy striping on hindquarters but variable leg patterns; intermediate body size. Often considered transitional between eastern and southern forms.[7] |