|Hybrid:||Ovis aries × Capra aegagrus hircus|
A sheep–goat hybrid (called a geep in popular media or sometimes a shoat[note 1]) is the offspring of a sheep and a goat. While sheep and goats seem similar and can be mated, they belong to different genera in the subfamily Caprinae of the family Bovidae. Sheep belong to the genus Ovis and have 54 chromosomes, while goats belong to the genus Capra and have 60 chromosomes. The offspring of a sheep-goat pairing is generally stillborn. Despite widespread shared pasturing of goats and sheep, hybrids are very rare, indicating the genetic distance between the two species. They are not to be confused with sheep–goat chimera, which are artificially created by combining the embryos of a goat and a sheep.
At the Botswana Ministry of Agriculture in 2000, a male sheep impregnated a female goat resulting in a live offspring. This hybrid had 57 chromosomes, intermediate between sheep (54) and goats (60) and was intermediate between the two parent species in type. It had a coarse outer coat, a woolly inner coat, long goat-like legs and a heavy sheep-like body. Although infertile, the hybrid had a very active libido, mounting both ewes and does even when they were not in heat. He was castrated when he was 10 months old, as were the other kids and lambs in the herd.
A male sheep impregnated a female goat in New Zealand resulting in a mixed litter of kids and a female sheep-goat hybrid with 57 chromosomes. The hybrid was subsequently shown to be fertile when mated with a ram.
In France natural mating of a doe with a ram produced a female hybrid carrying 57 chromosomes. This animal backcrossed in the veterinary college of Nantes to a ram delivered a stillborn and a living male offspring with 54 chromosomes.
In March 2014 a buck-ewe hybrid was born on a farm close to Göttingen in Germany. 
Also in March 2014, a male buck-ewe hybrid was born in Ireland.
There was a reported case of live births of twin geep on a farm in Ireland in 2018.
There was reported case of live birth of geep on a farm in Tábor in Czech Republic in 2020. Her name was Barunka and she had health complications after being born - owners of Barunka didn't know if it was goat or sheep, since goats nor sheep wanted her. Upon further inspection, they found out it's a geep.
There is a long-standing belief in sheep–goat hybrids, which is presumably due to the animals' resemblance to each other. Some primitive varieties of sheep may be misidentified as goats. In Darwinism – An Exposition of the Theory of Natural Selection with Some of Its Applications (1889), Alfred Russel Wallace wrote:
[...] the following statement of Mr. Low: "It has been long known to shepherds, though questioned by naturalists, that the progeny of the cross between the sheep and goat is fertile. Breeds of this mixed race are numerous in the north of Europe." Nothing appears to be known of such hybrids either in Scandinavia or in Italy; but Professor Giglioli of Florence has kindly given me some useful references to works in which they are described. The following extract from his letter is very interesting: "I need not tell you that there being such hybrids is now generally accepted as a fact. Buffon (Supplements, tom. iii. p. 7, 1756) obtained one such hybrid in 1751 and eight in 1752. Sanson (La Culture, vol. vi. p. 372, 1865) mentions a case observed in the Vosges, France. Geoff. St. Hilaire (Hist. Nat. Gén. des reg. org., vol. iii. p. 163) was the first to mention, I believe, that in different parts of South America the ram is more usually crossed with the she-goat than the sheep with the he-goat. The well-known 'pellones' of Chile are produced by the second and third generation of such hybrids (Gay, 'Hist, de Chile,' vol. i. p. 466, Agriculture, 1862). Hybrids bred from goat and sheep are called 'chabin' in French, and 'cabruno' in Spanish. In Chile such hybrids are called 'carneros lanudos'; their breeding inter se appears to be not always successful, and often the original cross has to be recommenced to obtain the proportion of three-eighths of he-goat and five-eighths of sheep, or of three-eighths of ram and five-eighths of she-goat; such being the reputed best hybrids."
Supposedly, most sheep–goat hybrids die as embryos. Hybrid male mammals are often sterile, demonstrating a phenomenon known as Haldane's rule. The Haldane phenomenon may apply even when the parent species have the same number of chromosomes, as in most cat-species hybrids. It sometimes does not apply when the species chromosome number is different, as in wild horse (chromosome number = 66) with domestic horse (chromosome number = 64) hybrids. Hybrid female fertility tends to decrease with increasing divergence in chromosome similarity between parent species. Presumably,[speculation?] this is due to mismatch problems during meiosis and the resulting production of eggs with unbalanced genetic complements. However, a buck-ewe hybrid born in 2014 died of pregnancy related complications in 2018 raising the question if the parent-species combination has an influence on hybrid fertility.
Blood transcriptome analysis of a buck-ewe hybrid and its parents revealed significant deviations from previously described imprinting schemes and a higher contribution from the goat genome to the genes expressed in the hybrid's blood. Due to the common genome, buck-ewe hybrid share 870 common genes with the maternal goat and 368 genes with the paternal sheep.
- "Mayo farm welcomes unusual arrival of twin geep". RTÉ News. April 3, 2018 – via www.rte.ie.
- Amos J (2000-07-03). "'Funny creature' toast of Botswana". BBC News. Retrieved 2006-08-19.
- Mine OM, Kedikilwe K, Ndebele RT, Nsoso SJ (July 2000). "Sheep-goat hybrid born under natural conditions". Small Ruminant Research. 37 (1–2): 141–145. doi:10.1016/S0921-4488(99)00146-7. PMID 10818315.
- Stewart-Scott IA, Pearce PD, Dewes HF, Thompson JW (April 1990). "A case of a sheep-goat hybrid in New Zealand". New Zealand Veterinary Journal. 38 (1): 7–9. doi:10.1080/00480169.1990.35605. PMID 16031565.
- Tucker EM, Denis B, Kilgour L (2009). "Blood genetic marker studies of a sheep-goat hybrid and its back-cross offspring". Animal Genetics. 20 (2): 179–86. doi:10.1111/j.1365-2052.1989.tb00855.x. PMID 2757269.
- Cribiu E, Matejka M, Denis B, Malher X (1988). "[Not Available]" [Chromosome study of a fertile female goat x sheep hybrid]. Génétique, Sélection, Évolution (in French). 20 (3): 379–86. doi:10.1186/1297-9686-20-3-379. PMC 2712502. PMID 22879333.
- Pauciullo A, Knorr C, Perucatti A, Iannuzzi A, Iannuzzi L, Erhardt G (October 2016). "Characterization of a very rare case of living ewe-buck hybrid using classical and molecular cytogenetics". Scientific Reports. 6 (1): 34781. Bibcode:2016NatSR...634781P. doi:10.1038/srep34781. PMC 5048133. PMID 27698378.
- "Geep: Rare 'goat-sheep' born on Irish farm". BBC. Retrieved 27 January 2021.
- "Z půlky koza, z půlky ovce. V Táboře se narodil unikátní kříženec" [Half-goat, half-sheep. A unique hybrid was born in Tábor] (in Czech). Novinky.cz.
- Hirsch J (30 May 2014). "Debunking the Geep: How Many Sheep-Goat Hybrids Are Real?". Modern Farmer Media.
- Falker-Gieske C, Knorr C, Tetens J (November 2019). "Blood transcriptome analysis in a buck-ewe hybrid and its parents". Scientific Reports. 9 (1): 17492. Bibcode:2019NatSR...917492F. doi:10.1038/s41598-019-53901-z. PMC 6877586. PMID 31767945.
- Although this would technically be the correct term for the offspring of a ram and a nanny goat, the term 'shoat' is normally defined as a hog that is less than a year old.