title: Comparative analyses of tooth wear in free-ranging and captive wild equids.
abstract: BACKGROUND
  Captive breeding has played a crucial role in the conservation of threatened equid species. Grazing ruminants and rhinoceros in captivity have less abrasion-dominated tooth wear than their free-ranging conspecifics, with potential negative consequences for their health. However, a similar study on wild equids in captivity is missing.
  
  
  OBJECTIVE
  The aim was to establish if different tooth wear patterns are exhibited by free-ranging and captive equids.
  
  
  METHODS
  Cross-sectional study of museum specimens comparing free-ranging and captive equids.
  
  
  METHODS
  Dental casts of maxillary cheek teeth of 228 museum specimens (122 from free-ranging and 106 from captive individuals) of 7 wild equid species were analysed using the extended mesowear method. Although teeth showing specific abnormalities were not scored, the presence of focal overgrowths (hooks) of the rostral premolars (106, 206) was recorded.
  
  
  RESULTS
  Captive Equus ferus przewalskii, E. grevyi, E. hemionus, E. quagga boehmi and E. zebra hartmannae have less abrasion-dominated tooth wear on their premolars than their free-ranging conspecifics (P<0.001). Fewer differences were exhibited between populations in the molars. No differences were exhibited in the distal cusp of the molars (110, 210) between populations, except in a small sample of E. kiang. Captive equids exhibited more homogeneous wear along the tooth row whereas free-ranging equids exhibited a tooth wear gradient, with more abrasion on premolars than molars. There were more rostral hooks on the premolars (106, 206) in the captive than the free-ranging population (P = 0.02).
  
  
  CONCLUSIONS
  Captive equids did experience less abrasion-dominated tooth wear than their free-ranging conspecifics, but the differences in tooth wear were less pronounced than those between captive and free-ranging wild ruminant and rhinoceros species. This indicates that feeding regimes for captive equids deviate less from natural diets than those for captive ruminants and rhinoceros but that factors leading to hook formation, in particular feeding height, should receive special attention. The Summary is available in Chinese - see Supporting information.
authors.affiliation: Bristol Zoological Society, c/o Bristol Zoo Gardens, UK.|School of Biological Sciences, University of Bristol, UK.
authors.forename: L A
authors.initials: LA
authors.lastname: Taylor
authors.affiliation: Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of Zurich, Switzerland.|National Park 'Bavarian Forest', Grafenau, Germany.
authors.forename: D W H
authors.initials: DW
authors.lastname: Müller
authors.affiliation: Bristol Zoological Society, c/o Bristol Zoo Gardens, UK.
authors.forename: C
authors.initials: C
authors.lastname: Schwitzer
authors.affiliation: Centre of Natural History (CeNak) - University of Hamburg, Germany.
authors.forename: T M
authors.initials: TM
authors.lastname: Kaiser
authors.affiliation: Veterinary Clinic Gessertshausen, Germany.
authors.forename: J C
authors.initials: JC
authors.lastname: Castell
authors.affiliation: Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of Zurich, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Clauss
authors.affiliation: Centre of Natural History (CeNak) - University of Hamburg, Germany.|Max Planck Weizmann Center for Integrative Archaeology and Anthropology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Schulz-Kornas
mesh_terms: D000818:Animals; D000835:Animals, Wild; D018397:Equidae / Q000502:physiology*; D013045:Species Specificity; D057085:Tooth Wear
keywords: Equus; captive; grazer; horse; nutrition; tooth wear; zebra; zoo