brachygnathia superior, congenital fetal hypothyroidism, elk, endocrine disruption, mule deer, pronghorn antelope, white-tailed deer
Digital Object Identifier (DOI)
Since spring of 1995 developmental malformations have been observed on many species of vertebrates. The most frequently observed of a range of skeletal anomalies is brachygnathia superior, also called mandibular prognathia, resulting from underdevelopment in length and width of the premaxillary bone forward of the upper premolars on ruminant species. To quantify these observations, facial anatomy was examined for bone and dental malformations on 1061 white-tailed deer (Odocoileus virginianus) that were accident-killed or died of natural causes between January 1996 and December 2010 in northern Ravalli County in the Bitterroot Valley of west-central, Montana, USA. Observations of brachygnathia superior on white-tailed deer increased from none observed on several hundred deer prior to spring of 1995 to >50% of 519 white-tailed deer examined between January 2001 and December 2010. Highest prevalence was 72% on 84 white-tailed deer fawns born 2007-2010. Smaller samples (196 total) of hunter-killed elk (Cervis canadensis), mule deer (O. hemionus), pronghorn antelope (Antilocapra americana), white-tailed deer and bighorn sheep (Ovis canadensis) heads from throughout Montana, examined for facial malformations during 2005-10, showed a high prevalence of brachygnathia superior (>40%) and a small number with mandibular brachygnathia (4%). Two small groups of domestic ruminants also had a high prevalence of brachygnathia superior (>50%). Our data indicate that this condition appeared abruptly in multiple species and has greatly exceeded any previously documented prevalence of cranio-maxillary malformations in wild ruminants.
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Citation / Publisher Attribution
Wildlife Biology in Practice, v. 7, issue 2, p. 15-29This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distri-bution, and reproduction in any medium, provided the original work is properly cited.
Scholar Commons Citation
Hoy, J. A.; Haas, G. T.; Hoy, R. D.; and Hallock, Pamela, "Observations of Brachygnathia Superior (Underbite) in Wild Ruminates in Western Montana, USA" (2011). Marine Science Faculty Publications. 927.