Observations of brachygnathia superior (underbite) in wild ruminates in Western Montana, USA

Abstract

Beginning spring of 1995 until present, unusual developmental malformations have been observed on many species of vertebrate and documented on individuals of four species of wild ruminates. The most frequently observed of a variety of skeletal anomalies is brachygnathia superior, also called mandibular prognathia or more commonly, underbite, caused by underdevelopment in length and width of the premaxillary bone forward of the premolars. Facial anatomy was examined for bone and tooth malformations on 724 white-tailed deer (Odocoileus virginianus) that were accident-killed or died of natural causes between January 1996 and December 2009 in northern Ravalli County in the Bitterroot Valley of west-central, Montana, USA. Smaller samples (145 total) of hunter-killed elk (Cervis canadensis), mule deer (O. hemionus) and pronghorn antelope (Antilocapra americana) from throughout Montana were examined for facial malformations in 2005-09. Incidences of underbite increased from none observed prior to spring of 1995 to more than 35% in 8 of 9 years since 2000 and over 70% in 2008 and 2009. This abnormality appeared abruptly, vastly exceeding expected and previously documented percentages in wild ruminates, and is a characteristic symptom of congenital hypothyroidism. Our data strongly indicates widespread interference with maternal and fetal thyroid hormone function has been occurring in wild ruminants in Montana since autumn 1994

The High Cost of Pesticides: Human and Animal Diseases

“…Brachygnathia superior (BS), the underdevelopment of the upper facial bones of ungulate species, has been photographed in countries around the world and posted on the Internet, usually labeled as under bite. In Montana and throughout the United States, wild and domestic ungulate species appear to have an extremely high prevalence of BS, including our main study species, white-tailed deer [11] as shown in the photos in Figure 9. The percentage of white-tailed deer with BS has increased significantly in this region since 1995, as shown in Figure 10.…”

“…Even with this extensive exposure to multiple wind drift and locally applied pesticides, almost no birth defects were observed or reported on developing young in Western Montana until 1995. An epidemic of multiple birth defects began being observed on many individuals of domestic and wild animals born that spring [10,11], with a significant increase in many of the birth defects over the study period, despite substantial annual variability.…”

“…Glyphosate working synergistically with other pesticide exposures, disrupting normal hormone and enzyme levels and/or functions at key periods during fetal development, are the most likely cause of the variety of birth defects found in white-tailed deer and other wild ruminant populations since spring 1995 [10,11].…”

“…Glyphosate and its synergistic effects with other pesticides, such as Chlorothalonil, are likely closely connected to the increasing prevalence of birth defects and health problems affecting the male reproductive organs since 1995 [10,11,85]. For example, genital hypoplasia, now very common, was almost unknown on white-tailed deer in years prior to 1995 [108] (Figures 28-30).…”

Congenital and Neoplastic Cranial Deformities in Wild Giraffe (Giraffa spp.)

“…In horses and cattle, congenital defects occur in about 1–4% of individuals and usually require surgical intervention for survival (Shaw et al 2015; Canatan et al 2020; Niwas et al 2020; Cunningham and Mead 2022). There are reports of congenital cranial deformities occurring in multiple species of wild ungulates (Wobeser and Runge 1973; Gogan and Jessup 1985; Smits and Bubenik 1990; Hoy et al 2011; Hata et al 2020; Cunningham and Mead 2022). In giraffe ( Giraffa spp.…”