Early explorers described huemul (Hippocamelus bisulcus) as stocky, massive and short-legged deer of mountains, comparing them to ibex (Cabra ibex), chamois (Rupicapra rupicapra), mountain sheep (Ovis canadensis) and mountain goats (Oreamnos americanus). Subsequent key paleontological work also claimed that huemul are mountain deer. However, all these comparisons of huemul to other ungulates were done without any supporting data. These historic events lead to: (i) the continued prevailing claim that huemul are mountain deer; and (ii) that their natural range is the Andean mountains, as evidenced by the current distribution. We found that early writings about huemul generally reported their rareness, disappearance or near extinction. References to stocky and short-legged huemul were casual remarks made about deer found mainly in refuge areas. Paleontological comparisons were based on a new fossil labelled as mountain deer which, however, has been shown to be a construct and declared a ‘nomen nudum’. Behaviour like the aggressive horseshoe stance and thick long hair dissimulate stockiness by distorting body shape. Comparing leg morphometrics of huemul and 12 other ungulates revealed that huemul cannot be associated with rock climbing species. Intraspecific proportional leg length is not static and is influenced by ecogeography, nutrition, physiology and factors affecting exercise. Thus, climate, altitudinal hypoxia and locomotor pattern employed according to terrain, predation and forage affect the appendicular skeleton. Nutritional deficiencies occurring in Andean mountains are notorious for affecting bone development, causing osteopathology and altering body shape. Frequent underdeveloped huemul antlers and high incidence of osteopathology support the effect from mineral deficiencies. Skeletal proportions are affected by numerous factors, causing large intraspecific variation. Relative metapodial length varies up to 70% in better studied cervids, and populations from different environments can be clearly distinguished. Huemul morphology does not overlap with rock climbing species previously considered analogous, but falls within the range of other cervids. We caution against the rigid application of modern huemul occurrences in interpreting past habitat use. The few historic extra-Andean accounts cannot be considered abnormal outliers. Huemul ecology must be interpreted in terms of first principles rather than applying direct analogues from the present. This allows us to begin to use the past to understand the present instead of repeating the fallacy of imposing the present on the past. Current efforts to recover remaining huemul are distinctly based on the assumption that huemul foremost belong in rugged mountains, because of their supposed special adaptions and resemblance to stereotype ungulates, also erroneously believed to only occur in rugged mountains elsewhere. We conclude that the present empirical comparisons support many other lines of evidence that huemul existed in treeless habitat and colonised Andean forests and higher altitudes secondarily. Habitat breath of huemul is thus more like that found in other closely related Odocoilines, promising tremendous new opportunities for recovery efforts.

The huemul (Hippocamelus bisulcus), an endemic Patagonian deer, has been endangered for decades. Although conservation in Argentina has been directed at the 350-600 remaining huemul, the population has not recovered. In initial studies on the potential effects of diseases on huemul population dynamics, skeletal remains collected between 1993 and 2007 in the Andes (41-45 degrees S, 71.5-72 degrees W) were examined macroscopically for osteopathologic changes. Bones from six huemul were free of lesions, findings were inconclusive in 13 huemul with less than three bones, and osteopathologic processes were detected in 13 adults. Considering the limited remains/case, the prevalence of osteopathy (52%) among adults probably is conservative; 63% showed mandibular, 100% maxillary, and 78% appendicular lesions. Although predation represented the actual cause of death, the observed skeletal lesions would affect predator avoidance, possibly explaining the low average adult age (3.1 yr) and lack of population recovery. Compared with other studies in ungulates, huemul were affected at a younger age, and they had more severe pathologic changes. Due to the chronic nature of disease, low huemul population density, physiognomy, and spatiotemporal pattern of lesions, we discard senescence; gender; fulminating infections; congenital anomalies; metabolic, endocrine, genetic, or neurologic disorders; parasitism or marasmus; and fluorosis as primary etiologic factors. We hypothesize that generalized secondary chronic alveolar osteomyelitis and osteoarthritis in huemul is related to the nutritional ecology of these animals. Selenium deficiency, which impairs bone metabolism and causes periodontitis in ruminants, occurs in the region and it is more prevalent at high altitudes. Traditional winter grounds at low elevations, sometimes far from high mountains, have been converted to livestock production, which has eliminated migratory behavior and keeps huemul in remote high-elevation refuges. Although this descriptive study contributes to huemul conservation, additional approaches are needed to investigate the etiology of this osteopathy and to close other gaps in knowledge on biology and ecology of huemul.

Volcanic tephra (ejected solids) result in varied impacts on ecosystems and livestock production. The recent Puyehue (2011) and Calbuco (2015) eruptions deposited large amounts of tephra in Chile and Argentina, affecting both livestock and wildlife in several ways. Impacts from Puyehue tephra on livestock were attributed initially solely to inanition, rumen blockage, eye problems, increased mechanical tooth wear; water consumption was considered without risk for humans and animals; and toxic effects were discarded. Subsequently, wildlife exhibited pronounced clinical signs of fluorosis and bone level exceeding 10 000 ppm of fluoride by 2014. Livestock including horses, cattle and sheep also had high levels of bone fluorine and clinical fluorosis. Tephra from Calbuco and Puyehue now overlap, containing on average 548 and 352 ppm fluoride, respectively. Dryness and eolic redeposition of tephra particularly east of the continental divide continues to re-expose domestic and wild ruminants. However, fluorosis and other related impacts like hypothyroidism, anaemia, and eosinophilia in ruminants also impact wool production. Although fluoride was discarded by others as a cause for the observed reduction in wool production, the specific effect of fluorosis on reducing wool production is well recognised, and occurs in sheep with less bone fluoride than reported from the Puyehue event. The rapid accumulation of fluoride in herbivores exposed to tephra from Puyehue coincides with reports that upon exposure to fluoride, sheep bone levels increased from 160 to 2300 ppm in only 3 months. The susceptibility of ruminants to fluorosis resides in their food processing: (1) intensive mastication and tephra size reduction, (2) thorough mixing of tephra with alkaline saliva during repeated rumination cycles, (3) water-soluble extraction in the rumen, and (4) extraction in the acidic abomasum. Lastly, the fluorosis may be further exacerbated by regional iodine and selenium deficiencies. Iodine deficiency may increase the incidence of dental fluorosis and the severity of damage, whereas selenium deficiency causes secondary iodine deficiency.

Huemul (Hippocamelus bisulcus) numbers had already declined drastically by the 1800s. Only ~500 animals remain along 1800 km of the Argentine Andes between 34 and 54°S, without cases of recolonisation or numerical responses. In Chile, at least two populations have increased; the remaining populations have either decreased or are assumed to be stable. During a Chilean–Argentine meeting in 1992 several factors were hypothesised to be important for huemul recovery (cattle, exotic trees, irrational forestry, exotic animals, illegal hunting, diseases, dogs, reduced numbers), but these can be rejected as key explanations for the general lack of recovery. Each factor may play an additive role – alone or in combination – in certain populations, but none of them are likely a primary cause. Our objective is to evaluate alternative factors and several indications warrant us to postulate that nutritional ecology instead plays a central role in the general absence of recovery. A wide range of antler quality is encountered among huemul today, with well developed specimens known primarily from historic times. If antler expression in huemul is homologous to other cervids, it follows that most extant populations are under suboptimal conditions. Another important clue is a high prevalence of age-independent osteopathy among adults. We hypothesised that such generalised secondary chronic alveolar osteomyelitis, osteoarthritis and periodontitis were hypothesised to relate to nutritional ecology. Meagre antler development with frequent asymmetry, high prevalence of osteopathy, and low recruitment rates could all be related to common and limiting nutritional factors known to cause the described phenomena. Initial investigations point to several lines of evidence that support the hypothesis that deficiency in iodine and selenium (Se) might be involved. Among other things, such deficiencies impair bone growth, reproduction, neonatal development, the immune and nervous systems, and cause periodontitis in ruminants. Se deficiency directly affects iodine metabolism. Only decades ago, overt iodine deficiency in humans living in these areas was very common. For free-ranging livestock, overt Se deficiency has been described in Chile: supported by geology, pedology, topography, and climatic patterns. It is well known that valley bottoms, flood plains, and habitats downwind from glacial areas provide higher provision of iodine and Se. The nexus to the nutritional ecology of huemul likely is the inaccessibility of most traditional winter ranges, elimination of migratory traditions, and concomitant elimination of source populations. Se and iodine provisions diminish with altitude, which at the same time increases physiological needs due to hypoxia, and intensified radiations and exercise. Most extant huemul populations occur in remote high-altitude refuges, or inaccessible Pacific coastal areas. Migration, an acquired behaviour, has been eliminated through past overhunting of this population segment; huemul being very vulnerable to human predation were killed by the thousands to feed people, dogs, chicken and pigs, and their skins were used for shelters. Huemul currently dispersing from refuges are generally being killed when entering former source areas now occupied by settlers and their dogs. Other ungulates driven into mountain refuges have been shown to be deficient in these trace minerals and responded well to mitigation of the deficiency. Thus, prevention of reaching traditional winter ranges or valley bottoms might result in inadequate mineral supply to huemul.