Recent advances in the nutritional ecology of the Patagonian huemul: implications for recovery

Abstract

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.

Elusive cranial lesions severely afflicting young endangered Patagonian huemul deer

“…1). Rather than expressing stress, this behavior concurs with consistent past descriptions of their initial curiosity and apparent fearlessness [10], or the recent experience of pre-capture interactions between several humans and 6 wild huemul ranging from 32 to 73 min and still allowing approaching them to within 10 m [11]. In the present case however, after extended delays, the authorities in charge of the National Huemul Program arrived the following day and > 16 h post-capture, with the aim to translocate the buck by 6.5 km before release.…”

Huemul heresies: beliefs in search of supporting data. 1. Historical and zooarcheological considerations

“…The correlation of latitude with lower elevation of utilisation, however, is artefactual due to omitting historic and zooarcheologic data; it is fallacious to imply latitude as a cause for the lower elevation of utilisation. Lower limits are determined by altitudes of adequate interior winter ranges and sea level on both sides of the continent, and the absence of huemul at low elevations and grasslands is due to displacement and elimination of migratory traditions (Conway 2005;Flueck and Smith-Flueck 2011c). These generalised descriptions of huemul, implying preferences, exclusiveness, or most favourable conditions are strong terms with specific ecological meaning, yet such casual statements are not enough to make these inferences.…”

“…Moreover, humans generally ignored starved animals or ones in poor condition due to lack of fat (Lupo 2007;Morin 2007), as documented for Natives historically hunting huemul after arriving on winter ranges, as follows: 'in stormy days, when herds of huemul came down from the Andes, we chose the fattest one to eat' (Díaz and Smith-Flueck 2000). However, such traditional migratory behaviour of huemul had been eliminated early on mainly by overhunting (Flueck and Smith-Flueck 2011c ).…”

“…Deer being the preferred species for hunting, temporary camps would remain if animals were within 50 km (Lovis et al 2005;Lupo 2007). Considering historic reports of the concentrations of huemul in winter (Flueck and Smith-Flueck 2011c), foraging conditions in the pre-Colombian era are likely to have been even superior in terms of hunter-gatherers. Bones of guanaco and huemul regularly coexist at archeological sites in lowland Andean foothills between 2500 and 6500 years old (De Nigris 2007).…”

Periodontal disease and fluoride bone levels in two separate Iberian red deer populations

“…A preliminary study showing the Ca : P ratios differing between regions but not between species has given us several clues in this aspect (Azorit et al 2011). Also, deficiency in iodine and selenium (Se) has been reported as a cause of periodontitis in ruminants and high prevalence of osteopathy (Flueck and Smith-Flueck 2011). Research into the global mineral content and possible deficiencies in certain minerals such as Se, P and Ca interacting with fluoride is necessary to understand the highest concentrations of fluoride in mandibles with periodontal disease, even the high prevalence of periodontal disease in younger animals.…”