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

FLUCK, WT; SMITH FLUECK, JM

Huilo Huilo

Congreso; 7th International Deer Biology Congress; 2010

Huemul (Hippocamelus bisulcus) numbers had already declined drastically by the 1800s. Only ~500 animalsremain 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 bestable. During a Chilean–Argentine meeting in 1992 several factors were hypothesised to be important for huemulrecovery (cattle, exotic trees, irrational forestry, exotic animals, illegal hunting, diseases, dogs, reduced numbers), but thesecan be rejected as key explanations for the general lack of recovery. Each factor may play an additive role – alone or incombination – in certain populations, but none of them are likely a primary cause. Our objective is to evaluate alternativefactors and several indications warrant us to postulate that nutritional ecology instead plays a central role in the generalabsence of recovery. A wide range of antler quality is encountered among huemul today, with well developed specimensknown primarily from historic times. If antler expression in huemul is homologous to other cervids, it follows that mostextant populations are under suboptimal conditions. Another important clue is a high prevalence of age-independentosteopathyamongadults.Wehypothesised that such generalised secondary chronic alveolar osteomyelitis, osteoarthritis andperiodontitis were hypothesised to relate to nutritional ecology. Meagre antler development with frequent asymmetry, highprevalence of osteopathy, and low recruitment rates could all be related to common and limiting nutritional factors known tocause the described phenomena. Initial investigations point to several lines of evidence that support the hypothesis thatdeficiency 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 deficiencydirectly affects iodine metabolism. Only decades ago, overt iodine deficiency in humans living in these areas was verycommon. 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 fromglacial areas provide higher provision of iodine and Se. The nexus to the nutritional ecology of huemul likely is theinaccessibility of most traditional winter ranges, elimination of migratory traditions, and concomitant elimination ofsource populations. Se and iodine provisions diminish with altitude, which at the same time increases physiologicalneeds due to hypoxia, and intensified radiations and exercise. Most extant huemul populations occur in remote high-altituderefuges, or inaccessible Pacific coastal areas. Migration, an acquired behaviour, has been eliminated through pastoverhunting of this population segment; huemul being very vulnerable to human predation were killed by thethousands to feed people, dogs, chicken and pigs, and their skins were used for shelters. Huemul currently dispersingfrom refuges are generally being killed when entering former source areas now occupied by settlers and their dogs. Otherungulates driven into mountain refuges have been shown to be deficient in these trace minerals and responded well tomitigation of the deficiency. Thus, prevention of reaching traditional winter ranges or valley bottoms might result ininadequate mineral supply to huemul.