Why the Patagonian huemul deer in Argentina fails to recover: An ecological hypothesis

FLUCK, WT; SMITH-FLUECK, JM

Prag, Czech Republic

Congreso; 6th international Deer Biology Congress; 2006

Research Institute of Animal Production, Praha, Czech Republic

Huemul (Hippocamelus bisulcus) numbers had declined drastically by the 20th century. First field studies in Argentina began in 1988. A preliminary list of hypothetical factors potentially important for huemul recovery was proposed in 1992. These factors are currently claimed dogmatically to cause declines and failure of recovery, though without supportive studies. We posit that other possible factors responsible for failing huemul recovery have not yet been considered: huemul likely are deficient in trace minerals important for recruitment. Only 350-600 animals remain along 1800 km of Argentine Andes, with no known cases of recolonization or numerical responses.    The main hypotheses (1992: cattle, exotic trees, irrational forestry, exotic animals, illegal hunting, diseases, dogs, reduced population size) can be rejected as explanations for the observed general lack of recovery. Current huemul refuges are likely deficient in iodine and selenium based on geology, pedology, climate, and incidences in Chile. They occur near the continental divide at high elevations, with high precipitation, far from the Pacific, and with vegetation growing on soils strongly influenced by igneous rocks, glaciation and volcanism. Lack of access to valley bottoms or former winter ranges would exacerbate low mineral intakes. Recruitment in Argentina have remained too low to allow recolonizations or population increases. The likely trace mineral deficiencies would affect reproduction and survival because huemul lack the opportunity to compensate these nutritional imbalance by migrating to more favorable valley bottoms and historical winter ranges. These deficiencies principally affect reproduction, neonatal development, and the immune and nervous systems. The latter might result in increased susceptibility to predation. Migration, an acquired behavior, has been eliminated through past overhunting of this segment of the population as huemul is very vulnerable to human predation and feral dogs. They were killed by the thousands to feed people, dogs, chicken and pigs, and skins were used for shelters. Huemul currently dispersing from refuges would likely be killed when entering former source areas now occupied by settlers. Other mountain ungulates have been shown to be deficient in these trace minerals and responded well to mitigation. Neonatal development, resistance to disease and depredation rates were positively affected.