Antler expression as a diagnostic tool for the Patagonian huemul deer

FLUCK, WT; SMITH-FLUECK JM

Harbin

Congreso; 8th International Deer Biology Congress; 2014

Northeast Forestry University

We analyze the antler expression in extant Patagonian Huemul deer (Hippocamelus bisulcus) to elucidate factors possibly explaining the lack of recovery of most subpopulations. Antler bone provides an excellent tool to interpret myriad biological, ecological, and environmental relationships due to its being a luxury appendage regrown annually. The principle factors influencing the phenotypic expression of antlers are age, nutrition, animal condition, social environment, and genetics. The correct interpretation of antler expression, therefore, is not a trivial matter. We review the past biogeography of the Southern Cone, behavioral aspects explaining the numerical reduction of the huemul population by >99%, and the descriptions of the first early reports about huemul. The literature on huemul is replete with stereotyped description of antlers, and thus erroneous interpretations are made that fail to appreciate the informational content of antlers. Using historical accounts, we elucidate how the common description of huemul as single-forked deer originated. We then compare historical and current information on distribution, age structure, densities, and relate it to health and antler expression as an ecological indicator of the population status. Whereas in the past huemul lived in areas producing antlers up to five tines, most current subpopulations exhibit males with either spikes or forks. However, as a few subpopulations today still produce antlers with three tines, we reject the claim that the norm for huemul antler expression is a simple fork and that additional tines are an abnormal expression. We discovered, however, that more frequently antlers showed highly deficient growth, that several subpopulations had other severe osteopathology affecting at least 57% of adults, and that several cases of broken leg bones in wild individuals have been documented. Our previous hypothesis about a causal relationship to nutritional deficiency of trace minerals like selenium (Se) has recently been corroborated: 1) from a first sampling of huemul blood for trace minerals, we found 73% of the animals to be Se deficient; and, 2) in a recent analysis of soil samples from areas typically used by extant huemul, we found all to be deficient in Se. We conclude that most remnant huemul subpopulations have survived in remote areas, largely due to their inaccessibility to men, but as these sites are marginal and frequently in high elevations (ie. thus likely with inadequate Se), antler expression is compromised, osteopathology frequent, and numerical recovery absent. Based on all these findings, we recommend that antler expression be used as a tool to recognize nutrient deficiencies in huemul subpopulations.