The huemul (Hippocamelus bisulcus) is endangered, with 1500 deer split into >100 subpopulations along 2000 km of the Andes. Currently occupied areas are claimed-erroneously-to be critical prime habitats. We analyzed historical spatiotemporal behavior since current patterns represent only a fraction of pre-Columbian ones. Given the limited knowledge, the first group (n = 6) in Argentina was radio-marked to examine spatial behavior. Historically, huemul resided year-round in winter ranges, while some migrated seasonally, some using grasslands >200 km east of their current presence, reaching the Atlantic. Moreover, huemul anatomy is adapted to open unforested habitats, also corroborated by spotless fawns. Extreme naivety towards humans resulted in early extirpation on many winter ranges—preferentially occupied by humans, resulting in refugee huemul on surrounding mountain summer ranges. Radio-marked huemul remained in small ranges with minimal altitudinal movements, as known from other subpopulations. However, these resident areas documented here are typical summer ranges as evidenced by past migrations, and current usage for livestock. The huemul is the only cervid known to use mountain summer ranges year-round in reaction to anthropogenic activities. Losing migratory traditions is a major threat, and may explain their presently prevalent skeletal diseases, reduced longevity, and lacking recolonizations for most remaining huemul subpopulations.

Conservation strategies for huemul (Hippocamelus bisulcus), listed as an endangered cervid by IUCN, have not helped to reverse its declining population trends. Recent evaluations of historical data revealed that they also inhabited lower valleys and grasslands as residents or only during winter. However, the dogma persists that huemuls do not need such habitats. To determine if more solid evidence exists to back up or refute our hypothesis that huemuls once inhabited lower valleys and grasslands, we researched the literature and discovered additional relevant historical sources on this species. These new findings substantiate that huemuls also occupied unforested areas, reaching the Atlantic coast, and resided on various islands including Tierra del Fuego, and that their co-occurrence with guanaco was frequent. Their extreme naivety towards humans resulted in their extirpation on winter ranges settled by humans, resulting in refugee huemuls year-round on remote mountain summer ranges. The ease by which indigenous people could kill them for subsistence and commercial export of hides to Europe, followed by the lowlands becoming modified by settlers and their exotic species facilitated the huemuls’ extirpation. The hypothesis of a dramatic modification of the original biogeographical distribution of huemuls is supported by anatomical and ecological features along with historical accounts. Sedentariness on only rugged summer ranges makes long-term survival of this species crucially challenging and requires sound conservation strategies that incorporate geographical areas of their former distribution.

Context: The Patagonian huemul, an endangered Odocoilinedeer, has an estimated 350–500 individuals remaining in Argentina. Today’s population size, representing a numerical reduction of >99% of original estimates, is fragmented into small groups along ~2000 km of Andean mountains. The species’ numbers were heavily reduced by past overexploitation and they disappeared in areas of high anthropogenic activity, predominantly the fertile valley bottoms. Aims: This research delineates the current potential distribution of Patagonian huemul by using climatic indicators, topographic and vegetational proxies, and anthropogenic pressure, to determine the relevance of the climatic envelope on current distribution. Methods: Occurrence records (latitude and longitude) were compiled (n = 159) by consulting the literature. Twenty environmental variables were used (WorldClim database) and two other representative environmental variables (normalised difference vegetation index (NDVI) and enhanced vegetation index (EVI)) were added to test their predictive power. We added the human footprint index (HFP) as a variable to control for model bias. Using the maximum entropy algorithm (MaxEnt), we modelled the species’ potential distribution. We designated the historical distribution as area M. Additionally, we calculated three areas of distribution: current, historical and potential. Finally, we calculated distributional retraction of the species and area lost per year. Key results: The model showed good predictive power (AUCTest = 0.764 ± 0.091). However, low values were obtained for AUCtrain and AUCprom for the different predictor scenarios. Although the model shows the interaction among several climatic, environmental, and topographic variables, the human footprint index (39.9%) was the variable that most influenced the current potential distribution of this species. Conclusion: Our model shows that most of Patagonia’s surface is climatically suitable for huemul. This suggests that the causes of distributional retraction are not related to limitations imposed by the climate envelope, but rather concur with recent research showing impact owing to the species’ behavioural response to anthropogenic activity. Implications: Current populations are small, fragmented, and confined to poor-quality sites. Although the species is currently found mainly within protected areas, management actions must be initiated that promote innovative strategies in unprotected areas, as well as high-value habitats, particularly as protected areas contain limited fertile lower-valley habitats.