Potential distribution model of Ovis canadensis in northern Baja California, Mexico

Resumen

The bighorn sheep is an iconic species in Baja California, being a key element for environmental conservation across its distribution range due to the huge dimensions of its habitat. In this regard, priority areas should be identified to propose feasible management practices. In this context, ecological niche models are essential because they are important methodological tools that indicate the suitability of the habitat for proper species development, based on field observations and multiple environmental variables as occupancy predictors. This investigation aims to identify the potential distribution range of the bighorn sheep in Sierra de Juarez using an ecological niche model. Indirect signs of the presence of bighorn sheep were sampled in Sierra de Juárez from January to June 2016 in order to gather evidence of the species, along with records from an aerial survey carried out in 2012. The ecological niche model was constructed applying the maximum-entropy algorithm assisted with the Maxent software. Ruggedness, orientation, slope, normalized difference vegetation index (NDVI), type of vegetation, and type of weather were used as predictive variables. In Sierra de Juarez, bighorn sheep inhabit an area of 49,844 ha with the following characteristics: climates ranging from very arid semi-warm [BWh(x’)] to very arid temperate [BWk(x’) and BWks]; natural vegetation comprising gallery and palm-tree patches; NDVI of 0.05 to 0.07; orientation of 0 to160°; slope of 0 to 65 %; and ruggedness of 35 to160 m (Figure 4). NDVI, vegetation type and ruggedness were the variables with the greatest contribution to the ecological niche model (Table 1). Bighorn sheep are distributed primarily in the northern and central regions of Sierra de Juárez (Figure 2). According to the niche model, these areas have environmental conditions that provide shelter and resources for this species. Therefore, it is hereby proposed to organize the local landowners to implement actions to protect the bighorn sheep habitat to warrant the conservation of this iconic species and its environment in the region studied.