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Therya

On-line version ISSN 2007-3364

Abstract

MARTINEZ-CALDERAS, Jesús Manuel et al. Potential distribution of the white-tooted woodrat (Neotoma leucodon Merriam 1984) and nest density in the southern Chihuahuan Desert. Therya [online]. 2015, vol.6, n.2, pp.421-433. ISSN 2007-3364.  http://dx.doi.org/10.12933/therya-15-223.

INTRODUCTION:

The white-tooted woodrat (Neotoma leucodon) is keystone in a variety of ecological processes. However, this specific rodent is considered a delicacy in the Southern region of the Chihuahuan Desert, which has resulted in uncontrolled exploitation. To date there are no studies to determine its population status, and it is not protected by the Mexican law. The objective of this study was to model the potential distribution of this species in the Southern Chihuahuan Desert, and to estimate the current population density.

METHODS:

The study area includes 12 Physiograpics Subprovinces (PSP), which cover the Southern portion of the Chihuahuan Desert, located in North-central Mexico. The initial study area has 88,338.4 km2, which we divided into a grid of 5 x 5 square km, obtaining 7,692 squares of which 233 were sampled. We draw rectangular quadrants of 10 x 100 m in the centroid of each square, where we collected the following habitat variables: soil type, vegetation type, slope, altitude, and presence of active nests. We obtained the nest density and a potential distribution model using Maxent, which included 25 predictive variables.

RESULTS:

We found evidence of the presence of the white-tooted woodrat in 69 sites. We located the species mainly in low terrain slopes with an altitude range of 1,701- 2,100 m. The results also indicate higher abundance in Xerosol soil associated with microphyllous desert scrub. The potential distribution area found was 60,766 km2 (68.8 %), in which the distribution probability was low (27.3 %), medium (25.4 %), and high (16.1 %). The average nest density was 545 km2. The variables that best explained the model of potential distribution (AUC 0.920 ± 0.017) were: soil type, vegetation type, vegetation cover, slope, aspect, two bioclimatic variables of precipitation, and three bioclimatic variables of temperature.

DISCUSSION AND CONCLUSIONS:

The distribution and abundance of small mammal populations often depend on interactions between environmental variables. In our study, the main habitat variables coincided with those found in other studies. The potential distribution was restricted to the Northern and central portions of the study area. Soil type, vegetation type and vegetation cover markedly influenced the potential habitat for the establishment of nests. Wright (1972) mentions that an increment of vegetation cover rises the density of rats, but only when the plants they eat are abundant, which in turn causes an increase in the number of nests. Nest density was low compared to other sites. The status of the population is worrisome; it is necessary to do more assessments on the species distribution and on its use as food source for the local people.

Keywords : Maxent; population abundance; semiarid environments; signs; soil type; vegetation type; wild rodents.

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