Demographic features and habitat preferences of the transvolcanic deermouse (Peromyscus hylocetes) in Colima, Mexico

Background/Question/Methods The transvolcanic deermouse (Peromyscus hylocetes) is endemic to the Cordillera Transvolcanica from west-central Jalisco eastward to Districto Federal and northern Morelos, México.  Relatively little is known about the basic ecology and demography of P. hylocetes.  We encountered P. hylocetes during mark-recapture studies in January 2006 and 2007 in north-central areas of the state of Colima, Mexico, giving us an opportunity to evaluate habitat preferences and demography of the species.  Each year five 100-station grids (10 x 10 configuration) were established with each station having one arboreal and one ground trap.  Grids were operated for 8 nights each (16,000 trap-nights total).  Habitat preferences were assessed for trap stations using measures from 14 structural vegetation characteristics taken for each station of each grid.  We employed logistic regression and nonparametric multiplicative regression (NPMR; program HyperNiche) to characterize sites frequented by P. hylocetes versus those where it was not found.

Results/Conclusions We caught 110 individuals a total of 343 times, with 33.6% of captures in arboreal traps.  The adult male:female ratio was 1:0.58, 87.2% were adults, 48.6% of adult females were pregnant or lactating, and no sexual dimorphism in mass was found.  The average distance from centroid of captures was 12.9 m.  Logistic regression produced an equation with 4 variables.  The species was caught at stations with less grass, shorter distances to nearest trees, more rocks, and a higher maximum canopy.  Using NPMR, 4 variables—percent litter, percent rocks, maximum canopy height, and average distance to nearest trees—were in the best model for the likelihood of P. hylocetes occurrence.  It is more likely found in areas where ground cover is predominantly rocks (75-90%) irrespective of the percentage of litter.  In microhabitats with <40% rocks, litter as ground cover gains increasing importance with the capture likelihood reaching 0.6 with 80-90% litter.  Likelihood of P. hylocetes occurrence increased as average distance from trees decreased, especially when in combination with a greater canopy height.  Overall, we found a strong microhabitat preference for more open rocky areas with little grass, an open understory, and nearby trees that formed a high canopy.