Spatial and Seasonal Dynamic of Abundance and Distribution of Guanaco and Livestock: Insights from using Density Surface and Null Models.

SCHROEDER N, MATEUCCI SD,MORENO P,GREGORIO P, OVEJERO R,TARABORELLI P, CARMANCHAHI PGABRIELA3; OVEJERO, RAMIRO2,4; TARABORELLI, PAULA2; MORENO, PABLO2; GREGORIO, PABLO2; BOLGERI, MARÍA JÓSE5; CARMANCHAHI, PABLO2

PLOS ONE

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2014 vol. 9

1932-6203

Monitoring species abundance and distribution is a prerequisite to assess speciesstatus and population viability, a difficult task to achieve for large herbivores atecological meaningful scales. Co-occurrence patterns can be used to infermechanisms of community organization (such as biotic interactions), although it hasbeen traditionally applied to binary presence/absence data. We combine densitysurface and null models of abundance data as a novel approach to analyze the spatialand seasonal dynamics of abundance and distribution of guanacos (Lama guanicoe)and domestic herbivores in northern Patagonia, to visually and analytically comparethe dispersion and co-occurrence pattern of ungulates. We found a marked seasonalpattern in abundance and spatial distribution of L. guanicoe. Guanaco populationreached its maximum annual size and spatial dispersion in spring-summer, decreasingup to 6.5 times in size and occupying few sites of the study area in fall-winter. Thisresults evidence the maintenance of the seasonal migration process of guanacopopulations, an increasingly rare event for terrestrial mammals. The maximum numberof guanacos estimated for spring (25951) is higher than total population size (10000)20 years ago, due both to counting methodology and population growth. Predictedabundance of large-livestock (cattle and horses) was more constant throughout theyear (3139-6022 animals). Livestock were mostly distributed near human settlements,as expected for the sedentary management practiced by local people. Herbivoredistribution was non-random, i.e., guanaco and livestock abundances co-variednegatively, in all seasons, more than expected by chance. Segregation degree ofguanaco and small-livestock (goats and sheep) was comparatively stronger than thatof guanaco and large-livestock, suggesting a competition mechanism betweenecologically similar herbivores, although various environmental factors could alsocontribute to habitat segregation. Future research should combine abiotic and bioticfactors with abundance data to better understand population dynamics of species ofconservation interest.