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'''Nest and space use in the lesser cavy, Microcavia australis''' 

Females of several rodent species engage in communal nesting, meaning that they use and rear their young together in shared nests. Establishing how communal nesting varies across species is critical for  comparative studies to examine the origin and the current adaptive value of this behavioral strategy. Comparative approaches are more powerful when data from a diverse a array of taxonomic groups are included. Herein, we report original field data to examine the social structure of a high altitude population of the scarcely known Microcavia australis (lesser cavy). In particular, we used radio-telemetry techniques to monitor nest use at night and daily home ranges and examine whether lesser cavies form nesting associations that are socially cohesive groups. We further timed our observations to breeding time of our study population (September-November) to assess opportunities for communal breeding. The night time telemetry of 24 radio-tagged cavies revealed seven nesting associations (i.e., communal nesting). These included 1-4 breeding females, and 1-2 breeding males. Nesting associations were stable in terms of identity of individual members and in the location of putative nest sites. Most associations used a single nest site, but some used two or three. We noted that all nest sites were located under dominant shrubs, but use of nest sites were unrelated to variations in shrub cover. Nest sites with more burrow entrances were more frequently used by radio-collared cavies. During day time, home ranges of cavies overlapped more with ranges of nest mates than with those of non nest mates, implying that nesting groups were socially cohesive units. Taken together, these data confirmed that this species is communally nesting, and, since communal nesting occurs during breeding time, our findings provide strong circumstantial evidence that lesser cavies engage in communal care of young ( LUIS A. EBENSPERGER*, PAULA TARABORELLI, STELLA M. GIANNONI, MARÍA JOSÉ HURTADO, CECILIA LEÓN AND FRANCISCO BOZINOVIC EN PRENSA JOUR MAMM;  Centro de Estudios Avanzados en Ecología & Biodiversidad, and Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile (LAE, MJH, CL, FB); Grupo de Investigaciones de la Biodiversidad, Instituto Argentino de Investigaciones de las Zonas Áridas, Consejo Nacional de Investigaciones Científicas y Técnicas, CC 507, 5500 Mendoza, Argentina (PT, SG)