Size, Site Fidelity, and Overlap of Home Ranges and Core Areas in the Socially Monogamous Owl Monkey (Aotus azarae) of Northern Argentina

Flurina M. Wartmann*, Cecilia P. Juárez, Eduardo Fernandez-Duque

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)


In addition to environmental factors, social variables such as group size may play an important role in explaining primate ranging patterns. In this study we investigated range sizes, site fidelity, and range overlaps of owl monkeys (Aotus azarae) in Northern Argentina. We calculated the size of home range and core areas for 18 groups in our study area. For the six most intensively studied groups we tested whether precipitation as a crude proxy for food availability or group size had an influence on range size, assessed the degree of site fidelity by quantifying overlaps of annual ranges and core areas, and calculated the amount of range overlap between neighboring groups for each year. We used the kernel density estimation method to calculate home ranges as 90% kernel and core areas as 50% kernel. Home range size (mean ± SD) was 6.2 ha (± 1.8) and core area size 1.9 (± 0.6). Rainfall and group size were not statistically significant predictors of range sizes. Site fidelity was high, with a range overlap of 82% (± 11) between consecutive years. Neighboring groups overlapped over 48% (± 15) of the outer parts of their group ranges and 11% (± 15) of their core areas. We found no evidence that larger groups occupy larger areas than smaller groups, suggesting that food availability might be above a critical threshold for owl monkeys so that larger groups do not need to extend their foraging areas to meet their energy requirements. Our findings indicate that ranges remain stable over several years as groups visit the same locations of fruit trees within their range. We showed that owl monkeys exhibit a considerable degree of range overlap. However, we suggest that this range overlap might be spatial rather than temporal, which maximizes access to clumped feeding resources in overlapping areas that are used at distinct times, while excluding other males from access to females in exclusively used areas.

Original languageEnglish
Pages (from-to)919-939
Number of pages21
JournalInternational Journal of Primatology
Issue number5
Publication statusPublished - 1 Oct 2014

Bibliographical note

The Ministerio de la Producción, Subsecretaría de Ecología y Recursos Naturales from Formosa Province and the Dirección de Fauna Silvestre de la Nación Argentina authorized the fieldwork. The authors thank Fundación ECO of Formosa, Argentina for logistical support and Estancia Guaycolec for permission to work on their premises. We acknowledge the efforts of all researchers, students, and volunteers who contributed to data collection, especially Victor Dávalos and Marcelo Rotundo. E. Fernandez-Duque thanks Anthony Di Fiore for early discussions that influenced the collection and organization of ranging data. We thank Anthony Di Fiore and Maren Huck for valuable comments on a previous version of this manuscript and Kathleen Woodhouse-Ledermann for proofreading. F. M. Wartmann is grateful for financial support by the Forschungskredit of the University of Zurich, grant no. FK-13-104 and for the hospitality and support received from Anastacia Gimenez and Rodrigo Flores during her stays in Formosa. E. Fernandez-Duque acknowledges the financial support during all these years from the Wenner-Gren Foundation, the L. S. B. Leakey Foundation, the National Geographic Society, the National Science Foundation (BCS- 0621020), the University of Pennsylvania Research Foundation, and the Zoological Society of San Diego. We thank the editors and two anonymous reviewers for their comments which helped to improve the manuscript.


  • Aotus azarae
  • Core area
  • Home range
  • Kernel density estimation
  • Site fidelity
  • Social monogamy
  • Territoriality


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