Sociality, exotic ectoparasites, and fitness in the plural breeding rodent Octodon degus

Joseph R. Burger, Adrian S. Chesh, Pamela Muñoz, Fernando Fredes, Luis A. Ebensperger, Loren D. Hayes

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Social animals are susceptible to high infection levels by contact-transmitted parasites due to increased conspecific interaction. Exotic parasites are known to have adverse consequences on native hosts. We examined the relationship between social group size and exotic ectoparasite loads, and adult infection levels with per capita fitness and offspring survival in the plural breeding rodent Octodon degus in central Chile. Degus at our site were almost entirely infected by two exotic ectoparasites: the fleas Leptopsylla segnis and Xenopsylla cheopis. Neither group size nor number of females per group predicted the abundance of either exotic flea species. The per capita number of pups (per capita fitness) that emerged from burrow systems used by known social groups was negatively correlated with abundance of L. segnis but not X. cheopis. On adults, X. cheopis abundance was three times greater than L. segnis but was not significantly correlated with per capita fitness. In females, L. segnis abundance was negatively correlated with peak body mass during pregnancy. Adult ectoparasite load was not correlated with offspring survival. Based on these results, we hypothesize that high infection levels of L. segnis result in decreased reproductive fitness of adult female degus but are not a cost of sociality because parasite loads are not predicted by social group size. Further work is needed to experimentally test this hypothesis and to determine if L. segnis serves as a vector for a deleterious pathogen. Lastly, the lack of native ectoparasites may explain why a previous study at our site determined that behavioral adaptations needed to cope with high ectoparasite burdens (e. g., grooming) are not extensive in degus; they simply have not had the coevolutionary time needed for selection of these behaviors.

Original languageEnglish
Pages (from-to)57-66
Number of pages10
JournalBehavioral Ecology and Sociobiology
Issue number1
StatePublished - Jan 2012

Bibliographical note

Funding Information:
Acknowledgements We thank Universidad de Chile, in particular, former field station administrator J.D. Garcia, for help in facilitating fieldwork, V. Quirici, C. León, R. Castro, L. Ortiz Tolhuysen, M. Pardue, N. Schaferkotter, and J. Childers for field assistance, and A. Edelman and R. Fiorillo for helpful comments on this manuscript. This work was funded by the National Science Foundation EPSCoR (#0553910), the Louisiana Board of Regents Research Competitiveness Program (#LEQSF 2007–2009-RD-A-39), The University of Louisiana at Monroe HHMI Program and the ULM Office of Academic Affairs, the Sigma Xi Scientific Society, the American Society of Mammalogists, FONDECYT grants 1020861 and 1060499 and by Centro de Estudios Avanzados en Ecología y Biodiversidad (FONDAP 1501-001). The authors declare no conflict of interest. Field procedures followed guidelines established by the American Society of Mammalogists Animal Care and Use Committee, were approved by the ULM Institutional Animal Care and Use Committee, and are in accordance with U.S. and Chilean laws (permit no. 1-58.205 [2711] by Servicio Agrícola y Ganadero).


  • Coevolution
  • Ectoparasites
  • Fitness
  • Fleas
  • Invasive parasite
  • Sociality

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology


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