Publications [#240899] of Charles L Nunn

Journal Articles

1. Rifkin, JL; Nunn, CL; Garamszegi, LZ, Do animals living in larger groups experience greater parasitism? A meta-analysis., The American naturalist, vol. 180 no. 1 (July, 2012), pp. 70-82, ISSN 0003-0147 [Gateway.cgi], [doi]
   (last updated on 2025/06/15)

   Abstract:
   Parasitism is widely viewed as the primary cost of sociality and a constraint on group size, yet studies report varied associations between group size and parasitism. Using the largest database of its kind, we performed a meta-analysis of 69 studies of the relationship between group size and parasite risk, as measured by parasitism and immune defenses. We predicted a positive correlation between group size and parasitism with organisms that show contagious and environmental transmission and a negative correlation for searching parasites, parasitoids, and possibly vector-borne parasites (on the basis of the encounter-dilution effect). Overall, we found a positive effect of group size (r = 0.187) that varied in magnitude across transmission modes and measures of parasite risk, with only weak indications of publication bias. Among different groups of hosts, we found a stronger relationship between group size and parasite risk in birds than in mammals, which may be driven by ecological and social factors. A metaregression showed that effect sizes increased with maximum group size. Phylogenetic meta-analyses revealed no evidence for phylogenetic signal in the strength of the group size-parasitism relationship. We conclude that group size is a weak predictor of parasite risk except in species that live in large aggregations, such as colonial birds, in which effect sizes are larger.

   Keywords:
   Animals • Birds • Fishes • Host-Parasite Interactions • Insects • Lizards • Mammals • Parasitic Diseases, Animal • Phylogeny • Population Density • Risk • Spiders • epidemiology • transmission*