AJP Featured Articles

High mortality associated with tapeworm parasitism in geladas (Theropithecus gelada) in the Simien Mountains National Park, Ethiopia.

Authors: India Schneider-Crease, Randi H. Griffin, Megan A. Gomery, Thore J. Bergman, Jacinta C. Beehner

Infection with the tapeworm Taenia serialis in geladas (Theropithecus gelada) is often characterized by large, protuberant cysts full of parasitic larvae. Longitudinal research on geladas in the Simien Mountains National Park (SMNP), Ethiopia, has monitored these cysts over ten years, facilitating one of the first long-term studies of the costs of endemic helminth parasitism in primates. We found high mortality associated with cysts in adults, with similar effects in both sexes. The high virulence observed in this system may be an adaptation of T. serialis to increase the vulnerability of geladas to predation by canids, which is necessary for the continuation of the parasite life cycle. We compared our results to those of a study on this system in a separate population on the Guassa Plateau (Nguyen et al. 2015), finding circumstantial evidence that SMNP females die more rapidly than Guassa females based on the comparative lack of successful interbirth intervals completed by SMNP females relative to Guassa females. While maternal cysts were associated with heightened infant mortality at both sites, maternal death drove this effect in the SMNP but not at Guassa. Because the T. serialis life cycle includes multiple host species and may be sensitive to ecological perturbations, the stark contrast in anthropogenic impact between the sites should be considered as a potential driver of these differences. Our study is one of the first to show explicit fitness costs of endemic helminth parasitism in primates, and points to individual- and population-level heterogeneities as important areas for future research.

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Extraction of honey from underground bee nests by central African chimpanzees (Pan troglodytes troglodytes) in Loango National Park, Gabon: techniques and individual differences.

Authors: Vittoria Estienne, Colleen Stephens, and Christophe Boesch

Great apes are outstanding in their tool use skills. Given their phylogenetic closeness to humans, they represent a crucial model for understanding the evolution of the cognitive abilities associated with complex tool use behaviors in our lineage. In this study we investigated the technique used by wild chimpanzees to extract honey from the underground nests of stingless bees. This technique is particularly interesting because these nests are highly inconspicuous, the resource is deeply interred and its location underground is unpredictable. We looked at the degree of complexity and flexibility of this technique and found that chimpanzees use very long and variable sequences of exploratory and extractive actions to reach the underground nests. Nevertheless, these sequences were structured in a non-random way. Additionally, individuals showed preferences for how they performed one specific action, that is, how they perforated the nest. Chimpanzees were able to infer the location of an out-of-sight resource by using indirect cues and reach it by performing a highly complex tool use techniquse. Our study emphasizes the role that exploiting insects and their products had in shaping the technological abilities and associated cognitive traits in human evolution, and highlights the occurrence of significant differences among individuals in multiple aspects of this tool use technique.

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