Relating demographics and social systems to declines in Asian Great Ape population
Catastrophic declines in wild populations of African gorilla and chimpanzees due to disease outbreaks have been reported in recent years, yet similar disease impacts are rarely identified for the more solitary Asian great apes, or for smaller primates. Researchers led by Sadie Ryan, Assistant Professor at the State University of New York College of Environmental Science and Forestry has recently published a study centered on the interaction between the social system and demographics of different primate species to determine if any of these behaviors or realities predispose them to potentially lethal pathogens. Through this study the researchers have identified interactions between social structure, demography, and disease transmission modes that create "dynamic constraints" on the pathogens that can establish and persist in primate host species with different social systems.
Intragroup contact structure - the social network - creates different constraints for different transmission modes, and the model underscores the importance of intragroup contacts on infection prior to intergroup movement in a structured population. When alpha males dominate sexual encounters, the resulting disease transmission dynamics differ from when social interactions are dominated by mother-infant grooming events, for example.
The study included the identification of five major primate social systems including solitary, monogamous, unimale, multi-male, and fission-fusion. They developed matrices, for five disease transmission modes including sexual, fecal-oral or local contamination, aggressive interactions such as biting and scratching, direct aerosol and vector transmitted disease. Pathogen transmission is highly dependent upon the rate of contact, which is naturally different from one primate species to the next.
In general, infections, which lead to immunity, require higher rates of transmission, which in turn roughly scales with the duration of immunity. This can also create complex epidemic dynamics such as those seen in classic studies of human diseases. Ryan's team focused on the constraints that social system and body size place on the initial establishment and impact of a non-immunizing infection.
"This has important repercussions for pathogen spread across populations," said the lead author, Dr. Sadie Ryan. "Our framework reveals essential social and demographic characteristics of primates that predispose them to different disease risks that will be important for disease management and conservation planning for protected primate populations."
Read more at SUNY ESF.
Orangutan image via Shutterstock.