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Collaborative Work Leads to Publication on Hyena Behavior

Michigan State University Distinguished Professor Kay Holekamp and her students have been observing hyenas as part of The Maasai Mara Hyena Project for more than 30 years, gathering data to help answer questions such as: how do hyenas inherit their mothers' social networks? What role do parasites play in interactions between hyenas and lions? Are there links between hyenas' early social experiences and their stress as an adult?

The latter is the basis for a new study published in Nature Communications co-authored by Holekamp and led by former MSU Department of Integrative Biology Ph.D. student Zachary Laubach. Additional IBIO contributors are graduate students Tracy Montgomery, Maggie Sawdy, and Professor Laura Smale (jointly appointed with Psychology).

Zachary, now a postdoctoral researcher at the University of Colorado, Boulder, said, "The focus of my research interests falls under the umbrella of developmental plasticity, or the ways that environmental and social experiences during one phase of life tend to cause changes that persist and have measurable effects later in life."

Kay Holekamp said, "One of the greatest things about long-term studies like ours is that they enable us to assess the lifelong consequences of variables acting on long-lived mammals very early in their lives. The cool and novel work that Dr. Laubach and colleagues have done here combines behavioral data from observations of mother-infant pairs and entire social networks among young hyenas in the Mara with very sophisticated molecular genetic analysis of patterns of gene expression and analysis of stress hormone concentrations later in life, thus revealing important long-term effects of the early social environment."

The three-decades long field study data were connected to individual fecal glucocorticoid metabolite samples (fGCMs), a non-invasive and ground-breaking monitoring technique in wildlife management for studying the physiological response of wildlife to a variety of stressors. Focusing on two windows of hyena early development'€”up to a year old--when parents are expected to have more influence, and 1-2 years old, when the "teenage" hyena establishes social networks'€”the scientists discovered that less maternal care during the infant's first year of life and less social connectedness once they are independent of the communal den were associated later in life with higher concentrations of stress hormones.

Next, the scientists wanted to see if they could mechanistically link positive early-life social experiences to these reduced stress hormones. In other words, did maternal care and teenage social networks make lasting changes to hyena DNA that played out later in life? The answer was yes. Less maternal care and less social connectedness early in life led to less global DNA methylation. Using a number of molecular biology techniques, including next generation DNA sequencing, they found that markers with respect to maternal care and stress hormones were related to genes found in humans to be associated with aging and immune function.

Zachary said, "Our data suggest that maternal care early in life seems to matter, and that these social networks, particularly in the subadult (teenage) phase, matter in terms of DNA methylation and stress hormone concentrations." His pioneering research will launch future investigations into maternal care and the immune system. "There's some interest to dive deeper into the mechanism we found here and relate early-life social experiences to aspects of immune systems and ultimately to fitness."