Woodrat diets Reveal a Nuance Beyond “Jack-of-All-Trades”
A comprehensive, eight-year study of woodrat populations across North America is challenging conventional understandings of dietary generalization in animals. Researchers from Utah State University and the North Carolina Museum of Natural Sciences, publishing in the Proceedings of the National Academy of Sciences, found that while woodrats exhibit a range of dietary approaches, even those considered “generalists” demonstrate surprisingly focused eating habits. The research was funded by the National Science Foundation.
The study, led by USU assistant professor Rebecca Weinstein, analyzed the diets of over 500 individual woodrats across 13 species and 57 populations. It revealed a spectrum of feeding strategies, from highly specialized species that consistently consume a narrow range of plants – potentially as a way to mitigate the risk of consuming poisonous vegetation – to generalists. However,Weinstein explains,these generalists aren’t the “jack-of-all-trades,master of none” often assumed. “They’re more accurately described as jacks-of-all-trades, master of some,” she says.
The research highlights the trade-offs inherent in both dietary specialization and generalization. Surprisingly,generalist woodrats were observed continuing to consume toxic plants like creosote even when less harmful alternatives were available,suggesting the energetic or behavioral costs of incorporating new food sources can outweigh the benefits.
“Even wiht hundreds of individuals and 13 species analyzed, we were struck by the sheer variety in their diets,” notes co-author and University of Utah distinguished professor, Denise Dearing. “Even the generalists are selective, demonstrating that both narrow and diverse diets come with associated costs.”
Woodrats prove to be an ideal model for studying animal diets due to their abundance, diverse habitats, and tolerance for consuming plants with potent chemical defenses. They readily consume plants like creosote, mesquite, and juniper, despite their high levels of alkaloids and terpenes. Furthermore, their small size and cooperative nature – readily providing fecal samples in traps – have allowed researchers to leverage cutting-edge DNA metabarcoding technology.
This technology, advanced by next-generation sequencing, has revolutionized dietary analysis, allowing scientists to identify the plants consumed by woodrats with unprecedented accuracy. Researchers tracked a single woodrat population over five years, combining dietary analysis of droppings with individual mark-recapture data to understand patterns at both broad landscape scales and within a single group.
Ultimately, Weinstein emphasizes, understanding the constraints on animal diets is crucial for predicting how species will respond to environmental changes and for gaining a deeper understanding of complex ecological interactions within food webs. The findings offer valuable insights into species persistence and the dynamics of changing ecosystems.
