Woodrats reveal how herbivores survive eating toxic plants

Plants protect themselves. They often produce chemicals that discourage animals from feeding on them. For herbivores, survival means eating enough food while avoiding dangerous toxins. This delicate balance shapes how animals forage and adapt to their environment.

The challenge is not only about survival in the present moment. It is also about long-term adaptation. Animals that fail to strike this balance risk starvation or poisoning, while successful ones pass on their strategies to future generations.

This ongoing evolutionary tug-of-war between plants and herbivores defines much of the natural world.

Utah State University ecologist Sara Weinstein believes these choices reveal much about survival. “Understanding how these animals navigate these choices is fundamental to understanding what these creatures need to survive and how species respond to changing conditions.”

Woodrats and toxic plants

Among the many plant eaters, woodrats offer a surprising case study. Native to North America, these rodents consume a wide range of plants.

“Woodrats are remarkable in their ability to eat truly awful, toxic plants,” said Weinstein. “If there are no other options, woodrats can consume plants like creosote bush, mesquite and juniper, which are full of disagreeable compounds like alkaloids and terpenes.”

Weinstein and colleagues from several universities recently published findings from an eight-year survey of woodrat populations across North America.

“Woodrats are a phenomenal model organism for understanding how wild animals make choices about what to eat,” Weinstein explains. Their habitats provide varied food choices, allowing researchers to study how animals decide among safer or riskier plants.

Analyzing the diets of woodrats

Unlike city-dwelling rats, woodrats avoid people. “Woodrats are very distant cousins of the better known, and omnivorous, New York pizza rat,” Weinstein noted. “You are unlikely to see woodrats, unless you’re in relatively undeveloped habitat.”

Despite their shy nature, woodrats are widespread across the United States. Their abundance makes them excellent research subjects, especially since multiple species often share the same environment.

“Compared to large herbivores like deer, moose or elephants, woodrats are much easier to capture and handle,” said Weinstein. “They also readily provide us with material for diet analyses, because they tend to defecate in traps.”

These droppings become data-rich samples. Weinstein noted that each sample combines about a day of food choices. This allows scientists to capture a snapshot of their diets.

Patterns in herbivore diets

Advancements in DNA metabarcoding, using next-generation sequencing, have transformed diet research.

“It’s a very powerful and accessible technique to characterize the unseen,” Weinstein said. This method has helped reveal important patterns in how herbivores eat.

Despite progress, dietary niche breadth remains poorly understood. The research shows that both specialization and generalization carry costs for herbivores.

“A longstanding notion is that if you’re highly specific in what you eat – you only eat one thing – then, if you lose access to that plant – say, it disappears because the ecosystem changes or an invasive species pushes it out – you’re going to be in trouble,” said Weinstein.

Generalists adapt more easily, shifting diets when needed. Yet the story is more complex. Most woodrat populations are generalists, but at the individual level, these generalists’ diets may not be as broad as we previously assumed, explained Weinstein.

“We tend to think of generalists as being a jack-of-all-trades, master of none. However, it looks like most generalists are more aptly described as jacks-of-all trades, master of some.”

Implications for ecosystems

Individuals often select consistent subsets of plants, helping them manage risks from toxins. These findings matter beyond woodrats.

“Ultimately, these constraints on animal diets have important implications for our understanding of food webs, species interactions and which populations are more likely to persist in changing ecosystems,” said Weinstein.

The study highlights how much we still have to learn about herbivores. By tracing dietary strategies across individuals, populations, and species, scientists gain insight into resilience and vulnerability in a changing climate.

In the end, the secret lives of woodrats remind us that even the smallest animals can unlock big lessons about survival.

The study is published in the journal Proceedings of the National Academy of Sciences.

Image Credit: Sara Weinstein

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