"When" is just as important as "what" in terms of animal diets. Scientists have pointed out that when examining ancient animals, it's crucial to understand when they ate the things they did in order to better understand their diet.
"Diet is one of the most important features of animals," Matt Davis, a Yale graduate student in geology and geophysics, said. "But often, we can't seem to agree on what animals ate. Grizzly bears, for example, eat different food at different times. If you looked at their diet in the spring, it would look like what wolves eat, but in the fall, bears eat mostly seeds, just like squirrels."
Scientists use diet reconstructions in order to find out information that helps them manage the habitats of endangered species, and also understand evolutionary changes in a species' function. They also use this to learn a bit more about ancient habitats and climates.
Unfortunately, diet proxies don't always agree. This is largely because researchers record what an animal eats over different lengths of time. This means that throughout the year, an animal's diet could be changing and researchers could not be recording that particular change.
This can be a big problem when it comes to researchers. For example, in one instance scientists unintentionally reversed the order of a food chain in a lake in East Africa due to the fact that they didn't factor in the different speeds that zooplankton and their predators absorb nutrients. In other words, researchers can misread the information that they gather and come to the wrong conclusion.
"The correct diet proxy depends on the question you're asking," Davis said. "We can't just look at stomach contents sampled yesterday and extrapolate them out for 1 million years."
The findings show that time scales are important when considering diet. More specifically, it's important to consider these time scales at each stage of research.
"By using different proxies like the chemical signatures in feathers and blood we can tell not just what a bird is eating but what it ate a year ago and how its diet changed since then," Silvia Pineda-Munoz, one of the researchers, said. "This is especially important for rare or endangered species because we can effectively time travel through their diet without harming the animal."
The findings are published in the March 18 journal Ecology and Evolution.
