Species specific preferences revealed in plant-based diets

The plants of Africa function as one of the world’s largest buffets for the multitudes of herbivores living there. Everything from gazelles to elephants wants some flora to much on, so how come these animals seem to get along so well? How are animals that can eat 330 pounds of food a day not clearing the savannah foot by foot, like a diverse group of giant goats? It turns out most grazers and browsers are quite picky eaters, and that that’s probably necessary to keep the ecosystem balanced.

To find out what each animal is eating, the easiest (non-invasive) ways to investigate their diets are to watch what goes in, and inspect what comes back out. The former option is harder than you may think, especially if you’re looking to be specific about which grasses and shrubs are being nibbled. And the latter option is difficult as well, as plants are often too ground up to identify, even under a microscope.

So researchers from the UiT Arctic University of Norway combined some cutting edge technology, called DNA metabarcoding, with hundreds of plastic baggies to get to the bottom of these dietary preferences. The team stalked these herbivores, waiting for them to poo, often after or during a meal. As soon as it was safe to approach, they’d then have to gather samples out of the dirt, grass or bushes, as the fresher feces were easier to analyze. That analysis involved both identification and DNA sequencing and comparing those finding to an established reference library, therefore allowing more specific readings of animal droppings than ever before.

Choosy eaters don’t need to share

This granular data revealed that most species are very picky eaters. For instance, Grevy’s zebras don’t have very similar preferences to plains zebras, and the two species can only agree on about 30% of their respective menus. By being selective, each animal can eat their preferred plants without conflicting with the neighboring species. It also means that each species plays an important role in the ecosystem, as they’re paired up with their own set of plants, pruning and distributing their seeds, rather than being generically happy with everything on the savannah. It also means that there is likely less overlap with domestic grazers, such as cattle.

Studies like this not only reinforce the notion that ecosystems are tightly interdependent, but should also help us plan future conservation efforts. It may also explain my kids’ desire to only eat macaroni and cheese all the time, leaving the carrots and lettuce for the grown ups.

Source: Grass Gourmands: A Herbivore Food Mystery On The African Savanna by Sujata Gupta, The Salt