Elephants get first dibs at the African savannah salad bar, which may force rhinos to dine on lower quality food and a more limited diet.

When elephants abound in an ecosystem, a South African study found that black rhinos (Diceros bicornis) tend to eat more grass than in nearby areas with fewer elephants. Grass contains more fiber per the amount of energy it contains, and thus provides rhinos with less nutrition per pound than other floral food sources.

However, when African elephants (Loxodonta africana) are absent, an analysis of rhino poop found evidence that the horn-headed herbivores devour a wider variety of vegetation, including leaves from shrubs, succulent plants and liana vines.

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“Despite extensive evidence of the effects of elephant on food resources in the Addo Elephant National Park (where the study was conducted) and elsewhere few studies have investigated the consequences of this for other large herbivores,” wrote the authors in the journal PLOS ONE. “Surprisingly, where this information exists, the emphasis has been on demonstrating that elephant facilitate herbivore access to habitat and increase the availability and quality of food. This is despite clear evidence that elephants limit herbivore abundances across ecosystems through their ability to monopolize resources.”

The elephant-enforced diet may harm rhino health. Analysis of the chemical composition of rhino droppings found that levels of the important nutrient phosphorus were lower in rhinos living in areas where pachyderms predominated.

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The International Union for the Conservation of Nature lists black rhinoceros as critically endangered.

IMAGE: Black rhino in Ngorongoro Crater. (Brocken Inaglory, Wikimedia Commons)