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Lack Of Large Carnivores Reshaped Ecology Of African Wildlife Park

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A Princeton University ecological study highlighted the significant impact of missing large carnivores in an African wildlife park. Justine Atkins and her colleagues proved it could change animal behavior, introducing a landscape of fearlessness. The bushbuck (pictured here), known for their shyness, eventually frequented the open plains and followed a novel diet.  ( Hans Hillewaert | Wikimedia Commons )

A civil war that ravaged Mozambique changed the ecosystem of Gorongosa National Park, according to a Princeton University ecological study.

Justine Atkins, a graduate student specializing in ecology and evolutionary biology, and her colleagues found out the war, which lasted for 15 years, made many animals disappear, particularly large carnivores. These included the hyenas, wild dogs, and leopards.

To be more specific, it led to a phenomenon called the trophic cascade.

A 'Landscape Of Fearlessness'

In the study published in Science on March 7, Atkins and her team observed the bushbuck, which were usually evasive antelope species, spending more time in the treeless plains of the park than in the woodlands. This behavior wasn’t present based on their research on the area before the war.

Their primary belief was they found the plants in the plains to be more palatable and nutritious, but the researchers hypothesized another, which was trophic cascade.

“Historically, the diverse group of predators in Gorongosa were effectively keeping herbivores confined to areas with lower predation risk,” said Robert Pringle, senior author and Princeton University associate professor.

“The elimination of predators broke the rules that ordinarily govern where herbivores go and what they eat, and that has effects all the way through the food chain.”

In this case, the missing large carnivores introduced a “landscape of fearlessness,” attracting the antelope to leave the woodlands and head to the plains, which affected the growth of the plants in the area.

Putting The Hypothesis To The Test

The interactions between animals and plants in an ecosystem are a lot more complex than people think. It took the group many years to come up with the right experiments for the study, which began in 2015.

They looked into aerial censuses and placed GPS trackers on the bushbuck. They also studied the animals’ scat to find out the exact plants they ate in specific locations, as well as their muscular and fat compositions to know the effects of plant consumption.

Atkins also simulated predator cues such as leopard calls and commercially available carnivore fake scat and urine, placing them in different areas of the plains. Using their diet analysis, she secured the plants such as waterwort in cages to prevent the antelope from eating them.

The Impact Of The Missing Carnivores

With their massive amount of information, they then concluded that, indeed, the missing large carnivores contributed greatly to the changes in animal and plant survival in the wildlife park.

Those who ate the plants in the plains turned out to be stronger and bigger than the ones who grazed in the woody areas since they consumed more protein.

Meanwhile, when the bushbuck smelled the scat and urine, they moved back to the woodlands, where they felt safer. Plants in the cages also grew faster.

The results of the study were crucial, especially since the population of large carnivores is dwindling. A 2017 study revealed intact carnivore guilds occupied less than 35 percent of the world’s land area. Most of these contractions were happening in Africa and Southeast Asia.

The solution may take a while, but it’s straightforward: re-introducing predators back into the plains. So far, the African wild dogs are back and hunting successfully, according to Paola Bouley, the park’s conservation associate director.

The research was only “exciting confirmation we are on the right track in Gorongosa, focusing strongly on top predator recovery to bring an entire ecosystem back in to balance,” she further said.

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