The Scientist - USA (2020-11)

44 THE SCIENTIST | the-scientist.com

International University marine ecologist Mike Heithaus. “A t

its core, oceans and land are the same because animals are

making the same kind of trade-offs—they’re trying to opti-

mize food versus risk.”

Broadcasting predator vocalizations is another approach to

interrogate predator trophic cascades, one that can more directly

assess the effects of fear on prey. Upon playing recordings of bark-

ing dogs in the intertidal zone on Canada’s west coast beaches, for

instance, Zanette’s team found that raccoons (Procyon lotor) spent

less time foraging, allowing crabs and fishes to increase in abun-

dance—a behaviorally mediated trophic cascade that extended

from a terrestrial habitat into the ocean.^18 Similar studies have

reported that underwater playbacks of mammal-eating killer

whales (Orcinus orca), but not of local fish-eating killer whales,

trigger harbor seals (Phoca vitulina) to dive to safer depths.^19

In Mozambique’s Gorongosa National Park, researchers have

sought to understand the historic impacts of losing nearly an

entire guild of top carnivores. Decades ago, the area had become

a battlefield during the country’s civil war, decimating popula-

tions of large animals, including leopards, wild dogs, and lions.

In 2019, Pringle, Princeton postdoc Justine Atkins, and their

colleagues reported that in the absence of these carnivores, the

typically forest-dwelling bushbuck (typicallytypicallytypically forest-dwelling forest-dwelling bushbuck bushbuck bushbuck ( (Tragelaphus sylvaticusTragelaphus sylvaticus) had ) had

44 THE SCIENTIST | the-scientist.com the-scientist.com

ECOSYSTEM EFFECTS: The Iberá wetlands in Argentina lost most

of their wildlife during the 19th century as people moved into the

remote area, but the region’s native species, including capybaras (top),

maned wolves (bottom left), and pampas deer (bottom right), are now

recovering, thanks in part to an ambitious ecological restoration effort.