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  • More often than not humans have a negative impact on the natural world.

  • But once in a while, an opportunity comes along to bring an ecosystem destroyed by us

  • back from the brink.

  • A national park in Mozambique is giving scientists, this very change by providing a unique

  • opportunity to restore an ecosystem and demonstrate the surprising role predators play in maintaining balance.

  • They're hoping to capitalize on a unique ecological effect observed in the natural world...

  • Fear.

  • This is Gorongosa National Park.

  • It's quickly becoming one of Africa's, and perhaps the world's, greatest wildlife restoration

  • stories.

  • We had really high densities of animals like buffalo, elephant and a host of other ungulate

  • species so it's very rich in its biodiversity and specifically in its large mammal populations.

  • Lions, leopards, hyena, were all here.

  • But the war pretty much wiped that out.

  • From 1977 to 1992 a civil war devastated Mozambique

  • and killed more than 90% of the large mammal populations in Gorongosa.

  • Though so many of the animals were gone,

  • many hunted with little protection during the war, the land and vegetation was still

  • largely intact.

  • So once rangers secured the park from poaching many herbivore populations began to rebound.

  • Others got a little bit of help from the scientists.

  • The elephant population is increasing.

  • Species like waterbuck, impala, reed-buck, warthog are just on the up.

  • So, this system is really ready for this type of recovery.

  • In comparison large carnivores didn't make such a strong recovery initially.

  • And while the waterbuck and the impala probably didn't mind.

  • Over time, a lack of large predators can tip the balance of the ecosystem,

  • we start to see these signs of imbalances and these missing pieces, very clearly in Gorongosa.

  • In the absence of fear, in the absence of predation, certain species just skyrocket.

  • The other thing we see are animals that are behaving a little differently to what we

  • would consider normal.

  • Without predators to keep the prey alert and in line, the herbivores can go wherever they please

  • in search of a good meal.

  • Bush-buck is normally a pretty reclusive species. They're not a species that normally drifts

  • out into the open.

  • But in the absence of predation we've actually seen bush-buck take those chances.

  • We'll see them out on open floodplain foraging on some pretty nutrient rich plants.

  • So in the absence of predation they're willing to take that risk and venture out into areas

  • that they usually seek refuge in.

  • Sounds ideal for the bush-buck.

  • But it's a warning sign of an ecosystem out of whack.

  • If animals don't stay in their lanes the whole system can spiral out of control.

  • This is where the predators come in.

  • Sure they eat some of the prey.

  • But importantly they instill what scientists call a landscape of fear, just the presence

  • of predators changes the prey's behavior, forcing them to be more vigilant and take

  • fewer risks.

  • Lions are one predator that was slowly recovering in the park.

  • And while they did their part in going after some prey animals.

  • They weren't doing enough.

  • A lion is an ambush predator. They hang out in tall grass on the edge of the floodplain.

  • And they take down their prey using stealth.

  • The ambush-hunting lions

  • were certainly being noticed by the prey species they went after, but their

  • tactics and territories were not enough to impact the whole park.

  • The team realized that other predators, with different hunting styles were needed - top of

  • their list was the painted wolf - a wide roaming pack predator, that had been well established in Gorongosa

  • before the war.

  • So there's nothing like a painted wolf on this continent, they're unique, they have

  • this gorgeous camouflage coat pattern and every individual is differently colored and differently

  • patterned, their teeth, their paws have evolved to support them being one of the continents most

  • exceptional hunters.

  • The African painted wolf is considered one of the most successful predators on the planet,

  • but how the animals hunt, specifically that they go after their prey using a different

  • hunting method than lions, was really why the painted wolf was chosen.

  • A painted wolf pack.

  • They're not stealthy in the least.

  • They chase down their prey and sometimes they'll go miles chasing down an animal.

  • So, very different ways of hunting, that actually complement each other in the ecosystem.

  • Bringing the predators back to Gorongosa was also an unprecedented opportunity to help

  • save the species.

  • There are only roughly 7000 painted wolves left on the planet, but reintroducing a species,

  • especially a predator is a massive undertaking.

  • The range of action includes many steps.

  • When they arrive in Gorongosa, they're kept in a temporary enclosure, where they're safe.

  • Once the pack arrives and they're

  • in the enclosure, we begin the process of habituation.

  • Most of those members in the pack that we want to bond have never met each other before

  • directly.

  • And we use a novel scent-marking procedure where we actually rub dogs while they're

  • still sleeping against each other to leave the scent on each other, so that when they

  • woke up, there wouldn't be so much aggression.

  • Paola and her colleagues kept the painted wolves in an enclosure, so that they would form a

  • well functioning pack before taking off on their own.

  • This careful scientific approach to conservation allowed Paola and her team to release the new

  • predators into the larger Gorongosa wildlife population, knowing there is a good chance

  • they could help rebalance the ecosystem and unleash the power of fear.

  • Right off the bat, it was really clear that the painted wolf reintroduction was succeeding.

  • The packs were hunting successfully.

  • We had different packs form on the landscape, we had pups born.

  • And in addition to thriving themselves, the painted wolves settled nicely into their role

  • as a regulating predator.

  • This is a long term,

  • effort, but even in these initial stages we're starting to see the signs of a system coming

  • back into balance.

  • Bush-buck that would be normally out in the open taking chances because there were no predators there before

  • are now more reclusive. And so, in a sense, you start to see species falling back into their

  • more predictive ecological lanes.

  • It's still too early to tell how Gorongosa will be affected as the painted wolves establish new generations.

  • It helps that the scientists collected so much data throughout their sustained conservation

  • efforts.

  • So, they'll be able to track any changes and developments in the ecosystem as they happen,

  • but there's already proof of success.

  • 52 new pups were born in 2020. 37have survived the denning stage, a survival rate of 71%, which

  • is incredible, compared to the average rate of less than 50%.

  • This brings the total Gorongosa painted wolf population to 85 dogs and five packs.

  • These are still the places where the complex ecology that supports a habitable planet,

  • still exists.

  • And so no matter where you go on this planet right now.

  • These systems need healers and defenders and so that's what drives us here, that's what gets

  • us up early and works late into the night is that opportunity to make a positive difference.

  • For more

  • on Gorongosa's landscape of fear and the return of the wild dogs, check out nature's

  • Fear Factor streaming now on pbs.org.

More often than not humans have a negative impact on the natural world.

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Painted Wolves: Why Is Fear So Important to an Ecosystem

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    林宜悉 posted on 2020/12/01
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