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Humans are pretty good at destroying things. Like habitats, animal populations... you catch my drift. But, there have been a few species that humans have helped bring back from the brink of extinction.

Special Thanks to: Royal Botanic Garden Sydney, Kākāpō Recovery, New Zealand Department of Conservation, and Dr. Andrew Digby.

Hosted by: Olivia Gordon
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Black-footed ferret:
Galapagos tortoise:
Bald eagle:
(Dr Andrew Digby and Bronwyn Jeynes, personal communication)
Humpback whale:
Wollemi pine:
Sea otter:

 Intro (0:00)

[SciShow intro plays]

Olivia: Humans have had a pretty big influence on planet Earth and on the things that live on it. And not all of that influence has been positive. Extinction rates, for example, are thought to be a thousand times higher with humans around than they would be without us. But not all endangered species are headed the way of the dodo or the thylacine. Some are actually making a comeback, thanks to conservation and research efforts around the world.

 Black-footed ferret (0:33)

Let’s start with a species that’s been brought back from the brink of extinction: the black footed ferret. Black-footed ferrets are specialized prairie-dog hunters, which make up around 90% of their diet. But American farmers weren’t quite so fond of prairie dogs, since they dug up the soil and made their fields less productive. So, throughout the twentieth century, prairie dogs were exterminated whenever possible.

Without prairie dogs, the black-footed ferrets were left with very little to eat, and their populations fell catastrophically. In 1998 the species was classified as “Extinct in the Wild” on the IUCN’s Red List of Threatened Species.

Luckily, there were still some ferrets in captivity. These ferrets were used to reintroduce the species to places in North America where prairie dogs still thrive. And now, black-footed ferrets are back to “Endangered” status, which is not great, but it’s better than extinct!

Not all reintroduction attempts worked, though. Some ferrets succumbed to diseases spread by other species, like canine distemper virus, which affects dogs as well as wildlife like raccoons and foxes; and sylvatic plague, a bacterial infection that mainly affects rodents. Others were eaten.

But researchers are on the case! They’ve developed a special ferret-friendly vaccine for canine distemper virus, and are working on an oral vaccine for sylvatic plague.

 Galapagos Tortoises (1:48)

In 2012, the world said farewell to Lonesome George, the very last Pinta Island tortoise. The Pinta Island tortoises may be lost forever, but around a dozen other closely related Galapagos tortoise species are doing much better these days.

Galapagos tortoises were well adapted for their tropical island environment, but they were not prepared for the arrival of humans and the other mammals we brought with us. The tortoises were so delicious and easy to catch that sailors would actually stack them up below deck as a food reserve. People also introduced goats that devastated tortoise habitats, and pigs and rats that devoured their eggs and babies.

Then, in 1959, the Galapagos Islands were established as a national park. People started trying to restore habitats for native species. They got rid of the rats and the goats, and worked on controlling other invasive species, like fire ants and brambles.

Meanwhile, captive breeding programs produced more giant tortoises. Most of the tortoises on rat-infested islands were old. And they were too big for the rodents to harm directly, but their eggs were destroyed year after year.

Thankfully, tortoises are long-lived and can reproduce well into old age. They were bred carefully to avoid inbreeding, and now Galapagos tortoise numbers are crawling back up.

 Bald Eagles (2:58)

DDT was a substance that seemed so promising at first. It was a super effective insecticide, mainly used for killing off mosquitoes, and was used a lot in the mid-20th century. It even won its discoverer a Nobel Prize. But DDT turned out to be a big problem for some species that we did want to keep around, like bald eagles and peregrine falcons.

DDT is a stable compound, so it isn’t easily processed or excreted by living things. The toxin builds up in insects’ bodies — even the ones it doesn’t kill. Animals that eat insects need to eat a lot of them, and with every insect, they got an extra dose of DDT. The animals that ate those animals got even more DDT, and the DDT concentration accumulated up the food chain.

Meat and fish-eating birds like bald eagles, which are at the top of the food chain, suffered unexpected and deadly consequences. DDT thinned their eggshells, making them more likely to crack while being incubated. Combined with shooting, lead poisoning and habitat destruction, bald eagle numbers took a really big hit. At one point, there were only 500 nesting pairs left in the lower 48 US states.

But once it was clear how bad DDT was, it was banned in the US in 1972 and then worldwide. Gradually, the pesticide got broken down in the environment, and the eggshells got back to their full strength again. Numbers still aren’t as high as they once were, but overall, they’re on the rise!

 Kākāpō (4:20)

Imagine a dumpy green owl the size of a small turkey, and you might be picturing something like the kākāpō! But this eccentric bird is actually a species of nocturnal flightless parrot.

Kākāpō were once abundant in New Zealand forests, but they were ravaged by invasive rats and stoats brought in by nineteenth century Western settlers. They’d never evolved a fear or defense against mammalian predators, and until recently the species was down to around 50 birds.

But a conservation group called Kākāpō Recovery are on a mission to bring the bird back to safe numbers. The birds’ slow, gentle nature may have gotten them in trouble in the first place, but it’s made their conservation easier! Since Kākāpō now live on just three predator-free islands, researchers can monitor every member of the species. They’ve learned a lot about the bird’s natural behavior, like breeding habits and food choices.

Numbers are now rising, and in 2016, more than 30 Kākāpō chicks were born between the 128 adults. But with such a population bottleneck, it’s not clear whether there’s enough genetic diversity left to keep the species healthy in the long-term.

So, to find out, Kākāpō recovery are crowdfunding the first ever species-wide genome sequence. Having DNA data from every living Kākāpō could help us learn more about issues like poor fertility and low vitamin D levels in many birds. Analyzing their genomes could determine whether these are genetic conditions, which could be vital for keeping this bizarre bird from extinction.

 Humpback Whales (5:47)

Historically, whales like the humpback have been hunted for meat, oil and blubber. Whales are slow breeders and babies can take years to reach maturity. So as demand increased, the population couldn’t replace itself, and numbers fell.

Then, in 1967, biologist Roger Payne discovered humpback whale song – drones, whoops, and clicks produced by males. Suddenly, everyone was talking about these complex sounds and the creatures that sang them – the sounds were even incorporated into pop music! Around the same time, conservation efforts to stop whaling took off. Campaigns became more vocal, and people piled onto boats that traveled out to stop the harpooning.

In 1982, countries around the world voted to ban commercial whaling, and the ban has allowed many whale species to recover, including the humpback. Back in the 1980s, humpback whales were considered endangered. But since then, their rating has improved to “Least Concern”,which is the best available spot.

 Wollemi pines (6:40)

Wollemi pines were only discovered in 1994, but they’ve been around for a really long time. Close relatives of these trees, and possibly even this species itself, are thought to go all the way back to the time of the dinosaurs. When botanists visited the only Australian woodland where wild Wollemi pine grew, they found that the trees’ age distribution was super weird.

It’s like finding a human village where everyone was either a senior or a toddler, and you’d wonder where everyone aged in between was! That’s something that’s still being investigated. But the single population was a more pressing concern. It would only take one major forest fire to wipe out the entire species, so they needed another home.

While reintroducing Wollemi pines to new areas in 2012, they learned a lot about the plants’ preferences for warm, well-lit places, which seemed to keep away fungal rot and allow them to grow better. Conserving and studying trees so similar to those from prehistoric times could teach us a lot about life in dinosaur-filled forests. Now that the trees are safer from extinction, you can even buy a Wollemi pine to use as Christmas tree!

 Sea Otters (7:45)

Sea otters are almost like aquatic teddy bears, they are all cute and floofy. But their fuzziness came with a price: Their fur is among the densest in the animal kingdom, and was highly sought after by people in the early 1900s. At one point, the species plummeted to just a few small colonies. But sea otters are now a protected species, and use of their fur has been banned.

The species has recovered significantly, although there have been some setbacks from things like habitat loss and oil spills. And the benefits go beyond the sea otters themselves. Bringing them back has had a positive cascade effect on their whole ecosystem.

Sea otters are keystone species, meaning their presence and activities have more positive effects than you’d expect, given their numbers. In this case, they control populations of sea urchins that otherwise wreak havoc on the kelp that supports much of their ecosystem. Kelp is a seaweed that forms huge underwater forests.

Each massive strand is tethered to the seafloor with a single attachment. Sea urchins feed on kelp tethers, chewing through them until they snap. The kelp, and everything living on them, floats away, leaving a flat, barren seascape. But sea otters control sea urchin populations, allowing kelp forests to thrive. Now that there are more otters around, their ecosystems are more stable.

 Outro (9:03)

So, human activity has definitely had a negative impact on a lot of other species, and it’s often difficult to undo that damage. But for these species, at least, we’ve been able to help.

Thanks for watching this episode of SciShow, and thanks especially to all of our patrons on Patreon who protect this show from extinction. If you want to help us keep making videos like this, just go to And don’t forget to go to and subscribe.