Why Can’t We Just Kill Off Invasive Species?

Invasive species destroying ecosystems are a huge problem, but there’s hope that we can help mitigate the damage.
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[music]. eradicating a species might sound like. something that's always bad we put a lot . of time and money into protecting life . on earth not destroying it but not all . eradication plans target a species. entire population just the parts that . end up in places we don't want them to . be invasive species can completely wreck . an ecosystem and we've tried all kinds . of different ways to get rid of them . over the years but some of those efforts . kind of backfired spectacularly take for . example australia's poster child for . invasive species the cane toad native to . southern and central america this toad . is huge. averaging between 12 and 15 centimeters . and will eat almost anything from . carrion to insects to that bowl of cat . food you left outside they'll also eat . smaller frogs and toads snakes snails . and small mammals basically if it fits . in the toads mouth and it can catch it. it'll lead it may be the saddest part of . the cane toad story is that they were . introduced to australia on purpose . farmers brought them in the 1930s to . control the beetles eating their . sugarcane crops. unfortunately the toads didn't stay in. the sugarcane fields and started . spreading across the continent in their . native environment the toads are eaten . by local fish reptiles birds and bugs . but in australia there are a few . predators that can eat them safely cane . toads are poisonous and predators not. adapted to their poison often died after . eating them the toads can also spray . poison from glands on their shoulders . which can cause intense pain and . temporary blindness in humans making it . both difficult and unpleasant to catch . them and when it comes to breeding there . like warty hopping tribbles . females lay clutches of up to 35,000 . eggs at a time and can lay two clutches . a year even though less than 1% of the . eggs make it to maturity that's still a . huge number of baby toads to deal with . add all of this together it's not hard . to see why estimates put the number of . cane toads in australia in the hundreds . of millions and despite efforts to . control them they're spreading moving. into 40 to 60 kilometres worth of new . territory every year but there may be . some hope for killing off the toads in . one of australia's native species meat . ants these little guys can kill and eat . toads without being affected by their . poison and since the toads aren't native. to australia they don't know to watch . out for the ants if scientists can . encourage meat ants to colonize places . where the toads like to hang out it's. possible they could make an . packt on the toad population some people . have also considered bringing in some of . the toads natural predators but that's a . risky proposition considering importing . non-native predators is what got . australia into this mess in the first . place the same control problems have . happened with other invasive species too . during the age of colonization ships . carrying explorers often brought along . stowaways like mice and rats so to . control them. sailors often introduced foreign . predators to take care of the pests you . know the phrase two wrongs don't make a . right. that's super applicable here one popular . import was the small indian mongoose a . voracious predator that was introduced . throughout the pacific islands the. caribbean japan and the mediterranean to . control invasive rodent and native snake . populations the mongoose was a favorite. because it will lead practically . anything it can catch and anyone . familiar with rikki-tikki-tavi knows . that a mongoose can cast just about . anything that ability was a problem . though because besides invasive rodents . they'll also eat plants fruit and eggs . making them a nightmare for native . wildlife the mongoose is credited with . the extinction of nearly a dozen species . across the globe which was really not . what the explorers who introduced them . had in mind and they carry rabies in . case he needed another reason to wonder . why we ever thought introducing them . everywhere was a good idea obviously . it's best to just avoid introducing . foreign species in the first place but . it is possible to eradicate them if . you're really dedicated what happened on . macquarie island half way between . australia and antarctica gives you some . idea of just how difficult eradication . can be but maybe also some hope when the . island was discovered by an australian . explorer in 1810 it became a hub for . seal and penguin hunting ships full of . hunters brought along mice and rats. which threatened their food stores so . sailors brought in cats to control the . rodents fast-forward 60 years when . another foreign species was introduced . the rabbit it was an old tradition meant. to provide sailors with food in cases . shipwrecks stranded them on a deserted . island of course rabbits multiply . incredibly fast and with lots of tasty . rabbits around the cats multiplied too . by 1970 there were more than a hundred . thousand rabbits decimating macquarie . islands plant life and the cats had . hunted two species of birds to . extinction conservationists were so . concerned about the rabbit problem that . they introduced yet another foreigner to. the party a rabbit disease called. myxomatosis it was fairly successful . reducing the rabbit population to less. than 20,000 within a decade but with . fewer rabbits to . the cats became even more dangerous to . mcquarrie's native bird population by . 1985 they done enough damage that . conservationists began a campaign to. shoot and kill all the cats you can . probably guess where this is going in . 2000 the last cat on macari was shot and . in less than a decade the rabbit . population was so out of control they'd . stripped nearly half the island bare to . prevent even more damage the tasmanian. government approved a 17 million dollar . program to hunt down and kill every . rabbit mouse and rat on the island the . first wave of the project kicked off in . 2011 spreading poison rodent bait all . over the landscape that killed off the . rats mice and many of the rabbits then . to kill off the remaining rabbits they . brought in the dogs before you facepalm . too hard the dogs were specially trained . rabbit hunters that left the island with . their trainers in april of 2014 after . two centuries of damage the eradication . was complete so there might be hope for . controlling some of the other invasive . species causing problems all over the . world but what's happened in cases like . these has taught us a lot about just how . difficult time-consuming and expensive . those efforts can be and how badly they . can backfire so next time you hear a . story about unwanted pets being dumped . into sewers think less mutant ninja's. and more ecological nightmare thanks for . watching this episode of scishow if . you're interested in learning more about . how invasive species take over . you can watch hank tell the story of . bunny and planet wonderful . [music]. .
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