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SciShow News starts the new year off with unusual animal news, including a crisis for the iconic monarch butterfly, and new research into what makes bowhead whales the longest-living mammals on Earth.

Hosted by: Hank Green
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 The Disappearing Monarchs (0:11)

The 1990's: They're pretty awesome, right? We had Gameboys and Pokémon and Boris Yeltsin and a whopping one billion monarch butterflies living on earth.

Unfortunately, a lot has changed since then. We still have Pokémon, but Boris Yeltsin was replaced by Vladimir Putin, who's not nearly as much fun, and the number of monarch butterflies has dropped by a whopping 90%. There are now only 35 million of the butterflies left.

So last week, the US Fish and Wildlife Service said it was gonna consider including the monarch butterfly on the endangered species list for the first time ever.

Scientists think the butterflies are disappearing at least in part because of a diminishing supply of milkweed, the plants that are the sole source of food for Monarch caterpillars.

Every year, Monarchs embark on an epic 4,800 kilometer migration between Canada and Mexico. Along the way, they stop in the upper Mississippi river basin, also known as the mid-west, and lay eggs underneath milkweed leaves, which, until recently, were all over the place. Then the larva hatch and feed on the plants.

Now, the mid-west is the agricultural heartland of the United State— if you live here and you eat food, you eat food from there.

Well, milkweed often grows in corn and soy bean fields. But over the past 20 years, more farmers have been using herbicides with the active ingredient glyphosate.

Glyphosate kills plants by blocking their enzyme pathways. Farmers can plant genetically modified crops that are resistant to glyphosate, and they can spray just sort of indiscriminately and their crops won't die.

But milkweed: that will die.

As a result, the Xerces Society for Invertebrate Conservation estimates that Monarchs have lost more than 660,000 square kilometers of milkweed habitat in the mid-west due to the use of glyphosate.

That's an area larger than France.

Scientists suspect that climate change and deforestation in Mexico may also be contributing to the Monarch's disappearance. So over the next year, the US Fish and Wildlife Service will review the proposal to list the iconic butterfly as an endangered species.

If it gets listed, that could mean extensive habitat protection on both public and private land in the united states. But even then, it'll be a long time before Monarchs get back to where they were in the 90's.

 The Longest-Living Mammal (2:07)

Now, if you ask a bowhead whale what it missed about the good old 90's, it would have to think back a lot further than the 1990's.

More like the 1890's.

Bowheads can live for over 200 years! The oldest of them ever found was 211, making them the world's longest-living mammal— at least that we know of.

They have 1,000 times more cells than a human, but they don't seem to suffer from the same rates of cancer or age-related diseases that we do. So in a study published this week, researchers sequenced the entire genome of the bowhead in order to figure out how these whales can live for so long!

A sequenced genome is kinda like a road app; it's establishing the locations and tiny genes within an organism's chromosomes.

By sequencing the genome of the bow-head and comparing it with other mammals, including humans, cows, mice, and their closest relative, the Minke whale, scientists discovered that many of the differences in bowheads' genes were associated with aging.

For instance, they know that the mutation in the gene that affects what's called the proliferating cell nuclear antigen (or PCNA), which helps repair DNA strands.

Every time one of your cells divides in two, there's an opportunity for a little bit of that DNA to be damaged. Think of it like photocopying a photocopy over and over again; eventually you're going to get some degradation.Too much DNA damage and the cell dies; this is all part of the aging process.

But PCNA acts like a leash, holding onto little bits of DNA that might break off during cell replication. The longer the bowheads' cells stay alive, the longer they stay alive, which may explain why they can enjoy centuries of swimming around in the Arctic and eating zooplankton and doing whatever else they do for fun.

The scientists stress that they have only identified the differences between bowhead genes and those of other mammals. More research needs to be done to figure out the secret to their record-setting longevity.

But we're one step closer to figuring out why some of these whales are older than me and my grandma and my great-grandma and the whole state that I live in.

 Closure (3:50)

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