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The date was July 30th, 2020, around 1700 hours.
The location: Frégate Island in the Seychelles, off the coast of East Africa.
A baby tern had fallen from its nest and taken refuge on a log, where it was
pursued, killed, and eaten by an unexpected predator. . . a giant tortoise.
Yeah, you may have heard the news: predatory tortoises.
The incident was caught on video and reported in the journal Current Biology,
and it’s the first time any tortoise has been caught in the act of
deliberately killing and eating prey.
Now we already knew that these tortoises aren’t strictly vegetarian.
They’ve been known to chow down on carrion, bones, and snail shells,
which can be valuable sources of extra nutrients.
But until now, we only had anecdotal reports of them actually hunting.
The tortoise in question is a female Seychelles giant tortoise, and the
chick is a lesser noddy tern, a species that nests in trees on that island.
In the video footage, the tortoise climbs up onto the log where the
chick is standing, and a low-speed chase ensues.
As the chick hops along the log, the tortoise follows,
neck extended, mouth open, and tongue retracted.
This posture is typical of aggressive behavior in tortoises.
It’s a clear sign that this tortoise wasn’t just reaching for food,
but planning to attack.
After a minute and a half of this pursuit, the chick reaches the end of the log.
But baby terns can’t fly, and they instinctively avoid dropping down to ground level,
so there was nowhere to go. The tortoise catches up to the chick
and, well . . . goes for the head.
A single bite crushes the chick’s skull, and then the tortoise swallows it whole.
It’s shocking to watch, but what’s really striking is that the tortoise
seemed to know what it was doing.
Trapping a chick on a log is a pretty effective hunting strategy, which makes
researchers suspect this wasn’t this particular predator’s first feathery dinner.
Given the anecdotal reports of other hunting tortoises, this might actually be a
common behavior, but one that we’ve only recently had the opportunity to witness.
See, Frégate is a private island managed for ecotourism.
The video was actually captured by the island’s deputy
conservation and sustainability manager.
Conservation efforts in recent years have successfully
revived declining populations of seabirds and tortoises.
Chick-hunting could be a strange new behavior developing among these tortoises.
Or it could be something they’ve done for a long time, and now that their
populations are recovering from endangerment, they’re back to their old habits.
But whether it’s new or just newly observed, conservation efforts are giving us a
chance to observe these species interacting like we never have before.
These tortoises aren’t the first supposed vegetarians to supplement
their diet with prey.
Numerous other herbivores, including deer, sheep, and cattle,
have been reported to eat insects, fish, baby birds, and eggs.
It may sound unusual, but animal-based foods can be high in protein and minerals
like calcium and phosphorus.
That can be helpful if the local vegetation is lacking in minerals,
or if it’s a strenuous time of year, such as mating season.
As for the tortoises, there’s still more to learn.
Like how common this behavior is, or how much nutrition they get from baby birds,
or if there are other critters on the menu.
What we do know is that this one has killed before. . . and she will kill again.
Ok, enough about birds in the mouths of tortoises.
Let’s talk about bacteria in the mouths of bears.
Another study in Current Biology explored nearly two centuries of bear spit to track
how humans have contaminated the environment with antibiotic-resistant bacteria.
And no, I’m not making this up. Let’s break it down.
We humans use a lot of antibiotics to fight off harmful bacteria
in our bodies and our food.
But improper use tends to drive bacteria to develop resistance to those antibiotics,
potentially developing into even more dangerous strains.
Resistant bacteria that develop in hospitals or farms can infect humans,
but they can also get into the water and soil and infect wildlife,
who can spread the bacteria to other wildlife and back to us.
That means it could be very helpful to understand how antibiotic-resistant bacteria
spread to wildlife, and how we can stop it.
So, researchers delved into a place most humans avoid: bear mouths!
Specifically, they collected dental plaque from more than 50 preserved specimens
of Scandinavian brown bears in the Swedish Natural History Museum.
Plaque is a time capsule for bacteria. It can last for thousands of years in
well-preserved museum specimens, keeping bacterial remains trapped inside.
And signals of antibiotic resistance can be found in that bacterial DNA.
From the 1800s to the mid-1900s, the bears’ bacteria showed
low levels of antibiotic resistance,
consistent with what we would expect to see occurring naturally.
But starting in the 1950s, resistant bacteria increased,
around the same time humans in Sweden started using antibiotics
on industrial levels.
We were accidentally creating resistant bacteria
and spreading them to local wildlife.
In fact, we were spreading them really far, way more than we expected.
Bears that lived far away from human settlements had about
the same amount of resistant bacteria as those who lived close by.
This was a surprise, because previous studies of wild populations of
foxes, deer, and even tapirs have shown that there is a connection
between proximity to humans and higher levels of antimicrobial resistance.
The researchers aren’t sure what caused this difference,
but it suggests that when antibiotic resistance gets into the environment,
it really gets in there.
But there was good news, too.
Starting in the 2000s, resistance levels in the bears’ bacteria decreased.
This was about 15 years after policy changes in Sweden began
reducing the use of antibiotics in medicine and agriculture.
Which shows that our actions can contaminate the environment,
but also that this contamination can be reversed.
This kind of microbial study could prove very useful in tracking ways we’ve
contaminated and polluted our surroundings,
and museums are full of handy research subjects.
Which means old museum specimens could find new life helping
us protect the environment, and ourselves.
If you’re thinking that predatory tortoises and protecting the environment through
century-old bear spit are the two weirdest things you’ve heard all week,
I think you’ll probably like our podcast. It’s called SciShow Tangents.
It’s where a bunch of smart people compete to show off the weirdest science facts
they can find, and it’s brought to you by the same folks who make SciShow.
If you’re interested, check it out wherever you find podcasts.
It’s called SciShow Tangents. It’s a lot of fun.
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