What's the longest journey you've ever been on and how did you manage to reach
your destination without getting lost? - I'm going this way! - Oh, we're going this way!
My recent trip to Belize took me 5,000 miles, 11 hours on a plane, six hours on a bus and
a lot of time zoning out while watching pretty terrible films. But long before we humans devised
our ingenious technology and transportation for getting around, animals of all kinds have been
making their own spectacular journeys across the globe. And that's what we're exploring on
CrowdScience from the BBC World Service. I'm Anand Jagatia, and I'm taking you on a two-part journey
to the Americas to try and understand some of the most impressive feats of animal migration on Earth.
- This is a greycap bird. This individual probably made about three or four trips already to Belize.
Birds like this greycap arrive in Belize from North America for the winter, year in,
year out, but how do they, or in fact any migrating animal, know where they're heading? It's something
that's been bothering one of our listeners in Kenya, called Moses. Here's his question:
Moses: Hi CrowdScience. My question is, how are long-distance migrating birds like the Arctic tern
able to navigate vast oceans and distances in flight? How come they never get lost? Similarly,
how do turtles not get lost traversing thousands of miles under ocean water?
Anand: Thanks Moses. It's such a great question and it's also a huge one. So much so, that we've decided to
make it into a two-part CrowdScience special: the science of how animals actually find their
way around is a fast-moving and really exciting area of research, and we're dedicating the next
episode to that. But before we can answer Moses's question about how animals navigate over such huge
distances, you need to understand where they go and why they go there in the first place,
and it's these amazing voyages that we're covering in this episode. So let's get to it.
David Barrie: The amazing thing is
that animals are migrating all over the planet, large animals, small animals, birds,
whales, insects, you name it, fish... Anand: This is David Barrie. He's a sailor with plenty of
his own experience navigating out at sea, but he's also written a book on animal migration called
Incredible Journeys.
DB: At one extreme you've got a bird like the Arctic tern which, with the help of
tracking devices, we now know may travel a hundred thousand kilometres in the space of a year between,
as it were, the Arctic and the Antarctic and back again, and then you've got a huge animal like the
humpback whale, which will spend a long period of time feeding down in the southern ocean around
Antarctica, building up its reserves of fat before cruising steadily north into warm waters around
the equator where it will breed and have its young. Then you've got the monarch butterfly, which is a
famous example of a migrant, and less famous, but I think almost as fascinating, is the bogong moth of
Australia, which starts its life in Queensland and then it flies about a thousand kilometres south,
travelling by night, and spends the summer months hidden away in little caves, little cracks in the
rocks on the top of the snowy mountains in new South Wales, and then amazingly at the end of
the summer months it emerges and then flies all the way back to Queensland, and we're now
beginning to get to grips with how these navigational feats are performed.
Anand: You might have seen some of the astonishingly long journeys that animals can make on television in wildlife
documentaries, and the fact that many animals, from whales to wildebeest, migrate over their lives
probably isn't news to you. But that wasn't always the case. People had some very different ideas for
what happened to the animals around them when they vanished for large parts of the year.
DB: Migration was kind of a controversial idea until the 19th Century. I mean, nobody was really quite sure where
birds went, for example, during the winter. And there were these bizarre theories that people
cooked up like, you know, swallows maybe went to sleep at the bottom of ponds during the winter
months when they disappeared. But it was really in the 19th Century that people finally confirmed
that migration was a real thing and it was first really established in relation to birds and
one of the more bizarre episodes was the discovery in north Germany of a stork which had been
shot with an arrow that was plainly of African origin. This poor wretched beast arrived in
northern Germany with this arrow stuck in it and and it was obvious that it must have been to
to Africa because of this arrow. So that was the first sort of hard evidence, if you like...
Anand: The poor bird was still alive, sort of struggling?
DB: Yes, it was still alive, I guess
it got shot because it ended up in a museum, poor thing. But after that, people of course
gathered more and more evidence of of migration in a whole host of different animal species.
Anand: It might sound slightly ridiculous that people back then seriously thought that swallows went to
sleep in the bottom of ponds, but when you think of the alternative: that swallows fly thousands
of miles from the uk all the way to South Africa, you can see why people were a bit sceptical that
migration was a real thing. Take the case of birds like the Arctic tern, which listener Moses asked
about, and David mentioned might travel a hundred thousand kilometres in a year. What could possibly
be worth the immense effort that a trip like that would involve? Why don't birds just stick to the
places where they're born?
Tim Guilford: Not all birds migrate by any means. In the tropics, long-distance migration
is relatively rare; in the seasonally constant rich tropical regions of Earth then it makes sense to
to breed and live all year round in approximately the same place.
Anand: This is Tim Guilford, professor of
animal behaviour at the University of Oxford, where he studies bird migration.
TG: But a very striking
feature of our planet is that it is seasonal, so as soon as you start getting into higher latitudes
then you have lots of sunlight in summer and not very much in winter, and this drives massive
seasonal differences in resource availability. In the Arctic, for example, is very unproductive
on land in the winter, a very harsh place to live, but in the short summer season it's almost constant
energy, and that feeds through into resources, plant growth, insects, and therefore food.
And so in order to exploit them, you've got to make these very long journeys. It's got to be a
trade-off between the risks and energetic costs of these long journeys, and the rewards of
essentially being able to exploit an endless summer. There are many different kinds of migration,
even long-distance migration, and different species and different groups of animals and
different groups of birds handle this problem in in very different ways. For example, some species
are only partial migrants, which means that only a proportion of the individuals will migrate,
and presumably there are differences between these individuals in their energetic balances or
whatever which makes the trade-off change. But in terms of how migration is sort of executed, if we
can use that word, this also varies between small songbirds, which have to make very long journeys
over harsh terrain, for them, like crossing the Mediterranean or the Sahara, places they can't stop,
and seabirds which can effectively stop wherever they want on their nonetheless long
journeys. So sometimes the dangers and the trials that have to be overcome lead to very different
kinds of migratory strategy.
Anand: Different species of birds will face different balances between
these trade-offs, and some species take their dedication to migration to the next level.
TG: Some really sustained migratory birds, like the bar-tailed godwit, they will start to digest, internally, the
organs that they don't need whilst they're on passage, whilst they're making these journeys,
they actually eat their own gizzards and stomachs, in large measure,
in order to make themselves lighter so they can carry more fuel, and then when they reach a stopover site,
or reach their destination, the first thing they do is to regrow those internal organs. I mean it's
an extraordinary level of preparation. You're only allowed to carry a small hand baggage, essentially,
on these long flights, and so you've got to adapt to that.
Anand: The food at their destination
must be unbelievably good for a bar-tailed godwit to eat part of itself just to get there.
Our understanding of bird migration has come a long way from thinking that birds hibernated at
the bottom of ponds. But how exactly have scientists mapped out avian flight paths
across the globe? Sounds like an obvious question, but birds have wings and we don't, so how have they followed them?
Well, much of it has been based on a deceptively simple system that was devised some
time ago, but is still used very much today.
TG: The classic technique was to place a mark, a little
metal ring, on a bird's leg, with an individual identity number and probably an address that
somebody who found the bird anywhere in the world could send the ring to, and then to plot
the distribution and timing of these recoveries of birds that have been ringed. So this ringing
started really at the very end of the 19th Century, I suppose, in Denmark, and has been going strong
ever since. Thousands of people still go out putting rings on birds of all sorts of different
species and people observe them with binoculars in different places or recover them from birds
that have finally died. And that information and the timing of these recoveries has allowed
scientists to reconstruct the migratory routes and journeys of many, many species over the decades.
Anand: Ringing, or banding, is a very clever solution for keeping tabs on bird populations.
It's a straightforward idea in theory, but in practice it takes a lot of work.
So to see how it happens in the feathered flesh and to hear about how it's useful, we're heading
to Belize, one of the top destinations for migrating birds in the Americas, in the hope
that we can catch some. We drive in our 4x4 along bumpy, muddy roads into the heart of Cockscomb Basin
Wildlife Sanctuary, which is co-run with the Belize Audubon Society. It's full of lush, tropical forest
and we've come to meet a team of biologists and birders who are working here for the next week.
- I like your t-shirt, by the way! What does your t-shirt say? - I'm not lost, I'm just bird watching!
This is project leader Abidas Ash. She's a bird biologist from the University of Belize's
Environment Research Institute.
Abidas Ash: We have a bird-banding station here for long-term monitoring.
We're catching and releasing birds, but while doing that we're actually
getting a lot more data on them, so we're looking at ageing, sexing, looking at the status of the bird,
the conditions of the birds, and tagging them.
Anand: You can hear that the dense trees
around us are full of birds which, just like me and producer Mel, are beginning to wake up
as dawn is breaking. It's a cool and clear morning and we've actually been really lucky with the
weather, because it's been raining pretty heavily for the past few days.
- 06:30? Okay yeah so it's 06:30.
The first step in putting a band on a bird is to catch yourself a bird, and that is no easy feat.
It involves using a series of specially designed nets that surround the research station
and a team of people, including our guide Emmanuel, who have to open them
up every morning.
Emmanuel: So we'll be opening nets every half an hour, and then here we have
net number 13, yeah. These nets are pretty much blind to the bird
so whenever a bird would fly, it will just fly through, and then we have what we call the pockets
and then that's where the birds get trapped.
Anand: Imagine a long volleyball net or a badminton net
which is made of very very thin fibres that are almost impossible to see in the dim morning light.
Trust me, I almost walked into a few. - So what happens, so the birds kind of come fly down to this sort of level?
Emmanuel: So most of our target species, they will fly low, like the warblers, the thrushes.
So now this is the the best time to have your nets open, when it's early morning,
because this is the time when the birds are usually active.
Anand: So the early bird catches the worm,
but the early bird-catcher catches the birds!
Emmanuel: Yeah! So banding has showed that yes, birds are more active early morning.
Anand: As the birds make their first flights through the canopy the team are hoping
that a few unwitting individuals will fly into the net.
Emmanuel: You have to be a trained extractor
for you to take out the bird. So usually it takes about a minute, because we try to do it fast so
the bird doesn't get stressed. Yeah. And then hopefully we get some birds in the net.
Anand: With all 16 nets assembled, we head back to the banding station, in a clearing in the jungle, to wait.
And while we do that, it's a good time to mention that you're listening to CrowdScience
from the BBC World Service. And this week is the first of a two-part special on animal migration.
So far, we've heard some of the reasons why animals bother travelling thousands of miles on a yearly
basis, when they could just stay put. And now we're meeting the scientists who are working out where
migratory birds in Belize fly off to. A career in monitoring bird migration takes a lot of patience.
So while we're wandering around waiting for the nets to fill up, I caught up with Abidas about what
makes Cockscomb such a sanctuary for wildlife. - So walking around this place, you can really
hear, especially at night, loads of different types of bird calls. How many different species of birds
live in the sanctuary?
Abidas Ash: I think about 300+ species have been recorded here in
the sanctuary, and here where we're doing some banding, in just six hours yesterday we recorded 72-75 species.
Anand: What's special about this kind of climate and this environment that the birds like?
Abidas: Well, it's all about resources availability. The wildlife sanctuary is pretty big and there is
just enough space for them to be able to occupy the area.
Anand: So is that why migratory birds might come here for the winter?
Abidas: Yes. Down here in Central and South America, that's where around that time we
have certain plant species that are fruiting, we also have abundance in insects as well.
Anand: Soon it's time to head back out and check on the nets. - So are you always a little bit nervous before you go out
and check the nets to see if you've got anything? Emmanuel: Of course, yeah, so what I'm more nervous about is
to get a stressed bird. So sometimes when a bird is tangled and it's getting stressed, you get stressed as well.
Anand: I'm still struggling to find my bearings, but the team quickly stride out in different directions.
- I'm quite nervous actually as well...
...hopefully it won't be an anti-climax.
Nothing in that net.
The first few nets are all empty, but then...
Abidas: So when we have a bird in the net we need to extract
the bird the same way the bird went in. So I'm just gonna take it out, and since this is a hummingbird,
there's usually different grips that you need to use to actually take out birds, so this
is pretty much a body grasp grip, where I'm just holding the body, some netting went around his head
so I removed all of that, and now I'm putting it into my bander script.
Anand: You make it look so easy!
Abidas: It's practise!
Anand: It's such a beautiful bird, so it's a really kind of emerald green
hummingbird with an orange bill.
Abidas: Yes, so this is a rufous-tailed hummingbird, see how green...?
Anand: Woah, it literally is like a jewel, it's so shiny it's like iridescent!
Abidas: Yes! I put it in the bag, so the bag is
for them to, you know, stay calm and not to fight, so they can breathe through and everything, and then
we're going to take it back again to the banding station where we have a couple more nets to check.
Anand: It's really impressive to see how deftly Abidas manages to rescue these delicate creatures from
inside the nets. We take the hummingbird back to the station, where Emmanuel and the others
also have full cotton bags gently pulsating with life inside.
The team immediately gets to work. Emmanuel delicately lifts each bird
from the bag and inspects them, looking at their size, weight, and
feather conditions, calling out what he sees, while somebody else notes it down.
Some of these are local species, while others are migrants. They examine the wing feathers
and they also blow on the soft downy covering on the breast and skull to expose the skin underneath,
and they make a whole bunch of other observations.
Abidas: For some species, the eye colour changes with age
the roof of the mouth could help with that as well, the shape of the feathers, and those
are characteristics we combine together and that helps us to determine the age of the bird.
Anand: Watching this slick, coordinated operation, it's clear how much knowledge and skill these guys have.
The last step is for Emmanuel to very carefully attach a thin aluminium band to the bird's tiny
leg with a set of pliers.
Emmanuel: When I started to do banding, this was the hardest part
for me, yeah, to place these bands on birds.
It's finicky work, but the serial number on the band
will mean that researchers can track this individual if it shows up again. And that's
really what we're hoping for, that we'll catch a migratory bird that already has a band on it.
And eventually, we get one.
Abidas: This is a good one.
Anand: So this has been caught before? Abidas: Yes. Let me check the band number actually.
Just based on this sequence, it is about two or three years ago that we caught this individual, so
this individual probably made about three or four trips already to Belize. This is a greycap bird
it's pretty much all on the east coast of America and some parts of Canada as well, and
it migrates all the way to Panama Anand: Wow, it's a really long way!
Abidas: Yes. So this one here decides
Belize is the best spot for me, so I'll stay here, spend my winter here, I've got enough food and everything.
Getting a bird that has been banded three or four years ago, that's really
good because it shows us that this specific habitat that we're actually monitoring is very important
for those birds that are coming back from year to year, to winter in this specific area, and it
means that there's a lot of food resources, water, space available for them to be able to stay there.
We're gonna see, hopefully someone catches them and recognise a band, and so we submit our data to the
Institute of Bird Populations, and they submit to the bird-banding lab, and then if you catch a bird,
or you find a bird with a band on it, so they send you data and tell you, ok, well this bird
was banded here, give you the exact locations, when it was banded, the age and the sex it was recorded as.
Anand: This routine of checking nets, extracting birds, examining, banding, and releasing
them repeats every 30 minutes all morning. In one of the quieter moments, Abidas asks me
if I want to give her a hand.
Abidas: So do you want to release it? Anand: Yeah I'd love to. So how do I hold it?
It's like when someone gives you their baby, you don't want to drop it!
Abidas: So you're going to put
your two fingers around the neck of the bird. So the neck of the bird is very narrow, so
you're not squeezing anything, ok, and then the rest of your fingers form a cage around the body
of the bird, just to keep everything intact, and then you stretch out your hand and from
there it will fly off. Anand: OK.
Abidas: You can make it fly this way instead, so... Anand: So... like this?
Abidas: Yes! There you go!
Yeah!
Anand: Amazing! Like a magician!
So why bother to collect all this data? Well, combining all of these snapshots of the bird's
health and their location to build up a picture of migration is vitally important for conservation.
And according to a recent report from 2018, 40% of bird species globally are falling. As migrant
birds make their long journeys, they need safe resting and feeding points along their routes,
and problems like habitat loss in one of these key stopover sites
could mean that our travelling birds don't get enough energy to make it to their destinations.
And so the data from stations like this one in Belize is really important for monitoring
populations and their survival, and for spotting issues happening to the birds along the way.
Cockscomb obviously can't do this alone, and it's part of a much bigger network of more than
200 stations all over Mexico, Central and South America called the MoSI programme. Through its work,
MoSI aims to understand what might be driving species declines, and how we can reverse that.
And there have been some success stories, like the wood thrush: a bird that's much beloved in North America,
which has benefited from the work at Cockscomb.
Abidas: The wood thrush is a species that has been
heavily studied just because their population was really declining, and you know no one really knew
what exactly was happening for the population to decline, and that's when they start focusing on
mostly where they're wintering, basically, and that's where they noticed that a huge factor
contributing to the decline is deforestation and forest degradation, and that's where a lot of
work and studies and research has been going on so that they can start working with communities,
working with different organisations and NGOs to try to help to mitigate that issue there, and from
there, that's where they start noticing that the thrushes are slowly coming back now, but you know it
took pretty much a village to try to ensure that that happened.
Anand: Seeing Abidas and her colleagues
find a bird that they'd already captured a few years ago illustrates how powerful banding can be,
despite it being quite a basic technique. But banding is really just the first step.
Modern technology means researchers can learn way more about bird migration than ever before.
Tim Guilford, who we heard from earlier, told me about the kinds of devices which he uses in his own research.
Tim Guilford: Miniaturisation of technology has really driven some amazing changes in what we're able to
discover about bird migration. In particular, there are two kinds of devices that we use in our work
on seabirds. One will be familiar to everyone, that's GPS (Global Positioning System).
You can put miniature GPS on birds as
small as songbirds now, actually, but we put them on shearwaters to track their foraging journeys
as they go out into the Atlantic and come back with food for their chicks, and this allows us to
understand a great deal about how they move, what drives their movements. There's another
technology that has now become very widespread in studies of migration, that's called the geolocator.
This is a little tiny device, it weighs maybe a gram, and you can fit this on a leg ring. It registers,
every day, light. And if you know the time of dawn and dusk from your light trace, and you
know the length of the day, these are the two bits of information that a mariner would use
to calculate their position anywhere on the globe, and these little devices store this information
on board every day of the year, and then when our seabirds come back to breed the following year,
we can download that information and reconstruct the bird's track, and that's
really given us enormous power in understanding the migratory journeys, stopovers, variation in
that, and of course the changes in migratory patterns driven by things like climate change.
Anand: Devices like this can give you a lot more than a snapshot. They go with the animal to places that
as humans we'd struggle to follow, and they can tell us about aspects of these journeys which
have remained mysterious until now.
TG: We're starting to learn now that the Arctic tern's journey is
more nuanced than that, and we think that many of them stop over in the central north Atlantic,
where there's a very rich area which attracts seabirds and other migratory animals from very
long distances as a kind of refuelling station. This has just been made into
a high seas marine protected area, the largest in the northern hemisphere, on the basis of
tracking data from birds around the northern hemisphere. So we're starting to discover these
hot spots of activity in migratory species far out at sea that we never knew about.
Anand: That story is a clear example of how tracking data can help with conservation.
But there are other ways of telling where animals have come from, besides using tracking devices.
TG: So as well as tracking birds using technology, we can also use their genetics nowadays
to identify which populations they came from and modern genotyping techniques are really
revolutionising the study of bird migration.
Anand: With just a single feather, it's possible to learn
a whole host of things about bird migration by sequencing the animal's DNA. And that's just what
Professor Kristen Ruegg does in her research at Colorado State University in the US.
Kristen Ruegg: We start by sequencing
bird genomes, so we try to understand how birds are related across geographic space.
So we build these maps of genetic relationships across their breeding range and then we
use information in the DNA of feathers collected anywhere across the annual cycle to do
what we like to call, like, ancestry websites for birds. So we genetically identify birds
captured anywhere along their annual cycle back to their breeding population of origin.
Anand: That's really clever. So you can get all of that information just from feathers?
KR: It really only takes, you know, a couple nanograms of DNA, tiny, tiny amounts of DNA, and we can get that DNA from
the tip of a feather, to sequence the whole genome, and then we use that information
to then identify the origin of the bird, and many other things we can get from the genome too.
Anand: Have you got like a room in your lab that's just full of all of the feathers that you've been analysing?
KR: Yes. Well actually there's many rooms, so it's a huge effort.
Anand: I was going to say, you could make a really cool museum or like an art installation
or something, or my producer was suggesting you could make a huge feather boa or something,
and use it as like a way of communicating the research!
KR: You know, when you come to my lab,
what it basically is, is like 15 freezers full of... so it's a lot less pretty than that, but
it's pretty massive in scale, yeah! Anand: So I'm really curious, what kind of stuff
can you learn from this genomic analysis why is the DNA information useful to you?
KR: One of the main things that we focus on with the Bird Genoscape Project
is understanding, you know, which populations are genetically distinct from other populations,
and that has important implications for their conservation, both from a legal perspective, like
how it provides the ability to document that a population is genetically distinct can
help with garnering protection for that particular population, you know, within a legal framework.
And in addition, those genetically distinct populations that are endangered or threatened might migrate to
different areas than other populations, so we can then use our our, you know, feathers collected from
somewhere else across the annual cycle to make these important population-specific connections
and understand sort of where across the full annual cycle of a bird, whether it be
breeding, migratory stopover, or wintering, an endangered population may be migrating, rather
than focusing across the entire breeding range, which can be overwhelming in terms of when you
have very limited conservation dollars.
Anand: This kind of genetic analysis can help researchers
work out if different populations of birds within a species might be facing different threats, which
can help to make more effective conservation policies. And once you've got a genome, one of
the really interesting things you can do is study the role of individual genes in migratory behaviour.
KR: The other sort of suite of genes that we've been involved in looking at are genes that are linked
to migratory timing, and these would also have kind of a link back to, you know, climate change
because as the climate changes, spring comes at different times, right, across the world,
and it's really important for birds to sync up the timing of their migration with the timing of peak
resource availability in spring, for most species,
and so being able to get that timing right is really important, and studies have shown, for
decades, that there's some component of migratory timing that is genetically controlled,
and so if you know, if we can identify the suite of genes that are important to migratory timing,
we can also use that to help inform, you know, which species might be able to adapt
to changing climate conditions, and which may not.
Anand: So potentially you can look at a population and
see whether there might be slight differences in the birds and the timings that they use to migrate?
KR: That's right. One of the important components of that is, if there is
what we call standing genetic variation, or genetic diversity, genetic variation at the genes
underlying migratory timing, let's say, then populations may be able to evolve
and respond to intense selection for differences in the timing cues, but if
there's a population with a lot less diversity at that gene controlling migratory timing, then they
may not have the capacity to respond to selective pressures or, you know, changing migratory timing.
Anand: Scientists now have a rich understanding of where birds travel on their migrations across the world,
which as we've heard is a big part of conservation efforts. But something which remains much less
clear is how birds manage these incredible feats. How can a starling accurately make it
thousands of miles to a destination it's never been to before? Research in this field is making
new discoveries all the time, and that's what we'll be hearing about on the next episode.
And we'll be turning to one of the greatest mysteries in the whole of the animal kingdom:
the navigational abilities of sea turtles. They can travel between whole continents over
the course of their lives, and yet return to the exact same beach where they hatched.
We'll be meeting a team who are tracking sea turtles off the coast of Florida, and joining
them on a trip out into the ocean on board their research boat.
- The boat's called the RV Luminia,
it's a third-generation turtle catching boat.
Anand: And this man, David Godfrey is our skipper.
David Godfrey: It's easy for us to monitor turtles on land and observe them, study them, but out in this marine environment
it gets really difficult to piece together all the different aspects of their lives, their physiology,
what they're eating, how they're behaving, so this in-water type of research is really important
to understanding, answering a lot of questions that we need to know to protect them, and this
idea of migration, where they're traveling at what times, is really critical to
protecting every life phase of these animals. So in Crystal River we have this area we know
is developmental habitat, we know they're spending a certain amount of time here, and we really want
to know at what point are they going to leave this habitat, and what are the next habitats they're
using that we may not know about. Because obviously things happen in the marine environment,
you've got commercial fishing activities, you've got... occasionally you have oil spills out here,
there's lots of recreational boating, mining, you name it, it's going on in the marine environment,
and we need to understand how our actions are affecting these animals,
and in order to ascertain that, we need as much information as we can about where these
animals are going, and those migrations are critical for long-term conservation.
Anand: Turtles may look peaceful and serene, but don't let that fool you; they are surprisingly fast and very
agile. Catching them quickly becomes a high-speed chase through the water, which we were not
expecting, and you need to hold on tight.
- That's a little green turtle right there, right side, throwing hard...
- Can somebody get a waypoint?
- We have green turtle, turning towards us... that's a ray, avoid that...
- You see it David? - Yup, I got it. - Small turtle.
- You thought it was a fish. - Directly ahead of us turning, alright hard right...
Anand: That's on the next episode of CrowdScience, where we'll be looking inside the brains and
the bodies of birds and turtles, to figure out how they find their way.
See you then! This week's CrowdScience was presented by me, Anand Jagatia, and produced by
Melanie Brown. If you have a question you want us to look at, then email us at crowdscience@bbc.co.uk
Thanks for listening! Bye!