Transcriber: H Maria Castro Reviewer: Francesca Blasi
What do you see behind me?
Well, most of you would say that it's a very cute baby rabbit.
But, if I asked Ralph or any other Australians,
the answers I would get would be pretty much
along the lines of "This is what kills our trees."
"This is what eats the food of our native animals."
and "This is what causes soil erosion".
"It's a horrid invasive species."
Now, invasive species are animals that have been brought outside
of their native range and have had a negative impact
in their new surroundings.
Negative impact. That's a bit of an understatement.
Invasive species are one of the top reasons for biodiversity loss.
And in fact one fifth of all animal extinctions
are due solely to invasive species.
Biological invasions also cause huge agricultural losses
and may even pose a risk to human health.
For instance, the Asian tiger mosquitoes have brought the yellow fever
from Asia to Southern Europe.
Now, the European Environment Agency
estimates that the economic losses caused by biological invasions
amount to 12 billion euros
each year.
So, it's not much of a surprise that wherever the invasive species appear,
they're pretty much hated.
After all, we are fighting a very costly environmental war against them.
Now, the war against invasive species, like any other war,
is not only about the big, gory battles.
It's also about espionage. It's about getting to know your enemy.
It's about new technological developments.
And, of course, about the drama of everyone involved.
I'm here to tell you the story of one of our invasive enemies.
And to tell you how a very powerful opponent
can challenge us in more ways than one.
OK, so let's begin.
In North America, there live these guys.
Very cute little brown animals, called mink.
They are brown and they are very soft.
In fact, they are so soft
that people thought it would be a good idea to wear their fur.
And, in the 1800's, a lot of fur farms opened in North America.
Very soon after that, the Europeans grew jealous of the luscious fur coats
and so, in the 1920's, fur farms opened in Europe.
Soon after that, some American mink escaped
and some were released intentionally.
And before we knew it, American mink
had established wild populations throughout Europe.
Now, what's wrong with that?
Well, mink are carnivores.
They are very, very efficient hunters.
European wildlife was not ready for this.
We have brought upon our continent a very powerful enemy.
Problem number one.
We have our own species of mink in Europe, the European mink,
and the American mink, being American, are bigger, more aggressive,
they breed better, they are much more efficient at hunting,
it's a classical case of oversized, oversexed, over here.
And because of that the European mink has been out-competed
from most of its native range.
In fact, it is now one of the most endangered European mammals.
American mink also pose a problem to seabirds.
Seabirds, such as terns and seagulls, tend to nest in colonies on small islands
off the coast, maybe about a kilometer or two off the mainland.
These islands used to be very safe because no predator could access them.
So, birds would lay their eggs directly on the ground.
Now, because we have the American mink,
these animals can swim to the islands and once they reach the islands
they're like a kid in a candy store. There are birds everywhere.
Mink may do what is called surplus killing,
which means that they will kill anything that they can sink their teeth into
without really thinking much ahead about food availability.
They just kind of go for it.
In fact, one mink borough was found to contain over 200 dead seagull chicks.
And it really is no surprise that seabird colonies of international importance,
when affected by American mink, can be reduced in size by even 50%.
And on top of that, the American mink also can cause local extinctions
of species that are its prey, for instance the water vole in parts of the UK,
or the desman in parts of Spain.
So we have brought upon ourselves a very, very powerful enemy.
We're talking here about an animal that can swim like an otter,
that can climb trees like a cat, and that can hunt on land like a fox.
It's not any old invader,
it's more like the American special forces unit.
It's so adaptable and so versatile, and because of this adaptability
it is very difficult to control, but it's also a challenge to study.
And yet they are very interesting, because when you look at mink physiology
you think "How does this animal even swim so well?"
Because, think of a mink: It's very skinny and long,
so it loses heat very fast.
That's a problem underwater.
Its paws are not well adapted to paddling.
It can't see well underwater and its fur is not waterproof.
And yet, as I have told you, it can swim to islands that are a kilometer or two
away from the mainland.
Also, in some sites, even 90% of their prey is aquatic.
So, how do they do that?
And how do we even know what they do?
Actually, let's take a step back.
How do we know, in general, what animals do in the wild?
Have you ever thought about that?
Because ideally, we would just observe animals directly.
But that is rarely possible and mink are not really
the easiest ones to look out for.
So, what we can do is we can look for droppings and tracks.
This is very useful, for instance for establishing what an animal
has been doing in which place.
It doesn't tell us that much about particular behaviors,
apart from the fact that an animal was pooping at some point.
Useful, but maybe not crucial.
What we can use are camera traps
and these provide fantastic pictures of animal behavior.
The problem with those is that you never know what will pose for your picture,
what will trigger your camera trap.
Because, for instance, you might set up a camera trap to look for wild cats
and you might get a wild cat or you might get...
This.
(Laughter)
A very curious monkey.
(Laughter)
Another good method for looking at animal behavior,
particularly at home-range sizes, is radio-tracking.
That is very common for studying animal territories on land.
But what if we want to look at animal behavior in water?
Dive patterns of different animals
have been studied for fully aquatic species,
such as seals or whales.
But mink are semi-aquatic,
which means that, while a whale is unlikely to jump out of the water
and then climb a tree and then catch a bird,
a mink will do just that, very often.
It transitions between the aquatic and the terrestrial habitats.
And what it does, behaviorally,
makes us think differently about data analysis.
It's something completely novel for biologists.
We're used to those seals and whales in terms of behavior.
So we have to re-think the way that we process our data.
And the way that we can study mink is using miniaturized time-depth recorders.
These are small logging devices and you can see one over here,
except here it is much larger, it's normally about this big.
These record temperature and depth over time and they tell us two things.
First of all, from the depth records we can find out more about mink diving.
Secondly, because we place the data-logger under the mink's neck,
we are able to look at concrete activities from the temperature records.
So what happens is that we look at an animal that curls up
when it's inactive, and so the data-logger under its neck warms up
and you can see here, on the left graph,
that the temperatures achieved by the data-logger are very high,
because it's snug underneath the mink's chin.
When the animal becomes active and it uncurls,
the air around us would hit the data-logger,
and so the temperature on it would drop,
as you can see on the second graph.
Finally, when the animal jumps into the water,
the data-logger temperature is even lower.
So we can determine different behavioral activities based on that.
It's a very simple method,
but it has not been used for mammals in a semi-aquatic environment.
Yeah, but so what?
Well, we learn from it two things.
First of all, we have the espionage factor,
so we found out more about mink.
We now know that mink are only active for about 20% of the day.
Which means that they must be pretty efficient as hunters in general,
because they sleep around for quite a lot of time.
But also what's very interesting is that they're not too fussed
when it comes to ambient temperature and diving.
In fact, the smaller and skinnier the mink,
the more times it would dive in a row.
For instance, a very small female would dive 80 times in a row. In winter.
And think about how small and how skinny this animal is.
And how cold the water is.
And then you'll put it in perspective,
it's quite a feat for a weasel-like animal to do that.
So, on one hand that tells us that they're very, very well adapted
to handling cold temperatures.
But on the other hand,
it must mean that they are not super-successful at hunting underwater.
Because, if they had been successful at fishing,
they would only need one or two dives, they'd dive in, they'd catch a fish,
and then they'd move on to the river bank to eat it.
And yet they require 80 dives in a row even.
They try hard, but they're not very successful.
So it would seem that our super-forces unit
is in fact more of a Jack-of-all-trades and a master of none.
But we also learned something else.
We have a new method that tells us how to study semi-aquatic behavior
in general, in many species, not just mink.
And that's important because animals that are dependent on
or adapted to living next to water can be found in pretty much
all mammalian orders and some of them, like mink, or like coypu, they're invasive
and others, for instance hippo species, are endangered
and before we decide to either control or conserve a certain species,
we need to find out as much as possible about its behavior and about its ecology.
And this is what we can now do thanks to methodology
that has been developed for the American mink.
It's a little bit like how, during the II World War,
the cracking of the Enigma
has pushed forward the development of early computers.
Wars come and go, but technology stays and can be applicable later as well.
But if you think of invasive species in general, we might feel very resentful
about the problems that they cause, the money that they cost us,
but we have to think about all the things that we can learn thanks to studying them.
For instance, the American Grey squirrel, that was brought into the UK,
forced us to study more virology.
The Canadian beaver, in Norway, forced us to study genetics.
The cane toads in Australia taught us more about toxicology.
All of these animals are supremely adaptable,
they're versatile, they're resilient,
they do fantastically well in their new habitat.
They're an evolutionary triumph.
But at the same time it's a tragedy that they face,
of being in the wrong place.
After all, in its native America, the American mink tends to be used
as a sentinel species, which means that it's considered
a very good indicator of water quality.
Which means that, because it eats a lot of fish,
potential pollutants could accumulate in its tissues
and so reflect the quality of the rivers.
But yet, in Europe, it's the public enemy number one.
But think about it: It is so because of us.
It's our greed for the luscious brown soft coats that have turned
this beautiful little animal into a voracious ecological catastrophe.
The story of invasive species, like any war story, is a sad one.
But we have to stop and think about the challenges put forward
by all those small animals, be it in terms of control
or in terms of research.
I wanted to end my talk with a joke about invasive species
but when I did a quick Google search for "invasive", "species" and "joke"
the only results that I got were websites saying that
"Invasive species are no joke."
And, while it is true, we can always learn something from them.
Thank you.
(Applause)