Hi I'm Nancy Simmons. I'm a curator of
Mammalogy at the American Museum of
Natural History and my research focuses
on the evolution and diversity of bats.
So today we're going to talk about the truth
about vampire bats. Many people know that
vampire bats exist but they don't know
very much about them. So, they in fact are
real animals. There's three living
species of vampire bats and they live
only in South and Central America. They
don't live in the Old World. They do feed
entirely on blood. One species prefers
mammal blood only to take its meals. And feeds
mostly on cattle these days. There are
two other species that also feed on
sleeping birds.
So, Nancy, you spoke about, you know, evolution as sort of one of your
interests.
How did bats come to feed on
just blood? How do you get a
vampire bat sort of evolutionarily?
Well, this- this specialization's evolved
only one time. The three species are very
closely related to one another, so we
think that blood-feeding evolved once
only. And nobody knows for sure how
blood-feeding evolved. There's a number
of different hypotheses and one of them
is that vampires initially evolved from
insect-eating bats that fed on the
insects that were found on wounds of
animals. So, for instance, an animal might
cut itself and develop a sore and then fly
larvae might lay their eggs there. And so
the- the insects attracted to the wound
might have been the initial food for
these animals. But nobody knows for sure
how blood-feeding evolved. We know that
it did happen, though, and that
happened once in bat evolution.
So, when we talk about vampire bats, what sort of
specializations and things do these
bats have for feeding?
Right, so vampire bats are really interesting. They have a number of
anatomical and physiological
specializations not seen in other bats.
One of the things that sets them apart
is their teeth, which doesn't come as a big surprise.
But their incisor teeth, their front
teeth, are modified into razor-like
blades that they can use for making very
fine cuts in an animal's skin and then
they lap at the blood that comes out
from this wound to get their blood meal.
They don't feed on very much blood - maybe
a couple of teaspoons will feed- will be
the entire meal for one bat for a night.
They have evolved specializations in
their saliva. They have anticoagulants in
their saliva that keep the blood from
clotting. So, of course if you're going to
feed from blood coming from a little
wound you've just made with your front
teeth, you don't want that wound to close up
too fast. And so their saliva actually
helps keep the blood flowing.
They have internal specializations, in
terms of they have a gut- basically their
intestines are designed to very quickly
process their blood meal because fluids
are heavy and if you're flying animal
you don't want to fill up with fluids
then be too heavy to fly. So, blood meals
pass very quickly through the bat
with this specialized anatomy.
of their digestive system. They also-
The common vampire bat feeds mostly on
cattle, which it approaches on foot on the
ground and they have modifications - they have
big thumbs, big powerful hind legs and
thumbs - so they can jump very quickly off
the ground to take flight from the
ground by leaping. So, they're- the muscles
in their hands and in their hind limbs are
stronger and developed in such a way to
allow this jump that we don't see in other bats.
That's awesome. And speaking of this, you've got a
vampire bat skeleton right here. -I do!
Can you talk a little bit about this?
And maybe how this is different
from other bat skeletons, maybe?
Well, one of the reasons I wanted to get
out this skeleton is to show the size of
a vampire bat
Some people think that vampires are
great big huge bats, but they're not.
They're quite small. So, you can see that
you know, the size of my thumb compared
to the size of the skull of this bat-
When I mentioned those big powerful
thumbs that we see- It's hard to
tell if you're not used to looking at
bat wings, but this very long thumb
sticking up here is something that we
don't see in most of the close relatives
of this bat. But in other respects it's
just a standard bat. It can fly very well.
Its wings are composed of elongated
finger bones. So, if you look at my hand
next to the bat's wing- Here's my thumb
sticking up. There's the bat's thumb and
here are the four fingers that support
the wing membrane. So bats fly using
modified forelimbs and very elongated
hand and finger bones, which support the
wing membrane.
Now, we have our first question and it's basically the same question
from Pam Irwin and Francisco Antonio
Gómez on Facebook who both ask, basically,
if- can vampire bats eat anything else.
Do they have the option to, like, eat and digest-
They don't. Occasionally an insect
piece has been found
in the feces of a vampire bat, but it's
thought this is just an accident,
basically, of feeding. They require blood meals
in order to survive. So, all three species
feed essentially exclusively on blood.
So, maybe mammal blood or it may be bird
blood, but that's- that's what they have
to have to live.
Vickki Desiderio on Facebook asks, "Do these
bats carry rabies, and what part of the
world would you find vampire bats in?"
So, all living vampire bats live
in South and Central America, so they
live in tropical and subtropical areas,
and only in the New World. So, if you go
to Mexico, you go to South America most
countries have vampire bats.
Yes, vampire bats can carry rabies.
However, it's also fatal to the bat, so
it's never present in very large-
I want to say concentrations- That's not the right word.
Anyway, vampires can't- can transmit
rabies, as can other mammals. So, rabies is present
in most wild mammal populations, at at least
some level and it is sometimes a problem
with vam- with vampire bats. Vampires -
particularly what's called the common
vampire, which is one of the three
species is present in very large population
numbers in some areas because of humans,
because we bring cattle, which are- it's
like bringing McDonald's to to the bat world.
So, for vampire bats having herds of
cattle allows them a very substantial,
very reliable food source. And so they
can be present in pretty large numbers in
places where there are large cattle farms.
And Vikki actually had another
interesting question: What do baby
vampire bats feed on? Do they start
right on blood or-
Well, vampire bats, like all bats, are mammals, and all mammals
feed their young on milk. So, baby
vampires nurse from their mothers until
they're large enough to fly and follow
the mother to learn how to find blood
meals. So, when they're small, they're
nursing and feeding on milk, just like all
other bats and all other mammals.
Fantastic. And we've talked about the
common vampire bat that is feeding on
cattle and stuff. Talk about these other two species
that feed on birds.
So, the other two species of vampires are less common and- the
white-winged vampire bat and the hairy-leg
vampire bat, and they feed on birds.
And if you imagine a forest- tropical
forest at night, all the birds that are active
during the day are sleeping, usually
perched up on branches and trees. And so
these vam- these species of vampires
specialize in finding those sleeping
birds and they creep up to them on the
branches. And they feed, usually from the
legs, which are not covered with feathers.
So they would make little cuts on the
leg and lap at the blood from the leg
or the foot of the bird.
Fantastic. And Nancy, I think one thing a lot of people will be curious
about is these South American bats that
live only in South and Central America -
how did they get sort of caught up in
vampire mythology?
So, you're talking about Dracula and the- all the vampire stories
from Transylvania and so on.
Well, it's thought that- Well, it's known that
the folklore of Eastern Europe in
particular was filled with zombies and
blood-feeding creatures and things in
the past, long before vampire bats were
known for sure. So they had a cul- they
had folktales in essence that involved
creatures of the night. And it wasn't
until real
vampire bats were discovered in South
America and the news was brought back by
the explorers that there were these bats
that fed on blood that that aspect of
the blood-feeders being bats that flew
around at night and came to you- that that got
wound up together. And it was really Bram
Stoker in the- in the- when he wrote Dracula and
later when it was made into movies and
so on that the idea of vampire bats got all
tied up with Halloween and Transylvania and
Dracula and all those stories. So, it's a bringing together
of basically folk myth and a little bit of
natural history of real animals to come
up with these stories.
Interesting.
Another great question from from Vikki Desiderio -
just killing it here, Vicki - who asks
are these bats problematic for
farmers and ranchers. And maybe to
jump off that a little bit, you know,
what's the effect that these bats
have on the animals they're feeding from?
Well, vampires can be a problem for
ranchers. If you have large terms of
animals and they happen to be of cattle, in
particular, and they happen to be near
vampire bat roosts they may be fed on a
lot by the bats. And so they're creating
small wounds in the skin of the cattle,
which can then become infected and can become
a problem in that way. It's not loss of
blood that's the problem. If you think of,
you know, a 2,000 pound cow, it can give up
two teaspoons of blood, or even 20 teaspoons
of blood, if there are, you know, 20 vampires come to feed on it.
So that's not the problem. It's more
the wounds and the potential infection,
particularly in the tropics that's the problem. And also of
course, people are concerned about rabies.
And so in some areas if there's a rabies
outbreak - it might not even stem
originally from the bats - the bats get
blamed for it. So, there's a lot of
misinformation going on about vampires
and what they do to these animals, often
in the communities where the cattle and the
vampires are present. So, part of what
bat scientists do is go into these
communities and talk to people about the
realities of the animals that they have
and what they're dealing with and try to
come up with effective means for
treating the problems without having to
kill all the bats.
Summer Dawn on Facebook
asks, "Are these bats also affected by
white nose syndrome?"
No. Vampire bats live
in the tropics mostly, and a little bit
into slightly closer to the temperate
zone, but they don't get up into the
parts of North America that are affected
by white nose syndrome. White nose
syndrome is a fungal disease that
affects bats that hibernate, and they
hibernate in the cooler parts of the range.
So, in the northern United States and in Canada is
where we're seeing the effects of white
nose syndrome. The population- All
populations of bats that live in warmer
climates are not affected by this fungus,
and the reason is that the fungus itself
is a cold-loving fungus. It doesn't grow
well at warmer temperatures and so, it- in
order to grow and have its negative effect
on the bats, the bats have to have a
low body temperature
that only comes with hibernation. And the fungus
itself can live in caves and mines, but
only where the temperature is low. When you get
into the tropics where the temperatures are
higher, it just can't live. So, that's why at
least the bats in tropical areas are
safe from white nose syndrome.
Also on Facebook, Daniel Nieves asks, "Do
fruit bats drink blood?"
Are there other species of bats
that display this behavior?
That drink blood? No. There are nearly 1,400 living bat
species and only three of them are
blood-feeding bats. And they're- As I said, they're
very closely related to one another, so
blood-feeding evolved only once in bats.
So, it's been a very successful experiment,
but it's only happened one time in bats. And
it's- you know, if you think of 1400
compared to three, it means that the vast
majority of bats feed on other things,
which are mostly insects, but some
species live on fruit. Some feed only on
nectar and pollen. Other bats feed on
fish or other vertebrates - hunting mice
and frogs and things like that. So,
there's a wide variety of diets across
bats. And one of those diets - highly specialized -
is to be a blood-feeding animal.
And we've talked about, you
know, the difference in feeding, you know,
habits. Are there vampire bats that do feed on
humans?
Yes. Vampire bats will feed on any mammal
that they can get access to and so
vampire bats will feed on humans if
people are sleeping in a situation where
there have no protection. So, if you sleep
in, for instance, a hammock in the tropics and
you don't have a mosquito net over it
you may get more than just mosquitoes.
You may have trouble with vampires
coming. And- and this may be a little bit
too much detail, but they tend to go for
the toes, which would be like sticking
out a little bit more. Fingertips, things
where they- you know,
that are distant from the body and
they'll creep up and people don't even
know they've been bitten.
I understand that, you know, the cuts are very
small and it's like a shaving cut or a
papercut. They're not very painful.
The bats are very stealthy because they
don't want to wake up their food source
because if they do and they will get
their meal. And so a person may just wake
up in the morning and find that they
have, you know, a cut on their foot and, you know, some
blood and they know they've been bit by a vampire.
Now, Nancy, I know a lot of your work has been in
South and Central America on bats.
Have you have been bitten by a vampire?
I've never been bitten by a vampire. I've handled
many, many vampires, but I'm very careful.
So, I and my colleagues who work on bats will
always wear gloves when we're handling
vampires, and we we take our time and we try
to be careful. I do know bat researchers that
have been not so careful and have been bitten, but
I have managed to avoid that myself. And for
safety's sake all of us who handle bats get
rabies vaccinations ahead of time before
we handle bats, so that we would never
dream of handling bats without being
inoculated for rabies. But the shots
that we get to protect us from rabies
are the same that every veterinarian,
every vet tech, every animal control
officer gets - these pre-exposure rabies
shots just to be on the safe side.
Gino Tusciano asks on Facebook, "Is the false vampire
an offshoot species of the vampire bat?"
Many bats, for one reason or another, have gotten the
name vampire. The false vampire bat isn't-
is a member of the same family of bats
that includes vampires, but they're
carnivores. They do not feed on blood.
They are quite dis- They've probably
been separate for 30 million years. So,
they're quite a distinct group, but there's
a number of bats, for one reason or
another, that have "vampire" in their name.
But only these - the three true vampires - are the ones that feed on blood.
Fantastic. I think we're going to take
one more question from Facebook, and
here with another great question, Vikki
Desiderio asks, "What's their lifespan and
and what's the sort of community of
vampire bats like?" Are they social?
Are they solitary?
That is a great question
because vampire bats are highly social.
They live in groups. They recognize one
another and they actually share blood
meals. So, if a group of vampires goes out
across the landscape and some of them
are successful in finding food on a
given night, but some are not, the ones
that are not will beg food from the ones that
did feed during the night when they go
back to the roost after searching for
food. And so, they will share- the ones
that are- that have fed will regurgitate
some blood for the ones that haven't
been so successful. And that way all the
members of the group survive. So, highly
social animals. I'm not sure how long
vampire bats live. I would guess- I
wouldn't be surprised if it was a decade
or more for an individual bat, because bats
as a rule are extremely long-lived
compared to their body size. So, a mouse may
naturally have a lifespan, you know,
that's measured in months.
A bat of the same body size will have a
lifespan measured in
years. And we know that some quite small bats
live for 30 years or more. So I don't-
I don't know offhand the lifespan of a
vampire, but could easily be a decade or more
for an individual animal.
Fascinating. Nancy, thank
you so much for joining us today.