Claire Corlett

Fish Food, Fish Tanks, and More
Mexican Fishing Bats

Mexican Fishing Bats


[Edward Hurme] We’re here in the Sea of
Cortez which is really a marine paradise. People come here to see the wildlife,
enjoy the beaches, see whale sharks, but I came here just for the bats. So there’s another marine mammal
that people often forget, which is the Mexican fishing bat. And this
is a bat that’s completely adapted for life at sea. And so while it lives on land
during the day, at night they go out over the open ocean, and try to catch fish and
shrimp. They are truly a marine mammal and I’m here to study these bats. I’m hoping to bring awareness to their
amazing behaviours, and help spur conservation. Because it is a threatened
species that’s living on these islands that are vulnerable to many different threats. So I’ve been coming to this island for
the past three years. This is my field site for my PhD. And it’s also the
largest known roost of these bats. I’m trying to understand how this bat
goes out over the ocean and finds fish. So we’ve been trying to use multiple steps
to get at this question. The first is to actually put GPS tags on the bats
and really see where they go. To get any GPS data about bats,
first you have to capture them. Early in the morning, we come
to where the bats live. It’s these slopes of loose rocks. We
walk around and then we listen carefully and say “ok I think there’s some
bats under here” and then we start to uncover the rocks and usually we
find a couple of individuals. Then we take the bats back to our
campsite. And from there we measure them, make they they’re nice and healthy, and
then we attach GPS trackers to them. Then we bring them back to their roost
site. We let them go early in the day, so they can have some time to recuperate
from the stress of being captured. And then, eventually, the sun starts to
set, the island starts to cool down a bit and the magic happens.
The bats start to emerge. They have to wait until it’s completely
dark because there’s a lot of predators around that are trying to snag
them as they come out. It’s absolutely incredible that they’re
able to manage such an insane task, going out, finding fish in the ocean, especially
because they’re restricted to catching fish right at the surface. So somehow these
bats know where fish are, that happen to rest right at the surface of the water.
When he’ll fly around and try to catch fish, he’s going to drag his feet and tail
membrane through the water. And if anything touches their feet, they scoop it up
into their mouth and eat while flying. From the GPS data it seems to take between
one hour and eight hours. It’s extremely variable. But once they’re full, then they
come back and spend the day in their roost. And so we then come back the next day, and
using radio telemetry we can track the bats and find exactly the individuals
we want and recover the tags and get all the information
that we need. We can see the bats flying 40, 50 kilometers
away from the island in a night. That’s just straight line distance from the island.
they’ll often fly 100 kilometers on their entire route. And they stop at multiple
sites searching for fish. It also appears that the bats don’t really
know where their food is going to be. From the GPS tracks they seem to go to
different places each night, which implies they can’t just return the the same place
over and over again. They cover such a huge area that being able to watch them
forage is pretty impossible in the field. So what we do, as well, is we set up
a flight cage on the island. And put a little pool inside of it. And from that we have a more confined
view of how bats actually explore their environment and respond to water. We’re trying to see how the bats detect
prey and also record the exact calls they use when they try to
catch a prey item. So the third part of the research is actually
trying to get out and see what it is like near where the bats are foraging. And we’re actually sampling the number of
fish using nets and also recording with ultrasonic microphones, the number
of bats that are around. So far the bats seem full, yet every time
we throw a net, we get nothing. So, uh, they definitely know
something we don’t. I never in my wildest dreams imagined
that I’d be here, studying bats on a desert island. You know, even in the hardest
times, when the sun’s beating down on me and we’ve been lifting rocks for hours each day,
it’s an incredible experience. We’re in a beautiful place and we’re working with such
a fascinating species. So as Baja becomes a more popular
place for people to visit, it brings a lot of problems such as
overfishing and potentially people bringing invasive species
with them that can really impact these environments. And so it’s
really important that while we want to enjoy this place, we also need to be
respectful and try to conserve the area. Being able to see very precisely where
individuals go could give us even more power in saying that we really need to protect certain
regions because they’re being used by endangered species. With the research that
I’m doing on Mexican fishing bats I’m hoping to bring awareness to their amazing
behaviour and help spur conservation that will ensure that these bats can go out
fishing each night, for years to come.

6 comments on “Mexican Fishing Bats

  1. Just back from the Sea of Cortez…wish I had known, as I would have looked for them. The Planktonic Bioluminescence was stunning and I wonder if the bats eat any of those?

  2. Life long lover of chiroptera. I really appreciate your hard work. Please continue to keep our small friends safe and promote the good nature they bring.

  3. Wow….tracking possibly the CUTEST LITTLE FUGLY WIGGLY critters from their ocean side home across the Sea and back again. What a hardship tour. You poor thing! Mawwwww! When I grow up can I be a bat researcher!!!!! PULEEEEEEZZZZE! :))))))))

  4. I figured a predatory bat would've used their mouth to grab, and the fact they use their feet is an interesting surprise

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