Tadpole Schooling and Parental Care in Leptodactylus insularum
For my doctoral disseration I will be examining
tadpole schooling and parental care in the frog, Leptodactylus insularum
in Gamboa, Panama. Females attend dense schools of tadpoles and lead them around
using a pumping behavior. Schooling behavior and parental care are usually studied
separately in anurans, and I hope to use L. insularum as a model species
to look at the interactions between tadpole schooling and parental care, as
well as parent-offspring communication. I also hope to untangle some of the
costs and benefits of tadpole schooling and female attendance to examine the
evolution of these unusual social behaviors. In the photo below, the female
middle of the school has at least 11 mosquitoes biting her! That's a cost (that I can relate to!)!
Leptodactylus insularum in Gamboa,
Panama breed during the rainy season (May - Dec) in shallow, temporary ponds.
Male and female frogs are sexually dimorphic,
with males having huge forearms and chests and thumb spines.
Males spread out within the pond and call
from underneath vegetation for females. I have yet to observe
amplexus, but the result is a foam nest with 5-8000 eggs. Females remain with the foam nests and resulting
school of tadpoles. (Toothpick = 6cm)
Tadpoles remain in dense schools throughout development,
and these schools are often attended by
females. I have not yet followed a school all the way until metamorphosis, but the tadpoles are constantly
feeding, very active and reach metamorphosis in only 17 days! very quickly! Here is a
metamorph that has it's adult coloration already!
I am using Visual Implant AlphaNumeric tags (Northwest
Marine Technologies, Inc.) to
mark individuals. I've had good success with the marking, but it requires handling of the frog for
identification. The tag in the photo below is from a recaptured female. You can see that the tag healed
perfectly and is visible with just a flashlight. I also photograph individuals so that I can identify them
without recapturing them nightly.
The tadpoles form very tight schools, which may
protect an individual from predation and allow
for increased activity levels, but it surely makes the whole group very conspicuous. And
I think there must be increased competition for oxygen and food within these dense schools!
In some of the schools there are many different
sized tapoles schooling together. In the first photo
you can see a large tadpole that already has hind limbs and a medium sized tadpole swimming amongst
the larger school of smaller tadpoles. Perhaps the tadpoles are all related and just grow at incredibly
different rates? Or more likely is that larger tadpoles become separated from their original schools and
school with any other L. insularum tadpoles they encounter? In the second photo there seems to be 2
different aged schools mixed together (the pointer shows a smaller tadpole and the toothpick is 6cm for
scale). I plan to look at paternity and determine if relatedness affects schooling behavior and parental care.
Clumping - Here is a video
of tadpoles showing a tendency to clump together.
They start out in a loose group and slowly start to clump until only the edges have active tadpoles!
The toothpick (6cm) is perpendicular to the observer for scale.
I have also found stationary cohesive schools
where the middle is almost completely still! In the
school below, there was increased protection from predators in the center (I saw an attack on a tadpole on
the outskirts), but I plan to look into the tradeoffs of these dense aggregations (specifically
decreased oxygen availability) and how these costs change throughout development.
Schooling attracts attention
- Here is a video of a school
during the day. You can see how
conspicuous they are with the reflected sunlight. It certainly enabled me to find them! But there must
be costs to being so visible (like attracting this tiger heron?). At the end of the video, the tadpoles start clumping
towards the bottom of the screen. It seems as if they are swimming on top of one another - perhaps they're
trying to get to the surface where oxygen is more available.
Bobbing for air
- In this video you can see older
tadpoles engaging in a bobbing behavior where they
sprint to the surface, (presumably) gulp air, and return to deeper water. They swim very rapidly and I have
a very difficult time following individuals or even getting a sense of how dense these schools are.
However, this is not a problem for the spiders, because I have observed successful predation on the
tadpoles exhibiting this behavior. The behavior isn't found as dramatically in younger tadpoles and I plan
to look at lung development to see if there is a physiological and behavioral shift to encourage aerial respiration.
Female aggressive behavior
While trying to take the temperature of some
foam nests, the attending females very aggressively
kept me away! Here is a video of two separate females attacking my hand. The first female grabbed my
hand with her forearms and the second head butted me. Both females made a grunting/hissing noise with each
attack. You can also see some threat behavior where the females stand up on all four legs or raise
their rear! Very exciting!!! What great mothers, I love them!
During my observations, the most common predators
were spiders. I would find spiders hunting
over the school, and often after only a few attempts, grab very large tadpoles, carry them out of
the water and feast on them for the next hour! crazy!! When this predation occurred, I would see
no obvious reaction from the attending mother or other tadpoles. In fact, on the night where I took
the following photo, I had 5 spiders eating tadpoles on the surface, and the school remained in the
same location for mulitple hours. This amazing photo below shows a Thaumasia spp. spider (in the
family Pisauridae, commonly called a Raft Spider, Fishing Spider or Nursery Web Spider)
feasting on a Leptodactylus insularum tadpole.
Spider predation and bouncing
- In this amazing video I
observed a fishing spider bouncing on
the surface of the water and producing concentric surface waves. The spider then darted forward and caught
a tadpole (not L. insularum). Then with the tadpole the spider darted forward again, dragged it onto some
vegetation, then darted away from me... right in the grasp of a larger nursery web spider!!! So the big spider was
eating the small spider who was eating a tadpole! Just like the cartoons of food chains in the ocean!
I also came across a larger spiders (ID?) sitting
next to a dead male tungara
frog. I can only assume that spider was a factor in the frog's death....
Kristiina Hurme, PhD Student
Any comments or questions? Please email me at
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