Amphibians page 2---Bullfrogs!
This page was born 04/29/2016.  Rickubis designed it.  (such as it is.) Last update: 
5/22/2017
Images and contents on this page copyright 2002-2017 Richard M. Dashnau 

Here are my other Brazos Bend and/or critter pages:
 ----------------------------------------------------------------                  OR,  FOR OTHER ANIMALS:
Alligators at Brazos Bend State Park Introduction                 Critters at Brazos Bend State Park Page 1
Snakes-nonvenomous 1-------------------------------------------     Critters at Brazos Bend State Park Page 3
Snakes-nonvenomous 2-------------------------------------------------Insects, non-toxic
Snakes-nonvenomous 3------------------------------------------------Spiders
Snakes-venomous------------------------------------------------------Mammals
Birds-Waders----Birds-Raptors---------------------------------    LIZARDS!

05/07/2017 Bullfrog calling...revisited    Last year,  I discovered that male bullfrogs' ears are twice as large as the females' not to hear better than the females. Instead, the large ear helps increase the power
of the bullfrog's call. That is, the large ears don't help them hear better....the large ears help them sound better!  Since then, I've been trying to get better video of male bullfrogs calling. I have finally captured
some video at 480 frames per second (FPS).  The video clearly shows the movement of the ear membranes.

   
The two images below are frame grabs from one of the video clips. The images show one ear membrane distended, and then collapsed. The video is at this link.

  

4/10/2016 Bullfrogs have been calling in the park. I'm a little ashamed to say that up until now, I'd never considered taking a close look at what they are actually doing. Bullfrogs are usually a bit shy, and tend to call
from cover--or, they'll stop calling and jump away before they can be seen. For the last few weeks the Bullfrogs have been calling along the Spillway Trail, and have been easy to see in the corner of Pilant Lake near
the Elm Lake water station. With all that "talking" going on, I was able to get a very good short video clip of a bullfrog calling, along with that odd "poot" sound that they sometimes make. I wondered about that sound,
and scanned the Internet for some hint about how or why it happens.  I discovered some interesting things about bullfrogs and their calls.
Bullfrogs actually make a number of different sounds. Males usually do the calling, though females may vocalize occasionally.  The most common is called an "advertisement call".  That's the loud "Ruh AMH", or "Jug o RUM"
call. The less-impressive "poot" noise is an "encounter call", or "territorial sound", and is made to warn off or challenge other male frogs that have wandered into a frog's territory.  One study shows that male frogs respond
more often to frogs calling from further away than to those closest--possibly since they already know where the nearest males already are, and therefore their territories. Also,in a particular area, different frogs will start
the chorus on different days. They sort of..."take turns". And, since calling is an "advertisement", it draws attention to the caller--and this includes territorial aggression by other frogs. Some male frogs avoid this aggression
by a behavior called "satelliting". The "satellite" frogs remain quiet during the advertisement chorus, although they know where the calling males are. When a female is drawn to one of the advertisers, the "satellite" frog
intercepts and mounts it before it can get to the calling male. Pretty sneaky, eh?  The study is referred to on this page.  But wait...things get a bit stranger.
The ears on male Bullfrog ears are about twice as big as the ears on female Bullfrogs. A Bullfrog's ear can be identified by the big circles just behind the eyes. Those circles are actually membranes (tympanic membranes)
which work like our eardrums. Vibrations through the air (sound) cause the membraned to vibrate, and that vibration is transmitted internally by mechanical linkages to the organs that change it to nervous impulses. Previously,
I'd read somewhere that the males' ears were bigger to give them better hearing during mating communication. But
apparently that's not the case. In this study: ("Function of the sexually dimorphic ear of the American
bullfrog, Rana catesbeiana:brief review and new insight", by Y. L. Werner1,*,†, J. Pylka1,‡, H. Schneider2, M. Seifan3, W. Walkowiak2, and U. Werner-Reiss4; I found it at this link) they find that although the male membrane is 
larger, there are some aspects of the anatomy of the male ears that offsets the larger membrane size. For example there is a cartilaginous pad in the middle of the ear where the sensor bone structure rests on the membrane 
(it's the dark center of the ear membrane).  On male frogs, this pad is thicker--which offsets any advantage from the larger membrane surface. After experimentation, the function of the male and female bullfrog ears was found to 
be not very different at all. So if the larger male bullfrog ear doesn't make it hear better than the female; WHY would it be that way? How could it benefit the male bullfrogs? 
This paper may have an answer: ("Tympanic sound radiation in the bullfrog Rana catesbeiana", by A. P. Purgue.)  The abstract is here. The experiments and results seem to show that as the frog calls, the ear membrane vibrates
and helps add power to the call. The larger ear helps the call by adding about 20 dB (decibels) at the "dominant frequency" of the call (about 250 Hz range) and adding about 60 dB at the high-frequency part of the call
(about 1000 Hz). The bullfrogs may be "calling" with their EARS!  After I'd learned this, I intended to shoot more video of bullfrogs calling (my camera has the reach) to see if I can catch this vibration-but the park is currently
flooded. However, when I examined my video, which I shot on 4/10/16, I found that it's possible to see the vibration. The video clip is short, and I've cropped and slowed down the area of the eardrum to show it better.  It looks like
it's moving! That is pretty amazing.


 

August 09, 2015  Bullfrogs are active around the park, although they were not calling this morning as they have been over the last few weekends. While I was walking West on the Spillway trail
(on my way back to the Nature Center to work a shift) I noticed one Bullfrog seemed to be watching something. It's hard to explain why this frog caught my attention, but I knew
that something was up. This could be partly due to my experiences with the Bullfrog I'd kept as a pet for quite a while long ago. I used to watch it hunt in its terrarium home.
Anyway, I had just enough time to start filming him with high-speed video. I didn't want to move closer and possibly scare him, so I stayed back where I was.
The sequence of pictures below are frames from the video clip. The video clip (filmed at 210 FPS) is  here (wmv).  I shot the RICKUBISCAM closeup as a photo with
a different camera.
The gender of a Bullfrog can be determined by looking at its ear membrane (the circle just behind the eye).  If it is smaller-or about the size of the eye, then the frog is female. If the
ear is larger than the eye (usually much larger--as in the picture), then the frog is a male--at least for Bullfrogs.
Bullfrogs will eat anything they can catch and cram down their throat. This can be worms, insects, crawfish, even smaller frogs. In this case, the prey seemed to be a fuzzy, white caterpillar.
I'd thought I might be able to identify it later, but there are MANY "fuzzy white caterpillars".  I was happy to be able to catch this frog's leap and slow it down.

IMAGE SEQUENCE OF THE FROG'S LEAP:

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It's not usually obvious, but frogs can turn their heads.  This head-turning is what caught my attention. As the frog focused on its prey, it turned its body ("aimed" its body) by
shifting position of its rear legs.
With the prey properly in its sights, the frog "fired" by jumping.

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Now an amphibian missile, the frog flew towards its target. Note the front legs tucked in close to the body. Imagine having to eat by launching yourself, FACE FIRST-at high speed-at
your food. Also consider
that this food is alive, and would fight back if it could.

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                                                                                 TONGUE GRAB!
Just before reaching its target, the frog launched its tongue.  What amazing timing this must take! The airborne frog, launched fast enough to fly horizontally, launched its
tongue with enough time to pull it and prey back into its mouth before hitting the water.
A Bullfrog's tongue is attached near the front of it's lower jaw (not near the back, as ours is). Therefore the tongue (which is sticky) flips out, snags prey, and flips it back
towards the frog's throat.  In the second picture above (TONGUE GRAB!), the tongue shows as the pinkish spot just in front of the frog.

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Then the belly-flop landing. With the prey having  been caught, stealth is no longer needed-although this kind of commotion can draw the attention of competing male frogs or
...predators of frogs.
The front legs have extended, also, and are sometimes used to push struggling prey into its mouth.

01/04/2009--Slow-Motion clip of a Bullfrog leaping out of frame at BBSP.  The video could have been better, but it still shows some interesting things. The frog expelled a string of large droplets near the top of its leap.
It seems to me that the droplets striking the water could be a form of visual (and aural) distraction. Since the stream hits within the flight path of the frog, watching eyes would be drawn to these splashes, while the camouflaged
frog could be lost from view.   Click this link for the video.

 

08/06/2006--Finally, there is  one more clip 4840 wmv . This is of a bullfrog calling, and the little "poot!" noise that Bullfrogs make sometimes after a bout of calling. 

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                                              HI  DIDDLE DIDDLE AMPHIBIAN BULL FIDDLE
                                                         VIDEO CLIP 4840 kb wmv
A large number of Bullfrogs can be heard in the clip. It is illegal to catch or molest any animal (with the exception of fish) at BBSP. Frogs cannot be legally caught IN ANY WAY at BBSP.  Although fishing is  allowed, State fishing regulations must be followed.  Leave the animals you see at BBSP alone, so that other visitors may enjoy seeing them (and also to avoid being ticketed and fined).

April 27, 2003 I have one more clip to answer a question that many visitors have asked. They keep asking what this loud "jug-o-rum" sound is.  The culprit is the Bullfrog (rana catesbeiana). I've finally been able to get one on video as it's calling(see WHERE'S THE BEER?, below; or see the clip flv video 308 kb ) . Listen to this, and compare to the various alligator bellows on my pages.
   ----------------------------------------------------------
---------------------------WHERE'S THE BEER?

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Brazos Bend State Park   The main page.

Brazos Bend State Park Volunteer's Page  The volunteer's main page.
 

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