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RE Richard W Travsky -Bones and stomach acid

(Rescued from truncation)
Thanks, Peter, for this fascinating information.

In a message dated 8/18/2010 5:14:12 P.M. Eastern Daylight  Time, 
croc1@99main.com writes:

As the past Superintendent of Reptiles at the Bronx Zoo, NY, and  a
crocodilian specialist, I've observed the feeding habits of many species  of
crocodilian in captivity and the wild.  The phenomenon of  occurring
crocodilian gastroliths is of particular interest.  However,  relative to 
consumption of prey/food-bones, perhaps I can offer the  following

In captivity, modern crocodilians are  sometimes fed food items such as 
pigeons with feathers, whole chickens,  chicken body parts with bone
included, whole white rats and mice, whole fish  such as mackerel, trout, 
halibut head parts that may include the bones  that form the gills.  In some
cases, beef meat with cut rib bones  several inches long may be fed. What 
be most germane is the question of  what do ingested large mammal bones look
like after being processed by the  animal? Obviously, any resulting fecal
material is easily observed under  captive conditions.  

However, bones, stones, metal objects, and  other ingested none-food items
may be held in the stomach as gastrolithic  materials for long periods of
time.  Such items may not pass out of the  stomach through the small pyloric
valve/opening into the small  intestine.  Balls of hair the size of beans
from ingested rats may  collect and totally fill the stomach.  Thick rib
bones may also remain  in the stomach.  Such items are not passed out as
fecal material but are  regularly regurgitated in-mass.  It is not unusual
for animal care staff  to find the crocodilian pool water surface totally
covered with small  pelleted balls of regurgitated rat hair, nor is it
unusual to find the  ingested thick beef bones, minus any flesh, on the
bottom of the pool the  animals are housed in.   

Simply put, when the mass of hair  balls, bones, and items that are too 
or not digestible but cannot pass  out of the stomach - fill the stomach to
capacity, the stomach is emptied by  regurgitation. Crocodilian scats or
fecal material does not contain large  grit, bone fragments, nor any
appreciable amounts of hair if at all.   Also, coins that are thrown into 
pool by the public are regularly found  in numbers, trapped in the stomach. 

Digestible materials may  include from observation: soft tissue, small thin
bones, cartilaginous  materials appear to fall into this category.  

Actual crocodilian  stools may be wet and loose, but most often are found as
an elongated,  intestine-formed, semi-solid amount of dark gray, fine-silted

In examining stomach contents of wild crocodilians such as Yacare caiman  in
the Brazilian Pantanal, that may feed on large aquatic snails, one finds  
the snails shell in the stomach, but the snail's operculum, in  great
quantities.  The operculum being retained from each snail  consumed. 

Likewise, the long bones, beaks from birds, and the skin of the  feet,
complete with toe claws, appearing as a skin glove, absent the legs  inside,
may be found in the pools of captive animals - presumably  regurgitated 
with hair balls or the center quill-vane from feathers,  but not the feather
filaments.  Thus looking at fossil crocodilian  food-bones in terms of 
scats may be inappropriate as they in fact may  be regurgitations. 

I published a short paper on the occurrence of  gastroliths in modern
crocodilians and I am happy to provide a copy if anyone  wishes it


Peter Brazaitis
Forensic  Herpetologist
155 Woodchuck Lane
Harwinton, CT 06791
Tel.:  860-485-0044
Cell: 860-480-2588
FAX:  860-485-9513

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