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Re: dino-lice



Thanks, Viv, I'll read these papers. But I know that Jack Horner won't like 
that first one.

I like your approach on this question, in trying to get basic estimates of the 
overall nutrient availability from carrion and its distribution, yet I fear 
that those estimates will be unreliable due to the vast unknowns regarding 
mesozoic ecology. (Even prevailing relative humidity could have a huge effect 
on the persistence of carcasses, right?).

My approach is to go to the fossil record and see if there is any useful 
information there. Do any gut contents or bone marks shed light on scavenging 
vs.predation? For this discussion I went back and looked at Hone, D.W.E. & 
Rauhut, O.W.M. 2009: Feeding behaviour and bone utilization by theropod 
dinosaurs. Lethaia, Vol. 43, pp. 232–244. 

http://eeb.bio.utk.edu/biologyinbox/unit1/readings/Hone%20&%20Rauhut%202009%20-%20Feeding%20behaviour%20and%20bone%20utilization%20by%20theropod%20dinosaurs.pdf

This paper documents tooth marks on bones and also gut contents of many 
theropods, but by no means all. To their list I would add Sinocalliopteryx 
(dromaeosaurid leg), Microraptor (mammal foot), and Confuciusornis (fish in 
crop). 

If a theropod is a scavenger, what will its gut contents look like? Will they 
be more likely to contain bone, since the predator that kills the animal might 
preferentially take the viscera? And a gut full of soft tissues, of course, 
probably won't preserve. From what I know of small theropod gut contents we 
usually see small animals that were probably swallowed whole, or else whole 
limbs of small animals. I'll look if I can find any supporting references on 
what scavengers' gut contents look like. Is it mostly small fragments, or whole 
limbs, or whole bones, or what.

Hone and Rauhut write: "if theropods were regularly consuming large pieces of 
bone, one would expect to find many more specimens ... with preserved bone mass 
in their chest cavities." I am not sure that I agree with this statement on its 
face, I think we need to find a way to support it. If some theropods 
preferentially ate soft tissue we might never be able to prove it. In the 
meantime the fact that 100% of known theropod gut contents DO include bone 
might suggest the opposite conclusion. 

-Jason 


On Apr 18, 2011, at 10:57 PM, Vivian Allen wrote:

> And another one, bit more directly relevant:
> 
> Carbone et al 2011: Intra-guild competition and its implications for
> one of the biggest terrestrial predators, Tyrannosaurus rex
> 
> http://rspb.royalsocietypublishing.org/content/early/2011/01/20/rspb.2010.2497.short
> 
> 
> 
> On 19 April 2011 03:39, Vivian Allen <mrvivianallen@googlemail.com> wrote:
>> Here we go: published arguments for discussion
>> 
>> Ruxton & Houston 2004: Obligate vertebrate scavengers must be large
>> soaring fliers.
>> 
>>  http://www.ncbi.nlm.nih.gov/pubmed/15135041
>> 
>> Can't get the full pdf because I'm in a hotel. Looks pretty good though?
>> 
>> 
>> Viv
>> 
>> 
>> On 19 April 2011 03:30, Augusto Haro <augustoharo@gmail.com> wrote:
>>> 2011/4/18 Tim Williams <tijawi@gmail.com>:
>>> 
>>>> When it comes to feeding on a carcass, the alvarezsaurs might well
>>>> have been the last to arrive at the scene.
>>> 
>>> Yes, but in this case the specialized morphology of the forelimb seems
>>> not so important for hide-cutting or breaking if carrion-eating.
>>> 
>>>> Having high visual and/or
>>>> olfactory acuity may not have been so important, because (a) many
>>>> carcasses would have been huge and (b) alvarezsaurs could be your
>>>> typical camp-followers, and trailed larger predatory theropods with a
>>>> view to a kill.
>>> 
>>> If large dinosaurs had low population densities, finding one by itself
>>> would be difficult, more making a living of these. In addition, for
>>> visual animals, it depends on how much exposed the corpse was. The
>>> possibility of finding one also would depend on how fast animals with
>>> greater acuity ingested the carcass after coming before. This does not
>>> count if following animals with better senses, or if not living
>>> primarily on corpses.
>>> 
>>>> I'm not suggesting that alvarezsaurs were obligate scavengers.
>>>> However, as noted by Longrich & Currie (2008), ant nests were likely
>>>> rare in the Mesozoic, and termitaria possibly absent altogether -
>>>> leaving wood-nesting termites as the only common social insect
>>>> contemporary with alvarezsaurs.  So there would seem to be slim
>>>> pickings indeed for a theropod that relied solely on ants and termites
>>>> as its food source.
>>> 
>>> Agreed on the need to eat more than social insects, but it seems to me
>>> more likely for they to pick small animals, seeds, or not though
>>> plants, than carrion-eating, because of not having recurved beaks or
>>> teeth. I think following large herbivores and searching for its
>>> droppings may provide many seeds, and perhaps also insects if waiting
>>> a time.
>>> 
>> 

Jason Brougham
Senior Principal Preparator
American Museum of Natural History
jaseb@amnh.org
(212) 496 3544