Re: dino-lice

[Jason Brougham <jaseb@amnh.org>]

I am reading a field study of Tasmanian Devils. One source of evidence that the 
authors use to distinguish scavenging from predation is the presence of fly 
larvae and pupae in the scats. I wonder if anyone has ever looked for these in 
dinosaur gut contents?


On Apr 19, 2011, at 10:51 AM, Jason Brougham wrote:

> 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
> 
> 

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