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Re: T. rex's vision as SUPPORT for scavenging activitiy...



Questions/comments below.

Don

----- Original Message ----
From: Tim Williams <twilliams_alpha@hotmail.com>
To: dinosaur@usc.edu
Sent: Monday, July 3, 2006 4:40:15 PM
Subject: RE: T. rex's vision as SUPPORT for scavenging activitiy...

Don Ohmes wrote:

>Any candidates for the role of volant scavenger(s) co-existing with T. rex?

A scavenging lifestyle was suggested for _Quetzalcoatlus_ back in the 
1970's, when this flying beastie was first described.  But as I learned from 
Darren Naish's blog...

http://darrennaish.blogspot.com/2006/04/why-azhdarchids-were-giant-storks_03.html

... the evidence to support a scavenger lifestyle for _Qutzalcoatlus_ and 
other azhdarchids is very weak.

I'd bet dollars to donuts that one day a Mesozoic bird (probably an 
enantiornithean) turns up with characters consistent with specialist 
scavenging.

When you go dollars to used donut holes, as opposed to just donuts, I'll know 
you are confident. Although I agree in the sense we aint seen much of what was 
there.

Considering the sheer bulk of many dinosaur carcasses around in the Jurassic 
and Cretaceous, scavenging seems like too good a niche to pass up.  Of 
course, it helps to have a strong digestive system.

Agreed. Pack hunters may have been very efficient, though. And big prey equals 
big packs, I'm guessing. (Not to open old wounds, LOL-- How many 100 kg 
climbing "terrestrial shark analogues" could a 60 ton carcass feed?)

>IF there is the presence of a population of volant scavengers, then timely 
>visual cues (eg, circling vultures) to any local large animal death exist, 
>and are detectable from distances up to 40 miles in an open environment.

AFAIK, nobody has suggested that tyrannosaurs could fly.  Apart from George 
Olshevsky, that is. :-)

Huh? Not me, that's for sure. Didn't follow this one, exactly. Bulky carcasses 
equals more time to walk to lunch (before it is all gone, or decomposed 
entirely).

Cheers

Tim







>
>Don
>
>
>
>



>From: don ohmes <d_ohmes@yahoo.com>
>Reply-To: don ohmes <d_ohmes@yahoo.com>
>To: dinosaur@usc.edu
>Subject: T. rex's vision as SUPPORT for scavenging activitiy...
>Date: Mon, 03 Jul 2006 13:13:37 -0700 (PDT)
>
>In my opinion-- obligate scavenger is not the most probable lifestyle for 
>T. rex, and there are strong arguments for a top predator lifestyle, as 
>well some against the obligate scavenger hypothesis. That said, there is no 
>doubt that the ability to scavenge/co-opt fortuitous mortalities in the 
>local large animal population is potentially advantageous for top 
>predators.
>
>The ability to detect fortuitous mortality in a timely fashion is obviously 
>critically important to efficient utilization of such resources, and any 
>sense used for detection is therefore subject to strong directional 
>selection. IF there is the presence of a population of volant scavengers, 
>then timely visual cues (eg, circling vultures) to any local large animal 
>death exist, and are detectable from distances up to 40 miles in an open 
>environment.
>
>Given the large size of resource animals extant in the Cretaceous, a 
>relatively large time window for utilization would exist. An open 
>environment, very large animals, and volant scavengers seems like an ideal 
>recipe for evolving keen (ie, long-range) daytime vision in a large 
>terrestrial predator.
>
>I don't know if this has been addressed before, in print. If it has, sorry 
>about the lack of reference.
>