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RE: Burrowing/hibernating mammals have lower extinction risk



>Robertson et al. (2004) highlight a burrowing habit as a likely survival
trait in the first hours of the Cenozoic, while Smith & Botha (2005) suggest
burrowing therapsids (as organisms adapted to dealing with periods of
dysoxia and hypercapnia) may have had a selective advantage over
non-burrowers at the P/Tr event.

     I must say I've never really understood this concept all that well.  I
can certainly see that burrowing would be advantageous during the first few
moments of a major catastrophic event, like a bolide impact -- it provides a
nice shield from things like shock waves, heat pulses, etc. that
non-burrowers don't enjoy.  But these are not the parts of catastrophic
events that induce extinctions -- it's the longer-term effects, like rapid
climate shifts, food web collapses, etc. that have those effects, and unless
there are burrowing vertebrates that never come to the surface and have an
entirely underground food web, I don't see how they're rendered immune from
these things.  For example, they still have to come up to the surface to
find food -- presumably non-burrowing food -- and if that food source is
severely impacted by the longer-term effects of the event, then the burrower
is going to have just as hard a time subsisting as anything else.  

     And, of course, burrowing is DISadvantageous in many aspects of
catastrophic events, such as lahars, tsunamis, and even massive fires (as
exemplified by the 85% mortality rate among burrowing desert tortoises in
the large tortoise preserve outside St. George during massive
lightning-induced fires in 2005).


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jerry D. Harris
Director of Paleontology
Dixie State College
Science Building
225 South 700 East
St. George, UT  84770   USA
Phone: (435) 652-7758
Fax: (435) 656-4022
E-mail: jharris@dixie.edu
 and     dinogami@gmail.com
http://cactus.dixie.edu/jharris/

"Life is the art of drawing
sufficient conclusions from
insufficient premises."
               -- Samuel Butler