COMPETING BATS, BIRDS & PTEROSAURS

[darren.naish@port.ac.uk]

Pterosaurs and birds probably didn't compete directly, but as 
pterosaur lineages died out, their ecological roles may have been 
occupied by birds. So-called competitive replacement is probably rare 
(see Benton 1996). On birds and bats, Ron wrote...

> Birds and bats coexist today, and some have suggested that this may 
> be primarily because bats are, generally, nocturnal whereas             
> relatively few birds are.  

There is some suggestion from ecologists that bats are nocturnal to 
avoid competition, mobbing or predation from birds. On some 
Mediterranean islands which lack birds of prey, the bats are diurnal. 
Day-flying bats are reportedly mobbed by hirundines. A _Nature_ 
article from 2000 (called 'Bats about the Arctic') discussed places 
where there is 24 hrs of sunlight and vespertilionids and hirundines 
hunt the same insects in the same place: it also addressed this issue. 

These observations imply that birds outcompete diurnal bats when the 
two coexist... maybe this is because bat flight apparatus is more fragile 
than feathers or, more reasonably, that bats are inherently constrained 
by their thermoregulatory abilities (bats overheat quicker in sunlight 
and cool quicker in cold air than birds - obviously because of their 
largely naked patagia). Could the same have been at all true of 
pterosaurs?

Microbats probably hunt more in daylight than we realise: a large 
recent study on pipistrelle stomach contents showed - to the surprise 
of the authors - that dragonflies (which apparently only fly in the day) 
made up a significant portion of items consumed (something like 40%).

Benton, M. J. 1996. On the nonprevalence of competitive replacement 
in the evolution of tetrapods, pp. 185-210. In: Jablonski, D. H. E. and 
Lipps, J. H. _Evolutionary Paleobiology_. Uni. Chicago Press.

"She may be the smartest animal in the world, but she's still an animal"

DARREN NAISH 
PALAEOBIOLOGY RESEARCH GROUP
School of Earth, Environmental & Physical Sciences
UNIVERSITY OF PORTSMOUTH
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