Re: Does this moa argument fly?

[bchoo@cyllene.uwa.edu.au (B. Choo)]

John Bois wrote:

>Moa and Elephant birds from Recent times were larger than any extant
>birds.  And they lived on islands (NZ and Madagascar respectively).  Two
>hypotheses have been offered for this phenomenon of gigantism on islands:
>
>1. The absence of competition from large mammalian herbivores allowed them
>to adapt into the large herbivore niche.
>
>2. The absence of predation by mammalian carnivores allowed them to
>evolve into large body size.
>
>Predictably, I favor #2.  And while there is no direct evidence either
>way, I wondered whether the following would be considered support, strong,
>weak, or otherwise, for #2.


Interesting...some small observations:

The NZ pre-human avifauna, while not threatened by any terrestrial predator
(pack-hunting Tuataras anyone?), still had to contend with attack from the
air (Haast's Eagle, Giant Harriers and Keas), why would the absence of
mammalian predators alone be a factor in the face of avian attack?
(admittedly the moas may have evolved before such forms were present on the
islands)

The Mihirungs (Dromornithidae) of Australia, some of which may have
surpassed the 500 kg mark, coexisted with both large mammalian herbivores
and terrestrial (mammalian and reptilian) predators.

Cheerio
Brian Choo