Re: attack on dinosaur--horrific video

[Dann Pigdon <dannj@alphalink.com.au>]

john bois writes: 

> > > many would-be predators don't like getting wet
> >
> > The eggs are not laid in water.
>
> They are laid in swamps--many nests are accessible only by getting one's 
> self wet.

[SNIP] 

> > > predatory threat can only come from 180 degrees not 360;
> >
> > No, croc nests are not directly next to the water.
>
> But a croc only has to scan 180 degrees--predators are not going to be 
> accessing the nest from the water.  And to do this a croc can lie as still 
> as a log waiting to ambush. This is an exceptionally effective strategy 
> whether animals are merely trying to get a drink of water or robbing a 
> nest.

In areas prone to flooding, croc nests are often on ground high enough to 
prevent the nest being inundated. In those cases a land-based attack on the 
nest can come from any direction. Many a croc has lost a few eggs to hungry 
varanids that sneak up behind the mother and quietly dig into the mound. 
It's unlikely that every single egg layed will be dug up and eaten though. 

Even if a nest mound is right next to the water (or on an island in a 
swamp), a varanid will happily take a swim to get to it - as will just about 
any other predator that habitually robs croc nests (since they're living in 
the same swampy area to begin with). 

The real benefit of a protective mother comes after the eggs hatch, when the 
hatchlings are wiggling about above ground (or in the water) for all to see. 
The act of burying the eggs is probably a better defence than actively 
guarding the nest, provided the number of eggs layed is large enough to 
offset predation (ask any marine turtle...) In fact, the presence of a 
nest-guarding mother probably *attracks* nest raiders. If you're a marine 
turtle that moves slowly on land and has no really effective means of 
attack, then guarding the nest is pointless. However if you're a large 
voracious carnivore that can move quickly and has a killer set of teeth, 
then the effectiveness of guarding the nest probably outweighs the fact that 
a guardian mother is a living billboard advertising a nest's location. 

___________________________________________________________________ 

Dann Pigdon
GIS / Archaeologist              geo cities.com/dannsdinosaurs
Melbourne, Australia             heretichides.soffiles.com
___________________________________________________________________