[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Gargling galahs!
From: Colin McHenry <firstname.lastname@example.org>
> > > My own suspicion is that, as in, say, ostriches, the dinosaurs were
> > > R-selected as eggs and K-selected as chicks ...
> >Or, mor precisely, a hybrid stategy.
> As far as I can recall my ecology lectures, 'r' and 'k' selection are
> properties of a population, and do not generally vary with respect to the
> age of an organism.
Exactly. That is why I "corrected" the above to "hybrid strategy".
That is valid because r and K selection are end points of a continuum.
> >On the other hand, the evidence from the Texas Chasmosaurus
> >mass-death site is that ceratopsian herds were mixed-age, ranging
> >from very young to full adult. his suggests parental care, and
> >supports mixed-strategy reproduction in at least Chasmosaurus.
> Not necessarily; if mortality is heavily biased towards younger age (and
> therefore smaller size), then once past these dangerous early years the age
> classes of the population will be of roughly equal size (in terms of
> numbers), all the way from juvenile to adult.
In fact the site was biased *against* small individuals. All of the
small skeletal elements were badly crushed, but there were rather
alot of them. The smallest size class represented by fragments was
well below a "juvenile" in size, and closer to a yearling, or younger.
Also, the adult size class actually had the *smallest* estimated
number of individuals (only three of four of the specimens were adults,
there were at least as many subadults, and a large, undetermined,
number of smaller individuals).
> If these ages classes mix
> into herds (this may be more probable with herbivorous species) then the
> pattern you describe will result. If the adults are defending their nests
> (and even new hatchlings) then the herd (or at least the parents) aren't
> going to be too far away, giving the young animals a chance to join up with
> the herd. This doesn't necessarily imply parental care of young once out of
> the nest - the only protection would be as part of the herd.
This is quite correct. But the herd membership appears to have started
within the first year of life - unlike in Maiasaura where herd the
juveniles appear to have stayed in separate herds.
The peace of God be with you.