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Re: Vegavis gen. nov. - new anseriform in today's Nature
There are also some sauropods-in-company trackways that appear to
indicate herding behaviour, with the smaller animals in the middle and
the largest to the front of the direction of travel.
Besides... is there a point in communal nesting (found in Auca Mahuevo at
least...) when the nests aren't guarded?
Right. There is nothing magical or superior about large clutch size
or r strategy _per se_. But they do indicated high mortality--and
high predator pressure!
They do not, however, indicate increased susceptibility to extinction. If
anything, they indicate the opposite ("sauropods are weed species").
And you can test your hypothesis by looking at clutch sizes over the
Cretaceous, to see if there's an identifiable trend.
I'm sure not enough Cretaceous nests are known yet.
If -- as does not seem implausible -- a sauropod takes 30 years to reach
full adult size, and then spends another 30 busy reproducing, and lays
only one clutch of 30 eggs a year (though if they can grow that fast
they can lay more), you're looking at 900 eggs; that's probably not
But if it's 20 years, 50 years, and 200 eggs a year -- still a tiny
fraction of maternal mass, smaller than pretty much all extant birds --
you're looking at ten _thousand_ eggs, and pretty good odds two of them
make it to stable reproductive adulthood, on average.
It could get more extreme still. Wasn't that 10-year-old *Apatosaurus*
almost adult? -- If we then additionally assume that large sauropods were
basically immune to predation (a more tenuous assumption than growth at
placental speeds), we can start wondering about their lifespans. A few years
ago a right whale was found to have been 211 years old when it was
harpooned. (Method: ratio of L- and D-amino acids in the eye lens.)
Mammals are compulsory K strategists,
(Time for nitpicking: many mammals are r-strategists by the actual
criterion. K-strategists reduce their fertility when they reach the carrying
capacity (K) of their environment, for example by increased stress via
increased intraspecific aggression; r-strategists don't, their reproductive
rate (r) stays as high as ever. Funnily enough, humans seem to be
r-strategists -- we can stand living in Shanghai with its 2,790 inhabitants
and I think this messes with our heads to a certain degree when thinking
about these questions, but treating offspring as Darwinian ammunition