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Re: [dinosaur] Dinosaur nest ecology and predation during Late Cretaceous

Note, also that the K / r-strategy dichotomy has long since fallen out of favour with ecologists as an explanation for animal life histories. See Reznick et al. 2002, for a good summary.

Reznick, D., Bryant, M.J., Bashey, F. 2002. r- and K-Selection Revisited: The Role of Population Regulation in Life-History Evolution. Ecology. 83(6):1509–1520.



From: David Marjanovic <david.marjanovic@gmx.at>
To: dinosaur-l@usc.edu
Sent: Tuesday, January 10, 2017 12:05 PM
Subject: Re: [dinosaur] Dinosaur nest ecology and predation during Late Cretaceous

> Hm...this seems like a new version of the old 'mammals ate all the dinosaur eggs!' scenario.

Worse: the old "mammals ate all the dinosaur eggs _precisely when_ the Chicxulub impact happened and apparently Deccan was going on, too!" scenario. I promise to read the paper soon.

> the whole argument seems to ignore the fact that dinosaurs in general appear to have been K-strategists to some extent; large numbers of offspring to offset serious losses. Nest failure was probably a feature and not a bug so we are definitely not looking at the loss of numerous eggs being something new to the later Cretaceous.

That's r-strategy, named after r for "reproductive rate", not K-strategy, named after K for "carrying capacity".

In the absence of predators or other causes of death, a population of r-strategists will grow as fast as its r lets it until or suchlike famine sets in; as a population of K-strategists grows under the same conditions, its r will decrease as K is approached, because K-strategists, unlike r-strategists, are sensitive to stress from overcrowding. In short, exponential increase for r-strategists, a sigmoid curve for K-strategists.

Usually, r-strategists have a lot of offspring that they use "as Darwinian ammunition" in the immortal words of our own Tom Holtz, while K-strategists have fewer offspring that they care for better. But that is not the definition. Specifically, it seems like humans are actually r-strategists: there are factors other than death that are decreasing our population growth, but a fertility decrease caused by population density doesn't seem to be one of them.