Overlooked 2002 compendium

[Stephan Pickering <stefanpickering2002@yahoo.com>]

As a supplement to Scott Sampson's fine paper in the
Tanke/Carpenter compendium, 'Speculatiions on the
socioecology of ceratopsid dinosaurs (Ornithischia:
Neoceratopsia)', I would high recommend Ian Hardy's
edited 2002 collection, Sex ratios: concepts &
research methods (Cambridge University Press),424pp,
especially chapter 18, Charlotta Kvarnemo & Ingrid
Ahnesjo, 'Operational sex ratios and mating
competition'. Potential reproductive rates (PRR)and
qualified sex ratio differ between sexes, and together
are pivotal components of OSR and the dynamics of
sexual selection in viable populations. Ms. Kvarnemo
and Ms. Ahnesjo add environmental factors to the flux
of mating competitions (OSR being the female:male
ratio, PRR being maximal reproductive rates of an
individual within a population). OSR in, e.g., a herd
of ceratopsians, is the key to enunciating and
predicting if males or the females are the dominant
competitors for breeding mates. The sexual difference
in PRR, as they write,is the potential number of
offspring produced per unit time. Inferences are
possible. Let us take, e.g., Phil Currie's 1989 paper
'Long distance dinosaurs' (or his earlier 1984 paper
with Peter Dodson 'Mass death of a herd of ceratopsian
dinosaurs'). One could count the number of
identifiable males and females, estimate their ages,
predicting OSR by inferring PRR by assuming females
and males in a ceratopsian herd had access to each
other. PRR, then, would be the potential number, as
Kvarnemo/Ahnesjo speculate, of offspring produced per
unit time 'or as the inverse "time out" for a clutch'.
Sexual differences in PRR among ceratopsians would be
influenced by foliage available, age/size
distributions, seasonal temperatures. PRR and OSR are
constrained for both female/male, although I think it
probable that, among ceratopsians and hadrosaurs, as
with sauropods, females dominated all social groups in
both size and behavioural strategies.

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