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Annexe III
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Yearling mass was measured as the number of days between birth and death (natural death or
sacrifice) for juveniles aged of one-year old, at least. The number of days between the birth
and the last measure of mass was added as fixed effect in the statistical analyze of yearling
mass.
A backward stepwise procedure was used to select final minimal models, according to the
Akaike information criteria (AIC) for model comparison (Crawley, 1993; Burnham &
Anderson, 1998).
RESULTS
Change in egg mass during the course of incubation
According to every best minimal model, there was a highly significant positive effect of time
on egg mass (Table 2.1). We decided to interpret our results in terms of change in egg mass
among incubation time and not in terms of eggs mass, further denoted as egg growth rate.
Only interactions with time were thus considered with interest in our analyses and are detailed
in the following part.
In the first tested model, we found a significant clutch effect on egg growth rate during
incubation (Table 2.1, model 1). We also found a significant effect of initial egg mass in
interaction with the “memory effect” of substrate water potential encountered five days
before. Moreover, we pointed out a significant and positive effect of the substrate water
potential on egg growth rate, with a higher growth rate on the wet substrate than on the
intermediate and dry substrates respectively (Figure 1). This latter effect has also been
detected as significantly different between the periods of incubation. The “memory effect”
was also significant with a different effect between the three different periods of incubation
and between the substrate moisture at the current time (Table 2.1, model 1). Finally, we
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