Figure 1.
Comparison of varying models for growth trajectories in Komodo dragons.
Contrasts the typical male and female trajectories expected for the von Bertalanffy growth function (VBGF; top panel) and generalized additive mixed model (GAMM; lower panel) for growth rate in relation to life-history transitions throughout ontogeny. Essentially because the GAMM is non-deterministic it was expected that maximum growth is predicted in the juvenile period of development whilst all surplus energy minus maintenance costs is channelled into growth. A dimorphic sexual maturation growth phase is predicted to occur with sex-specific differences reflecting different growth allocation decisions underpinning reproduction. Due to limited adult mortality associated with the dragons being apex predators, animals should be dying mostly as a result of old age, which potentially means there is a period of time when negative growth could be observed. These phenomena are not accounted for by the von Bertalanffy function.
Figure 2.
Map of Komodo National Park (KNP) and the location of the 10 field sites used in this study.
Four sites were located on each of the large islands of Komodo (Lse, Lli, Lla, Lwa); and Rinca (Lbu, Lba, Lto, Lda). Single sites were located on each of the small islands of Gili Motang and Nusa Kode (Gm and Nk respectively).
Figure 3.
Size-specific growth curves (GAMMs; generalized additive mixed models) for Komodo dragons.
These GAMMs model growth as predicted by mean body size (cm SVL; snout-vent-length). (a) All dragon growth records, (b) males (blue) and females (red/pink) compared. Dotted curves represent point-wise 95% confidence bands around fitted models. Note the female curve in (b) is not extrapolated beyond the maximum SVL at which animals were caught.
Table 1.
Parametric and non-parametric terms of the generalized additive mixed model (GAMM) modelling growth rate of Komodo dragons.
Figure 4.
Size-at-age growth curves for Komodo dragons, derived by numerically integrating size-specific growth curves (Figure 3B).
Male (blue) and female (red/pink) growth records compared. Dotted curves represent point-wise 95% confidence bands around fitted models. Note the female curve is not extrapolated beyond the maximum SVL at which animals were caught.
Figure 5.
Age-specific growth curves for Komodo dragons, derived by numerically differentiating size-at-age growth curves (Figure 4).
Male (blue) and female (red/pink) growth records compared. Dotted curves represent point-wise 95% confidence bands around fitted models. Note the female curve is not extrapolated beyond the maximum SVL at which animals were caught.
Figure 6.
Sex-specific size and age frequency distributions for Komodo dragons.
Comparison of male (blue) and female (red) frequency distributions in (a) body size (cm SVL) and (b) predicted age.
Figure 7.
Relationship between population density (lizards/km2) at each site and site mean growth rates (cm SVL/yr).
Dotted curves represent 95% confidence bands for the mean predicted curve. Points indicate mean growth rates for each site by population density. Horizontal error bars are standard errors of site population density means. Vertical error bars are standard errors of site mean growth rates.
Table 2.
Model selection summary for the eight models explaining growth rate variation of Komodo dragons at ten sites in eastern Indonesia, 2002-2010.