IWMC.org - 2nd Symposium - Terrestrial Resources

Commercial Use and Export of Chamaeleonid and Phelsumid Lizards in Madagascar – An Experiment in Adaptive Management Robert W. G. Jenkins Chair of the CITES Animals Committee

Although detailed demographic studies of natural populations of Phelsuma spp, Furcifer spp and Calumma spp are lacking, data on clutch size, clutch frequency, incubation period, and age at first reproduction are available for several species from captive breeding studies. These data suggest that the demographic parameters of Phelsuma, Furcifer and Calumma follow the same general patterns determined for many other small to medium-sized lizards. Most lizards similar in size to phelsumas and chameleons that have been studied become sexually mature at 8-18 months of age. Data on captive phelsumas verify that the smaller species can begin breeding as young as six months and larger-bodied species in the range of 8 - 14 months. Even the larger-bodied chameleons may begin breeding as young as six months. Phelsuma spp produce only two eggs per clutch, but each female can produce up to ten clutches annually. Therefore, a population as few as 1,000 females potentially could produce 20,000 offspring annually -10,000 of which can be expected to be females. Even if all the adult females in the population survived to breed in only one year, only 10 per cent of the neonates would have to survive to maturity in order to sustain the population at 1,000 adult females. However, in reality some percentage of adult females will survive to breed in subsequent years, therefore fewer than 10 per cent annual survival of neonates would actually be needed to sustain populations.

Using 10 per cent as a rough estimate of survivorship necessary to maintain population levels, at least 18,000 phelsumas (males and females) per year could be removed from a population that included 1,000 mature females without seriously affecting the population. Because of natural mortality (predation, disease, etc) and the tendency to collect larger adult lizards, commercial collectors should not be allowed to take as many as 18,000 individuals from this hypothetical population. However removal of 1-5 per cent of the excess annual production (180-900 individuals) by commercial collectors is unlikely to have an adverse affect even if some adult females are included. Indeed, limited selective removal would be counter-balanced to some extent by decreasing natural mortality caused by density-dependent factors. Furthermore, the removal of a component of the population may promote immigration from adjacent populations.

Similar calculations can be done for chameleons, in which several Malagasy species like Furcifer pardalis have been shown to mature very quickly (about 6 months of age) and have high natural mortality. In such cases the majority of individuals are not expected to survive more than one year in nature. Although chameleons have fewer clutches per year (4-6) than Phelsuma spp, the mean clutch size is much larger (8- 50 eggs per clutch).

It should be apparent from the above that the export quotas that are being proposed are very conservative. Further indications of their conservative nature comes from two additional considerations. The estimates of relative size of geographic distribution and confirmed sites of occurrence, are minimal. Additional surveys will undoubtedly reveal many new populations and expand the geographic distributions of most species.

Even if each species averages only one individual per square kilometre over its entire estimated range, the annual export quotas that have been proposed are still far below the total populations sizes. For example, at one individual per km2, the total populations of Phelsuma modesta and Furcifer parsoni are calculated to be 15,000 and 60,000 individuals respectively. The proposed export quota for each of these species (1,800 and 1,000 respectively), represents 12% and 1.6% respectively of total population size. Both species, particularly P. modesta, are known to exist in far greater numbers than the estimated one individual per km2. Although Phelsuma modesta has one fourth the geographic range size of Furcifer parsoni, this species has been assigned a higher
export quota because it survives well in degraded habitat (P. modesta is extremely abundant occurring commonly on hotel shrubbery and walls, whereas Furcifer parsoni does not do well in degraded habitats).

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