Abstract
M.Sc.
The Nile crocodile (Crocodylus niloticus) has been classified as vulnerable in the South
African Red Data Book. The large numbers of crocodile farms in southern Africa provide
a potential source of animals for restocking, and conservation authorities would support
such measures if the genetic implications thereof can be assessed. The purpose of this
study was to compare the levels of genetic variation in three populations of crocodiles
bred for commercial utilisation with levels in a wild crocodile population in South Africa
and those reported for wild crocodiles in Zimbabwe. Gene products of 53 protein-coding
loci were analysed by horizontal starch gel electrophoresis. Low levels of polymorphism
(0 to 3.8%) and heterozygosity (0 to 0.02) were present in all the populations studied, but
the wild populations exhibited higher levels of variation than the commercial populations.
Significant (P<0.05) differences in allele distributions occurred at three loci (GPI-A,
PEP-Bl and MDH-2) in the populations studied, but no fixed allele differences were
observed. This result indicates that some populations of commercially bred crocodiles are
not suitable for release into wild populations where they could interbreed with wild
crocodiles because the induced changes in genetic profile may have important genetic,
physiological and/or ecological implications for the wild population. A similar situation
will result if the crocodiles escape from crocodile farms, either during flooding or due to negligence.