The major plasma esterase in the tammar wallaby was identified as a ca
rboxylesterase by inhibition studies and polymorphism with six variant
s was observed by isoelectric focusing (pH 4.2-4.9), followed by stain
ing for esterase activity. Family studies demonstrated an inheritance
of six codominant alleles, ESA,B,C,D,E,F, and population studies revea
led marked differences in the allele frequencies in five Australian po
pulations of tammar wallabies.