Carbonic anhydrase ($CA_{1}$) enzyme variations of one hundred and forty six specimens of $Mus~ domesticus$, $Mus~ macedonicus$ (House mice) and one hundred and twenty specimens of $Rattus~ rattus$ (Roof rat) and $Rattus~ norvegicus$ (Brown rat) were examined by the field work conducted in 23 localities in the line of Ankara-Bolu Zonguldak. It was determined that $CA_{1}$ was fixed to two different homozygous alleles in both house mouse species. In the roof rat samples, $CA_{1}$ was fixed to two homozygous alleles at different frequencies in two groups formed according to the colour of the back fur. A single homozygous allele was detected at the $CA_{1}$ locus of brown rat samples. It was observed that these four species were separated in the UPGMA tree made according to allele frequencies. In this respect, it was evaluated that $CA_{1}$ could be a molecular marker that can be used to distinguish these species.