Wannan ya faru ne saboda dalilai guda biyu, na farko da aka tabbatar a cikin cat hybrids, cewa lokacin da chromosome ƙidaya na namiji ne mafi girma, haihuwa rates sauke. The ƙananan samar da progesterone na jenny kuma iya haifar da farkon embryonic hasara. Bugu da kari, akwai dalilai ba kai tsaye alaka da haifuwa ilmin halitta. Saboda daban-daban mating hali, Zebra jacks ne sau da yawa mafi shirye su rufe mares fiye da stallions ne don haifuwa jennies. Bugu da ƙari, mares ne yawanci ya fi girma fiye da jennies kuma ta haka ne suna da mafi isa dakin domin samar da zuriya a cikin mahaifa, sakamakon haka a cikin wani ya fi girma hinny.
64 ƙwayoyin halittar jini