 Quaggas have been reported gathering into herds of 30 – 50 individuals and sometimes travelled in a linear fashion . They may have been sympatric with Burchell 's zebra between the Vaal and Orange rivers . This is disputed , and there is no evidence that they interbred . It could also have shared a small portion of its range with Hartmann 's mountain zebra ( Equus zebra <unk> ) . 
