Comparison of the 87Sr/86Sr signatures of archaeological osteological material with features of geological provinces can be applied to determine the places of birth and living of individuals. Such reconstructions were conducted for both humans and domestic animals at the Late Bronze–Early Iron Age sites of the Crimea. The Crimean Peninsula is an interesting testing polygon for such research because it is characterized by a diverse geological situation within a relatively small area. The initial data allowed us to distinguish between three groups of mobility at the Bai-Kiyat I settlement and two groups at the Dolgii Bugor site. The Bai-Kiyat I site is located on the seacoast, so the proxy line for this area will correspond to the value of the ratio of strontium isotopes in seawater (0.7092). The inhabitants of this settlement, including a child from a burial on the settlement, are characterized by this value of strontium isotopes. Other groups include nonlocal people. The data obtained indicate that the steppe zone of the Northern Black Sea region was an ecumene, within which active mobility of groups of people was registered. This mobility is associated primarily with the pastoral type of economy in the period from the Chalcolithic to the Early Iron Age.