Kaniv reserve covers the right bank upper part (14.15 square km), the flood land islands of Kruhlyk and Shelestiv (4,96 square km), and the Zmiini islands near the left bank of the Dnieper (1.16 square km). A total of 51 mammal species have been recorded in the reserve. Most have been observed in the upper part (45), fewer on the flood land islands (33) and least on the Zmiini islands (27). Only one third of all species have been recorded from all parts of the reserve (19). Three rare mammals are known from the reserve, and 6 of its species are included into "The Red Book of Ukraine". Two species are not resident, but only visit the reserve. On the islands, populations of hoofed mammals and predator mammals are more dense. Elk and wild pig use the islands only during the breeding season and when they are feeding young. The most favorable conditions for fox and raccoon are are on the flood land islands. In the upper part of the reserve, in very shadowed hornbeam-beech forests, these species live along the reserve border and are rather rare. Mouse-like rodents form specific populations in some habitats, and these differ in species composition and abundance. Even in the upper part of the reserve on meadow-steppe plots with different plant species, rodent communities and their dominant species vary. Species diversity and abundance of mammals thus depends first of all on habitat (availability of protection, food etc.). Sharp fluctuations in population numbers are characteristic for mouse-like rodents, some insectivores (mainly due to abiotic agents) and hoofed mammals, which frequently cross the border of the reserve because of unsufficient space for survival outside, mainly due to human pressure.