This scientific-popular book gives a detailed information about activity signs (tracks, scats, dens, other shelters, grooming spots, marking, feeding remains etc.) of mammals in the European forest zone. The materials, skills and knowledge for the book were gradually gained by the author during almost 40 years in Naliboki Forest in the central-western part of Belarus and in Paazierre Forest in the northern part of Belarus. After the short Introduction (Chapter 1), mammal activity signs are represented for various ecological situations. These items compose Chapter 2. Chapter 3 gives basic activity signs for the whole mammal species diversity in the European forest zone including both native and exotic species.