It is shown that crude oil induces a nonspecific response of the organism of small mammals to the pollution, which is a stress-factor for the animals. Metabolism, including the energy metabolism, intensifies, hematopoiesis processes are affected, lymphocytes migration to the bloodstream increases, and the proportion of pycnomorphic cells in different tissues grows, indicating a direct toxic effect of oil, and overall escalation of the stressful situation. Adaptation was found to have specific features depending on the species, and on sex and age within a species. The hypothalamic-pituitary-adrenal system plays an important part in the process of adaptation.