Inbreeding occurs when closely related individuals mate with one another. Inbreeding may happen in a small population or due to other isolating factors; the consequence is that little new genetic information is added to the gene pool. Thus recessive, deleterious alleles become more plentiful and evident in the population. Manifestations of inbreeding are known as inbreeding depression.A general loss of fitness often results and may cause high infant mortality, and lower birth weights, fecundity, and longevity. Inbreeding depression is a major concern when attempting to protect small populations from extinction.