Seasonal changes in hippocampus size and spatial behavior in mammals and birds

The hippocampus of mammals and birds is involved in the processing of spatial information about their environment. Its size positively correlates with spatial activity with home range size in particularly if closely related species in both mammals and birds are compared. Can this pattern also be seen in ontogenesis, the individual life of animals, under cyclic and seasonal changes in behavior that are typical for many mammal and bird species? This brief review of data obtained through observations of natural populations and laboratory experiments offers evidence that hippocampus morphology and spatial behavior can simultaneously undergo seasonal phenotypic changes. With respect to seasonal dynamics, a statistically significant positive correlation between hippocampus size, home range size, locomotor activity, and exploratory behavior in small mammals is shown. New information has been found about seasonal changes in the hippocampus and spatial behavior related to food caching and brood parasitism in some bird species. Many facts obtained during observations of representatives of different taxonomic groups among animals give evidence that, in their ontogenetic process, there are one-way and interrelated seasonal changes of spatial behavior and morphology of the part of the brain that functionally conditions this behavior. The morpho-physiological mechanisms of seasonal changes in the hippocampus are analyzed.