The changes in vegetation that result when feral horses overpopulate a region affects bird species by removing plants upon which they feed, as well as altering the habitat of the birds and their prey. Feral horse grazing is also linked to a decline in reptiles and amphibians due to habitat loss. In addition, the grazing and trampling near waterways influences aquatic fauna. In areas frequented by horses, crab densities are higher, increasing the propensity for predation on fish. As a result, fish densities decline as the removal of vegetation renders them more susceptible to predation.