Mammals of the National Parks

The mammals are a small group and are relative newcomers. Mammals arose from reptiles. Mammals are hairy, milk-producing, warm-blooded animals. Most mammals give birth to living young. Many mammals have a home range and a defended area, evidence of territoriality. Plants are consumed by the majority of mammals. Types of feeders are herbivores and carnivores. No animal is safe from aggression. Flight is a commonly employed defense mechanism. Some animals may remain motionless to escape detection by a predator. Thick skin may be defensive in nature. Additional defense means are coloration and quills. Specialized defenses include noxious odors, noise, teeth, hoofs and claws, horns and antlers, poison, and warning display. There are various levels of dormancy. In deep hibernators metabolism may sink to 1/75 of its active rate. The amount of weight loss varies with the species. In order to have social structure among animals there must be communication. Sight communication may be of great importance in addition to or in place of sound. Sound mechanisms may be used for both communication and orientation. Social behavior may help an animal to survive and reproduce. A population grows in the same fashion as the animal. Influences favoring population growth may be genetic or ecological. As a population increases its predators increase. Social structure helps to alleviate stress. From the standpoint of evolutionary biology, the animal's function is to reproduce. In mating behavior animals vary from promiscuity to monogamy. Gestation in mammals ranges from eight to twelve weeks to two years. The number of young is lower in animals with a better survival potential.