29.2 Animals in Their Environments Lesson Overview 29.2 Animals in Their Environments

THINK ABOUT IT   As twilight falls on a coral reef, its inhabitants act like New York commuters during evening rush hour. Daytime “workers” head for home. For a time, twilight predators menace any straggling daytime fishes disoriented by the gloom. Then the night creatures emerge and take over the coral metropolis. At dawn, the cycle reverses.

Behavioral Cycles How do environmental changes affect animal behavior?

Behavioral Cycles How do environmental changes affect animal behavior?   Many animals respond to periodic changes in the environment with daily or seasonal cycles of behavior.

Behavioral Cycles Behavioral cycles that occur daily, like those on coral reefs, are called circadian rhythms. You sleep at night and attend school during the day in another example of a circadian rhythm.

Behavioral Cycles Other cycles are seasonal. For example, many species are active during spring, summer, and fall, but enter into a sleeplike state, or dormancy, during winter. Dormancy allows an animal to survive periods when food and other resources may not be available.

Behavioral Cycles Another type of seasonal behavior is migration, the seasonal movement from one environment to another. Migration allows animals to take advantage of favorable environmental conditions. For example, each year, green sea turtles migrate back and forth between their feeding grounds on Brazil’s coast and their nesting grounds on Ascension Island.

Social Behavior How do social behaviors increase an animal’s evolutionary fitness?

Social Behavior How do social behaviors increase an animal’s evolutionary fitness?   Choosing mates, defending or claiming territories or resources, and forming social groups can increase evolutionary fitness.

Courtship For sexually reproducing animal species, evolutionary survival requires individuals to locate and mate with another member of its species at least once.   Courtship is behavior during which members of one sex advertise their willingness to mate, and members of the opposite sex choose which mate they will accept. Typically, males send out signals—sounds, visual displays, or chemicals—that attract females.

Courtship In some species, courtship involves a ritual, which is a series of behaviors performed the same way by all members of a population for the purpose of communicating.   Most rituals consist of specific signals and responses that continue until mating occurs.

Courtship For example, gannets bond by engaging in “beak-pointing”—intertwining their necks while pointing their beaks to the sky.

Territoriality and Aggression Animals often occupy a specific area, or territory, that they defend against competitors. Territories usually contain resources, such as food, water, nesting sites, shelter, and potential mates, which are necessary for survival and reproduction.   If a rival enters a territory, the “owner” of the territory attacks in an effort to drive the rival away.

Territoriality and Aggression For example, grizzly bears will often mark their territories with their fur and scent by scratching their backs on rough surfaces, such as trees or signposts.

Territoriality and Aggression While competing for resources, animals may also show aggression, threatening behaviors that one animal uses to exert dominance over another.   For example, fights between male elephant seals over territory and of females often leave both rivals bloodied.

Animal Societies An animal society is a group of related animals of the same species that interact closely and often cooperate.   Societies can offer safety from predators and can also improve animals’ ability to hunt, to protect their territory, to guard their young, or to fight with rivals.

Animal Societies Members of a society are often related to one another.   The theory of kin selection holds that helping relatives can improve an individual’s evolutionary fitness because related individuals share a large proportion of their genes. Helping a relative survive therefore increases the chance that the genes an individual shares with that relative will be passed along to offspring.

Animal Societies The most complex animal societies (other than human societies) are found among social insects such as ants, bees, and wasps.   In social insect colonies, all individuals cooperate to perform extraordinary feats, such as building complex nests. Members of insect societies also share a high percentage of genes.

Animal Societies All workers in an ant colony are closely related females. Worker ants are sterile. For this reason it is advantageous for them to cooperate to help the queen (their “mother”) reproduce and raise the other workers (their “sisters”). Male ants function only to fertilize the queen’s eggs.

Communication How do animals communicate with others in their environments?

Communication How do animals communicate with others in their environments?   Animals may use a variety of signals to communicate with one another. Some animals are also capable of language.

Communication Often, animal behavior that involves more than one individual requires communication—the passing of information from one organism to another. The specific techniques that animals use depend on the types of stimuli their senses can detect.

Visual Signals Many animals use visual signals to communicate.   In many animal species, males and females have different color patterns, and males use color displays to advertise their readiness to mate. Some animals, such as fireflies, even send signals using light generated within their bodies.

Chemical Signals Animals with well-developed senses of smell can communicate with chemicals.   For example, some animals release pheromones, chemical messengers that affect the behavior of other individuals of the same species, to mark a territory or to signal their readiness to mate.

Sound Signals Many animals use visual signals to communicate.   In many animal species, males and females have different color patterns, and males use color displays to advertise their readiness to mate. Some animals, such as fireflies, even send signals using light generated within their bodies.

Language The most complicated form of communication is language. Language is a system of communication that combines sounds, symbols, and gestures according to rules about sequence and meaning, such as grammar and syntax.   Many animals, including dolphins, elephants, and primates, have complex communication systems. Many species, including honeybees, convey complex information using various kinds of signals.