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 The daily changeover on coral reefs is an example of regular cycles in nature.   Many animals respond to periodic changes in the environment with daily or seasonal cycles of behavior. Circadian rhythm - behavioral cycle that occurs daily ex. Sleep at night and work during the day

Behavioral Cycles Dormancy – aka hibernation – behavioral cycle that occurs seasonally active during spring, summer, and fall, but enter into a sleeplike state during winter allows an animal to survive periods when food and other resources may not be available

Behavioral Cycles Migration – the seasonal movement from one environment to another many species of animals migrate – often over long distances allows animals to take advantage of favorable environmental conditions ex. – 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 Whenever birds sing, sheep butt heads, or chimpanzees groom each other, they are engaging in social behavior. Social behaviors can increase an animal’s evolutionary fitness. This includes:   choosing mates (courtship) defending or claiming territories or resources (territoriality & aggression) forming social groups (animal societies & kin selection)

Courtship Sexual reproduction requires individuals to locate and mate with another member of its species at least once. This ensures evolutionary survival.   Courtship – behavior during which members of one sex (usually males) advertise their willingness to mate, and members of the opposite sex (usually females) choose which mate they will accept typically, males send out signals—sounds, visual displays, or chemicals—that attract females sometimes involves an elaborate series of behaviors, or 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 blue-footed boobys “dance” by alternately lifting each of their feet

Territoriality and Aggression Many animals behave in ways that prevent other individuals from using limited resources. Often these animals occupy a specific area. Territory – a specific area that animal occupies defends against competitors 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 (ex. zebras are safer when in a group) improve animals’ ability to hunt, to protect their territory, to guard their young, or to fight with rivals. For example, in African dog packs, adult females take turns guarding all the pups in the pack, while the other adults hunt for prey.

Animal Societies Members of a society are often related to one another. Elephant herds consist of mothers, aunts, and their offspring. Males are kicked out when they reach puberty.   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 extreme examples of relatedness, and 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 In an ant colony, all workers in the colony are closely related females – which means they share a large proportion of each others’ genes. 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 Because social behavior involves more than one individual, it requires communication — the passing of information from one organism to another. Animals may use a variety of signals to communicate with one another. Some animals are also capable of language. 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. Many animals have eyes that sense shapes and colors at least as well as humans do. Squids, which have large eyes, change their color to broadcast a variety of signals.   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, including insects, fishes, and many mammals, can communicate with chemicals.   For example, some animals (lampreys, bees, and ants) 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 Most animal species that have vocal abilities and a good sense of hearing communicate using sound. For example, dolphins communicate in the ocean using sound signals. Bottlenose dolphins each have their own unique “signature” whistle that functions to inform others of who is sending the communication. Elephants also make distinctive sounds, both with their vocal apparatus and with their feet, that can identify them. Elephants can send messages that the recipient feels rather than hears.

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. Some even seem to have “words” – calls with specific meanings such as “lions on the prowl.” Many species, including honeybees, convey complex information using various kinds of signals. However, untrained animals don’t seem to use the rules of grammar and syntax we use to define the human language.