Reproductive Behavior

Elaborate behaviors have evolved around the process of reproduction in many animals. These behaviors often differ between males and females. Differences generally center around attracting or competing for a mate. Reproductive behaviors may help animals recognize members of the same species, or members of the opposite sex. They may also be indicators of good health.

Sexual Selection

Animals generally choose mates based on certain traits or behaviors. This tendency creates a process called sexual selection. Traits or behaviors that increase an individual's ability to acquire a mate will appear with increased frequency in a population. The female bowerbird in Figure 44-8 chose this male based on his ability to build and decorate an attractive bower. His offspring will probably build bowers in a similar way.

Another means of attracting a mate involves certain behaviors, called courtship. In some species, courtship can include a complex series of behaviors called rituals. Courtship rituals are instinctive behaviors that are performed the same way by all members of a population and that may help animals identify receptive mates of the same species. Most courtship rituals consist of specific signals and responses that indicate willingness to mate.

Mating Systems

Mating systems increase the likelihood that young will survive. Male polygamy (more than one female), monogamy, and female polygamy (more than one male) are reproductive strategies that are determined primarily by the amount and type of parental care required by the young. Monogamy is favored in situations in which there are advantages to both parents raising the young. In birds, for example, it would be difficult for one parent to protect the nest and the hatchlings while also providing enough food for the young. This type of situation may explain why birds tend to be monogamous.

Parental Behavior

Parental investment is the time and energy an individual must spend to produce and nurture offspring. The benefit of parental care is that it increases the likelihood that young will survive to adulthood. The costs are that parental care can generally only be provided for a small number of young because of the large energy investment by the parent. Usually, females invest more in parental care than males do. In mammals like the whales in Figure 44-9, the female carries the young within her body during development, and after birth the young must nurse. In some species, the male provides the majority of parental investment. Male seahorses, for example, carry the eggs until they hatch.

Word Roots and Origins monogamy from the Greek mono, meaning "one," and gamus, meaning "marriage"

figure 44-9

Whales provide extensive parental care for their young. Baby mammals are often born rather helpless and learn about their environments from parents.

Whales provide extensive parental care for their young. Baby mammals are often born rather helpless and learn about their environments from parents.

figure 44-10

Ants use chemical communication in the form of a pheromone trail, which other ants will follow. The ants above are following a trail on a leaf.

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