Answers to Review Questions

1. Young mammals play to teach them behaviors that will be useful when they get older as they approach and reach adulthood. No wolf puppies get hurt during such play, but they bite mainly around neck, throat, & hind legs just like hunting adults do. When older, they will hobble prey by breaking the large tendons in the hind legs of their prey. They will then go for the throat of their prey to kill it. The play teaches the young wolf predator skills useful to adult wolves and allows these skills to be practiced. Fox puppies exhibit similar behavior, but with a twist. In lean times, the play between young foxes intensifies; in extremely lean times, the stronger pups kill and eat the weaker ones. This is a somewhat brutal occurrence, but it ensures the survival of at least a few young foxes so that they can send their genes into the next generation. In addition to practicing hunting skills, wolf puppies establish social bonds and dominance hierarchies that will define pack structure for years to come. They also learn to handle competition.

3. Kittens and puppies play in characteristic but different ways; these two mammals at the same stage of life react differently when presented with the same stimulus. If you present a kitten with a ball of yarn, invariably, it draws back its head and bats the yarn with extended claws. They are generally silent as they play and their tails twitch. Puppies, on the other hand, are most likely to pounce flat-footed on a ball of yarn. They also bite, bark, and their tails wag. Moths instinctively move toward a light. Dogs bark at strangers more or less instinctively. Migratory behavior in birds appears to be instinctive, especially its timing which is normally quite precise. In the spring in the Northern Hemisphere, the days start to lengthen. As this happens, the birds in Central and South America change. Their behavior becomes restless; they migrate to nesting grounds hundreds of miles from their wintering grounds. As mentioned earlier, movements are precise. For example, swallows that winter in South America arrive back at Capistrano, CA within a few days of March 19. Many think that the begging of a hatchling bird for food the first time it is offered by a parent is instinctive. Another example of an instinctive behavior is seen in geese. If an egg rolls out of a goose's nest, the female will retrieve it; the behavior will continue even if the egg is removed. The salivation seen in dogs when presented with food is also instinctive. The withdrawal of tube worms into their tubes when a shadow passes over them is an instinct as well.

5. Those who thought nature was the explanation for behavior (ethologists) believed that all behavior was innate and instinctive. Those who believed in nurture (comparative behaviorists) believed that the environment was largely responsible for behavior. An example of their positions is the way they interpret begging behavior in baby birds. The first time a hatchling bird is approached by a parent, it begs for food; all baby birds of a particular species beg in exactly the same way. Baby birds did not need to learn this behavior, they appear to be born with it. It is clearly an innate behavior according to the ethologists. Comparative behaviorists say the parents teach the young to beg by stuffing food in their open mouths. When later experiments indicated that before hatching, birds make and respond to noises of their nest mates and adults, the comparative behaviorists wondered if young birds could learn to beg prenatally. It was hard for ethologists to accept that innate behaviors could be modified by learning and equally difficult for comparative behaviorists to accept that genetic factors could dominate the learning experiences of an animal. The controversy between the nature and nurture positions raged for over a decade and stimulated numerous experiments on each side. These studies advanced considerably our understanding of animal behavior. As a result, the distinction between the two fields narrowed, leading to the belief that both innate factors and learning are important.

7. Yes, behavioral traits can evolve. A good example from nature is the case of California garter snakes. The species of garter snakes in California appears in two populations. The coastal population of garter snakes primarily eats banana slugs, which they sense by flicking their tongues to detect odor of the banana slugs. These coastal garter snakes respond appropriately to cotton swabs soaked in essence of slug. Inland snakes, on the other hand, eat mostly tadpoles and small fish; they ignore banana slugs even if they are the only food available. The ability to sense slugs has a genetic basis; if the offspring of females from one population are crossed with males from the other population, they exhibit intermediate abilities to sense the slugs. This feeding behavior may have evolved in the following way. Assume that the inland population was the original population; since banana slugs are not native to North America, this is a likely assumption. Sometime after the slug's introduction, garter snakes started to move to coastal regions. A few of the migrating snakes possessed a rare allele allowing them to detect the odor of banana slugs. These snakes took advantage of the new food source that happened to be abundant in coastal regions. Consequently, they survived and left more offspring in the next generation than snakes that rejected the slugs. Thus, the slug-detecting allele dominates at the coast, but is rare inland.

9. The physiological needs of an organism can influence its behavior. In fact, the needs of an organism may vary seasonally or if it changes its location in some way; when an organism's needs change for such reasons their behavior will usually vary accordingly. Examples would be organisms exhibiting food-seeking behavior when they are hungry or animals that are reproductively active only during certain parts of the year. For instance, during colder seasons, the testicles of many temperate and northern males are relatively small, inactive, and recessed into the body cavity. During these seasons, males are generally gregarious, tolerant of other males and non-territorial. As the seasons change and it gets warmer, their physiological state and behavior change. The testicles enlarge, descend from the body cavity and begin to actively produce sperm and male hormones. The males become generally intolerant of other males, more territorial and solicitous to females. Other environmental changes, like the lengthening of days, stimulate the production of certain hormones in the brain which, in turn, control changes in both the animal's physiology and behavior.

11. An evolutionarily stable strategy is that which results in the most offspring or relatives. By definition, it cannot be replaced or bettered once most individuals of a population adopt it unless environmental conditions change. An example would be the pack hunting of lions or the solitary hunting style of leopards in which they ambush their prey.

13. Piloting involves sequential recognition of landmarks by an organism to get itself to its destination. Compass orientation, on the other hand, involves moving in a particular direction for a prescribed length of time. For return trips, animals reverse direction and travel for similar times or distances. Unlike piloting, landmarks do not seem to play a major role. The animals seem to have an internal clock and compass and/or a way of measuring the distance traveled. True navigation involves finding the way by means of an internal map coupled with an internal compass. Piloting may not require "knowing" the direction of travel as long as each successive landmark is visible or able to be sensed from the previous one beginning at the start of the journey. If any landmark can not be sensed at any point along the trip, the animal must have somewhat of a sense of direction to get it to the next landmark. Compass orientation requires knowledge of direction and the ability to measure time and/or distance as, to some extent, does true navigation. True navigation may make use of all three elements: landmarks, a clock, and a compass, but may depend on one more than another. All three levels of orientation require that the animal has some sort of "program" on board that will get it to its destination, a "flight plan", if you will. Furthermore, the goal of each is the same - for the animal to get where it is going.

15. First of all, to avoid becoming food, animals must be vigilant. It also helps if they are difficult to see. Many animals are cryptically colored to blend into their backgrounds so that they are less detectable by predators. Many animals will couple this cryptic coloration with an ability to remain immobile. They will often freeze upon detecting a predator. Some animals change their coloration to match seasonal or momentary changes in the environment, making them more difficult to see. Many animals avoid predators by resembling some object that a predator is likely to ignore. Some organisms possess body markings that resemble eyes or antennae at the rear of their wings or bodies. This will often prevent a predator from approaching them from behind and result in a prompter warning of the predator's approach. Some animals possess chemical or physical defenses like noxious odors, bad taste, poisonous secretions, stingers, or antlers to discourage predators from seeking them out for a meal. These animals often have striking or distinctive colorations that predators can remember. Some animals resemble other animals that predators find undesirable, a phenomenon called mimicry. This may keep the predators away from them. Animals may simply run away from a predator or signal the predator that they are fully capable of escape or that they are capable of inflicting injury on a potential predator. Some animals startle predators by remaining still until a predator is almost upon them at which point they make a loud noise or sudden motion, startling the predator long enough to allow them to escape. Group behavior is also used as protection against predators. It is difficult for predators to focus on a single individual as prey when it is located in a group. Groups thus can confuse predators.

17. Monogamy occurs when only one male breeds with only one female. Eider ducks and Canada geese are both monogamous although their relationships persist for different lengths of time. In some cases, monogamous pair bonds persist until one or both of the partners die. In other cases, the bonds last for shorter periods of time, e.g. one mating season. Polygyny occurs when one male mates with multiple females; this is the most common vertebrate mating system. Prairie chickens, moose, lions, elephant seals, and hummingbirds are examples of organisms that exhibit polygyny. Polyandry occurs when individual females mate with numerous males; this is the rarest mating strategy seen. Phalaropes, small shore birds, exhibit this mating strategy.

19. Almost any mode of behavior can communicate. Sounds are especially important for many species - dogs bark, birds sing, frogs croak, crickets chirp, etc. Behaviors that are intended to be seen are important to many animals. A dog defending his yard from an intruder stares, stands stiffly, raises his tail and neck hairs. Odors are the basis of much animal communication. Female moths release pheromones on the night air to attract males. Canids have a complex system of glands near the anus that conveys much information on topics such as sex, sexual receptivity, willingness to fight, age, and maybe individual identity. Many animals mark territorial perimeters with odoriferous chemicals secreted in the urine or by special glands. Touch is also a means of communication. Primate social grooming is an example of this. Unusual forms of communication are found in animals living in specific environments. Animals living in perpetually dark environments often generate their own light, like phosphorescent fish living in ocean depths, glowworms, and fireflies. Certain frogs and insects tap out messages in soil or wood to attract mates and water striders tap out vibrations on pond surfaces to attract mates; a different pattern of vibrations warns away competitors. Certain fish living in highly turbid waters generate and communicate by electric fields. They are similar in that they convey information. All of these types of communication lead to modifications in the recipient's behavior that benefits the sender of the communication. Finally, in all of these types of communication it is the intent of the sender to send the information. The major difference between them is the nature of the signals and the specific message being sent. The type of information being sent with these signals varies quite a bit. Some of the easiest behaviors to recognize are those used in agonistic encounters, actions involved in conflict. This type of behavior occurs both within and between species. Within the species, these displays are designed to resolve conflicts with a minimum amount of injury to those involved in conflict. Such agonistic behavior within a social group will often lead to the establishment of dominance hierarchies. Such dominance hierarchies create group stability and efficiency. They minimize conflicts and help to organize such things as feeding under various environmental conditions and mating and appear to enhance a species' chances at survival. Animals about to mate also communicate; these communications often start with behaviors that are very similar to agonistic encounters. In many birds, these displays do more than establish pair bonds; the stimulus-response give-and-take of mating rituals is necessary in order for gametes to mature. Communication is also the basis for individual and group identification. It helps to maintain the cohesiveness of flocks of birds and helps to maintain the structure in insect societies. Safety is also a potential benefit of sociality; it has led to two forms of behavior: alarm calls and distress signals. The first member of a group to spot danger will often emit a short, explosive burst of sound to warn the other members of the group. While placing himself at risk, it can save other members of the group from danger. Many animals, when trapped or cornered by a predator, vocalize loudly. Among social birds and mammals, this often results in drawing others toward the threatened individual. The flock may mob or otherwise confuse the predator into releasing their prey. The behaviors that mark these communications like those of agonistic interactions or mating behaviors are often similar in structure. The purpose of all of such behaviors is to enhance the survival of and maintain order within the species. Thus, the purpose of such communications while accomplished by different means (chemical, behavioral, etc.) is the same. The different behaviors address different aspects of life: reproduction, survival, escape from predators, maintenance of social order, etc.