BIOLOGY Life on Earth WITH PHYSIOLOGY Tenth Edition Audesirk Audesirk Byers

Transcription

1 BIOLOGY Life on Earth WITH PHYSIOLOGY Tenth Edition 25 Animal Behavior Audesirk Audesirk Byers Lecture Presentations by Carol R. Anderson Westwood College, River Oaks Campus

2 Chapter 25 At a Glance 25.1 How Do Innate and Learned Behaviors Differ? 25.2 How Do Animals Communicate? 25.3 How Do Animals Compete for Resources? 25.4 How Do Animals Find Mates? 25.5 Why Do Animals Play? 25.6 What Kinds of Societies Do Animals Form? 25.7 Can Biology Explain Human Behavior?

3 25.1 How Do Innate and Learned Behaviors Differ? Behavior is any observable activity of a living animal Some examples of behavior include Moths fly to a light Honeybees fly to a cup of sugar-water Bluebirds sing Wolves howl Frogs croak Humans dance, play sports, and wage wars

4 25.1 How Do Innate and Learned Behaviors Differ? Innate behavior can be performed without prior experience Innate behaviors are performed in reasonably complete form the first time an animal of the right age and motivational state encounters a particular stimulus For example, a red squirrel will attempt to bury a nut when presented with it for the first time

5 25.1 How Do Innate and Learned Behaviors Differ? Innate behavior can be performed without prior experience (continued) Some innate behaviors can be recognized by their occurrence immediately after birth, before any opportunity for learning presents itself The female cuckoo birds lay their eggs in the nests of other bird species to be raised by the unwitting adoptive parents After a cuckoo egg hatches, the cuckoo chick will display the innate behavior of shoving the nest owner s eggs out of the nest to eliminate competition for food

6 Figure 25-1 Innate behavior A cuckoo chick ejects an egg A foster parent feeds a cuckoo

7 25.1 How Do Innate and Learned Behaviors Differ? Learned behaviors require experience Natural selection may favor innate behaviors in many circumstances A gull chick pecks at its parent s bill after hatching The capacity to make changes in behavior on the basis of experience is called learning An example of learning is the process by which a human learns language Another example is a sparrow s use of stars for navigation

8 25.1 How Do Innate and Learned Behaviors Differ? Learned behaviors require experience (continued) Habituation is a decline in response to a repeated stimulus A common form of learning is habituation, defined as a decline in response to a repeated stimulus The ability to habituate prevents an animal from wasting its energy and attention on irrelevant stimuli For example, a sea anemone will retract its tentacles when touched, but will stop retracting if the touch is repeated frequently

9 Figure 25-2 Habituation in a sea anemone After many touches, the anemone habituates and no longer responds Touched for the first time, the anemone withdraws

10 25.1 How Do Innate and Learned Behaviors Differ? Learned behaviors require experience (continued) Habituation is a decline in response to a repeated stimulus (continued) The ability to habituate is generally adaptive Humans habituate to nighttime traffic sounds, as country dwellers do to choruses of crickets and tree frogs Each may initially find the other s habitat unbearably noisy at first, but eventually stops responding to the novel sounds

11 25.1 How Do Innate and Learned Behaviors Differ? Learned behaviors require experience (continued) Conditioning is a learned association between a stimulus and a response A more complex form of learning is called trial-anderror learning in which new and appropriate responses to stimuli are acquired through experience

12 25.1 How Do Innate and Learned Behaviors Differ? Learned behaviors require experience (continued) Conditioning is a learned association between a stimulus and a response (continued) Animals are faced with naturally occurring rewards and punishments and can learn to modify their behavior in response to them A hungry toad that captures a bee quickly learns to avoid future encounters with bees

13 Figure 25-3 Trial-and-error learning in a toad A naive toad is presented with a bee. While trying to eat the bee, the toad is stung painfully on the tongue. Presented with a harmless robber fly, which resembles a bee, the toad cringes. The toad is presented with a dragonfly. The toad immediately eats the dragonfly, demonstrating that the learned aversion is specific to bees.

14 25.1 How Do Innate and Learned Behaviors Differ? Learned behaviors require experience (continued) Conditioning is a learned association between a stimulus and a response (continued) Trial-and-error learning is an important factor in the behavioral development of many animal species This type of learning plays a key role in human behavior For example, a child learns which foods taste good or bad, that a stove can be hot, and not to pull a cat s tail

15 25.1 How Do Innate and Learned Behaviors Differ? Learned behaviors require experience (continued) Insight is problem solving without trial and error In certain situations, animals seem to solve problems suddenly, without prior experience This kind of sudden problem solving is called insight learning, because it is superficially similar to how humans mentally manipulate concepts to arrive at a solution

16 25.1 How Do Innate and Learned Behaviors Differ? Learned behaviors require experience (continued) Insight is problem solving without trial and error (continued) In certain situations, animals seem to solve problems suddenly, without prior experience (continued) In 1917, Kohler showed that a hungry chimpanzee, without any previous training, could stack boxes to reach a banana suspended from the ceiling Epstein and colleagues performed an experiment showing that pigeons may be capable of insight learning

17 25.1 How Do Innate and Learned Behaviors Differ? There is no sharp distinction between innate and learned behaviors No behavior is totally innate or learned All behaviors are a mixture of the two

18 25.1 How Do Innate and Learned Behaviors Differ? There is no sharp distinction between innate and learned behaviors (continued) Seemingly innate behavior can be modified by experience Behaviors that seem to be performed correctly on the first attempt without prior experience can later be modified by experience For example, a newly hatched gull chick is able to peck at a red spot on its parent s beak, an innate behavior that causes the parent to regurgitate food for the chick to eat

19 Figure 25-4 Innate behaviors can be modified by experience

20 25.1 How Do Innate and Learned Behaviors Differ? There is no sharp distinction between innate and learned behaviors (continued) Seemingly innate behavior can be modified by experience (continued) Habituation can also fine-tune an organism s innate responses to environmental stimuli For example, young birds crouch down when a hawk flies over but ignore harmless birds such as geese Early scientists hypothesized that only the very specific shape of predatory birds provoked crouching

21 25.1 How Do Innate and Learned Behaviors Differ? There is no sharp distinction between innate and learned behaviors (continued) Seemingly innate behavior can be modified by experience (continued) Using an ingenious model, Tinbergen and Lorenz, two of the founding fathers of ethology, tested and confirmed the hypothesis

22 25.1 How Do Innate and Learned Behaviors Differ? There is no sharp distinction between innate and learned behaviors (continued) Learning may be governed by innate constraints Learning always occurs within boundaries that help increase the chances that only the appropriate behavior is acquired Example of this concept includes a robin, whose ability to learn songs is limited to those of its own species; the songs of other species are excluded

23 25.1 How Do Innate and Learned Behaviors Differ? There is no sharp distinction between innate and learned behaviors (continued) Learning may be governed by innate constraints (continued) The innate constraints on learning are perhaps most strikingly illustrated by imprinting Imprinting is a form of learning in which an animal s nervous system is rigidly programmed to learn a certain thing only during a certain period (sensitive period) of development

24 25.1 How Do Innate and Learned Behaviors Differ? There is no sharp distinction between innate and learned behaviors (continued) Learning may be governed by innate constraints (continued) Imprinting is best known in geese, ducks, and chickens These birds learn to follow the animal or object that they most frequently encounter during an early sensitive period In the laboratory, these birds may imprint on a toy train or other moving object

25 Figure 25-5 Konrad Lorenz and imprinting

26 25.1 How Do Innate and Learned Behaviors Differ? There is no sharp distinction between innate and learned behaviors (continued) All behavior arises out of interaction between genes and the environment Ethologists realize that no behavior can be caused strictly by genes or strictly by the environment The relative contributions of heredity and learning vary among animal species and among behaviors within an individual

27 25.1 How Do Innate and Learned Behaviors Differ? There is no sharp distinction between innate and learned behaviors (continued) All behavior arises out of interaction between genes and the environment (continued) The nature of the link between genetics and environmental components is not well understood, but some evidence exists Bird migration is learned by experience through navigation with celestial cues

28 25.1 How Do Innate and Learned Behaviors Differ? There is no sharp distinction between innate and learned behaviors (continued) All behavior arises out of interaction between genes and the environment (continued) Naive migrating birds, hatched only months earlier, travel properly from one location to another without any previous experience The birds, thus, appear to be born with the ability to migrate; it must be in their genes

29 25.1 How Do Innate and Learned Behaviors Differ? There is no sharp distinction between innate and learned behaviors (continued) All behavior arises out of interaction between genes and the environment (continued) Genetically controlled ability to migrate is supported by hybridization experiments with blackcap warblers This species breeds in Europe and migrates to Africa Birds from western Europe travel in a southwesterly direction to reach Africa Birds from eastern Europe travel to the southeast

30 25.1 How Do Innate and Learned Behaviors Differ? There is no sharp distinction between innate and learned behaviors (continued) All behavior arises out of interaction between genes and the environment (continued) If birds from the two populations are crossbred in captivity, however, the hybrid offspring migrate due south the intermediate between the orientations of the two parents This suggests that parental genes of which offspring inherit a mixture influence migratory direction

31 Figure 25-6 Genes influence migratory behavior breeding range winter range

32 25.2 How Do Animals Communicate? Animals frequently broadcast information Sounds uttered Movements made Chemicals emitted Level of aggression Readiness to mate If this information evokes a response from other individuals, and if that response tends to benefit the sender and the receiver, then a communication channel can form

33 25.2 How Do Animals Communicate? Communication is the production of a signal by one organism that causes another organism to change its behavior in a way beneficial to both Although animals of different species may communicate, most animals primarily communicate with members of their own species The ways in which animals communicate are astonishingly diverse Visual displays, sound, chemicals, and touch

34 25.2 How Do Animals Communicate? Visual communication is most effective over short distances Animals with well-developed eyes use visual signals to communicate Visual signals can be active, in which a specific movement or posture conveys a message Visual signals may be passive, in which the size, shape, or color of the animal conveys important information, commonly about its sex and reproductive state

35 Figure 25-7 Active visual signals

36 Figure 25-8 A passive visual signal

37 25.2 How Do Animals Communicate? Visual communication is most effective over short distances (continued) Active and passive signals can be combined Like all forms of communication, visual signals have both advantages and disadvantages On the plus side, visual signals are instantaneous and can convey a variety of messages in a short period, and they are quiet and unlikely to alert distant predators

38 25.2 How Do Animals Communicate? Visual communication is most effective over short distances (continued) Like all forms of communication, visual signals have both advantages and disadvantages (continued) On the negative side, visual signals are generally ineffective in dense vegetation or in darkness, and they are limited to close-range communication

39 Figure 25-9 Active and passive visual signals combined

40 25.2 How Do Animals Communicate? Communication by sound is effective over longer distances As with visual signals, sound signals are almost instantaneous But unlike visual signals, sound can be transmitted through darkness, dense forests, and murky water Acoustic signals can also be effective over longer distances than visual signals The low, rumbling calls of an African elephant can be heard by elephants several miles away

41 25.2 How Do Animals Communicate? Communication by sound is effective over longer distances (continued) Different messages can be conveyed by variations in sound pattern, volume, and pitch For example, ethologist Thomas Struhsaker, studying vervet monkeys in Kenya, found that they produced different calls in response to threats from each of their major predators: snakes, leopards, and eagles

42 25.2 How Do Animals Communicate? Communication by sound is effective over longer distances than visual signals (continued) The use of sound is not limited to birds and mammals Male crickets produce species-specific songs that attract female crickets of the same species The high-pitched whine of a female mosquito, as she prepares to bite, alerts nearby males that she may soon have the blood meal necessary for laying eggs

43 25.2 How Do Animals Communicate? Communication by sound is effective over longer distances than visual signals (continued) The use of sound is not limited to birds and mammals (continued) Male water striders vibrate their legs, sending speciesspecific patterns of vibrations through the water, attracting mates and repelling other males Many species of fish produce croaks, grunts, or other sounds

44 Figure Communication by vibration

45 25.2 How Do Animals Communicate? Chemical messages persist longer but are hard to vary Chemicals produced by individuals that influence the behavior of other members of the same species are called pheromones Pheromones can carry messages over long distances and take little energy to produce They are typically not detectable by other species, and so do not attract predators

46 25.2 How Do Animals Communicate? Chemical messages persist longer but are hard to vary (continued) Chemicals produced by individuals and that influence the behavior of other members of the same species are called pheromones (continued) They can act as a signpost, persisting over time and marking an animal s boundaries While chemicals convey critical information, fewer and simpler messages can be conveyed than with sight- or sound-based systems

47 25.2 How Do Animals Communicate? Chemical messages persist longer but are hard to vary (continued) Pheromones can cause immediate changes in the behavior of the detecting animal For example, foraging termites that discover food lay a trail of pheromones from the food to the nest, and other termites follow the trail

48 Figure Communication by chemical messages

49 25.2 How Do Animals Communicate? Chemical messages persist longer but are hard to vary (continued) Pheromones can also cause physiological changes in the detecting animal For example, the queen honeybee produces a pheromone, queen substance, which prevents other females in the hive from becoming sexually mature

50 25.2 How Do Animals Communicate? Chemical messages persist longer but are hard to vary (continued) Pheromones can also cause physiological changes in the detecting animal (continued) Mature males of some mouse species produce urine containing a pheromone that influences female reproductive physiology The pheromone stimulates newly mature females to become fertile and sexually receptive to the male

51 25.2 How Do Animals Communicate? Chemical messages persist longer but are hard to vary (continued) Humans have harnessed the power of pheromones to combat insect pests Controlling pests with pheromones has major environmental advantages over conventional pesticides, which kill beneficial as well as harmful insects and foster the evolution of pesticide-resistant insects

52 25.2 How Do Animals Communicate? Chemical messages persist longer but are hard to vary (continued) Humans have harnessed the power of pheromones to combat insect pests (continued) In contrast, each pheromone is specific to a single species and does not promote the spread of resistance, because insects resistant to the attraction of their own pheromones do not reproduce successfully

53 25.2 How Do Animals Communicate? Communication by touch helps establish social bonds Physical contact is used to establish and maintain social bonds among group members, as seen in humans and other primates Gestures include kissing, nuzzling, patting, petting, and grooming

54 25.2 How Do Animals Communicate? Communication by touch helps establish social bonds (continued) Communication by touch is not limited to primates In many other mammal species, close physical contact helps cement the bond between parent and offspring Species in which sexual activity is preceded or accompanied by physical contact can be found throughout the animal kingdom

55 Figure Communication by touch Bab oon s Lan d snai ls

56 25.3 How Do Animals Compete for Resources? The contest to survive and reproduce stems from the scarcity of resources relative to the reproductive potential of populations The resulting competition underlies many of the most frequent types of interactions between animals

57 25.3 How Do Animals Compete for Resources? Aggressive behavior helps secure resources A manifestation of competition for food, resources, or mates is aggression, or antagonistic behavior, between members of the same species Aggressive behaviors include physical combat between rivals, which can injure or kill the participants As a result, natural selection has favored the evolution of symbolic displays or rituals for resolving conflicts

58 25.3 How Do Animals Compete for Resources? Aggressive behavior helps secure resources (continued) A manifestation of competition for food, resources, or mates is aggression, or antagonistic behavior, between members of the same species (continued) These displays allow competitors to assess each other on the basis of size, strength, and motivation, thus determining a winner without injury or death

59 25.3 How Do Animals Compete for Resources? Aggressive behavior helps secure resources (continued) During aggressive displays, animals may exhibit weapons, such as claws and fangs, and often make themselves appear larger Competitors often stand upright and erect their fur, feathers, ears, or fins These visual displays are typically accompanied by vocal signals such as growls, croaks, roars, or chirps Fighting is usually a last resort

60 Figure Aggressive displays A mal e bab Sar cast ic frin

61 25.3 How Do Animals Compete for Resources? Aggressive behavior helps secure resources (continued) In addition to aggressive visual and vocal displays, many animals engage in ritualized combat Deadly weapons may clash harmlessly or may not be used at all The ritual allows contestants to assess the strength and the motivation of their rivals The loser slinks away in a submissive posture that minimizes the size of the body

62 Figure Displays of strength

63 25.3 How Do Animals Compete for Resources? Dominance hierarchies help manage aggressive interactions In a dominance hierarchy, each animal in a group establishes a rank that determines access to resources Though aggressive encounters occur frequently while the dominance hierarchy is being established, once each animal learns its place, disputes are infrequent

64 25.3 How Do Animals Compete for Resources? Dominance hierarchies help manage aggressive interactions (continued) In a dominance hierarchy, each animal in a group establishes a rank that determines access to resources (continued) Dominant individuals obtain most access to the resources needed for reproduction, including food, mates, and space Among male bighorn sheep, dominance is reflected in horn size

65 Figure A dominance hierarchy

66 25.3 How Do Animals Compete for Resources? Animals may defend territories that contain resources In many animal species, competition for resources takes the form of territoriality, the defense of an area where important resources such as mates, food, and shelter are located Territorial behavior is most commonly seen in adult males, and territories are usually defended against members of the same species, who compete most directly for the resources being protected

67 25.3 How Do Animals Compete for Resources? Animals may defend territories that contain resources (continued) Territories are as diverse as the animals defending them, and examples include A tree where a woodpecker defends acorn storage sites A small depression in the sand used as a nesting site by a cichlid fish A hole in the sand that is home to a crab An area of forest providing food for a squirrel

68 Figure A feeding territory

69 25.3 How Do Animals Compete for Resources? Animals may defend territories that contain resources (continued) Territoriality reduces aggression Acquiring and defending territory requires considerable time and energy, yet territoriality is seen in animals as diverse as worms, arthropods, fish, birds, and mammals

70 25.3 How Do Animals Compete for Resources? Animals may defend territories that contain resources (continued) Territoriality reduces aggression (continued) Territoriality provides some important advantages As with dominance hierarchies, once a territory is established through aggressive interactions, relative peace prevails as boundaries are recognized and respected Niko Tinbergen demonstrated this principle in an experiment using stickleback fish

71 Figure Territory ownership and aggression Two sticklebacks establish territories in an aquarium Both fish are placed in A s territory; A attempts to attack B, which assumes a submissive posture Responses reverse when both fish are placed in B s territory A B A B A B A s territo ry B s territo ry A s territo ry B s territo ry A s territo ry B s territo ry

72 25.3 How Do Animals Compete for Resources? Animals may defend territories that contain resources (continued) Competition for mates may be based on territories For males of many species, successful territorial defense has a direct impact on reproductive success Males who successfully defend the best territories have the greatest chance of passing on their genes Females may choose males whose territories are large in size, and have abundant food and secure nesting areas, thus increasing survival chances of her offspring

73 25.3 How Do Animals Compete for Resources? Animals may defend territories that contain resources (continued) Animals advertise their occupancy Territories are advertised through sight, sound, and smell If a territory is small enough, its owner s presence along with aggressive displays is sufficient defense

74 25.3 How Do Animals Compete for Resources? Animals may defend territories that contain resources (continued) Animals advertise their occupancy (continued) Vocal displays are a common form of territorial advertisement Male sea lions and crickets using vocal displays

75 25.3 How Do Animals Compete for Resources? Animals may defend territories that contain resources (continued) Animals advertise their occupancy (continued) The husky trill of the male seaside sparrow is part of an aggressive display, warning other males to steer clear of his territory The importance of singing to seaside sparrows territorial defense was demonstrated by ornithologist M. Victoria McDonald, who captured territorial males and operated on them in a way that left them unable to sing

76 25.3 How Do Animals Compete for Resources? Animals may defend territories that contain resources (continued) Animals advertise their occupancy (continued) The husky trill of the male seaside sparrow is part of an aggressive display, warning other males to steer clear of his territory (continued) The males unable to sing could not defend territories or attract mates, but regained their lost territories when they recovered their singing ability

77 Figure Defense of a territory by song

78 25.4 How Do Animals Find Mates? In many sexually reproducing animal species, mating involves copulation or other close contact between males and females Before animals can successfully mate, they must identify one another as Members of the same species Members of the opposite sex Being sexually active

79 25.4 How Do Animals Find Mates? Signals encode sex, species, and individual quality Individuals that waste energy and gametes by mating with members of the wrong sex or wrong species are at a disadvantage in the contest to reproduce Natural selection favors behaviors by which animals communicate their sex and species to potential mates

80 25.4 How Do Animals Find Mates? Signals encode sex, species, and individual quality (continued) Many mating signals are acoustic Animals often use sounds to advertise their sex and species Male grasshoppers, crickets, frogs, and birds all produce mating calls

81 25.4 How Do Animals Find Mates? Signals encode sex, species, and individual quality (continued) Many mating signals are acoustic (continued) Females may compare the songs of rival suitors to assess the relative quality of the males For example, the male bellbird uses its deafening song to defend large territories and to attract females from great distances

82 25.4 How Do Animals Find Mates? Signals encode sex, species, and individual quality (continued) Many mating signals are acoustic (continued) Females may compare the songs of rival suitors to assess the relative quality of the males (continued) A female flies from one male to another to listen to its earsplitting song, and compare the songs between different males, perhaps choosing the loudest as a mate

83 25.4 How Do Animals Find Mates? Signals encode sex, species, and individual quality (continued) Visual mating signals are also common Displays are used by males to attract the attention of females For example, the elaborate construction projects of the male gardener bowerbirds and the scarlet throat of the male frigate bird advertise sex, species, and male quality

84 25.4 How Do Animals Find Mates? Signals encode sex, species, and individual quality (continued) Visual mating signals are also common (continued) These signals may be risky, making it easier for predators to find the males, but are necessary because females won t mate with males that lack the appropriate signal

85 Figure Sexual displays A bowerbird bower A male frigate bird

86 25.4 How Do Animals Find Mates? Signals encode sex, species, and individual quality (continued) Visual mating signals are also common (continued) Females, in contrast, typically do not need to attract males or assume the risk of a conspicuous signal, and so in many species are drab in comparison to the males

87 Figure Sex differences in guppies

88 25.4 How Do Animals Find Mates? Signals encode sex, species, and individual quality (continued) Visual mating signals are also common (continued) The intertwined functions of sex recognition and species recognition, advertisement of individual quality, and synchronization of reproductive behavior commonly require a complex series of signals, both active and passive, by both sexes

89 Figure Courtship of the three-spined stickleback A male, inconspicuously colored, leaves the school of males and females to establish a breeding territory. As his belly takes on the red color of the breeding male, he displays aggressively at other red-bellied males, exposing his red underside. Having established a territory, the male begins nest construction by digging a shallow pit that he will fill with bits of algae cemented together by a sticky secretion from his kidneys. After he tunnels through the nest to make a hole, his back begins to take on the blue courting color that makes him attractive to females.

90 Figure Courtship of the three-spined stickleback An egg-carrying female displays her enlarged belly to him by assuming a head-up posture. Her swollen belly and his courting colors are passive visual displays. Using a zigzag dance, he leads her to the nest. After she enters, he stimulates her to release eggs by prodding at the base of her tail. He enters the nest as she leaves and deposits sperm, which fertilize the eggs.

91 25.4 How Do Animals Find Mates? Signals encode sex, species, and individual quality (continued) Chemical signals can bring mates together Pheromones can also play an important role in reproductive behavior A sexually receptive female silk moth, for example, sits quietly and releases a chemical message that can be detected by males up to 3 miles away

92 25.4 How Do Animals Find Mates? Signals encode sex, species, and individual quality (continued) Chemical signals can bring mates together (continued) Water is an excellent medium for dispersing chemical signals, and fish commonly use a combination of pheromones and elaborate courtship movements to ensure the synchronous release of gametes Mammals often rely on pheromones released by the female during her fertile periods to attract males

93 Figure Pheromone detectors Antennae detect pheromones Noses detect pheromones

94 25.5 Why Do Animals Play? Many animals play Pygmy hippopotamuses push one another, shake and toss their heads, splash in the water, and pirouette on their hind legs Otters delight in elaborate acrobatics Bottlenose dolphins balance fish on their snouts, throw objects, and carry them in their mouths while swimming Baby vampire bats chase, wrestle, and slap each other with their wings

95 25.5 Why Do Animals Play? Animals play alone or with other animals Play can be solitary or within a group Often, young of the same species play together, but parents may join in Play can be social Social play typically includes chasing, fleeing, wrestling, kicking, and gentle biting

96 25.5 Why Do Animals Play? Animals play alone or with other animals (continued) Play seems to lack any clear function and is abandoned in favor of feeding, courtship, and escaping from danger Play typically borrows movements from other behaviors (attacking, fleeing, stalking, and so on) Play is potentially dangerous Many young humans and other animals are injured, and some are killed, during play

97 Figure Young animals at play Polar bears Chimpanzees Red foxes

98 25.5 Why Do Animals Play? Play aids behavioral development It is likely that play has survival value and that natural selection has favored those individuals who engage in playful activities One of the best explanations for the survival value of play is the practice hypothesis

99 25.5 Why Do Animals Play? Play aids behavioral development (continued) The practice hypothesis suggests That play allows young animals to gain experience in behaviors that they will use as adults That by practicing these acts in play, the animal gets skills that will later be important in hunting, fleeing, or in social interactions

100 25.5 Why Do Animals Play? Play aids behavioral development (continued) Play is most intense early in life when the brain develops and crucial neural connections form John Byers, a biologist at the University of Idaho, suggests that species with larger brains are more playful than those with small brains Because larger brains are linked to greater learning ability, this relationship supports the idea that adult skills are learned during juvenile play

101 25.6 What Kinds of Societies Do Animals Form? Sociality is a widespread feature of animal life Most animals interact at least a little with other members of their species Many spend the bulk of their lives in the company of others, and a few have developed complex, highly structured societies

102 25.6 What Kinds of Societies Do Animals Form? Group living has advantages and disadvantages Living in a group has both costs and benefits Benefits to social animals include Increased ability to detect, repel, and confuse predators Increased hunting and food-finding efficiency Potential for division of labor Increased likelihood of finding a mate

103 25.6 What Kinds of Societies Do Animals Form? Group living has advantages and disadvantages (continued) On the negative side, social animals may encounter Increased competition within the group for limited resources Increased risk of infection from contagious diseases Increased risk of offspring being killed by other members of the group Increased risk of being spotted by predators

104 25.6 What Kinds of Societies Do Animals Form? Sociality varies among species The degree to which animals of the same species cooperate varies from one species to the next Some types of animals are solitary, where interactions between adults consist of brief aggressive encounters and mating; an example is the mountain lion

105 25.6 What Kinds of Societies Do Animals Form? Sociality varies among species (continued) Other types of animals are either occasionally or permanently part of simple social groups For example, coyotes are solitary when food is abundant, but hunt in packs when food becomes scarce Musk oxen form herds that function as a unit when threatened by predators such as wolves In this case, male oxen form a circle with horns pointed outward around the females and the young

106 Figure Cooperation in loosely organized social groups

107 25.6 What Kinds of Societies Do Animals Form? Sociality varies among species (continued) A small number of species, most of which are insects or mammals, form highly integrated cooperative societies Some cooperative societies are based on behavior that seems to sacrifice the individual for the good of the group Young, mature Florida scrub jays may remain at their parents nest and help them raise subsequent broods instead of breeding

108 25.6 What Kinds of Societies Do Animals Form? Sociality varies among species (continued) Some cooperative societies are based on behavior that seems to sacrifice the individual for the good of the group (continued) Worker ants often die in defense of their nest Ground squirrels may sacrifice their own lives to warn the rest of their group about an approaching predator These behaviors are examples of altruism behavior that decreases the reproductive success of one individual to benefit another

109 25.6 What Kinds of Societies Do Animals Form? Forming groups with relatives fosters the evolution of altruism When individuals perform self-sacrificing deeds, alleles that contribute to this behavior are not eliminated Other members of the group are close relatives of the altruistic individual Because close relatives share alleles, the altruistic individual may promote the survival of its own alleles through behaviors that maximize the survival of family

110 25.6 What Kinds of Societies Do Animals Form? Forming groups with relatives fosters the evolution of altruism (continued) This concept is called kin selection Kin selection helps explain the self-sacrificing behaviors that contribute to the success of cooperative societies

111 25.6 What Kinds of Societies Do Animals Form? Honeybees live together in rigidly structured societies Scientists have long struggled to explain this social structure where most individuals never breed, but instead labor to feed and protect the offspring of another individual Honeybees, ants, and termites are examples

112 25.6 What Kinds of Societies Do Animals Form? Honeybees live together in rigidly structured societies (continued) Honeybees have a rigidly organized caste system based on functional position in the colony

113 25.6 What Kinds of Societies Do Animals Form? Honeybees live together in rigidly structured societies (continued) They emerge from their larval stage into one of three preordained roles 1. Queen: There is only one queen per hive, and her role is to produce eggs and regulate the lives of the workers 2. Drones: All drones are males, and serve as mates to the queen 3. Workers: All workers are sterile females; they perform a variety of functions depending on age

114 25.6 What Kinds of Societies Do Animals Form? Honeybees live together in rigidly structured societies (continued) A worker s tasks are determined by her age and by conditions in the colony A newly emerged worker starts life as a waitress, carrying food such as honey and pollen to the queen, to other workers, and to the developing larvae

115 25.6 What Kinds of Societies Do Animals Form? Honeybees live together in rigidly structured societies (continued) A worker s tasks are determined by her age and by conditions in the colony (continued) As she matures, special glands begin to produce wax, and she becomes a builder, constructing perfectly hexagonal cells of wax in which the queen deposits her eggs and where the larvae develop Her final role in life is that of a forager, gathering pollen and nectar as food for the hive

116 25.6 What Kinds of Societies Do Animals Form? Honeybees live together in rigidly structured societies (continued) Forager worker bees communicate sources of nectar to other foragers by using a waggle dance

117 Figure Bee language: the waggle dance 40 If the dance is performed on a vertical wall inside the hive, the angle (from vertical) of the waggle run represents the angle between the sun and the food source up 40 The rate of circling communicates the distance to the food source If the dance is performed on a horizontal surface outside, the waggle run is aimed at the food source

118 25.6 What Kinds of Societies Do Animals Form? Honeybees live together in rigidly structured societies (continued) Pheromones play a major role in regulating the lives of social insects Honeybee drones are drawn irresistibly to the queen s sex pheromone (queen substance), which she releases during her mating flights This substance is also licked off her body by the workers, rendering them sterile and leaving only one reproductive queen in each hive

119 25.6 What Kinds of Societies Do Animals Form? Naked mole rats form a complex vertebrate society The nervous systems of vertebrates are for more complex than those of insects, and we might expect vertebrate societies to be proportionately more complex With the exception of human society, they are not that much more complex One of the most unusual societies among non-human mammals is that of the naked mole rat

120 25.6 What Kinds of Societies Do Animals Form? Naked mole rats form a complex vertebrate society (continued) The queen is the largest individual in the colony, and prevents ovulation in rival females by physically stressing rival females A division of labor among workers exists based on size Small, young rats clean the tunnels, gather food, and tunnel Larger mole rats fling the dirt into the air, adding it to a cone-shaped mound

121 Figure Naked mole rat workers

122 25.7 Can Biology Explain Human Behavior? The behaviors of humans, like those of all other animals, have an evolutionary history The techniques and concepts of ethology can help us understand and explain human behavior Human ethology is less rigorous science than animal ethology People cannot be treated as laboratory animals, devising experiments that control and manipulate the factors that influence their attitudes and actions

123 25.7 Can Biology Explain Human Behavior? The behavior of newborn infants has a large innate component Because newborn infants have not had time to learn, we can assume that much of their behavior is innate Sucking, which can be observed in a human fetus, is innate Other behaviors include grasping with the hands and feet and making walking movements when the body is held upright and supported

124 Figure A human instinct

125 25.7 Can Biology Explain Human Behavior? The behavior of newborn infants has a large innate component (continued) Another example is smiling, which can occur soon after birth Infants up to 2 months old will smile in response to a stimulus consisting of two dark, eye-sized spots on a light background As the child s development continues, learning and further development of the nervous system interact to limit the response to more correct representations of a face

126 25.7 Can Biology Explain Human Behavior? The behavior of newborn infants has a large innate component (continued) Newborns in their first 3 days of life can be conditioned to produce certain rhythms of sucking when their mothers voice is used as reinforcement In experiments, infants preferred their own mother s voices to other female voices, as indicated by their responses

127 25.7 Can Biology Explain Human Behavior? The behavior of newborn infants has a large innate component (continued) Newborns in their first 3 days of life can be conditioned to produce certain rhythms of sucking when their mothers voice is used as reinforcement (continued) The infant s ability to learn his or her mother s voice and respond positively to it within days of birth has strong parallels to imprinting, and may help initiate bonding with the mother

128 Figure Newborns prefer their mother s voice

129 25.7 Can Biology Explain Human Behavior? Young humans acquire language easily Species have a predilection for specific types of learning that are important to their mode of life Humans have an inborn predilection for the acquisition of language Infants are able to distinguish among consonant sounds by 6 weeks after birth Humans typically acquire a 28,000-word vocabulary by the age of 8

130 25.7 Can Biology Explain Human Behavior? Behaviors shared by diverse cultures may be innate Another way to study the innate bases of human behavior is to compare simple acts performed by people from diverse cultures This comparative approach has revealed several gestures that seem to form a universal, and therefore probably innate, human signaling system

131 25.7 Can Biology Explain Human Behavior? Behaviors shared by diverse cultures may be innate (continued) Some gestures include Facial expressions for pleasure, rage, and disdain Greeting movements such as an upraised hand or the eye flash, where the eyes are opened widely and the eyebrows are elevated

132 25.7 Can Biology Explain Human Behavior? Behaviors shared by diverse cultures may be innate (continued) The evolution of neural pathways underlying these gestures presumably depended on the advantages that accrued to both senders and receivers from sharing information about the emotional state and intentions of the sender

133 25.7 Can Biology Explain Human Behavior? Behaviors shared by diverse cultures may be innate (continued) A species-wide method of communication was perhaps especially important before the advent of language, and later remained useful during encounters between people who share no common language

134 25.7 Can Biology Explain Human Behavior? Humans may respond to pheromones Martha McClintock, in the early 1970s, hinted at the possible existence of human pheromones She found that the menstrual cycles of roommates and close friends tended to become synchronized It was suggested that this synchronization was due to some chemical signal passed between the women The actual molecules that cause effects on menstrual synchronization remain unknown, as does their function

135 25.7 Can Biology Explain Human Behavior? Studies of twins reveal that there are genetic components of behavior Twins are an opportunity to examine the hypothesis that differences in human behavior are related to genetic differences

136 25.7 Can Biology Explain Human Behavior? Studies of twins reveal that there are genetic components of behavior (continued) If a particular behavior is heavily influenced by genetic factors, identical twins are more likely to share the behavior than fraternal twins Identical twins: Arise from the same egg and have identical genes Fraternal twins: Arise from individual eggs fertilized by different sperm and have different genes

137 25.7 Can Biology Explain Human Behavior? Studies of twins reveal that there are genetic components of behavior (continued) Studies involving identical twins separated at birth are particularly revealing, showing that twins reared apart have personalities just as similar as those reared together The differences in their environment had little influence on their personality development

138 25.7 Can Biology Explain Human Behavior? Biological investigation of human behavior is controversial The field of human behavioral genetics is controversial because it challenges the belief that environment is the most important determinant of human behavior We now recognize that complex behavior in nonhuman animals combines elements of both innate and learned behaviors

139 25.7 Can Biology Explain Human Behavior? Biological investigation of human behavior is controversial (continued) It seems certain that our own behavior is influenced by both our evolutionary history and our cultural heritage The debate over the relative importance of heredity and environment in determining human behavior continues and is unlikely ever to be fully resolved

140 25.7 Can Biology Explain Human Behavior? Biological investigation of human behavior is controversial (continued) Human ethology is not yet recognized as a rigorous science, and it will always be hampered because we can neither view ourselves with detached objectivity, nor experiment with people as if they were laboratory rats Despite the limitations, there is much to be learned about the interactions of learning and innate tendencies in humans