Z203/ Unit 7 Ch 36: Animal Behavior

Transcription

1 Z203/ Unit 7 Ch 36: Animal Behavior I. Ethology: Science of Animal Behavior A. Overview - science of behavior in the animal s natural habitat - roots in 1872 work of Charles Darwin (1904 Expressions of Emotions of Man & Animals) - questions: 1. Proximate causes How (physiologic function of behavior) Hormonal Neural 2. Ultimate causes Why (what selection has taken place to drive this) - centers on idea that behaviors have genetic components & can be isolated & traced - Sociobiology is the ethological study of social behavior (originated w/ E.O. Wilson 1975) - Social behavior is cooperative/reciprocal that permits a group of one species to become organized & is represented by four pinnacles 1. colonial invertebrates (Portuguese man-of-war) tightly knit composites 2. social insects (ants, bees, termites) sophisticated communication systems 3. Dolphins, elephants, & some primates highly developed social systems 4. Humans w/ their unique social behavior - behavior ecology focuses on individual behavior that maximizes reproductive success & studies mate choice, foraging, parental investment, etc 1

2 II. Principles of Classical Ethology A. Early Work Konrad Lorenz & Niko Tinbergen laid down basic concepts in animal behavior 1. Innate behavior recognized: fixed action patterns (FAP) behaviors called stereotypical behaviors 2. stimulus that triggers behavior known as releaser 3. sign stimulus are responses to one specific aspect of the releaser 4. alarm call of adult bird may release a freeze response in a chick 5. stickleback fish became aggressive at sign of another male s red flank/belly 6. automatic programmed responses are most efficient in wild conditions (not unusual & artificial conditions) Geese: rolling egg response EXAMPLES Stickleback Fish: male aggressive response Moth: ultrasonic pulse & wing tuck Mayflies: polarized light & egg laying Human infants: tactile response Cheek & hand reponses 2

3 III. Control of Behavior: Innate & Learned A. Innate Behavior 1. invariable & predictable inherited stereotyped behaviors 2. independent of learning, but depends on interactions during development 3. important for survival, esp. in young w/ little parenting 4. can equip animal for immediate response at birth or hatching 5. complex animals w/ longer lives have more time for social interactions & learning European Starling migration tests direction distance Bird Songs chicks raised in isolation base tune B. Genetics of Innate Behavior 1. most innate behaviors complex of many interacting genes 2. some behavioral differences w/in species show simple Mendelian transmission 3. Honeybee Hygiene: - honeybees susceptible to bacterial disease called American foulbrood - bees remove dead larvae from hive; reduces chance of infection from spreading - strain of bees hygienic uncap cells containing rotten larvae & carry them out 3

4 - two components of behavior are 1. detection & removal of cell caps 2. removal of larvae - individual homozygous recessive for uncapping - individual homozygous recessive for removal - cross hygienic bees w/ nonhygienic bees; all heterozygous hybrids are nonhygienic - other backcrosses yield uncap/non-removers; nonuncap/removers, etc 4. most inherited behaviors show intermediate not simple segregation 5. crossbreed lovebirds that carry nest material either in beak or in feathers produced hybrids that confuse carrying behavior 4

5 C. Learning & Diversity of Behavior 1. Learning is the modification of behavior through experience 2. Five Categories often studied: A. Habituation - Experiments w/ marine snail Aplysia snail withdraws gills for protection when siphon prodded - if repeatedly prodded, soon ignores stimulus - if noxious stimulus added to prodding, it becomes sensitized & rapidly withdraws gills - behaviors traced to neural p/w, connecting sensory neurons to motor neurons that control muscles - repeated stimulation diminish release of neural chemicals (reduced transmission) - sensory neurons still fire off, but less chemical equal less response - must increase neural chemicals in response to sensitization - shows response involves changes in levels of neural chemicals Moving to new location: country noise city noise 5

6 D. Imprinting (Innate & Learned combined) - imposes a stable behavior in young animals by exposure to particular stimuli during a critical period of development (irreversible) - newly hatched ducklings follow mother; if isolated, follows 1 st large object it sees "Konrad Lorenz hand-reared goslings which imprinted on him" - brief sensitive period when imprinting occurs & bond lasts for life - Other Examples: Salmon & native streams, birds songs Critical Windows for bird songs - songs of sparrows are important territorial calls & rely partially on learning - baby reared in isolation sings a rudimentary song - sparrow must hear normal adult song in critical period (10-50 days) after hatching young sparrows doesn t learn songs of different species E. Imitation Behavior - Hunting skills learned from parents (cats, dogs, etc) 6

7 F. Innovation Behavior - Analyze problems & think of solutions without previous experience Chimps using boxes to reach bananas Japanese Macaques & sweet potato washing then rice grains G. Association Behavior - "Trial & Error" aka "Classical Conditioning" Pavlov & dogs Dog & skunks/porcupines Birds & Monarch butterflies IV. Social Behavior A. Definitions - any response of one animal to another of the same species is social behavior - social aggregations depend upon signals from animals themselves - breeding may be an adult social behavior in some (temporal or seasonal) 7

8 - others form strong monogamous relationships for life - social bonds often form between adult & young until they are fledged or weaned B. Cost/Benefit Ratio of Sociality Advantages: - passive & active defenses; safer in a group - alarm calls bring many to attack predator - larger group chances of being eaten - close proximity of genders synchronizes reproduction female estrous & male proximity - sounds & displays trigger pre-reproduction endocrine changes in birds (gonad development) - benefits in cooperative hunting; huddling for mutual protection from weather; division of labor; learning potential & communication - transfer of innovative behaviors documented in macaques (washing potatoes & wheat sifting) Disadvantages - camouflaged individuals survive predation by being dispersed in habitat - large predators need large amounts of food - ecological situations determine solitary or social strategy (resources availability) - disease (increase spread) 8

9 C. Aggression & Dominance - social species must cooperate, but each looks out for their own interests competition for food, mates, shelter, etc - Aggression is offensive physical action or threat to force others to abandon something - Agonistic behaviors are broader category including any activity related to fighting aggresion or threat vs conciliation or retreat - most reserve dangerous weapons for securing prey, not against own species - ritualized display is a behavior that has been modified through evolution to make it effective in serving a communicative function (often to minimize harm to animals involved) wide array of animals fights involve ritual Jousts: fiddler crabs claw fights, rattlesnake dances, puffing fish, giraffe necking, bighorn sheep head-butting - subordination ritual usually observed, loser runs away or signals defeat - dominance hierarchy 1 st described by Schjelderup-Ebbe in barnyard chickens pecking orders (weaker members may die in times of food shortage) 9

10 D. Territoriality - territory is a fixed area from which intruders of same or other species are excluded - territorial defense occurs in wide range of animals: insects, crustaceans, fish, amphibians, lizards, birds, mammals, etc - may be an alternative to dominance behavior - high cost of maintaining territory may outweigh benefits - most energy expended in establishing a territory, less usually in defense - territory size varies from large (several miles) to size of nest in sea birds & often seasonal - home ranges rather than territories used in many mammals, ranges may overlap - baboon troop may switch ranges to obtain more resources E. Mating Systems - behavioral ecologists classify mating systems by extent males & females associate during mating monogamy associated between 1 M & 1 F at a time polygamy includes all male & female systems with more than one mate, 2 types: polygyny indicates 1 M & several F polyandry includes 1 F & several M - sexual dimorphism often seen in birds mammals (male looks different from female, often with brighter colors, larger size, ornate morphology) - reverse sexual dimorphism seen in few animals (female birds of prey often larger, female phalaropes more colorful) 10

11 F. Altruistic Behavior & Kin Selection - animals behaving selfish less, placing themselves at risk for the benefit of others WHY? APPEARS TO DECREASE FITNESS! - Group-selection theory suggested animals helped other for the good of the species but wasn t supported by field studies (cheaters exist) Kin-Selection 1. William Hamilton (1964) proposed kin selection theory 2. fitness not just measured by animal s own offspring, but by increase or decrease in genes shared in gene pool Increases Fitness indirectly 3. alleles shared closely w/ parents & siblings 4. inclusive fitness is the relative # of individual s alleles that are passed on to future generations from one s own offspring or that of related individuals 5. explained the mathematics that allows eusocial insect workers to give up reproduction & aid the queen in haplodiploid systems: workers are 75% related to their sister queen s offspring 50% relatedness of own offspring if they were fertile & mated 6. places high value on being able to recognize kin from non-kin 11

12 V. Animal Communication A. Signals - through communication, one animal can influence behavior of another - animals limited to communication using sounds, scents, touch, & movement - most animal communication is by signals; human have learned & highly variable language to supplement - each signal conveys one message & cannot be rearranged to construct new kinds of information - song of a cricket signals species, sex, location, & social status of the sender & cannot alter the song B. Chemicals: Sex Attraction in Moths - pheromones: virgin & silkworm moths have special scent glands to attract female adult moths smell w/ large antennae (thousands of sensory hairs receptors) - chemical communication evolves easily since there is selection for any improved detector (increases reproductive success) C. Movement/ Body Language (Honeybees) - Waggle Dance: communicate location of food used when worker has located rich food source dance is figure-eight pattern on vertical surface of comb inside the hive waggle run in middle of figure-eight indicates direction relative to sun tempo of waggle is inversely related to distance Round Dance used when food very close dancing less common when food plentiful 12

13 D. Display Communication - display is a behavior that serves a communicative purpose - moth pheromones, bee dances, gull alarm calls, & courtship dances are all displays - elaborate displays of bluefooted boobies ensure that the message is understood - redundancy of display ensures both partners are committed in courtship E. Communication between Humans & Other Animals - humans may have difficulty determining what sensory channel an animal is using - Animal Cognition: 1. General term for mental function, including perception, thinking & memory 2. Recent studies: A.Non-human primates & African gray parrots Parrots can vocalize like humans; work w/ African gray parrots reveals ability to identify shapes, colors, & numbers Researchers taught chimps to use 132 words in American Sign Language 3. Studies of animal cognition attempt to detect extent some animals are capable of self-awareness & various levels of reasoning 4. Care must be taken to avoid Anthropomorphism 13