Transcript Slide 1
Animal Behavior • Behavior – an animal’s response to stimuli in its environment – – • capacity for behavior is inherited but inherited behavior can be modified by experience Learning involves persistent changes in behavior that result from experience Most behavior is adaptive – – Behavioral ecology (ethology) is the study of animal behavior in the natural environment from an evolutionary perspective Natural selection tends to favor behaviors that contribute to the survival of an animal allowing it to pass its genes to its offspring Behavior depends on the interaction of genes and environmental factors • All behaviors or the capacity for behavior is inherited in some way – all behavior has a genetic basis, the capacity to learn is inherited • Behavior is modified by the environment (even innate behaviors) • innate behavior – inborn or instinct – genetically programmed behaviors • behavior involves all body systems, but depends primarily on the nervous and endocrine systems • behaviors are influenced by the readiness of the animal (human baby cannot walk until muscles and neurons are sufficiently developed) • behaviors are influenced by environmental signals (a young sparrow is hatched with a rough genetic pattern of its song but requires social interaction and listening to adult males to develop its ability to sing its specific song) • many behaviors depend on coordinated sequences of muscle actions called motor programs (example – walking in newborn gazelles) – fixed action pattern (FAP) – motor program behaviors that once activated by a simple sensory stimulus, will be continued to completion regardless of sensory feedback – example – egg-rolling in European graylag goose – when an egg is removed from nest and placed in front of goose, she will reach out with her neck and roll egg back into nest – if egg is quickly removed during egg-rolling, goose will continue head and neck movements even though egg is gone – video clip –FAPs can be triggered by a sign stimulus or releaser – a simple signal that triggers a specific behavioral response (i.e. male stickleback fish aggressive response to red stripe) Animals learn from experience – Learning is a change in behavior due to experience • Habituation – a type of learning in which an animal learns to ignore a repeated, irrelevant stimulus (ex. pigeons in a city park learn by repeated harmless encounters that humans are not dangerous and don’t waste energy constantly flying away) Learning Imprinting – a behavioral bond that forms during a critical period (usually within a few hours of birth or hatching) between baby and mother – newly hatched birds imprint on the first moving object (even a human or inanimate object) – usually object is their mother – Process of imprinting is genetically determined but the bird learns to respond to a particular animal or object Konrad Lorenz demonstrated imprinting in graylag geese • he divided a batch of eggs into two groups • one group was reared normally by the mother and showed normal behavior (following mother around for food, shelter and protection) • the other batch was isolated from mother and hatched in an incubator • goslings spent the first few hours after hatching with Lorenz • imprinting occurred and gosling treated Lorenz as their mother • these goslings became socially dysfunctional in adult life – they continued to prefer Lorenz to other geese and even attempted to mate with humans Learning Classical Conditioning – occurs when a behavior that is normally triggered by a certain stimulus comes to be triggered by a substitute stimulus which previously had no effect on the behavior • Pavlov – found that if he rang a bell just before feeding a dog, the dog formed an association between the sound of the bell and food • eventually, the dog salivated at the sound of the bell even in the absence of food • Pavlov called the physiologically meaningful stimulus (food) the unconditioned stimulus • the normally irrelevant stimulus (bell) that became a substitute was the conditioned stimulus • many predators become conditioned to the scent or sound of potential prey Learning Operant conditioning – a spontaneous behavior is reinforced • animal does something to gain a reward – the reward provides positive reinforcement for the behavior • Skinner did extensive research on operant conditioning using a “Skinner box” - a rat is placed in a cage with a moveable bar, random actions of rat result in its pressing the bar, rat receives food, rat learns the association between pressing bar and obtaining food • negative reinforcement – causes an animal to stop a behavior to avoid a punishment or negative experience • thought to be the predominant learning process found among animals, including humans Learning Insight learning – learning that uses recalled events to solve new problems – most complex form of learning – seen in primates and some birds and other mammals – also known as “reasoning” Playing – many young animals “play”, which appears to be a way to practice adult patterns of behavior Biological rhythms affect behavior – a variety of behavioral cycles occur among organisms – Circadian rhythms – daily activities that appear to follow an internal rhythm – controlled by an internal, biological clock that is adjusted or reset by environmental cues – Diurnal animals most active during the day – Nocturnal animals are active during the night – Crepuscular animals are active during dusk and dawn – Lunar cycle – some biological rhythms are tied to changes in tides and phases of the moon (marine organisms such as grunions beach themselves to deposit eggs and sperm at precisely the high point of the tide) • Biological clocks seem to result from the interaction of a number of biochemical processes – pineal gland is thought to play a role in timing systems of birds, rats, humans, and some other vertebrates – regions of the hypothalamus also are part of biological clocks in mammals • Migration – involves interactions among biological rhythms, physiology, and environment – Migration – a periodic long distance movement from one location to another – adaptation to environmental change (moving from an area that seasonally becomes less hospitable) – Environmental cues trigger physiological responses that lead to migration (ex. changes in day length) – Direction of migration may be according to celestial, magnetic, or olfactory cues • Examples of migration include arctic terns, swallows, white stork, blue whale, grey whale • Foraging behavior – feeding behavior involves locating and selecting food, as well as food gathering and food capture – – Optimal foraging – foraging by animals which optimizes time and reward – animal maximizes energy obtained per unit of foraging time (which maximizes reproductive success) Animals may adopt varying foraging strategies to optimize reward Examples of Optimal Foraging Behavior 1. Starlings (Sturnus vulgaris) • • • • • Feed their young mostly crane-fly larvae obtained by probing their beaks in the soil Starlings become less efficient at probing for larvae as the number of larvae they are holding in their beaks increases The fewer journeys back to the nest, the less time and energy is used in transporting the larvae to offspring Optimum number of larvae for starlings to catch and carry back to nest depends on the distance between the foraging area and the nest In observed starlings, number of larvae caught and transported has been found to be very close to theoretical optimum 2. Bluegill Sunfish (Lepomis macrochirus) • • • • • • Feed on Daphnia (“water flea”) At low densities of Daphnia, fish will eat all sizes of prey At medium densities, fish will eat moderately sized prey At high densities, fish eat mostly larger prey Consuming small numbers of larger prey takes less energy than large numbers of smaller prey, hence the preference for larger prey At lower densities, smaller prey has to be consumed to get enough food in total • Social Behavior – the interaction of two or more animals, usually of the same species – may benefit animals by allowing cooperation and division of labor (ex. insects) examples of social behavior includes schooling of fish, herds of zebra (confuses predators), social foraging (a pack of wolves has more success hunting), and societal behavior – • society – an actively cooperating group of individuals belonging to the same species and often closely related (bee hive, flock of birds, pack of wolves) • Communication is necessary for social behavior – communication – occurs when an animal performs an act that changes the behavior of another organism – communication important in finding food, warning of danger, indicating social status, identifying members of same species, indicating sexual maturity or readiness – Animals communicate in a wide variety of ways including auditory, visual, tactile, chemical or electrical signals (ex. bird songs, alarm responses, and hierarchal dominance patterns in wolves) • Pheromones – chemical signals secreted by animals that convey information between members of a species – may result in immediate or long term effects – often involved in sexual responses • Dominance hierarchies – ranking of status in which each organism has more status than the organisms that are lower in rank – suppresses aggression – once hierarchy is established, little time is wasted in fighting – many factors affect dominance – often influenced by sex hormones Many animals defend a territory • most animals have a home range – a geographical area that they seldom leave • some animals exhibit territoriality – defend a section of the home range from other organisms • territoriality is well studied among birds • territoriality decreases aggressive conflicts • territoriality is closely tied to reproductive behavior • Sexual selection – in many species individuals actively compete for mates – – – sexual selection – type of natural selection which occurs when individuals vary in their ability to compete for mates dominance may indicate a male’s quality to a female females may choose mates based on ornamental displays (ex. brightly colored male birds) – Mating systems: • polygyny – males mates with many females • polyandry – female mates with several males • monogamy – organisms have only one mate for the breeding season (very common in birds) or for a lifetime (much less common) – pair bond – stable relationship between two animals of the opposite sex that may ensure cooperative behavior in mating and rearing of young (common in birds) Courtship – specialized behavior that precedes the fertilization of eggs by a male – highly ritualized in most animals, follows a set pattern in different individuals of the species – (see example of sticklebacks in Kent text) • Many organisms care for their young – benefit is the increased probability that offspring will survive – cost includes a reduction in the number of offspring that can be produced and the risks taken in protecting offspring from predators – natural selection favors parental care in species in which the benefits to offspring survival outweigh the costs of decreased opportunities to produce additional offspring Social Insects • Elaborate societies are found among the social insects – ex. ants, bees, and wasps – most studied is the honeybee – these societies show four main characteristics: cooperative care of young, overlapping generations, division of labor and communication Honeybee Society – – – – honeybee society generally consists of single adult queen (only fertile female), up to 80,000 worker bees (all female), and at certain times, a few males called drones that fertilize newly developed queens members are divided into different groups called castes, each with a specific task (care for young, find food, defend colony, remove dead members) – different castes allows for division of labor composition of bee society is controlled by queen – she secretes an antiqueen pheromone that inhibits the workers from raising a new queen and prevents development of ovaries in the worker bees if queen dies or leaves, lack of the pheromone stimulates the workers to feed some larvae special food that promotes their development into new queens Honeybee Communication Communication is accomplished through a series of body movements called a dance • if a scout bee finds a rich food source within 50m of the hive, the scout performs a round dance which excites the other bees and causes them to fly short distances in all directions from the hive until they find the nectar • if the food is distant, the scout performs a waggle dance which follows a figure-eight pattern • dances convey information about both distance and direction Altruistic behavior • an animal’s primary mission is to live long enough perpetuate its genes • some animals spend time and energy helping others – this type of helpful behavior is mutualism • reciprocal altruism – one animal helps another with no immediate benefit, however, at some later time the animal that was helped repays the debt • altruistic behavior – one individual behaves in a way that reduces their individual fitness and increase the fitness of the recipient of the behavior – natural selection may favor animals that help a relative because the relative’s offspring carries some of the helper’s genes – this concept is known as inclusive fitness because it includes the genes an animal perpetuates in its kin as well as the genes it perpetuates in its own offspring • Kin selection – form of natural selection that increases inclusive fitness through the breeding success of close relatives (ex. low ranking prairie dogs act as sentries, risking their own lives to protect their siblings and ensure that the genes they share in common continue to the next generation) Examples of Altruistic Behavior 1. Naked Mole Rats • Live in colonies of up to 80 individuals in burrow systems in parts of East Africa • One female is dominant and is the only one to reproduce • “Frequent workers” dig the tunnels and bring food • “Infrequent workers” are larger and occasionally help with heavier tasks • “Non-workers” live in the central nest and protect breeding female and offspring • If a predator threatens the colony, workers are sent out to be sacrificed so that the queen and her young can live • Mole rats in a colony are almost genetically identical • Good example of kin selection • Burrows are a very harsh environment to live in – probably could not survive in that environment without social organization • A colony of social organisms is sometimes considered to be one “super-organism” 2. Vampire Bats of Costa Rica • Live in groups and feed at night by sucking blood from larger animals • If one bat in group fails to feed for more than 2 consecutive nights, it may die of starvation • Bats that have fed successfully regurgitate blood for a bat that has failed to feed • Good example of reciprocal altruism because bat that donated food to a hungry bat may in the future receive blood when it is hungry • There is an advantage for the whole group, because benefit of receiving blood when starving is greater than the cost of donating blood after feeding well Taxis and Kinesis • simple behaviors involving the locomotion of organisms or cells in response to a specific external stimulus – forms of behavior which help to keep an individual animal in a favorable environment • Kinesis – a random movement in which the rate of movement is related to the intensity of the stimulus but not its direction – involves a simple change in activity rate in response to a stimulus (ex. sowbugs and woodlice become more active in dry areas and less active in humid ones, a simple behavior that tends to keep these animals in moist environments) – animals do not move toward or away from specific conditions, but since they slow down in a favorable environment, they tend to stay there • Taxis – a more or less automatic, oriented movement toward or away from some stimulus. – positive taxis is movement toward the stimulus (ex. flatworms moving toward food – chemotaxis or Euglena moving towards light – phototaxis – negative taxis is movement away from the stimulus (earthworms moving away from the light)