Behaviour is influenced by innate and learned factors. Baby sounds (human and bird) are coded by innate neural templates, but young animals must learn and practice the sounds which make up adult repertoires. The motor and memory elements are essential to behaviour. Animal behaviour is one of the oldest studied areas in biology. Pre-agricultural societies needed to understand animal behaviour in order to survive.
Innate = Inborn or present at birth.
Behaviour = What an animal does and how it does it.
Fitness is a central concept in animal behaviour. Since natural selection works on genetic variation caused by mutation and recombination, organisms should have features that maximise fitness over time. Animals are expected to engage in optimal behaviours:
Optimal behaviour = A behaviour that maximises individual fitness.
Optimal behaviour is a valid concept if behaviour is genetically influenced and subject to natural selection. An experiment was carried out that demonstrated that genes influence behaviour.
Two species of lovebirds were interbred. Female Fischer's lovebirds cut long strips of nesting material, which are carried individually to the nest. Female Peach-faced lovebirds cut short strips and carry several at a time by tucking them into her back feathers.
Hybrid females cut intermediate length strips and tried, but failed, to transport them by tucking into back feathers. They learned to carry strips in their beaks, but never gave up all tucking behaviour.
Phenotypic differences in the behaviour of the two species are based on different genotypes. Innate behaviour can be modified by experience. Learned behaviours are typically based upon gene created neural systems that are receptive to learning.
Behavioural ecologists assume animals use optimal behaviour to increase fitness. Therefore because behavioural ecology is based on the assumption that behaviour increases fitness, it leads logically into hypothesis testing and the scientific method for problems in behaviour research.
Behavioural ecology = A field of study that assumes animals increase fitness through optimal behaviour.
Because behaviour is assumed to increase fitness, questions about ultimate causation, or the reasons why behaviours exist are evolutionary questions.
Ultimate causation = the evolutionary reason for the existence of a behaviour.
The immediate mechanism or how a behaviour is expressed is the proximate cause. Proximate causes may be internal processes or environmental stimuli.
Proximate causation = The immediate cause and/or mechanism underlying a behaviour.
Proximate causation limits the range of behaviours upon which natural selection can act. Proximate mechanisms produce behaviours that ultimately evolved because they increased fitness
Example: Behaviour - Bluegill sunfish breed in spring and early summer.
Proximate cause: Breeding is triggered by the effect of increased day length on a fish's pineal gland.
Ultimate cause: Breeding is most successful when water temperatures and food supplies are optimal.
Example: Behaviour - Human "sweet tooth".
Proximate cause: Sweet taste buds are a proximate mechanism that increases the chances of eating high-energy foods.
Ultimate cause: Sweet, high-energy, foods were rare prior to mechanised agriculture. Increased fitness associated with consuming these foods is the ultimate reason for the natural selection of a "sweet tooth".
Ethology pre-dates behavioural ecology. Relying on descriptive studies, ethologits discovered that many behaviours were innate.
Ethology = Descriptive science based on studies of animals in the natural environment.
Innate behaviours may seem purposeful, but animals with innate behaviours are unaware of the significance of their actions. For example some cuckoos are brood parasites. Females lay eggs in the nests of other species. Within hours of hatching, the otherwise helpless cuckoo pushes its host's eggs and/or chicks out of the nest.
Konrad Lorenz, Niko Tinbergen and Karl von Frisch shared the 1973 Nobel Prize for physiology or medicine for their work in ethology.
The most fundamental concept in classical ethology is the fixed-action pattern (FAP).
Fixed-action pattern = A highly stereotyped, innate, behaviour.
Once a fixed-action pattern is triggered, the behaviour continues until completion even in the presence of other stimuli or if the behaviour is inappropriate. A fixed-action pattern is triggered by an external sign stimulus or releaser. Fixed-action patterns are adaptive responses to natural stimuli. Strange responses can be initiated by presenting unnatural situations to animals with fixed-action patterns.
Sign stimulus = An external sensory stimulus which triggers a fixed-action pattern.
Example: Niko Tinbergen noticed male three-spined stickleback fish responded aggressively to red trucks passing by their tank.
Fixed-Action Pattern: Male sticklebacks attack other males that enter their territories.
Sign stimulus: The red belly of the invading male. Sticklebacks attacked nonfish-like models with red on the ventral surface.
Example: Parent/young feeding behaviour in birds.
Fixed-Action Pattern: The begging behaviour of newly hatched chicks (raised heads, open mouths, and loud cheeps).
Sign stimulus: Parent landing at the nest.
Example: Greylag goose egg retrieval behaviour:
Fixed-Action Pattern: Rolls the egg back to the nest using side-to-side head motions.
Sign stimulus: The appearance of an object near the nest. If the goose loses the egg during the retrieval process, it stops the head motion, but continues the "pulling" motion of retrieval. It must sit down before it notices the egg at which time another retrieval FAP is initiated. If an inappropriate object (toy dog, doorknob) is placed near the nest, the goose retrieves it but may not keep or incubate it.
Example: Female digger wasps place a paralysed cricket in their nest that serves as food for the young wasp after it hatches.
Fixed-Action Pattern: She places the cricket 2.5 cm from the nest.
Sign stimulus: Nest site.
Fixed-Action Pattern: She enters the nest and inspects it.
Sign stimulus: Presence of cricket 2.5 cm from the nest.
Fixed-Action Pattern: She exits the nest and retrieves the cricket.
Sign stimulus: Presence of cricket 2.5 cm from nest. If the cricket is moved during the nest inspection stage, the wasp will retrieve the cricket and repeat the FAP from the first step. She cannot get past the "inspect the nest" step if the cricket is not where she left it when she tries to retrieve it.
Digger wasp with prey.
Sign stimuli are usually simple characteristics (e.g. ultrasonic bat sounds trigger avoidance behaviour in moths). Sign stimuli may be specific choices from an array of possibilities.
Example: Herring gull chick feeding behaviour. The adult lowers its head and moves its beak. The chick pecks the red spot on the beak, causing the adult to regurgitate.
Fixed-action pattern: Pecking the red spot on the beak.
Sign stimulus: Red spot swung horizontally at the end of a long, vertical object.
Herring Gulls feeding young.
Natural selection favours cues associated with the relevant behaviour or object. Some randomness is probable in fixing upon one of many possible sign stimuli for a FAP. An animal's sensitivity to general stimuli and its sign stimuli are correlated. For example, frogs' retinal cells are sensitive to movement. Movement is the sign stimulus that releases the tongue-shooting FAP in frogs. A frog starves if surrounded by motionless flies. A supernormal stimulus may elicit stronger responses than natural stimuli. For example, when given a choice between an egg and a volleyball, a Greylag goose ignore the egg and tries to retrieve the volleyball.
Supernormal stimulus = Artificial stimulus that elicits a stronger response than occurs naturally.
Learning = is the modification of behaviour by experience.
Nature versus Nurture
While European ethologits were discovering innate behaviours in nature, American psychologists were finding learning abilities in lab animals. Thus began the debate over nature versus nurture.
Nature versus nurture = The debate over whether instinct or learning is of primary importance in animal behaviour.
Modern biologists feel that behaviour is a result of genetic and environmental factors. Some behavioural aspects seem to be due primarily to either instinct or learning. Language differences among people are learned behavioural variations on an innate ability to vocalise. Likewise songbirds have regional "dialects". Most Drosophila (fruit flies) have an activity cycle of 24 hours. There are individuals with 19 hour cycles. The difference is due to genetic variation.
Learning versus Maturation
Individuals may improve behaviours over time. This is often attributed to learning but, in some cases, may be due to developmental changes in neuro-muscular systems as animals mature.
Maturation = Development of neuro-muscular systems that allows behavioural improvement.
This is when animals stop responding to stimuli that do not provide appropriate feedback. For example grey squirrels respond to the alarm calls of other squirrels. They stop responding if the calls are not followed by an attack ("cry-wolf" effect).
Habituation = Learning to ignore irrelevant stimuli or stimuli that do not provide proper feedback.
Imprinting is a form of learning closely associated with innate behaviour. Konrad Lorenz conducted an experiment with Greylag geese.
Goslings imprinted on mom.
A clutch of goose eggs was divided between the mother and an incubator.
Results Goslings reared by the mother behaved normally and mated with other geese. The incubator goslings spent their first hours of life with Lorenz and preferred humans for the rest of their lives. They even tried to mate with humans.
Konrad Lorenz, Goslings imprinted on "mom".
Conclusions Greylags have no innate sense of "mother" or "gooseness". They identify with and respond to the first object with certain characteristics they encounter. The ability or tendency to respond is innate. The object to which the response is directed is the imprinting stimulus. For Lorenz's geese, the imprinting stimulus was movement of an object away from the young.
Imprinting stimulus = An object in the environment to which the response is directed.
For example, salmon return to the stream they were hatched into spawn. The imprinting stimulus is the unique chemical composition (odour) of the hatching stream. Imprinting is distinguished from other types of learning by its irreversibility and the presence of a critical period during which imprinting can occur.
Critical period = A limited time during which imprinting can occur.
Imprinting is usually thought to involve very young animals and short critical periods. Imprinting may occur at different ages with critical periods of varying durations. Adults require a critical period to "know" their young. Prior to imprinting on their young, adult herring gulls defend strange chicks. After the imprinting period, they kill and eat strange chicks. Sexual imprinting (or species identity) occurs later than parental imprinting and has a longer critical period. Male finches cross-fostered by two different finch species imprinted on the wrong species when they developed a sexual identity. Part of the problem of attempting to rear endangered whooping cranes under sandhill crane parents - whooper chicks attempted to court sandhill cranes - sandhills thought whoopers were goofy! While irreversibility and critical period characterise imprinting, they are not always fixed. The cross-fostered finches eventually mated with females of their own species.
Associative learning = The learning process where animals associate one stimulus with another.
Classical conditioning is a type of associative learning where a specific, or conditioned, response is elicited by a specific stimulus. A Russian physiologist, Ivan Pavlov induced dogs to salivate when they heard a bell. The dogs learned to associate the bell with powdered meat that was the normal stimulus for the salivary response.
Classical conditioning = A process in which an animal learns to respond to an external stimulus which does not normally elicit that response.
Pavlov in his lab.
Operant conditioning, or trial-and-error learning, is another type of associative learning. B.F. Skinner put lab animals in a box with a variety of levers. Test animals learned to choose only those levers that yielded food.
B. F. Skinner
Operant conditioning = A process where an animal learns to associate one of its behaviours with a reward or punishment and then tends to repeat or avoid that behaviour.
English tits learned to open milk bottles left on doorsteps and drink the cream. One or more of the birds discovered its probing behaviour was rewarded when directed at the bottles. Operant conditioning is the basis for most animal training and is common in nature. It appears that genes influence the outcome of operant conditioning.
Observational learning = The ability of animals to learn by observing the actions of others.
Observational learning allows new behaviours to become established and passed on to succeeding generations. The speed with which the tit milk drinking behaviour spread throughout England indicates observational learning on the part of the birds. Song development in many birds involves observational learning as individuals listen to and eventually adopt the songs of older birds.
Play has no apparent goal but uses movements closely associated with goal-directed behaviours. Young predators playfully stalk and attack each other using motions similar to those used to capture and kill prey. Play occurs in the absence of distracting external stimuli. However play is potentially dangerous or costly. For example young vervet monkeys are at higher risk of being caught and eaten by baboons when they are at play. In a study of young goats, 1/3 sustained play injuries that resulted in limps.
What is the selective advantage of play?
Practice hypothesis: play is a type of learning that allows the perfection of survival behaviours. However, play movements rarely improve after the first few practices.
Exercise hypothesis: play keeps the cardiovascular and muscular systems in condition and is common in young animals because they do not exert themselves in other ways while they are under parental care.
Lion cubs play.
Insight learning is also called reasoning.
Insight learning = The ability of animals to perform appropriate behaviours on the first attempt in situations with which they have no prior experience.
Insight learning is best developed in primates. A chimpanzee placed in an area where a banana is hung too high to reach, but where boxes are scattered about, will "size" up the situation, stack the boxes, climb up and retrieve the banana.
The Ultimate and Proximate Bases of Learning
Ultimate bases of learning
Behaviours are relatively fixed patterns controlled by simple stimuli. Fixed pattern responses can be modified in their details by simple kinds of learning. The capacity to learn is a product of evolution and adaptation that enhances fitness. Learning is subject to natural selection in that learning is programmed to occur at specific times in the maturation process and is based on a limited set of stimuli.
Proximate bases of learning are poorly known. Some studies link simple learning to internal biochemical or physiological changes.
Most animals repeat behaviours at regular intervals (daily, seasonally). Animals carry out behaviours when their particular ecological niches can be exploited most profitably from a survival and fitness standpoint. This can cause behavioural rhythms. The proximate bases for rhythms are not obvious. Circadian (daily) rhythms are regulated by environmental cues. Such rhythmic behaviour is based on exogenous (external) and endogenous (internal) factors. Circadian rhythms are strongly influenced by endogenous factors, or the biological clock. Internal rhythms do not match environmental time so exogenous cues are used to keep the cycles in sync. Light is the most common exogenous cue.
Flying squirrels are normally active at night. Flying squirrels were placed in constant darkness and their activity monitored.
Rhythmic activity continued. Since normal cycles deviate from the 24 hour clock, the test squirrels eventually were out of phase with the environment.
Biological clocks are intrinsic, but the timing of rhythmic behaviour must be adjusted to environmental cues to remain in sync.
Even when endogenous factors are present, the internal, proximate, timing mechanism is unknown. A biochemical, possibly molecular, clock has been hypothesised. It is unclear if endogenous clocks are important in longer cycle rhythmic behaviours. Breeding and hibernation are partially based on physiological and hormonal changes linked to exogenous factors such as day length.
Studies have concentrated on the proximate mechanisms animals use to detect and respond to external cues that guide movements. The ultimate bases for oriented movements are related to animal adaptations to different environments and the development of behaviours that bring them to those environments at the proper time of the year. Animals use a variety of cues to guide them in their movements.
Kinesis involves a change in activity rate in response to a stimulus. Sowbugs are more active in dry areas and less active in humid regions. This behaviour tends to keep them in moist areas.
Kinesis = A randomly directed change in activity rate in response to an environmental stimulus.
Taxis is a directed movement toward or away from a stimulus. Housefly larvae are negatively phototactic after feeding. Presumably this makes them less visible to predators. Trout are positively rheotactic. Swimming against the current keeps them from being swept downstream.
Taxis = A semi-automatic, oriented, movement toward or away from a stimulus.
Migration is the most commonly known type of oriented animal movement. Migrants generally make an annual round trip between two regions (e.g. birds, whales, some butterflies, some pelagic fish).
Migration = The seasonal movement of animals over relatively long distances.
Migrating animals use three mechanisms: piloting, orientation and navigation.
Piloting = Movement of animals from one landmark to another.
This behaviour is used over short distances, and is not useful at night or over the ocean.
Orientation = Movement of animals along a compass line.
Animals that use orientation can detect compass directions and travel in a straight line to a destination.
Navigation = The ability of animals who can orient along compass lines to determine their location in relation to their destination.
Migrant starlings captured in the Netherlands were released in Switzerland. Juvenile birds oriented in a straight-line to Spain. Adults navigated a new route to their wintering grounds in northern Europe. Many birds use celestial points for orientation and navigation. These animals need an internal clock to compensate for the movement of the sun and stars. The indigo bunting avoids the need for an internal clock by fixing on the north star. Some birds, bees and bacteria orient to the Earth's magnetic field. The mechanisms are poorly known, but magnetite, an iron-containing ore, has been found in animals that orient to the magnetic field.
Generalists are animals that feed on many items. They are not efficient collectors of any single food, but take advantage of multiple options when foods are scarce. Often generalists concentrate on abundant prey. Generalists develop a search image for a favoured item. If the item becomes scarce, a new search image is developed. Search images let generalists combine efficient short-term specialisation with generalist flexibility.
Search image = The ability of a generalist feeder to learn the key visual characters of a prey item.
Specialists are animals that feed on specific items and usually have highly specific morphological and behavioural adaptations. They are extremely efficient foragers. Food habits are fundamental to an animal's niche and may be shaped by interspecific competition and evolutionary factors.
Natural selection should favour foraging strategies that maximise gains and minimise costs in terms of calories gained and expended. Other criteria such as nutrient gain may be equally important. Foraging costs include energy needed to locate, catch and eat food; the risk of being caught by a predator while feeding; time taken from other activities such as courtship and breeding. Behavioural ecologists analyse trade-offs to predict optimal foraging strategies. These trade-offs include predation risk vs. energy gain - energy gain vs. handling time. For example, small mouth bass eat minnows and crayfish. Since no preference is shown, each may be optimal under different conditions. Minnows have more useable energy per unit weight than crayfish, but are harder to catch. Crayfish are easier to catch, but more difficult to subdue.
Animals modify behaviour to keep the ratio of energy gain to loss high. This ability is probably innate, although learning may be involved.
Bluegill sunfish eat small crustaceans. Optimal foraging theory predicts the proportion of small to large prey will vary with the density of the prey populations. At low densities, sunfish should not be selective but at high densities, they should concentrate on larger prey.
Sunfish were more selective at higher prey densities, but not to the extent predicted. Young fish were less efficient than adults. Younger fish may be less able to judge size and distance due to incompletely developed neural systems.
Maturation and learning may result in increased foraging efficiency in adults.
Social behaviour is any interaction between two or more animals and may involve conflict or co-operation. Co-operating individuals usually maximise individual benefits even if it costs other participants.
Agonistic behaviour = A contest of threat displays which continues until a participant submits and yields access to a resource (e.g. mate, food territory).
Ritual behaviours are prevalent so it is rare that participants are seriously injured.
Ritual = Symbolic behaviour that minimises the possibility of serious injury to the antagonists.
Natural selection favours ending a contest as soon as a winner is established because further conflict could injure the victor as well as the vanquished. For example canines show agonistic behaviour by trying to look larger. They bare teeth; erect ears, tail and fur; stand upright; and make eye contact. The loser submits by sleeking its fur, tucking its tail and looking away.
The top ranked member of a social group controls the behaviour of the members of the group. The second ranked animal controls everyone except the top individual and so on down the line to the lowest ranked animal.
Dominance hierarchy = A linear social organisation within a group.
The top ranked animals are assured access to resources. Low ranked animals do not waste energy or risk harm in combat. Wolf packs typically have a female dominance hierarchy. The top female relies on food availability to control mating in the pack.
Territories are defended areas typically used for feeding, mating, rearing young etc.
Territory = An area defended from conspecifics.
Territory size varies with the species, territory function, and the amount of resources available. For example some species defend territories during the breeding season and form social groups at other times of the year. It should be noted that territories are not home ranges. Home ranges are areas which animals inhabit but do not defend. However territories and home ranges may overlap. Territories are usually successfully defended by their owners. Owners usually win because a territory is more valuable to the owner since he is familiar with it. Ownership is continually proclaimed - this is the primary function of a bird song, red squirrel chattering and the bellowing of sea lions. Others use scent marks or patrols to announce their presence. Defence of a territory is usually directed at conspecifics who are most likely to compete directly for the same resources. Dominance hierarchies and territoriality tend to stabilise population densities by assuring enough individuals reproduce to result in relatively stable populations from year to year.
The correlation between mating behaviour and reproductive fitness is vital to behavioural ecology.
Species often have a complex courtship ritual unique to that species. Courtship's are a series of fixed-action patterns alternately triggered by the participants. Ritual courtship's probably evolved from behaviours that once had a direct meaning. For example, male balloon flies spin oval silk balloons which they carry while flying in a swarm. The swarm is approached by females seeking mates. A female accepts a male's balloon when they fly off to copulate. In a related species, the male brings a dead insect for the female to eat while they mate. In another species, the insect is presented inside a silk balloon, possibly because silk helps subdue the insect or makes it look larger. Balloon flies eat nectar. The ritual has evolved into bringing something that was once associated with food. It is as if, over evolutionary time, a suitor wooed a lady with diamonds, then with a box containing diamonds and finally with an empty box.
Courtship assures each partner that the potential mate is not a threat, is the proper species, the proper sex and in the correct physiological condition. Courtship may allow one or both sexes to choose a mate from a number of candidates. Females are usually more discriminating than males because they normally have a greater parental investment. In most animals the eggs are usually larger and more costly to produce than sperm. However gametes of placental mammals are closer in size, but females invest considerable time and energy carrying young before birth.
Parental investment = The time and resources an individual expends to produce an offspring.
Competition among individuals of the same sex (usually males) may determine which individuals of that sex will mate. Most males mate with as many females as possible. They compete with other males for mates and may try to impress females. In most species males perform more intense courtship displays than females. Secondary sex characteristics may be highly developed in males (e.g. deer antlers, bird colours).
There are two ultimate bases for mate selection.
1. If the other sex gives parental care, it is best to choose the most competent mate. For example, male common terns bring fish to potential mates as part of the courtship ritual. This behaviour may be a proximate indicator of his ability to feed the chicks. Some females prefer males with the most extreme and energetic courtship displays or secondary sex characteristics. These characteristics may be proximate indicators of the male's health.
2. Genetic quality is important when males provide no parental care and sperm are their only contribution to offspring. Some species have a communal area where males display; this is called a lek. Females visit the lek and choose a mate. The proximate basis for her choice is a preference for males that court the most vigorously and have the most extreme secondary sex characteristics. It may be difficult to determine if differential mating success among males is due to male-male competition, female choice or both. For example Three-spined stickleback courtship is based on stereotyped releasers and FAPs. Despite this, the female can back out of the courtship anytime. The female's choice is probably ultimately based on the quality of the male's parental care, because only male sticklebacks give parental care.
Promiscuous = A mating system with no strong pair bonds or lasting relationships.
Monogamous = A mating system where one male mates with one female.
Polygamous = A mating system where an individual of one sex mates with several of the other.
Polygyny is a mating sub-system where one male mates with multiple females (BLACKBIRDS).
Polyandry is a mating sub-system where one female mates with multiple males (PHALAROPES).
The needs of the young are an important ultimate factor in the evolution of mating systems. Most birds are monogamous. Young birds often require significant parental care. A male may ultimately increase his reproductive fitness by helping a single mate rear a brood than by seeking additional mates. Polygyny is common in birds where the young are able to care for themselves soon after hatching. Males can maximise their fitness by seeking additional mates.
Another factor influencing mating systems and parental care is the certainty of paternity. For example young born of eggs laid by a female definitely contain the female's genes, but even in monogamous species, the young could have been fathered by male other than the female's normal mate. The certainty of paternity is relatively low in species with internal fertilisation because mating and birth (or egg laying) are separated over time. Exclusive male parental care is rare in birds or mammals. The certainty of paternity is higher when egg laying and mating occur together, as in external fertilisation. Parental care, when present, in fishes and amphibians is as likely to be by males as by females. When parental care is given by males, the mating system may be polygynous with multiple females laying eggs in a nest tended by a male.
Communication = The intentional transmission of information between individuals.
Behavioural ecologists assume communication has occurred when an act by a "sender" produces a change in the behaviour of another individual, the "receiver". However Ethologits assumed communication evolved to maximise the quantity and accuracy of information. Behavioural ecologists argue that communication evolved to maximise the fitness of communicators.
Animals lie. Mimicry often is adaptive to the sender and maladaptive for the receiver.
Male and female Photinus fireflies communicate by a characteristic pattern of flashes. Females of the predatory firefly genus Photurus mimic the female Photinus flash pattern, attracting male Photinus fireflies which they kill and eat. This is not just for an extra meal. These males contain defensive chemicals that Photuris females can incorporate into their own bodies and use to repel predators, such as spiders.
Big Dipper Firefly, Photinus pryalis (L.)
In some mammals, a new dominant male kills young born too soon to be his offspring. Without dependent young, females ovulate sooner, allowing the new male to father their young. Hanuman langur females in the early stages of pregnancy solicit copulation's from new dominant males. When they give birth shortly before young fathered by these males would appear, they may deceive the male into treating their young as his own. An evolutionary consideration is the mode used to transmit information. Animals use visual, auditory, chemical, tactile and electrical signals. The mode used to transmit information is related to an animal's lifestyle. Most mammals are nocturnal and use olfactory and auditory signals. Animals that communicate by odours emit chemical signals called pheromones. Pheromones are important releasers for specific courtship behaviours and are the cues and scouts release that guide other ants to food. Birds are mostly diurnal and use visual and auditory signals. Diurnal humans also use visual and auditory signals. If we could detect the chemical signals of mammals, then mammal sniffing might be as popular as bird watching.
A complex communication system is found in honeybees. In order to maximise foraging efficiency, workers communicate the location of food sources which change as flowers bloom and new patches are found. Karl von Frisch studied honeybee communication. He found individual bees communicated to other bees when they returned to the hive. The returning bees "dance" to indicate the location of food. If the source is <50m, the bee does a "waggle dance", moving rapidly sideways in tight circles and regurgitating nectar. Workers leave the hive and forage nearby. If the food is farther away, the bee does a "waggle dance", a half-circle swing in one direction, followed by a straight run and then a half-circle swing in the other direction. This dance indicates location in two ways:
1. The angle of the run in relation to the vertical surface of the hive is the same as the horizontal angle of the food in relation to the sun.
2. Distance to the food is indicated by variations in the speed at which a bee wags its abdomen during the straight run.
Behaviour that maximises individual reproductive success will be favoured by selection; regardless of how much damage such behaviour does to another individual, local population, or species. Animals occasionally exhibit apparently unselfish or altruistic behaviour.
Altruistic Behaviour = A behaviour that reduces an individual's personal welfare but benefits others.
When parents sacrifice their well being to produce and aid offspring, they increase their fitness because it maximises their genetic representation in the population. Like parents and offspring, siblings share 1/2 their genes, so selection might favour helping one's parents produce more siblings, or even helping siblings directly. Selection might result in animals increasing their genetic representation in the next generation by "altruistically" helping close relatives. The inclusive fitness includes assistance to relatives that maximises individual fitness. The coefficient of relatedness is the proportion of genes that are identical in two individuals because of common ancestry. The higher the coefficient of relatedness, the more likely an individual is to aid a relative.
Prairie dog warns others of the colony of danger.
Inclusive fitness = The reproductive fitness of an individual as measured by its offspring and assistance to the reproductive efforts of close relatives.
Kin selection = The mechanism of increasing inclusive fitness.
The contribution of kin selection to inclusive fitness varies among species. It may be rare or non-existent in species that are not social or disperse widely. In predicting if an individual will aid relatives, behavioural ecologists have derived a formula that combines coefficients of relatedness, costs to the altruist and benefits to the recipient. If kin selection explains altruism, then examples of unselfish behaviour should involve close relatives. Belding's groundsquirrels give alarm calls when danger appears. These calls alert other squirrels but increase the risk to the alarm givers. Females remain near their birth sites and are usually related to other members of the group. Only female give alarm calls. Worker bees are sterile, however they labour on behalf of a single fertile queen. Workers sting intruders, a behaviour that defends the hive but results in the death of the worker. The queen is the mother of all the bees in the hive. Nesting red-cockaded woodpeckers are aided by 2-4 nonbreeders that assist in all aspects including incubation and feeding young. Nest helpers are older offspring of the breeding pair or siblings of one parent that have been unable to establish a breeding territory. Helpers may eventually inherit the territory.
Altruistic behaviour toward non-relatives sometimes occurs. This behaviour is adaptive if there is a reasonable chance of the aid being returned in the future. Reciprocal altruism only occurs in stable social groups where individuals have many opportunities to exchange aid.
Cognition = Knowing, including awareness and judgement.
It is difficult to determine if animals are aware of themselves and their surroundings. The method used, behaviourism, does not test for cognitive functions.
Behaviourism = A mechanistic approach which describes behaviour in terms of stimulus and response.
Cognitive ethologits think cognitive ability arises through natural selection and forms a phylogenetic continuum stretching into evolutionary history.
Cognitive ethology = A view that sees conscious thinking as an inherent part of animal behaviour.
The book, Socio-biology by E.O. Wilson (1975) present the thesis that social behaviour has an evolutionary basis. This thesis proposed that behavioural characteristics are expressions of genes favoured by natural selection. This rekindled the nature-versus-nurture controversy.
An example of the debate involves cultural taboos on incest. Incest avoidance is adaptive because inbreeding may increase the frequency of genetic disorders. In nature we see that many species avoid incest. As well most human cultures have taboos forbidding incest. Is there an innate aversion to incest or is this an acquired behaviour?
The argument in favour of the "nurture or learned behaviour" position is: cultural taboos are unnecessary if the behaviour is innate, therefore incest avoidance is a learned behaviour and the social stigma attached to incest is based on experience.
The argument in favour of the "nature or genetic behaviour" position is: the occurrence of incest taboos in many cultures is evidence for an innate component and taboos are simply proximate mechanisms that reinforce a behaviour that ultimately evolved because of its effect on fitness.