A6 Ethology Flashcards
What is ethology?
Ethology is the study of animal behaviour in natural conditions.
Animals are adapted to their natural habitat in their behaviour. If we remove them from this habitat and place them in a zoo or laboratory, animals may not behave normally because they may not receive the same stimuli as in their natural habitat. For this reason it is best whenever possible to carry out research into animal behaviour in their natural habitat rather than in an artificial environment.
How are natural selection and behaviour linked?
Natural selection can change the frequency of observed animal behaviour.
Natural selection can effect the frequency of behaviours, if animals are separated and develop different habits and behaviours and are then put in contact again, they will compete and only those with the useful behaviours will survive.
Behaviour that increases the chance of survival and reproduction will become more prevalent in a population.
How are Coho salmon adapted for breeding? (Learned behaviour)
Coho salmon breed in rivers, then when the adults have bred they die, and the young, after about a year, go into the ocean to live, they return to the river to breed themselves.
The Coho salmon can form two different breeding populations, this increases their chances of survival. They can either turn into Jacks or Hooknoses. The Hooknoses are larger and fight with other males to fertilise eggs. The Jacks are smaller and sneak up without being seen in order to fertilise eggs.
Whether a salmon becomes a Jack or a Hooknose depends on growth rate, if it grows quickly then it can return to the river and sneak up on the eggs and will become a Jack. If it grows more slowly then it will remain in the ocean for about a year longer and be significantly larger and be a hooknose.
Give an example of innate behaviours increasing chances of survival?
Female lions. Female lions come into oestrus at the same time. Female lions can only breed when they come into oestrus. This has several advantages, the females have their cubs at the same time so are all lactating while the cubs are suckling, so they can suckle each other’s cubs when they are hunting, increasing the cubs’ chance of survival. Also a group of male cubs of the same age are ready to leave the pride at the same time so can compete for dominance of another pride more effectively. This is because when males reach around 3 they are expelled from the group and have to go and compete to take dominance over another. This is most effective if they are fighting in two’s. Then once the dominant of another pride they kill off the male cubs and breed with the females to ensure the stronger male genes are passed down and the weaker are not.
Give an example of the genetic basis of behaviour changing by natural selection?
The blackcap, Sylvia atricapilla breeds during the northern summer. Until relatively recently, populations of blackcaps that breed in Central Europe including Germany almost all migrated to Spain and Portugal for the winter, where the weather is warmer and the availability of food is greater. During the second half of the 20th century a few blackcaps from the population in Germany were found to be migrating to Britain and Ireland instead. The numbers of blackcaps overwintering in Britain rose rapidly to more than 10%. There are several possible reasons for this change in migration behaviour. Global warming has led to winters being warmer in Britain so the migration to Germany is not necessary. Many people in Britain feed wild birds in winter which may facilitate survival of over wintering blackcaps more than in Spain, which may prompt earlier migration to breeding grounds. Blackcaps that arrive earlier take the best territories - another advantage of overwintering in Britain.
How was the blackcap research carried out?
It was done rigorously, because lots of people say things about evolution or natural selection and although they may be obvious they are only stories until tested. So the blackcap test was done very carefully.
Eggs were collected in Germany from parent birds that had migrated to Spain. The young were reared without their parents so that they could not learn from them and when they migrated the direction was recorded. Birds whose parents had migrated to Britain tended to fly west wherever they were reared and birds whose parents had migrated to Spain tended to fly south-west. They therefore responded migratory stimuli in the same way as their parents, indicating that the direction of migration is genetically determined, and can thus be subjected to long-term evolutionary change under natural selection.
Give an example of the evolution of altruistic behaviour by natural selection?
Female vampire bats live in colonies of 8-12 individuals, with the same individuals roosting together for several years. They feed off mammalian blood each night. If a bat fails to feed for two or three consecutive nights they risk death from starvation. However this rarely happens because when the bats return to the roost at the end of the night, those that have fed regurgitate blood for those that have not.
How do we know their behaviour is altruistic?
- There may be siblings or mothers with daughters in a group but tests have shown that there are unrelated females who also share blood, so blood sharing is not a kin-selection.
- giving blood to an individual who has not fed incurs a cost to the giver because some of their daily diet is lost, so blood sharing is not merely cooperation - it is genuine altruism.
We might not expect this in natural selection. We expect natural selection to not promote behaviour that incurs a cost, because it should reduce the chance of survival, reproduction and the passing on of genes. Blood sharing is an example of reciprocal altruism. Individual A gains a benefit from giving blood to Individual B because Individual B survives and can share blood on later if individual A fails to feed. It only occurs in stable groups of females that roost together as it aids the chances of survival and reproduction of all the members of such groups.
What does altruistic mean?
Behaviours that benefit others; selfless
Give an example of increasing chances of survival by optimal prey choice?
Studies have shown that the prey chosen by animals tends to be the type that gives the highest rate of energy in return. For example the shore crab prefers to eat mussels of intermediate size when presented in an aquarium with equal numbers of each size. This is because mussels of intermediate size are the most profitable in terms of the energy yield per second of time spent breaking open the shells.
Give an example of mate selection?
Males in many birds of paradise have many almost excessive features for example, very colourful tails and complicated and eye-catching courtship dances, which do not help with flying or catching prey or food. The coloured plumage and courtship dances of birds help to avoid interspecific hybridisation by allowing females to by allowing females to determine if a male belongs to their species, but this could be achieved in much more subtle ways than those used by birds of paradise and biologists have long speculated on the reasons for exaggerated traits.
Darwin explained them in terms of male selection - females prefer to mate with males that have exaggerated traits. The reason may be that these traits indicate overall fitness. If a bird of paradise has enough energy to flow and maintain elaborate plumage and repeatedly to carry out very vigorous courtship displays it indicates that the male must have fed efficiently. If it can survive in the rainforest with the encumbrance of its tail feathers and with bright plumage that makes it visible to predators, it is probably well adapted in other ways and is therefore a good mate to choose. Over the generations females that selected males with showier plumage and more spectacular courtship dances have produced offspring fathered by males with greater overall fitness. Natural selection has therefore caused these traits to become exaggerated.
What is the difference between changing learned and innate behaviour?
Learned behaviour can spread through a population or be lost from it more rapidly than innate behaviour.
Innate behaviours can only be modified by natural selection because they are programmed into an animal’s genes, there must be variation in the alleles that affect the behaviour and a change in allele frequencies in the population due to one behaviour increasing the chances of survival and reproduction over the other patterns of behaviour. However innate behaviours take no learning time and are present the second an individual is born.
Other patterns of behaviour are either partially or entirely learned - although these take longer to develop in an individual, they do not involve changes in allele frequency and can spread in a population relatively rapidly as one individual learns from another. Chimpanzees show many examples of tool use that is learned, with considerable variation between the groups of chimpanzees in the types of tools used. If one individual discovers a new use of an object as a tool others can learn it quickly. But they can also disappear from a population quickly, an example is a blue tit feeding on cream.
What is an example of the development and loss of learned behaviour?
Blue tits were first observed pecking through the aluminium foil caps of milk bottles left outside houses, to drink the cream. This behaviour was really quickly discovered over 150 kilometres away, which is much more than blue tits normally fly. The speed of it shows that it is learned rather than innate. During the Second World War they stopped delivering milk for 7 years, this is longer than the average life of a blue tit which is 5 years. But when the deliveries restarted again the blue tits were once again stealing cream from them. Then recently it was reported that they had stopped, this may be because it was not beneficial anymore because much less milk is delivered.
