9a

• Behavioural Ecology


  The evolutionary and ecological basis of behaviours, how animals adapt their behaviour to the environment, and how behaviour affects survival and reproduction
• Decisions


  1. Why do animals do what they do?

  2. What are the selective advantages of these behaviours?

  3. What triggers a change or choice of behaviour?
• Behavioural Ecology


  • Many branches and aspects that affect the ecology of the animals, here tying to focus on those that impinge on other species and ecosystems and less on e.g., reproductive strategies
• Ethology


  The study of animal behaviour from an evolutionary prospective
• Proximate mechanisms


  Neuronal, hormonal, anatomical mechanisms
• Ultimate causes


  Selection pressures that shaped the evolution of the behaviour
• Tinbergen's four questions


  • Adaptation / Function - how does the behaviour increase the animal's fitness? (Ultimate)
  • Evolution - how did the behaviour evolve and how has selection changed it over time? (Ultimate)
  • Causation - what are the triggers or stimuli that cause the behaviour to be performed? (Proximate)
  • Ontogeny - how has the behaviour changed over the lifetime of the animal? (Proximate)
• Inheritance of behaviours


  • Behaviours can be learned or inherited
  • Much of animal behaviour is unlearned (innate) and stereotypic (always exactly the same)
  • Stereotypic behaviour is often species-specific
• Hawk/Goose effect


  • Baby birds show a reaction to a hawk-like silhouette (cower) but no reaction to a goose-like silhouette
• Lorenz's study of courtship behavior in ducks


  • Hybrid offspring expressed some elements of each parent's display, but in novel combinations – they were inherited
  • Females were not interested in males performing hybrid displays: evidence that sexual selection had shaped these genetically determined behaviors to be reproductive isolating mechanisms
• Genes do not encode behaviour; but gene products such as enzymes can affect behaviour by starting series of gene-environment interactions that underlie development of proximate mechanisms
• Inheritance of songbird songs

  • Male songbirds have species-specific songs used in territorial displays and courtship
  • White-crowned sparrows must hear the song when they are nestlings, even though they do not sing it for a whole year
  • As males approach maturity, they begin singing and match song with the stored memory
  • If the bird is deafened before starting to sing, it will not develop the species-specific song
• Learning


  • Animals are capable of learning and developing a new response to a stimulus
  • Behaviours can be quite plastic
  • Animals are capable of learning from each other
• Behavioural influences


  • There may be a multitude of potential triggers (situations that produce innate responses) but especially for complex or learned behaviours there can be numerous influences or conflicting pressures
• Costs to behaviours


  • Animals have limited resources and so have to make decisions about how they spend these
  • This can be considered in terms of a cost-benefit analysis – will they get more back than they have expended? What are the risks involved?
• Three basic costs to actions

  • Energetic: the actions of the animal cost energy
  • Risk: increased chance of death, injury or infection etc. as a result of the behaviour
  • Opportunity: potential benefits that are forfeited or lost from taking the action
• Dominant male deer during breeding season

  • Encounters an unhealthy-looking female accompanied by a young male - what are the potential costs if he tried to mate with her?
• Optimal Foraging


  • Foraging (finding and processing food) in particular is well studied in terms of costs and benefits
  • How long will it take to find a given food item, how much effort is involved, what will be the return?
  • The state of the animal is important in these calculations
• Optimal foraging


  • Predicts that animals will make choices that maximise their energy intake
  • The more rapidly they can take in the fuel they need, the less opportunities are lost and the fewer risks are taken
• Reindeer foraging


  • Prefer to feed on plant species where a single bite takes in the most leaf mass, maximising energy intake and reducing predation risk
  • In areas of low predator density, they can persists on smaller plants by foraging time increases
• Factors that vary in food

  • How easy it is to find
  • How easy it is to process
  • Energetic value
  • Nutritional value
  • Palatability
• Crab foraging on mussels

  • Prefer mid-sized mussels as a prey item
  • Small mussels are easy to open, but contain very little inside
  • Large mussels contain a lot of meat inside but take a lot of time to process
  • Mid-sized mussels have the optimal trade-off of effort to process and energy return for that effort
• Foraging by time


  • Some animals may balance effort primarily by time rather than energy
  • Some bees chose to forage according to the time taken to reach a location and parasitoid wasps by the amount of time taken to find a potential host
• Galapagos marine iguana


  • Juveniles primarily feed in the intertidal zone, adults underwater
  • Are more efficient at swimming than walking, but get cold in the sea – takes time to warm up again
  • Larger animals chill slower in water
  • Intertidal times are limited
  • Ends with a complex balance of time and energy to forage effectively at different sizes and at different times

  
• Landscape of Fear


  • Foraging is not just about food, but it is also about risk
  • Animals can carry a mental map of areas to avoid or limit their time there
• Deer and elephants


  • Deer avoid valleys in winter in the western US due to deep snow and vulnerability to wolves
  • Elephants that raid crops approach and leave farms in a similar way to waterholes to minimise risk of exposure
• Ideal Free Distribution


  • Describes how animals should optimise where they forage to maximise their intake
  • Ideal means they have a perfect knowledge of the environment and the quality of patches, and Free means they are free to move between patches
• Analyses of real world examples show some support for the Ideal Free Distribution model, but the real world is rather more complex
• Resource defence


  • When is a resource worth defending?
  • Dung beetles take three basic approaches to using this resource
• Ideal free distribution (IDF) model


  • Describes how animals should optimise where they forage to maximise their intake
  • Assumes animals have perfect knowledge of the environment and quality of patches
  • Assumes animals are free to move between patches
• Analyses of real world examples show some support for the IDF model
• Examples supporting IDF model

  • Bumblebees distribute themselves 'evenly' among patches of flowers when scaled by flower number and nectar availability
  • In African wild dogs, pack size correlated with prey density when travelling time was factored in
• The IDF model provides a baseline or null model for examining animal distributions
• Resource defence


  When a resource is worth defending
• Dung beetle strategies for using dung

  • Roll some of it away to bury
  • Make a ball within the pat
  • Tunnel into the soil beneath to make an egg chamber
• Dung beetle strategies


  • Tunnellers are horned animals that defend a resource, and rollers are hornless and do not
  • Dung is a limited but valuable resource
  • Rollers can steal each other's balls, but by taking it away they are protecting it
  • Female tunnellers may compete with each other for dung to make the biggest brood ball, while males guard the dug tunnels to protect the ball and the egg
• Living in groups


  • Provides a cost-benefits trade off
  • Competition is usually most intense with other members of the same species
  • Risks include increased competition, disease spread, attracting predators, and risk of EPCs for low ranking animals
• Advantages of living in groups

  • Vigilance - multiple animals scouting for predators, can increase feeding times
  • Dilution - when attacked, there are numerous possible targets so any individual is less at risk
  • Group defence - groups may be capable of fending off threats that individuals are not
• Group foraging


  • If resources are plentiful, groups may form passively
  • May be increased efficiency (food escapes to another)
  • May be able to tackle new (especially bigger) prey
  • May be able to find food more effectively if it is patchy
  • Can also share knowledge (how to handle food, learn of new patches etc.)
• Bovids


  • Antelope and their kin
  • All are herbivores (grazers and browsers) and vary from c. 1 kg to 1 t
  • All species are predated by various carnivorans
  • Must trade off between feeding and vigilance
  • Also issues of body size (need more food, but can digest tough plants) and competition for reproduction