Behavioral Ecology: Optimal Behavior and Adaptation

Behavioural Ecology Introduction

• Behavioural ecology seeks to understand why animals exhibit particular behaviors by examining their functional significance.
• The session explores how a particular function is considered adaptive and discusses methods to determine if a behavior is adaptive.

Optimal Behavior

• Appropriate physical structures and functions are vital for passing genes to the next generation.
• Suitable behaviour is equally important for animals' survival and reproductive success.
• A character is adaptive if it aids in reproduction or survival within a specific environment.
• The term "optimal" can replace "adaptive," denoting that a trait or character is well-suited for an environment's needs.

Short Term Optimality

• Short term optimality refers to optimizing particular function in an animal’s daily life.
• An insect searching for food can optimize its energy expenditure by using the most efficient method.

Long Term Optimality

• Long term optimality views behavior as optimal if it leads to viable offspring, measurable by reproductive success
• Reproductive success is the ability to pass genes to the next generation, based on the number of offspring that reproduce.
• Fitness is related to reproductive success
• Indicators of reproductive success include egg survival, juvenile survival to fledging, and the number of inseminated mates.

Darwinian Fitness

• Darwin used term "fitness" to describe the capacity to produce offspring; he didn't define the term itself
• Individuals with the most suitable traits in population will survive better than others.
• According to Darwin, an individual's fitness depends on the ability to survive to reproductive age, success in mating, and the fecundity of the mated pair.

Inclusive Fitness

• Darwinian fitness does not explain all behaviours, leading to the concept of 'inclusive fitness’
• Darwinian fitness considers the fitness of an individual, while inclusive fitness considers the fitness of a gene pool
• Worker ants contribute to the survival of the ant colony, sharing genes with other ants
• Natural selection effectiveness depends on a mixture of genotypes in a population, relating to environmental conditions
• Natural selection maximizes inclusive fitness, i.e fitness of a gene pool: animal's fitness depends on reproductive success and that of its relatives.

Measuring Adaptability of a Behavior

• Adaptations are now explained using terms from economics
• Behavioral ecologists describe behaviour optimality using terms like cost, benefit, and budget constraints.

Cost Benefit Analysis

• Cost can be the price and time spent preparing the meal
• Benefits can be the satisfaction and nutritional value of having the meal
• Choosing an option is limited by a budget constraint: the income of each family
• The family unable to survive if an un-optimal option is chosen

Measuring/investigating function of a behaviour

• Methods to investigate or measure adaptation of a specific behaviour answers to questions about the function of this behaviour

Comparative Method

• Comparing particular behaviour in related species

Optimality Theory

• Finding put why behaviour in particular species is performed in such a way but not in other way

Game Theory

• Finding out why variations in behaviour exist and survive in a behaviour
• Game theory: interactions between two individuals (contest) or among many (scramble)

Mobbing Behaviour of Black Headed Gulls

• Breed in Europe in spring and summer and migrate to North Africa during winter
• Nest in open grassy lands with many gulls
• Mobbing: gulls fly towards approaching predator or humans with calls, defecation, diving, and attacking.
• Mobbing scares predators.
• There is an evolutionary cost of the action (risk of injury/death, energy expenditure) and evolutionary benefits

Comparative Approach

• Studies adaptations at the species level to understand why a particular species shows a behaviour and others don't.
• Ground nesting gulls show mobbing behaviour to prevent predation
• Gulls nesting on vertical cliffs do not show mobbing behaviour

Optimality Theory

• For black-headed gulls, mobbing requires getting close to the predator for a good effect
• However, the danger of injury or being killed also increases
• Optimal distance is where the chances of injury/death and effectiveness of mobbing behaviour balances, which is three meters
• Optimality theory: trying to predict the distance where cost benefit is maximal

Game Theory

• Social interactions within a species affecting the costs and benefits of alternative traits
• Daring mobbers approach the predator closely and effective in chasing predator
• Cautious mobbers wait at a distance while daring mobbers attack the prey to wait
• Cautious mobbers are more unlikely to get killed
• It is most important for daring mobbers to be apart of the survival of black headed gulls
• Equilibrium important where both daring and cautious mobbers enjoy equal fitness; have optimal mobbers to protect

Testing Adaptive Value of a Behaviour

• Testing the adaptive function of a specific behaviour
• Using the hypothesis makes it easier to make a prediction with these methods: additional observation and experimental procedures

Predictions of the Adaptive Value

• Prevent from destroying their nesting sites
• To prevent predators from feeding on its nestlings and eggs
• Prevent predators from attacking and feeding in adult black headed gulls

Evaluation of the Hypothesis

• Direct observation easily finds out about function of a particular behaviour
• Hans Kruuks studied predation of black-headed gull colony for two years: black-headed gulls attack more crows and herring gulls than more other animals
• Experimental evidence reduces predation of eggs of the black-headed gulls, meaning the eggs reduce predation of eggs
• Kruuk experimented disturbing egg predators in order to test it

Functions of Shell Removing Behaviour in Black Headed Gulls

• Shell removing behaviour: adults remove broken shell from nest
• Protect newly babies from broken edges of shell
• Prevent bacteria and microorganism could breed in the fluid
• Colour is difficult for predators to differentiate apart with patterns, but can hatch white interior from shell
• Tinbergen experimented artifical nests with eggs of black-headed gulls and he placed broken eggshells to see
• Shell removal prevents from predators being attracted to the nests

Summary

• Behavioural ecology studies the behaviour functions based on ecology and evolution
• Adaptive or optimal trait helps in reproductive success, process or survival

Learning Outcomes

• Behavioural ecology
• Survival and competition with animals
• Reproductive success
• Function or optimality of behaviour
• Prediction of possible behaviour