Animal Behaviour and Responses to the Environment - Study Notes

Behaviour refers to what an organism does and how it does it in response to internal and external stimuli. Traditionally, behaviour has been defined as the response of an organism to a stimulus, which can be anything from a simple reflex to complex social interactions. The study of behaviour aims to understand the timing, purpose, and mechanisms behind an individual's actions, focusing on how these behaviours contribute to an organism's survival and reproduction.

Levels of Analysis in Behaviour (Tinbergen's Framework)

Tinbergen identified four critical levels of analysis when studying animal behaviour, which help to dissect the complexity of actions:

1. Ontogeny (Development): This level examines how behaviour develops over the individual’s lifespan, investigating both genetic predispositions and environmental factors that shape behaviour. Key questions include:

   • How does behaviour develop during an organism's life?

   • What interactions exist between genetic factors and environmental influences?

   • What role do experiences play in learning and behaviour adaptation?

2. Causation (Sensory-Motor): This focuses on the immediate stimuli that elicit behaviour, including physiological responses and the sensory and motor processes involved. This level explores aspects like:

   • What sensory inputs trigger specific behaviours?

   • How do the nervous and endocrine systems interact to produce a response?

3. Phylogeny (Ancestry): This level questions the evolutionary history of a behaviour, analyzing how it might have been altered or retained through evolutionary time. By tracing back through genetic lineages, researchers can determine:

   • How have specific behaviours evolved in related species?

   • What historical contexts influenced the development of these behaviours?

4. Adaptation (Function): Here, the emphasis is on why a behaviour is advantageous, assessing its function and the ways in which it enhances the organism's fitness in terms of survival and reproduction. Researchers may ask:

   • How does this behaviour contribute to reproductive success?

   • What ecological pressures shaped this behaviour?

Each of these levels can be categorized into proximate (mechanistic factors determining immediate responses) and ultimate (evolutionary factors explaining the presence of behaviours through natural selection) explanations.

Infanticide in Lions as a Case Study

Infanticide in lions offers a compelling case study that can be analyzed through Tinbergen's four levels:

• Mechanism: Factors such as sex-linked genes, learning experiences (environmental influences), and hormonal influences (e.g., increased testosterone in males) contribute to this behaviour. The physiological and hormonal changes in males, particularly after the takeover of a pride, influence their propensity for infanticide.

• Ontogeny: The development of the behaviour may be linked to age, social learning, and previous experiences within pride dynamics. Young males learn through observation and trial, understanding their roles within social structures.

• Causation: Physical traits (e.g., the strength of jaws, size of paws) and chemical cues from females in oestrus play a role. Males may respond to specific pheromones that signal receptivity, influencing their aggressive behaviour.

• Phylogeny: Understanding the behaviour’s history within the Felidae family reveals its evolutionary perspectives, suggesting that infanticide may have been selected for due to benefits that increase reproductive success, providing a selective advantage.

This behaviour is ultimately viewed through an adaptive lens, questioning how it contributes to the survival of the species and the reproductive strategy of the individual lion.

Understanding Adaptive Behaviour

Adaptive behaviour is defined as a heritable trait that enhances an individual's survival or reproductive success compared to non-adaptive behaviours. This concept encapsulates various behaviours, such as mobbing in ground squirrels, where the action is considered adaptive if it significantly increases survival rates against predators. Factors that make behaviours adaptive may include:

• Increased survivorship and reproductive output.

• Effective resource acquisition.

• Optimized interactions with conspecifics (members of the same species).

Cost-Benefit Analysis in Behaviour

Understanding behavioural traits requires evaluating their costs and benefits. Every action has associated fitness costs and benefits, and behaviours that yield net positive outcomes tend to be favoured by natural selection. Optimality theory is often employed to analyze these trade-offs, leading to more efficient behaviours that align with survival needs. Key considerations include:

• What are the fitness costs associated with a behaviour, including energy expenditure, risk factors, and time costs?

• What are the potential benefits gained, including resources, mates, and territory?

Example: Territory Size in Convict Cichlids

Using cost-benefit analysis to determine optimal territory size illustrates this concept:

• Benefits include access to valuable resources like food and mates, while costs encompass the energy spent on territory defense and the risks inherent in territorial disputes.

Studies have shown that both benefits and costs typically increase with territory size, presenting a challenge in finding the optimal size that maximizes net gains. This relationship can be defined mathematically as:
NB(s) = B(s) - C(s)
Where:

• NB(s) is the net benefit,

• B(s) is the benefit function,

• C(s) is the cost function.

Experimental Design to Test Cost-Benefit Analysis

In an experimental setup by Praw and Grant (1999), varying territory sizes were placed in controlled environments (aquariums) to measure the net benefits obtained by territory owners. The design included elements that ensured benefits grew with territory size but exhibited diminishing returns, while costs increased concerning intrusions by competitors.

Results of Analyses

1. Benefits showed a quadratic relationship with territory size, indicated by the function:
   B(c) = -0.024 \times c^2 + 0.44 \times c - 1.51

2. Costs were also found to increase quadratically:
   C(c) = 0.0064 \times c^2

3. Net Benefits calculated from these functions indicated that optimal territory size resulted in maximum fitness; the fastest growth rates in territories were found at approximately 7 cells in diameter based on various interactions involving food intake and competition.

Conclusion

The analysis of behaviour through Tinbergen's levels provides a comprehensive framework to understand the complexities of animal actions. By employing concepts like adaptive behaviour and cost-benefit analysis, researchers can deepen the insights into the survival strategies of various species, highlighting the intricate balance between environmental demands and evolutionary adaptations.