noc19-bt09 Lecture 09-Study of Behaviour and behavioral Ecology

Study of Behaviours and Behavioural Ecology

What is Behavioural Ecology?

• Behavioural ecology examines the evolutionary basis for animal behaviour influenced by ecological pressures.

• It explores the relationship between ecological factors and animal behaviour, contributing to our understanding of evolution.

Understanding Animal Behaviour

• Behaviour encompasses how organisms respond to stimuli in their environment, leading to specific actions or responses.

• Ethology is the scientific study of animal behaviour, covering various topics such as:

• Foraging behaviours: How animals decide what to eat.

• Anti-predator behaviours: Strategies animals use to avoid predators.

• Social behaviours: Interactions within groups.

• Mating behaviours: Courtship and reproduction strategies.

Cost-Benefit Analysis in Behaviour

• The cost-benefit approach assesses whether the benefits of an action outweigh its costs, guiding behavioural decisions.

• Example: A tiger evaluating whether to hunt a sambar based on distance and terrain complexity.

• If hunting costs (energy expenditure) exceed benefits (nutrition gained), it may choose not to pursue.

Territory Size and Its Implications

• The relationship between territory size and cost/benefit analysis is crucial for understanding animal behaviour.

• As territory size increases:

• Benefits initially rise but eventually plateau due to limited prey consumption capacity (e.g., a tiger can only eat a certain number of animals).

• Costs increase significantly as larger territories require more energy for defense.

Conclusion on Cost-Benefit Dynamics

• A balance must be struck between territory size, hunting success, and energy expenditure.

Understanding Territory Size and Animal Behavior

The Relationship Between Territory Size and Benefits

• The concept of territory size is discussed, indicating that having too many animals in a territory can lead to diminishing returns. Initially, benefits increase but eventually plateau.

• A specific territory size is identified where the cost of defense exceeds the benefits gained, suggesting that tigers will avoid such territories.

• An optimal territory size exists where the profit (benefit minus cost) is maximized. This point is crucial for understanding animal behavior regarding territoriality.

• Profit levels are compared across different territory sizes (P1, P2, P3), with P2 being identified as the maximum profit point due to favorable benefit-cost ratios.

• Analysis of costs versus benefits helps explain why certain behaviors are preferred by animals, emphasizing energy expenditure versus return on investment.

Group Living in Carnivores: Why Do Lions Live in Groups?

• The discussion shifts to group dynamics among carnivores, particularly lions. It introduces a theoretical model linking group size to hunting success rates.

• Hunting success increases with group size; one lion has a 30% success rate while two lions improve this to 50%. Larger groups can approach near-total success if cooperation is maintained.

• Cooperation among lions is essential for maximizing hunting efficiency; lack of cooperation leads to reduced effectiveness during hunts.

• Real-world observations show that lion behavior often falls between full cooperation and individualistic approaches when hunting in groups.

Costs and Benefits of Group Living for Male Lions

• The analysis continues by examining male lions' experiences within groups. Sharing paternity becomes a significant cost when multiple males coexist in a pride.

Understanding Group Living in Lions and Herbivores

Benefits of Group Living for Male Lions

• Group living increases access to mates and provides protection against infanticide, as male lions that take over a pride will kill existing cubs to mate with the females.

• The concept of fitness is discussed; it emphasizes not just producing offspring but ensuring their survival and reproductive success across generations.

• Despite the cost of sharing paternity, male lions benefit from cooperation within groups, which helps protect their offspring from being killed by incoming males.

Advantages for Female Lions (Lionesses)

• Lionesses live in groups primarily for kin support in raising cubs and territorial defense, despite facing lower food intake due to group size.

• The balance between costs (lower food per individual) and benefits (help from kin and better territory defense) influences lioness group dynamics.

Group Living in Herbivores: A Comparative Perspective

• Similar to lions, herbivores like bisons also benefit from group living; they can defend against predators more effectively when united.

• A study shows that wolves hunt more efficiently when cooperating, making it harder for solitary bisons to survive if they lag behind.

Cost-Benefit Analysis of Group Living

• While group living enhances foraging efficiency through cooperative hunting, it introduces competition for food and increased disease risk among members.

• The potential benefits include reduced predation risks due to collective defense strategies; however, larger groups may attract more predators.

Additional Considerations on Mating Dynamics

• Increased access to mates is a significant advantage of group living; however, this comes with costs such as loss of paternity rights and brood parasitism risks.

Ecological Interactions and Alarm Calls in Ground Squirrels

Community Interactions and Benefits

• The interaction between langurs and chitals illustrates ecological behaviors where both species benefit; chitals access food dropped by langurs while gaining predator alerts from the langurs' elevated position.

• Langurs benefit from chitals as they can detect predators at a lower height, showcasing a mutualistic relationship that highlights cost-benefit analysis in community interactions.

Alarm Calls: Costs vs. Benefits

• Ground-dwelling squirrels face a dilemma when spotting predators: whether to issue an alarm call that warns their group but also risks attracting the predator's attention.

• Giving an alarm call has costs, such as energy expenditure and increased visibility to predators, while the primary benefit is alerting other group members to danger.

• The decision to call involves personal risk for the caller, raising questions about altruism versus self-preservation within population dynamics.

Kin Selection in Alarm Calling Behavior

• Research indicates that ground squirrels must weigh individual risks against group benefits when deciding to give alarm calls, leading to discussions on altruism.

• A study showed observed calling rates exceeded expected rates among adult females (65% vs. 41%) but were lower for males (8% vs. 25%), indicating differing motivations based on gender roles.

• Females tend to call more frequently due to kin selection; they are often related to others in their group, thus prioritizing the survival of relatives over their own safety compared to males who leave after maturity.

Conclusion: Understanding Altruism through Kin Selection

Understanding Altruism and Group Selection

Evolution of Self-Sacrificing Behavior

• Organisms exhibit self-sacrificial behavior to save relatives, indicating that such behavior has evolved over time due to its fitness benefits.

• The question arises: how does sacrificing oneself lead to increased genetic fitness? This suggests a deeper connection between individual actions and gene survival.

Kin Selection vs. Group Selection

• Kin selection refers to natural selection favoring traits that benefit groups rather than individuals, operating more slowly than individual selection.

• Hamilton's rule explains the dynamics of kin selection, where genes increase in frequency based on relatedness and reproductive benefits versus costs.

Hamilton's Rule Explained

• The formula r times B > C illustrates that the genetic relatedness (r), multiplied by the reproductive benefit (B), must exceed the cost (C) for altruistic behavior to be favored.

• In ground squirrels, alarm calls serve as an example where one individual's sacrifice increases survival chances for many, enhancing overall group fitness.

Decision-Making in Sacrifice

• An individual's choice to sacrifice depends on their genetic relatedness to others; higher relatedness increases the likelihood of self-sacrifice for group survival.

• If an individual is closely related to many in a group, sacrificing itself can ensure greater gene propagation compared to saving only itself.

Genetic Benefits of Sacrifice

• Haldane's perspective highlights that sacrificing oneself for siblings or close relatives can be evolutionarily advantageous since it preserves more shared genes than lost.

• The concept of genetic identity by descent emphasizes that saving multiple relatives through sacrifice can outweigh personal loss in terms of gene survival.

Territoriality as a Behavioral Strategy

Understanding Territoriality

• Territoriality involves competition within species (intraspecific) or between species (interspecific), leading to behavioral exclusion from defended spaces.

Territorial Behavior in Tigers and Its Ecological Implications

Understanding Territoriality

• Territoriality is a behavior where an animal, like a tiger, excludes others of different species from its territory using auditory, visual, or olfactory signals along with aggressive behaviors.

• Tigers communicate their presence through growling (auditory), scratching trees (visual), and marking territory with urine (olfactory), effectively signaling to other animals that the area is claimed.

Population Ecology Insights

• Population ecology examines interactions among individuals of the same species within a shared habitat; territoriality is one significant interaction type.

• Examples include tigers hunting each other or penguins displaying ritualized behaviors to assert dominance over territories.

Costs of Territorial Behavior

• The evolution of territorial behavior raises questions about its costs versus benefits. Key costs include increased energy expenditure for patrolling and defending territory.

• Engaging in aggressive displays can lead to higher predation risks since animals focused on territorial disputes may become vulnerable to predators.

Benefits of Maintaining Territory

• Despite the costs, territorial behavior offers benefits such as exclusive access to resources—food and mates—reducing competition among individuals.

• By establishing territories, animals limit competition for resources, which can enhance survival rates and reproductive success.

Regulation of Population Size Through Territoriality

• Territorial behavior helps regulate population sizes by limiting breeding pairs based on available space; if too many pairs occupy an area, they cannot find suitable nesting sites.

Understanding Territoriality in Birds

The Impact of Food Availability on Territory Size

• Birds may allow other birds to occupy territories if their energy is used to defend a larger area than necessary.

• Increasing the number of insects available can lead birds to reduce their territory size by half, indicating a direct relationship between food supply and territorial behavior.

• Environmental factors, such as wind patterns or flower blooms, can influence insect populations, thereby affecting bird territoriality.

Experimental Study on Flower Density and Territory Size

• An experiment showed that higher flower density leads to smaller territory sizes for birds due to increased food availability.

• Behavioral ecology helps explain various natural phenomena including population and community interactions through the study of behaviors like territoriality.

Methods for Studying Animal Behavior

Activity Patterns Analysis

• One method involves plotting activity patterns over time; for example, comparing tiger and chital densities reveals low overlap (24%).

• Chitals are most active during early morning and late evening when tigers are less active, showcasing predator avoidance behavior.

Overlap Between Carnivores

• In contrast, tigers and jackals show a greater overlap (67%), indicating different behavioral dynamics among carnivores.

Creating Ethograms: A Tool for Behavioral Observation

Defining Behaviors

• An ethogram catalogs behaviors exhibited by animals during observation periods; it begins with defining specific actions like walking or standing.

Methodology in Ethogram Creation

• The process includes scan sampling and focal animal studies followed by time budget analysis to understand animal activities comprehensively.

Behavioral Observation Techniques in Animal Studies

Overview of Behavioral Scanning

• The process involves noting the activities of various animals at specific times, creating a comprehensive scan of their behaviors from start to finish.

• A table is created to document starting and ending times for each observed behavior, allowing for a clear understanding of what each animal was doing during that period.

Focal Animal Study Method

• In this method, researchers focus on one individual animal at a time, observing its behaviors over a designated period.

• A detailed table is generated showing the specific behaviors exhibited by the focal animal within set timeframes.

Time Budget Analysis

• The analysis reveals that feeding is the most dominant behavior (44% of observed time), followed by walking (30%) and looking around (17%).

• Looking behavior often correlates with predator awareness; increased vigilance may occur if threats are present.

Insights on Age and Behavior

• Juveniles exhibit less looking behavior compared to adults due to parental protection, indicating an evolutionary adaptation for safety.

• Sub-adult males engage in auto grooming as they transition towards adulthood, highlighting behavioral changes associated with maturation.

Evolutionary Implications of Behavior

• Behaviors are evolutionarily selected based on their contribution to individual or group fitness; cost-benefit analyses help explain why certain behaviors are favored.