Animal Behaviour & Comparative Physiology

Course Overview - Course: BI310 Animal Behaviour & Comparative Physiology - Lecturer: Dr. Tara Dirilgen, Email: tara.dirilgen@mu.ie ## Practical Information - Practical 2 Date: Friday, 21st November 2025 - Time: 13:30 - 16:00 - Location: Lab 3, Callan ## Animal Behavior Topics Outline 1. Groups 2. Biological Rhythms 3. Migration, Homing and Navigation 4. Antipredator Behaviour (Dr. Grace Hoysted) ## Why Form Groups? - Examples: - Shoal of sardines - Rookery of zebra - Flock of starlings - Reference: James Crombie, The Irish Times, 4 March 2021 ## Social Structures in Animal Groups - Social Groups vs. Aggregations: - Animals may aggregate due to attraction to specific environmental features (e.g., food). - True social groups often involve complex interactions, cooperative behaviors, and sometimes a division of labor beyond simple responses to each other's presence. - Extreme group living observed in social insects, such as: - Honeybee castes - Termite castes - Animals in social groups respond to each other’s presence. ## Advantages of Group Living ### Main Advantages - Protection Against Predators - Improved Foraging for Food - Protection from Physical Factors ### Protection Against Predators - Mechanisms of Protection: - Improved Vigilance: - Many predators depend on surprise. Prey must remain vigilant to escape. - In groups, individuals spend less time watching for predators as they benefit from others’ vigilance. - Dilution Effect: - The larger the group, the smaller the chance of any individual being targeted by a predator. - Shielding: - Group members can use each other as shields against predators by positioning themselves behind others to reduce their own exposure. - Predator Confusion: - Many animals moving simultaneously make it difficult for predators to focus on a single prey individual, creating a sensory overload or 'flicker fusion' effect. - Group Defensive Behavior: - Includes mobbing, where groups distract predators. #### Improved Vigilance Example - In a group of starlings, foraging time was observed: - Alone: 12% of time spent in surveillance - In a group of 10: 47% of time spent foraging, with a fewer number of look-ups per minute (11 vs. 23). #### Group Vigilance Research - Larger flocks of pigeons are less successfully attacked by goshawks due to the early flight response of pigeons. #### The "Selfish Herd" Concept (Hamilton) - Group members might benefit from the vigilance of others without sharing the responsibility, but the first to spot the predator may have a better escape chance. - Each individual attempts to use others as a shield, making the best move for survival while facing the risk of increased conspicuousness. #### Dilution vs. Conspicuousness - An individual antelope in a herd of 100 has a $1/100$ chance of being eaten. A herd is less likely to attract 100 more attacks than a solitary individual, demonstrating the benefit outweighs the cost. - Example from pond skater groups indicated that the larger the group, the lower the attack rate per skater. ### Protection Against Physical Factors - Animals in larger groups, such as Camargue horses, experience reduced biting fly attacks for better survival. - Example: Emperor penguins huddle together for warmth during egg incubation, reducing individual surface area exposure to cold and conserving body heat. ## Foraging Benefits of Group Living - Finding Good Sites: Animals can locate food better in groups. - Cooperative Hunting: - Example: Lionesses and killer whales (orcas) demonstrate hunting cooperation, allowing them to take down larger or more formidable prey than a single individual could manage. - Honey Bees: Communicate food location through a waggle dance. #### Information Centers Concept - Birds in communal nests (e.g., rooks) can share knowledge about the location of rich food sources. - Predictions from Information Centre Theory: - Birds are expected to leave in groups and fly in the same direction, which is observed in barn swallows and cliff-nesting swallows. ### Disadvantages of Group Living - Increased Conspicuousness: - Predation risks increase as group size grows exemplified by fieldfare nests attracting more predators compared to solitary nests. - Competition in Feeding: - Direct competition among group members may hinder individual success, which can manifest as scramble competition (indirect, over a limited resource) or contest competition (direct confrontation). - Disease Transmission: Increased proximity can lead to higher disease spread as seen in cliff swallows with ectoparasites. - Cuckoldry and Mate Competition: In red-winged blackbirds, individuals may mate with non-kin. - Cannibalism: Example with bluegill sunfish where a male may eat his neighbor’s eggs. ### Group Living Dynamics - Evolution of Group Living: It’s presumed the benefits outweigh the costs. - Optimal Group Size: Represents the maximum fitness achieved while balancing costs and benefits.- Optimal group size varies with environmental factors, food availability, and competition. - Yellow Eyed Juncos Study: Determined optimal group size results in lower combined time spent in vigilance and fighting. ### Optimal Group Size Models - Environmental factors, such as predator risk and food cover, play a role in determining ideal group sizes. - Stability: Optimal groups may be unstable, with fitness varying at the smallest and largest sizes. #### Reading Material - Manning & Dawkins (2012), An Introduction to Animal Behaviour, Chapter 7: Social Organisation. - Davies, Krebs & West (2012), An Introduction to Behavioural Ecology, Chapter 6: Living in Groups. #### Example Exam Question - Discuss the advantages and disadvantages of living in groups, and the concept of “optimal group size”. ## Exam Information - Weight: 60% of overall grade - Format: 1.5 hours, Answer TWO questions, ONE from each of the two sections. ## Grading Criteria Overview Grading will occur based on the following: - Addressing topic 15 marks - Knowledge and understanding 25 marks - Reading of relevant literature (supplied) 15 marks - Reading of relevant literature (additional) 10 marks - Synthesis of material 25 marks - Structure and presentation 10 marks

Total: 100 marks