Animal Behavior Review Final Exam PDF

Lecture 21 - Animal Behaviour in a Changing World ❖ Anthropocene: human activity is the major influence on the Earth’s ecosystem Climate change, Land-use change, Pollutants Invasive species, Harvesting, Conversion of natural areas into urban and agricultural...

Lecture 21 - Animal Behaviour in a Changing World ❖ Anthropocene: human activity is the major influence on the Earth’s ecosystem Climate change, Land-use change, Pollutants Invasive species, Harvesting, Conversion of natural areas into urban and agricultural landscapes ❖ Importance of behavioural changes Animals can adjust their behaviour to alter their responses to environmental change ❖ Timescape: duration of time that exhibits fitness-relevant heterogeneity in biotic and/or abiotic factors of interest Time is an “essential currency of life”: finding food, avoiding predators, and reproducing requires animals to be active at the right time and in the right place Daily timescapes: variation in predation risk Seasonal timescapes: variation in precipitation Evolutionary timescapes: variation in allele frequencies ❖ Evolutionary trap: resource that an organism perceives as attractive despite being associated with reduced fitness ❖ Human activity creates novel timescapes some species perceive humans as predators, leading to fear motivated shifts in behaviour timing species may change activity timing due to o human mediated changes in activity timing of predators, competitors, or introduced species ❖ ​Ecological effects of novel activity timing individual level: shifting activity times can affect physiology population level: lower recruitment, access resources or detect predators is impaired by being active at new times community level: diminish or amplify competition, predation ecosystem level: change nutrient flows if altered species interactions disrupt processes like herbivory ❖ Mismatch hypothesis: ecological effects of novel activity timing arise via activity-timing mismatches within and between species Bird → butterfly = Bird → smaller bird Activity-timing mismatch occurs when individuals or species perceive and respond to timescape modification differently, changes the overlap in daily activity timing within or between species ❖ Timescape modification hypothesis: both the duration and temporal configuration of human disturbance influence the ecological effects of novel activity timing Timescape loss: temporal duration of disturbance Timescape fragmentation: temporal configuration of disturbance ❖ Biogeographic timescape compression hypothesis: effects of novel activity timing vary latitudinally due to biogeographic variation in factors that restrict the optimal time for activity ❖ Fear generalization: Consistent individual differences (personalities) s in correlated fear responses to two or more disparate sources of danger Lecture 20 - Territoriality ❖ Territoriality is the “defense of an area” ❖ Economic defensibility: trade-off in costs versus benefits for maintaining a territory individuals will only defend territory if benefits > costs Benefits: Increased access to food or resources, Potential fitness benefits of producing more offspring, Survival Costs: Time, Energy (foraging), Potential injury/death To be adaptive, the fitness benefits of having a territory must be weighed against the costs of the aggression and defense required to establish and maintain it ❖ Resource holding potential: The inherent capacity of an individual to defeat others when competing for useful resources Territory quality influences the structure of the genome in ways that affect survival, Telomeres shorten in birds in the low quality habitat more than birds wintering in high quality habitat Birds with longer telomeres return to the breeding grounds more frequently, suggesting relationship between survival, telomere length, and winter habitat quality Male territory holders in the mangroves leave wintering grounds sooner, Claims best territories and quick access to females when they arrive ❖ Arbitrary contest resolution hypothesis: states that the resident always wins territorial battles, residents consistently winning prevents other strategies from becoming advantageous ❖ Resource-holding potential hypothesis: Residents have an edge in physical combat. In most species, territory holders tend to be larger and more aggressive compared to other members of their species. This physical advantage ensures they retain their territory. Red-shouldered Widowbird Example: In some species, holding territory isn’t solely about body mass or size. males with larger or redder shoulder patches are more successful in holding territory, patches signal male quality or fitness ❖ Payoff asymmetry hypothesis: Residents place higher value on the territory than do rivals, Territory holder values the territory more than the intruder, creating a payoff asymmetry if the two were to fight for that territory ❖ Winner effect: winning an aggressive interaction often enhances the likelihood of winning a subsequent interaction, spike during challenges, low during breeding It was developed to explain the trade-off between Parental care and Male competition for resources (testosterone) Bystanders to Challenges: Assessed testosterone and determined those that observed aggressive interactions had higher testosterone Lecture 19 - Habitat Selection ❖ Habitat selection: process by which animals choose where to live based on biotic and abiotic factors, Habitat use: how animals use the features of their chosen habitat Influenced by: Abiotic factors, Biotic factors, Intrinsic factors Abiotic factors: Climate, Topography, Resource availability biotic factors: Predation risk, Reproduction, Competition for resources Predation risk: prioritize safety when choosing habitats Only certain % of areas are available for habitat because of predators Reproduction: select habitats that maximize access to mates or conditions for raising offspring State-dependent selection: reproductive needs dictate spatial and temporal resource use Late Gestation: Select forests and avoid habitats with open areas or sparse vegetation cove, must support increased energetic demands prior to giving birth Farrowing (reproduction): Contracted home range size, Prefer hardwood forests with high quality food and dense cover Offspring care: Increase home range size to balance foraging needs with offspring protection, offer combination of concealment and access to food Competition for resources: Avoid areas where competition is intense, both intraspecifically and interspecifically Density-dependent habitat selection: how the population density of a species influences where individuals choose to live or settle, choose less crowded areas to reduce competition ❖ Ideal free distribution theory: animals distribute themselves across habitat patches based on resource availability and competition Animals will distribute themselves in a way that maximizes their fitness behaviour results in an ideal balance where all individuals achieve approximately the same fitness, regardless of the habitat they choose (animals with low quality habitat is less competition there gets more resources then higher quality habitat with more competition) Isodar: line created by plotting the population density in one habitat against the density in another habitat, how animals distribute themselves between two habitats over time linear and has a positive slope, distributing themselves between habitats according to the Ideal Free Distribution (IFD): pop. density in one habitat increases, the density in the other habitat increases proportionally, maintaining equal fitness. deviations from linearity suggest other factors may influence distribution: graph when individuals in Habitat 1 and Habitat 2 have the same fitness despite differing population densities ❖ Intrinsic Factors: animal’s biological and behavioural tendencies Learned Behaviors: changes in habitat preferences based on personal experience or social interactions; learning to select a habitat Social Learning: Animals observe and mimic experienced members of their group: elephants  Trial and Error: Animals test different habitats and stick with those that maximize survival or reproduction Genetic Predisposition: Inherited preferences for specific habitats, shaped by evolutionary history Natural Selection: Species evolve preferences for habitats where they are most fit Physiological Adaptations: Traits like dense fur, specialized feeding appendages, or fat storage evolve to suit specific habitats Personality: Persistent behavioural differences among individuals that remain consistent over time and across different situations, Boldness, shyness, aggression, risk-taking Lecture 18 - Foraging Behaviour ❖ Forging: the set of actions, strategies, and decisions that animals use to search for, locate, capture, and consume food or other resources necessary for survival and reproduction Foraging behaviour is goal oriented, dynamic, and involves ‘decision-making’ Energy optimization, Food availability, Predation risk, Reproductive and social status, Learning and cognition, Competition, Habitat features, Human influence ❖ Optimal foraging theory: animals maximize their net energy gain while minimizing the costs associated with finding and consuming food Benefits: Energy gained from food (measured in calories) Costs: Energy expended in searching for food (search time) and handling the food (handling time) Searching: Time spent locating food Marginal Value Theorem: Predicts how long an animal should stay in a resource patch before moving to a new one. It balances the benefits of feeding in the current patch against the costs of staying there or traveling to a new patch benefit of feeding declines to equal the average intake rate from the environment, once staying in the patch yields no better results than moving to another, the animal should move on Larger prey offers more energy but may take longer to handle, animals should favor prey that maximizes net energy gain Short Travel Time: Animals should spend less time exploiting a patch Long Travel Time: Animals should spend more time exploiting a patch to offset the energy cost of travel ❖ Net Caloric Intake: caloric cost of gathering food must be less than caloric benefits gained by eating the food ❖ Foraging and Fitness: energy obtained from food supports survival, reproduction, and offspring care The ability to maximize net caloric intake directly impacts survival and reproductive success Male foraging success influences female mate choice, foraging success not only supports male survival but also increases mating opportunities, enhancing reproductive success ❖ OFT Models: assume animals maximize caloric energy gain, but actual foraging behaviour is influenced by biology of the forager and prey characteristics that reduce profitability Example: Oystercatchers do not always choose the largest mussels, even though larger mussels might contain more calories ❖ Factors Beyond Calories: animals do not always select or hunt for food as efficiently as possible, has Nutritional needs Predation risks and habitat competition influence decisions ❖ Foraging under Predation predation risk influences foraging behaviour, OFT should not focus only on calories gained vs expended, but also where predators are or will be  If foraging exposes an animal to the risk of sudden death, we expect foragers to sacrifice short-term caloric gain for long-term survival ❖ Landscapes of Fear The need to balance finding food and avoiding predators creates a “landscape of fear.” prey animals perceive their environment in terms of safety and danger, shaping their movement and behaviour Life-dinner principle: An asymmetrical arms race between predators and prey where staying alive usually trumps eating, since forgoing on meal is much less important than forgoing one life Prey animals (dugongs) adjust their foraging strategies based on perceived predation risk, balancing energy intake against survival, eat top of leaves instead of digging from roots Eg: Behavioral Changes in Elk: After the reintroduction of wolves, elk altered their foraging behaviour, female elk increased vigilance by 50%, spending less time eating and more time scanning for predators, elk with wolves present consumed 25% less food ❖ Evolutionary game theory: the adaptive value of behaviours (or strategies) in populations where the success of a strategy depends on what others in the population are doing Evolutionarily Stable Strategy: when adopted by a majority of the population, cannot be invaded or replaced by an alternative strategy introduced by a small minority if a small number of individuals adopt a new strategy, they would not outperform those sticking to the ESS traits tied to successful strategies (roving or sitting) will spread and replace less effective food-acquiring techniques over time ❖ Frequency-Dependent Selection: a form of natural selection where the fitness of a particular phenotype depends on how common it is in the population Negative: fitness of a phenotype decreases as it becomes more common Positive: fitness of a phenotype increases as it becomes more common African cichlid fish: Both persist because prey fish might learn attacks and avoid that side Lecture 17 - Predation and Anti-Predator Behaviour ❖ Predator: A predator is an organism that hunts, captures, and consumes other organisms (prey) to obtain energy and nutrients. Predators typically have adaptations, such as speed, strength, camouflage, or sharp teeth and claws, that aid in locating, capturing, and subduing prey Ambush, Pursuit/Active hunting, Pack or cooperative hunting, Kleptoparasitism (stealing food) ❖ Prey: Prey are organisms that are hunted, captured, and eaten by predators. Prey species often have their own adaptations for avoiding predation, such as camouflage, heightened senses, or behaviors like fleeing, hiding, or group living to reduce individual risk. Ecology of fear: how the threat of predation impacts prey animals’ behaviours Fear: response to perceived threats that motivate animals to take actions to maximize their chance of survival ❖ Landscape of fear: explores how prey animals perceive and respond to variations in predation risk within their environment Physical landscape: habitat features that interact with the biology of predators and prey to determine their distributions and interactions Predation risk landscape: actual or potential threat of predators in different areas of an ecosystem ❖ Anti-Predator behaviour: Prey respond to predation risk with various risk management strategies tailored to different spatial and temporal scales Proactive – behaviour is adjusted to reduce risk prior to predator encounter Dilution effect hypothesis: associating in groups makes it less likely that any one individual will be depredated Confusion effect hypothesis: moving as a group may reduce the likelihood of predators capturing prey because of their inability to single out and attack individual prey confuse predators that have difficulty tracking a single object Selfish herd hypothesis: individuals in a group (or herd) attempt to reduce their predation risk by putting other individuals between themselves and the predator Active/Reactive – behaviour is adjusted when the threat is imminent Active Social Defense Mobbing: increases likelihood of escape/chasing off the predator, Can lead to injury or death Vigilance: More eyes means a greater likelihood that a predator will be spotted, Usually subordinates that are relegated to the role Cooperative social defenses can occur between species (rhinos and birds) ❖ Optimal Theory: Evolutionary theory organisms have evolved traits that are optimal under certain environmental conditions, balancing costs and benefits Curve of Benefits and Costs Northern Bobwhite Quail Quail form groups to enhance survival by reducing predation risk These groups aim for an optimal size that maximizes the survival benefit while minimizing the costs of movement and resource competition ❖ Super-predator: A super-predator is a term used to describe a predator that exerts an exceptionally high impact on other species through its predation habits. Super-predators typically hunt at rates much higher than natural predators, often targeting larger animals or high-value species. Humans (deer example) Humans hunt deer and create trauma, makes deer extra vigilance and sensitive to sound due to humans, from enduring predator while forging →permanent reduction in forging and less offspring Lecture 16 - Cognition ❖ Cognition: the ability to acquire, retain, process, and use information, which can involve a more flexible application of that knowledge to enhance fitness ❖ Testing Cognition Mirror self-recognition test: mark placed on the face or head of an individual who can then observe their reflection in the mirror. If the individual touches or directs behaviour toward the mark, conclusion is that the subject demonstrated self-awareness Numerical competency: ability to recognize and process numerical quantities Ability to estimate and count objects/events can enhance survivorship and reproduction,“More” or “less” concept In robins, showed accurate discrimination when comparing smaller quantities (e.g., 1 vs. 2, 2 vs. 3). When comparing larger quantities (>10), robins struggled to distinguish differences ❖ Numerical Discrimination Magnitude effect: many species can distinguish numerical quantities when the options involve small quantities Easier for individuals to distinguish 1 from 3, rather than 6 from 8 Disparity effect: individuals more often select larger quantity as the difference between options increases May be able to distinguish 2 from 5, but not 4 from 5 ❖ Memory and cognition: Cognition involves the retention of information, Animals benefit from remembering not only locations in their environment that provide safety or food but also skills or associations they have learned Cache: food stored in a hidden location for later retrieval ❖ Behavioural flexibility: ability to alter behaviour in response to environmental stimuli Reversal learning: After individual learns to associate a food reward with one of two stimuli, the conditions are reversed and the individual needs to learn to associate a food reward with the alternate stimulus ❖ Cognitive performance Fitness: Individuals with higher cognitive ability should be able to learn faster, more rapidly innovate new behavioural strategies, remember important spatial locations, all increase an individual’s fitness Reproduction: females with higher cognitive scores tend to hatch more clutches of eggs annually Mate preference: Phase 1: Females often prefer to mate with males based on phenotypic traits, Phase 2: Half nonpreferred males were trained to open problem boxes to obtain food, while preferred males received no training: Choice trial -> females switched preference to initially unpreferred male ❖ Cognition and the brain Suggested increased brain size allows for greater behavioural flexibility and innovation in ways to acquire food Does increased caching behaviour correlate with increased HF size? Yes! Based on 23 species, there was a strong association between reliance on food cache and HF size (hippocampal formation) Lecture 15 - Learning and Cognition ❖ Learning: relatively permanent change in behaviour as a result of experience Process by which animals modify their behaviour, or adapt to their environment in ways that increases their fitness ❖ Evolution of learning Dynamic: In a dynamic environment (e.g., Habitat A and B, each with a 50% probability of high fitness), conditions are unpredictable. Learning is not as favored because past experiences may not reliably predict future outcomes. Fixed: In a fixed environment (e.g., Habitat A with a 100% probability of high fitness and Habitat B with a 0% probability), conditions are stable and predictable. ❖ Habituation: individual reduces or stops responding to a repeated stimulus allows animals to ignore unimportant stimuli and focus their attention and energy on more critical cues ❖ Imprinting: rapid learning that occurs in young animals during a short, sensitive period and has long-lasting effects ❖ Classical Conditioning: a neutral stimulus becomes associated with an unconditioned stimulus, resulting in the neutral stimulus eliciting the same response as the unconditioned stimulus ❖ Operant Conditioning (Trial-and-Error Learning): : A learning process where an animal's behavior is shaped by the consequences it produces (rewards or punishments) Positive Reinforcement: Adding a pleasant stimulus to increase behavior (e.g., giving treats for good behavior). Negative Reinforcement: Removing an unpleasant stimulus to increase behavior (e.g., stopping a loud noise when a correct action is performed). Positive Punishment: Adding an unpleasant stimulus to decrease behavior (e.g., scolding for bad behavior). Negative Punishment: Removing a pleasant stimulus to decrease behavior (e.g., taking away toys for bad behavior). ❖ Social learning: Social learning refers to acquiring information or behaviours by observing other individuals, rather than through direct experience Social learning may be favoured by selection when it reduces the time and energetic costs of learning ❖ Local Enhancement: A strategy where the presence of another individual serves as a cue to focus on a specific location or resource animals may gather at a location where others are present, assuming the presence of a resource ❖ Public Information: using the observed actions or outcomes of others to assess the quality or quantity of a resource ❖ Teaching: Teaching involves active participation by an experienced individual (the teacher) to facilitate learning for a naïve conspecific (student) The teacher modifies its behavior in the presence of the pupil. The behavior incurs a cost for the teacher. The pupil learns skills or knowledge faster than they would independently Lecture 14 - Communication ❖ Communication: the transfer of information from one individual (sender) to another (receiver) that affects current or future behaviour and the fitness of one or both individuals ❖ Signal: A coevolved message between a sender and receiver that contains information ❖ Cue: An unintentional and unselected transfer of information between sender and receiver ❖ Information Interpretation of potential information is critical because it can influence the fitness of both the sender and the receiver, dominance rank, sex etc.. Alarm signaling Information can be used to warn others of approaching predators ❖ Evolution of signals Preexisting trait hypothesis: signals evolve from traits or behaviours that already existed in an organism. These traits, while not initially intended as signals, provide useful information to other individuals in the environment and eventually evolve into more specialized signals through a process called ritualization Behavioural: grooming Preexisting bias hypothesis: Signals evolve through receivers pre existing biases, which are biases in their sensory systems that detect some features of the world better than others and that can be exploited by sender signals via sensory exploitation Sensory exploitation: happens when a sender creates signals that trigger responses favorable to them, using the receiver’s established sensory preferences Males acquire orange pigmentation from their diet (plants rich in carotenoids), Females evolved a visual preference for orange due to a foraging advantage—plants with orange pigments may indicate high-quality resources, Males exploit this sensory bias by developing orange spots, which attract females for mating ❖ Communication framework Honest signaling: both sender and receiver obtain a fitness benefit (+/+) Honest signaling relies on the costs associated with producing or maintaining the signal to ensure reliability Production cost: a cost associated with the production of an expensive signal Badges of Honor: These are signals (like physical traits) that represent dominance or size. While they may not cost much to produce, maintaining their credibility often comes with a maintenance cost, such as the risk of challenges from competitors Deceitful signaling: The sender benefits, but the receiver incurs a fitness cost (+/-) Novel Environment Hypothesis: suggests that the behaviour evolved in an environment different from the current one, response persists because there hasn’t been enough time for the species to adapt to the new conditions Net Benefit Hypothesis: sensory mechanism resulting in the response is generally beneficial, even though it sometimes results in fitness losses, On average, the benefits of reacting to signals outweigh the occasional costs of deceitful signals  Deceitful signals evolve when the costs of false responses are lower than the costs of failing to respond at all Eavesdropping: The sender incurs a fitness cost, while the receiver gains a fitness benefit (-/+) ❖ Multimodal Signaling: Animals often use multiple senses for communication (e.g., visual, tactile, acoustic, chemical). Multiple Message Hypothesis: Different modalities convey separate pieces of information Redundant Signal Hypothesis: Different signals provide the same information, offering reliability even if one modality fails due to environmental noise or other factors Lecture 13 - Social Behaviour ❖ Collective behaviour: the synchronized movement of individuals following a series of basic interaction rules ❖ Interaction: non-independence between individuals’ movements ❖ Types of social behaviour Mutual benefit: Both interacting individuals receive a fitness benefit Mutual benefit occurs when two or more individuals cooperate, resulting in advantages for all parties involved Altruism: Recipient receives a fitness benefit but donor pats a fitness cost Selfishness: Donor benefits but the recipient does not Spite: Neither the donor nor recipient benefit, and both pay a cost spite is rare because it involves a cost to both the actor and the recipient ❖ Altruism and Reciprocity Reciprocal altruism/reciprocity: Individuals help others with the expectation that the favor will be returned in the future Occur only among individuals that remain together long enough to repay the favour Indirect Reciprocity: Helping behaviour is rewarded not by the recipient but by third-party observers who witness the altruism Prisoner’s dilemma: Game theory framework used to study cooperation and defection, Cooperation is beneficial but difficult to maintain because defection offers immediate individual rewards Beneficial to always defect ❖ Kleptoparasitism: A specific form of selfishness where an individual steals food collected by another ❖ Cooperative Breeding: A system where more than two individuals contribute to raising offspring For group fitness: Helpers often forego their own reproduction to assist others, typically due to ecological or genetic constraints ❖ Evolution of Cooperative Breeding Kin selection hypothesis: Cooperative breeding evolves because helpers gain indirect fitness benefits by supporting close relatives, increasing the survival and reproductive success of shared genes. Group Augmentation Hypothesis: individuals survive or reproduce better by living in larger groups Ecological Constraints Hypothesis: when resources required to breed are limiting, individuals delay dispersal and remain their natal territory to help raise their relatives Life History Hypothesis: specific life history traits, such as high juvenile and adult survival play a role in the evolution of cooperative breeding by creating a surplus of individuals in a habitat  Benefits-of-Philopatry Hypothesis:If staying in the natal territory gives you better survival chances or resources than leaving to start your own, it’s better to stay and help the group. Temporal variability hypothesis: environmental uncertainty promotes cooperative breeding because having helpers at the nest allows birds to breed successfully under both good and bad conditions ❖ Load-lightening: Helpers reduce the workload of parents in offspring care ❖ Individual Differences in Cooperative Behaviour Animal personality: Refers to behaviors that are consistent and repeatable over time within an individual across different situations Behavioural Syndrome: Consistency in behavior across multiple contexts (e.g., foraging, mating, defending) ❖ Facultative Altruism Obligate altruism: Helpers cannot reproduce, and only gain fitness benefits indirectly Facultative altruism: Helpers retain the potential to reproduce, and maximize their lifetime inclusive fitness as a combination of both direct and indirect fitness ❖ Social organization Singular breeding: Social groups contain only a single breeding female and reproductive skew is high, meaning reproductive success is concentrated in a few individuals Plural breeding: Social groups contain multiple breeding females and reproductive skew is lower Reproductive conflict can be high for breeding positions because there are more breeding opportunities ❖ Reproductive Senescence: Refers to a decline in reproductive capacity as organisms age The Grandmother Effect: When older females become less likely to reproduce, they may shift roles to help raise younger generations Lecture 12 - Mating Systems ❖ Types of mating systems Both sexes must weigh costs and benefits of mating decisions Males and females often have different motivations for attempting to mate multiple times Most mating systems are plastic and can vary among populations of the same species The greater the potential to monopolize mates or resources, the greater the likelihood that mating systems in which one sex mates multiply will evolve ❖ Monogamy: A mating system in which one male mates with one female, and one female mates with one male. (extremely rare) Social Monogamy: Form of monogamy in which a male and female form a pair-bond by one or both may also mate outside the pair-bond Genetic Monogamy: Form of monogamy in which a male and female form pair-bonds and mate only with each other Less time, no STD, less predation risks ❖ Mate Limitation Hypothesis: Monogamy evolves when potential mates are scarce or widely dispersed ❖ Mate Guarding Hypothesis: Monogamy evolves when individuals have the ability to restrict mating behaviour in their partner ❖ Mate Assistance Hypothesis: Monogamy evolves when resources are so critical to successful reproduction that both parents are necessary to rear young ❖ Infanticide Hypothesis: Monogamy evolves to reduce the risk of infanticide by other males ❖ Polyandry: A mating system in which a female has several partners in a breeding season Females giving all mates equal chances for fertilization ensures higher mean fitness for offspring Paternity Dilution: males are uncertain about their paternity, this discourages infanticidal behaviour because harming the young might mean killing their own offspring ❖ Indirect Benefits of Polyandry Good Genes Hypothesis: Females mate with multiple males to produce offspring with superior genetic quality or viability Genetic Compatibility Hypothesis: Polyandry increases the likelihood of acquiring genetically compatible sperm, reducing risks of poor offspring viability Genetic diversity hypothesis: Females mate with multiple males to ensure their offspring have a variety of genes Inbreeding Avoidance Hypothesis: Females mate with multiple males to avoid mating with a closely related male ❖ Direct Benefits of Polyandry  Additional Resources hypothesis: females gain access to more resources (like food, shelter, or territory) provided by males Additional Care hypothesis: Females mate with multiple males to ensure more males are involved in caring for their offspring ❖ Polygyny: A mating system in which a male fertilizes the eggs of several partners in a breeding season Female defense polygyny hypothesis: When resources are evenly distributed, but females form groups to access resources/dilute risk of predation, males will follow and guard a group of females Resource defense polygyny hypothesis: When resources are clumped, attract multiple females, and are easily defensible, males will guard the resources – and by extension the females – by setting up a territory Lek polygyny hypothesis: Males display in a small area (called a lek) to attract females but don't defend resources or females Scramble competition polygyny hypothesis: When resources are distributed heterogeneously and females do not form groups, males will seek out females ❖ Female Distribution Theory: If females range widely to find dispersed resources, male territories may overlap with multiple females, creating opportunities for polyandrous or polygynandrous systems, If resources are abundant or supplemented, females reduce their ranges, leading to monogamy or fewer mates Polygyny threshold The point at which a female will gain higher fitness by mating with an already mated male than with a bachelor ❖ Evolution of Lek polygyny Hotspot hypothesis: Males cluster in places (“hotspots”) where the routes frequently traveled by receptive females intersect Hotshot hypothesis: Subordinate males cluster around highly attractive males to have a chance to interact with females drawn to “hotshots” Female preference hypothesis: Males cluster because females prefer sites with large groups of males, where they can quickly or safely compare the quality of many potential mates ❖ Polygynandry: A mating system in which both males and females have several partners with whom they form pair-bonds Social cooperation among males and females in resource-scarce conditions ❖ Promiscuity: A mating system in which both males and females have several partners without forming pair-bonds Prioritizes genetic diversity without the cost of parental care, Resources and mates are widely available Lecture 11 - Reproductive Behaviour ❖ Intrasexual vs Intersexual Selection Intrasexual selection: members of one sex (within) (typically males) compete directly with each other for access to mates Male giraffe vs Male giraffe Intersexual selection: Sexual interactions between the sexes that can influence mate This occurs when one sex (typically females) selects mates based on certain traits or behaviors displayed by the opposite sex A male peacock displaying its colorful tail feathers to attract a female ❖ Alternative Reproductive Tactics Alternative Reproductive Tactic (ART): Different reproductive strategies within a single sex of a species Genetic ARTs: fixed for life, meaning an individual's reproductive strategy is predetermined by their genetic makeup This can lead to disruptive selection, where intermediate-sized individuals are less fit compared to either extreme Conditional ARTs: flexible and can change based on environmental cues or social conditions In socially hierarchical groups, smaller males might compensate for their lack of size or dominance by adopting sneaky or alternative reproductive behaviors ❖ Factors Influencing Alternative Reproductive Tactic (ART) Evolution Body size and size-dependent competition, Territory availability, Mortality risk, Growth costs Sperm competition: Males compete not only physically for mates but also at the gamete level after mating Females mating with multiple males increases the relevance of sperm fitness, Advantageous sperm traits (speed, longevity) become critical in fertilizing the egg ❖ Paternity Assurance Mate Guarding: individual guards their mate to prevent them from mating with anyone else Costs: It requires significant energy and time, potentially at the expense of finding other mates or resources Beneficial because it reduces the probability that a female will mate with another male and dilute or remove the sperm from the guarding male ❖ Female Mate Choice Benefits Females evaluate potential mates based on physical traits, experience, cognitive ability, and other factors  Direct benefits: Increase the fitness of the choosing female through material advantage like parental care, access to resources, safety from predators, reduced harassment Indirect Benefits: Increase the fitness of her offspring by endowing them with specific genes or combinations of genes ❖ Cryptic Female Choice: female ability to select which male’s sperm fertilizes their eggs after mating with multiple males. Postcopulatory Sexual Selection: Females may retain or discard sperm from certain males. Resource Allocation: Females may invest more resources in offspring sired by preferred males. Hormonal Adjustment: Some females adjust testosterone levels in offspring based on the mate’s attractiveness. ❖ Runaway Selection Model: A genetic correlation between female preference and male traits can lead to the evolution of extreme male traits over time Females prefer certain male traits, over generations, the preference and the trait become more exaggerated, potentially leading to costly or risky traits ❖ Chase away Sexual Selection: Some male traits that attract females may reduce female fitness, providing no real benefit to the female Initial Exploitation: A novel male trait exploits preexisting female sensory biases. Fitness Decline: Female fitness decreases as males exaggerate these traits. Counter-Evolution: Females increase their mating threshold to reduce being exploited, leading to a cycle of male exaggeration and female resistance