week 3-4 Flashcards
Definition of Lek Mating System
A type of polygyny where males defend a small territory used only for displaying to attract females.
Males gather to display, and females visit the lek to choose a mate, after which they raise young alone.
Characteristics of Lek Mating Systems
Males defend tiny, adjacent territories in a lek, with no resources provided to females.
Mating success is highly skewed, with a few males often securing the majority of matings.
Example: Sage grouse – one male may have nearly 50% of copulations in a season.
Why Don’t Males Defend Larger Territories?
Females are too dispersed and unpredictable in time – males cannot effectively defend a large area.
Example: Grouse species with lekking males often have females with larger home ranges.
Population density too high for territory defense to be economical – high competition makes large territories unfeasible.
Example: Uganda kob – lek behavior observed only at high population densities.
Hotspot Hypothesis
Males gather at areas where females predictably travel, increasing male visibility and attraction.
Hotshot Hypothesis
Males gather around a highly attractive male (hotshot), gaining attention from females interested in him.
Female Preference Hypothesis
Females prefer large groups of males (leks) as it reduces the time and energy needed to find a mate.
Simultaneous Polyandry
One female mates with multiple males who share a territory and defend it jointly.
Sequential Polyandry
Female mates with multiple males sequentially, laying separate clutches that each male cares for alone.
Why Do Males Accept Polyandry?
Forced by female scarcity – leaving reduces their chances of reproductive success.
Cruel bind – low likelihood of finding a new mate if they desert.
polygynandrous System Characteristics
Both sexes have multiple partners simultaneously, with intense sexual competition.
Example: Dunnocks – males and females mate with multiple partners and engage in sperm competition behaviors like cloacal pecking.
Polygyny-Threshold Model
Females may accept polygyny if territory quality is high enough to offset the costs of sharing a mate.
Infanticide to Reduce Polygyny Costs
Secondary females may kill the primary female’s offspring to increase male care for their own offspring.
Sexy-Son Hypothesis
Females may accept polygyny if sons inherit attractive traits from their father, potentially increasing reproductive success.
Types of Parental Care
Egg Incubation: Maintaining optimal temperature, preventing desiccation, and aeration.
Example: Birds incubate eggs; sticklebacks aerate eggs by fanning.
Predator Defense: Driving away or warning of predators.
Example: Birds dive-bomb threats near nests.
Feeding Young: Directly feeding at the nest or leading them to food.
Example: Mammals produce milk; pigeons make crop milk.
Sanitation: Removing feces and parasites.
Example: NZ birds are less tidy due to low historical predator risk.
Teaching Skills: Guiding young in finding food and avoiding dangers.
No Parental Care: Eggs left to develop on their own.
Example: Salmon abandon eggs post-spawning.
Parental Care Strategies Across Species
Female-Only Care: Common in mammals and lekking species; males often desert post-mating.
Male-Only Care: Seen in polyandrous birds, some fish, and frogs.
Biparental Care: Both sexes provide care, often with varied roles.
Example: Birds and canids, where both parents might incubate or feed young.
Helper-Assisted Care: Non-breeding individuals help a breeding pair, often through kin selection.
Kin Selection and Helping Behavior
When individuals are more likelu to behave altruistically to relatives than other species/groups. Kin selection is a type of natural selection that favours the RS of an individuals relatives even at the cost of an own individuals surivial or reproduction
Definition of Parental Investment
Any activity that increases offspring survival at the cost of the parent’s future reproductive potential.
Costs and Benefits of Parental Care
Parental investment has diminishing returns: past a certain point, extra care yields little benefit to offspring but increases costs to the parent.
Optimal investment (green line) balances parent survival and offspring fitness.
Parent-Offspring Conflict: Occurs when parents invest less than what offspring desire, due to competing future reproductive interests.
Brood Parasitism and Extrapair Copulations
Extrapair Copulations: Females mate with additional males, resulting in mixed paternity.
Brood Parasitism: Females lay eggs in others’ nests, either within or between species.
Example: Shining cuckoo lays eggs in grey warbler nests; cuckoo chick mimics warbler’s sounds and scent.
Parental Care and Offspring Survival
Parental care boosts offspring survival.
Example: Removing male dark-eyed junco from brood decreases reproductive success.
Survival Rates:
Two parents: 65% survival after 24 days.
One parent: 30% survival.
No parents: 0% survival.
Energetic Costs of Raising Young
Caring for young requires high energy for food gathering and predator defense.
Increased Predation Risk for Adults
Defending young increases risk of predation, varying by species:
Example: North American (NA) vs. South American (SA) birds:
NA birds, with lower adult survival and larger clutches, take more risks to feed young.
SA birds, with longer lifespans and fewer young, are less likely to take risks.
Impact of Nest and Adult Predators on Behavior
Nest Predator (e.g., Blue Jay): NA birds reduce nest visits to avoid detection.
Adult Predator (e.g., Hawk): SA birds avoid risks that threaten their survival, prioritizing future reproduction.
Loss of Future Mating Opportunities
Caregiving can reduce opportunities for future matings, creating conflicts:
Example: St. Peter’s fish – mouth-brooding limits female mating chances.
Males more likely to desert if there’s a female-biased sex ratio, while females desert if male-biased.
Why Do Females Typically Invest More in Parental Care?
Past Investment (“Concorde” Fallacy): Females have already invested more in eggs, but this alone doesn’t justify ongoing care.
Certainty of Maternity: Females are more certain of their maternity than males are of paternity, reducing the perceived cost of investing in unrelated young.
Lost Mating Opportunities: Males lose more mating opportunities due to faster recovery times between matings.
Parental Care in Mammals
Female Care: Universal, mostly due to lactation (97% species).
Male Care (rare): Includes carrying young, defending against predators, or feeding.
Parental Care in Birds
Biparental Care: Most common (~90% of species), but females often invest more.
Roles: Incubating, defending young, feeding, and brooding.
Parental Care in Reptiles
Absent in most species, except for some crocodilians and Amazon turtles where females provide care by guarding eggs or young.
Parental Care in Amphibians
Male-only and female-only care equally common. Rare biparental care.
Example: Some frogs carry eggs to prevent desiccation and predator attacks.
Parental Care in Fish
Present in ~20% of fish families with high variability: male-only care most common (9:3:1 ratio of male:biparental
Parental Care in Insects
Rare, mostly female-only; male-only care occurs in waterbugs.
Example: Dung beetles (biparental care) prepare brood chambers.
paternity Certainty Hypothesis
External Fertilization: Males are more certain of paternity (e.g., sees fertilization), increasing investment likelihood.
Internal Fertilization: Less certainty due to time lag between insemination and laying, leading to lower male investment.
Gamete Order Hypothesis
Internal Fertilization: Male can desert post-mating; female is unable to desert until eggs are laid.
External Fertilization: Male remains to fertilize eggs, increasing association with young.
Association Hypothesis
Prior association with embryos predisposes a sex to care for young:
Internal Fertilization: Female is closer to offspring (pre-adapted for care).
External Fertilization: Male territory often overlaps with brood, fostering male care.
Example: Sticklebacks build nests and care for eggs, benefiting from both proximity and low opportunity costs for future matings.
How Much Parental Care?
The level of parental care depends on weighing costs (energy, predation risk, and lost mating opportunities) against benefits (offspring survival).
The decision depends on:
Condition of Offspring: Health and vigor of the young.
Age of Offspring: Older offspring may be more valuable.
Relatedness: Degree of genetic certainty influences care.
Condition of Offspring
Parents invest more in healthy offspring:
Example: Hihi (stitchbird) nestlings with redder mouths (indicating better health) received more food from parents.
Red mouth color linked to better health and enhanced begging display, encouraging more parental provisioning.
Age of Offspring and Parental Care
Parental care typically increases as offspring age due to reduced future costs.
Example: Red-winged blackbirds show more aggressive nest defense as chicks grow, diving at perceived threats more intensely over time.
Relatedness and Parental Care
Males should ideally adjust care based on genetic relatedness:
Example: Dunnocks—males feed more frequently if they sire more of the offspring.
Counter-Example: Yellow warblers and tree swallows don’t adjust care based on relatedness, despite a high rate of extra-pair paternity.
Reasons Males May Not Adjust Care for Unrelated Offspring
Male Care is Essential:
If the benefit of care (increased offspring survival) outweighs the cost of lost paternity, males may continue to care.
Especially relevant in seasonal breeding environments with limited future mating opportunities.
Unawareness of Cuckoldry:
Males can only reduce care if they have information on paternity.
Example: Dunnocks use copulation frequency with a female as an indicator of paternity.
Some females, like chickadees, avoid detection by sneaking extra-pair copulations.
Kin Recognition and Parental Investment
Males generally lack mechanisms to recognize kin specifically:
Example: Mexican free-tailed bats use olfactory and vocal cues for recognition, but these cues are learned and not effective for males.
“Green Beard” Hypothesis: Recognition based on unique traits, but open to deception, so not a reliable kin recognition strategy.
Intrabrood Conflict
Offspring compete for parental resources because each is more related to itself than to siblings.
Interbrood Conflict
Current brood may demand more resources at the expense of future siblings.
Example: Galapagos fur seals—when resources are limited, older pups continue nursing longer, leading to high mortality of newly born siblings.
Parent-Offspring Conflict Overview
Optimal investment levels for parents are often lower than what offspring would prefer.
Sibling Conflict and Relatedness:
Greater conflict expected when half-siblings (lower relatedness, r = 0.25) are involved, as seen in birds where half-siblings engage in more aggressive begging behaviors than full siblings (r = 0.5).
Can Parent-Offspring Conflict Be Resolved?
Resolution may occur if offspring demands and parental provisioning co-adapt.
Chicks may beg for food to ensure survival; if begging is effective, it may lead to higher provisioning from parents to reduce begging behaviors and protect against predators.
Evolution of Behavioral Strategies Against Disease
Animals are in a constant struggle against pathogens and have evolved behavioral strategies to minimize infection risks, including:
Avoiding areas with pathogens.
Avoiding individuals that are infected.
Avoiding Pathogen-Filled Habitats
Female grey tree frogs choose oviposition sites based on the presence of Pseudosuccinea snails, which act as intermediate hosts for parasitic trematodes.
They avoid ponds with infected snails, demonstrating a behavioral adaptation to reduce the risk of infection.
Avoiding Diseased Individuals
Healthy lobsters avoid communal dens shared with infected individuals, likely using chemical/olfactory cues to detect infections.
Infected lobsters do not avoid healthy individuals, highlighting a social cost of communal living.
Selective Foraging to Reduce Parasite Risk
Dik-diks avoid feeding near dung middens to reduce the risk of nematode infections.
They choose foraging sites that minimize exposure to areas where fecal contamination is high, balancing nutrition and parasite risk.
“Moving House” to Avoid Parasites
Bluebirds prefer unused nest boxes over previously used ones to reduce ecto-parasite risks, even with competition for limited nesting sites.
Sociality and Pathogen Risk
Larger colony sizes correlate with increased flea infestations due to the ease of pathogen spread.
Benefits of social living (predator mobbing, mating opportunities) come with costs of higher disease risks.
Spreading Risk through Schooling
In schools, fish experience fewer parasite attacks, showing that larger group sizes can dilute individual risk.
Can Animals “Self-Medicate”?
lue tits add aromatic plants to their nests, reducing bacterial richness and improving chick health, illustrating a form of self-medication.
Grooming to Reduce Pathogen Load
Birds spend a significant portion of their day preening to manage ecto-parasite loads, with allopreening observed in breeding pairs to reach hard-to-groom areas.
Eating Dirt (Geophagy)
Many primates engage in clay consumption, which may help absorb harmful compounds and act as a form of preventative self-medication.
Advertising Health through Behavior
Ornamental traits in animals, such as coloration, serve as honest signals of health status to potential mates, influencing mate choice.
Health Advertising via Clean Bottoms
The conspicuous white feathers around the cloaca may serve as an advertisement of gastrointestinal health, as maintaining cleanliness would be difficult during infections.
