Animal Behavior: Territoriality, Dispersal, Migration, and Reproductive Strategies

Recall: Replace former resident with new resident

New resident gains resource holding power of that territory, causing fights to last longer.

European Robin Experiment

The winner was determined by how long the replacement had been on the territory, not by how long the ex-resident had been in captivity.

European Robin Experiment - Group 1

Day 1 resident bird removed and replaced immediately. Day 10 former resident reintroduced after 9 days. Ex-resident lost the battle and left by day 10. Replacement always won.

European Robin Experiment - Group 2

Replacement resident introduced later on. Replacement always lost.

Replacement Residents

Replacements gain motivation and resource-holding power.

Boundary Disputes

Boundary disputes take time and energy.

The Dear Enemy Effect

When neighbors treat familiar rivals as "dear enemies."

Kangaroo Rat Example

Kangaroo rat "ninjas" use senses and powerful legs to avoid rival snakes.

Dispersal

When an animal leaves its natal (birth) territory.

Dispersal in Belding's Ground Squirrel

Females dispersed slightly but stayed close to natal territory, while males dispersed significantly farther away.

Adaptive Outbreeding

Dispersing increases the odds of breeding with unrelated individuals and reduces the risk of genetic problems.

Male Mammal Dispersal

Male mammals typically disperse farther than females because males cannot defeat same-sex rivals.

Female Mammal Dispersal

Females may stay closer because they receive help from their mothers.

Migration

The regular back-and-forth movement between relatively distant locations by animals that use resources concentrated at both locations.

Ruby-Throated Hummingbird Migration

Travels from Canada to South America, about 3,500 miles.

Bar-Tailed Godwit Migration

Travels 6,900 miles in 8 days.

Sooty Shearwater Migration

Travels over 60,000 km per year, making it the distance champion.

Evolution of Migration

Migration likely started with short-range migrations in South America and became exaggerated over time if it increased fitness.

European Blackbird Conditional Migration

Some blackbirds migrate in the fall while others remain residents. The same bird can switch between migrant and resident strategies from year to year, suggesting migration is a conditional strategy.

Migration and Dominance

Migration occurs as contests increase in frequency, and individuals who remain are typically older and more dominant.

Behavioral Strategies

Genetically encoded behavioral rules or patterns.

Equal Fitness Principle

If two behaviors exist in a population, they should see equal fitness on average.

Migration Decisions and Fat Reserves

Birds with more body fat orient themselves south for longer migrations, while birds with less energy reserve orient west and make pit stops.

Red-Eyed Vireo Migration

Birds with more fat reserves go south for longer-distance migration, while birds with less fat go west and stop as needed.

Conclusions About Resource Holding Power

Differences in physical abilities and payoff asymmetries lead to differences in motivation to defend resources.

Conclusions About Migration

Migration is costly, likely evolved from short-range migration, and may be a conditional strategy.

Migration and Fitness

If migration provides fitness benefits, migration genes become stronger over time.

Reproductive Behavior

Behaviors related to mating and reproduction.

Birds of Paradise

Birds from New Guinea known for elaborate singing, dancing, and courtship displays.

Sexual Selection

The advantage certain individuals have over others of the same sex and species in relation to reproduction.

Sexual Selection and Natural Selection

Sexual selection is a subset and special form of natural selection related specifically to reproduction.

Satin Bowerbird Key Stimulus

Adult male performs a courtship display on a juvenile male that resembles a female.

Satin Bowerbird Competition

Adult male destroys the juvenile male's nest after the juvenile leaves.

Satin Bowerbird Communication

Adult male may practice courtship displays on juvenile males, who act as illegitimate receivers.

Bower Quality and Cognitive Ability

Birds with better bowers have higher mating success, fewer parasites, and larger brains.

Bowerbird Reproductive Success

Females usually mate with one male, while males mate with many females.

Sexual Differences Theory

Behavioral differences between sexes evolved in response to differences in gamete size, number, and parental care.

Human Gametes

Humans produce large eggs and small sperm.

Fruit Fly Sperm

Fruit fly sperm can be 20 times longer than the fly itself but still weigh much less than eggs.

Gamete Investment

Bodies invest resources differently into gametes.

WHO Sperm Count Reference Range

A single ejaculate contains about 39-928 million sperm.

Male Reproductive Gain

Males gain more from mating because sperm are inexpensive compared to eggs.

"Sperm is Cheap, Eggs are Expensive"

Different reproductive investments create pressures for sexual selection.

The Coolidge Effect

Males that have copulated to satiation with one female regain sexual interest quickly when introduced to a new female.

Choosy Females Experiment

Females were much less likely than males to accept casual sexual opportunities.

Parental Investment

Female reproductive success depends more on mate quality and offspring care than on the number of mates.

Males vs. Females in Reproduction

Males compete for mates, while females choose mates and invest more in parenting.

Operational Sex Ratio

The ratio of sexually active males to sexually receptive females.

Sexual Differences and Operational Sex Ratio

Paternity is less certain than maternity, males lose fertilization opportunities when providing parental care, and females often gain little from repeated copulation.

Biased Operational Sex Ratio

Usually there are more sexually active males than receptive females, increasing competition among males.

Sex Role Reversal in Katydids

Changes in operational sex ratio can reverse mating roles between males and females.

Katydid Nuptial Gifts

Males attract females with food gifts or secretions to secure mates.

Katydids When Food is Scarce

Females compete for males because male spermatophores become valuable nutritional gifts.

Katydids When Food is Abundant

Males compete while females choose mates.

Examples of Sex Role Reversal

Seen in some fish species with brood pouches, Mormon crickets, and some Empid flies.

Panorpa Scorpion Fly Conditional Strategy

Large males guard dead insects, medium males offer salivary deposits, and small males attempt forced copulation.

Panorpa Scorpion Fly Experiment

Removing large males caused medium males to guard insects and small males to guard saliva deposits.

Conditional Mating Strategies

Animals actively choose the mating strategy that benefits them most rather than being rigidly tied to one behavior.

Side-Blotched Lizard Strategies

Orange males dominate territories, yellow males sneak matings, and blue males are monogamous.

Ruff Bird Mating Behavior

Dominant males defend display courts, satellite males stay nearby, and female mimics sneak around courts.

Inherited Mating Strategies

Strategies are inherited and must produce equal fitness on average through frequency-dependent selection.

Behavioral Strategies

Fixed and genetically locked strategies.

Conditional Strategies

Flexible strategies that depend on circumstances.

Behavioral vs. Conditional Strategies

Behavioral strategies require equal fitness on average, while dominant individuals in conditional strategies choose the best option.

Sperm Competition

Competition among males for fertilization success of their sperm.

Onthophagus nigriventris Beetles

Hornless males develop larger bodies and testes, producing more sperm.

Sperm Swamping

Smaller males can overwhelm the sperm of larger males through larger ejaculates.

Damselfly Sperm Removal

Male damselflies use spiny penises to remove sperm from previous mates before releasing their own sperm.

Male Dunnock Behavior

Male dunnocks peck females' cloaca before copulation, causing females to eject previous males' sperm.

Mate Guarding

Remaining with a female after mating to reduce the chance of rival fertilizations.

Costs of Mate Guarding

Includes lost fertilization opportunities, energetic costs, and risk to life.

Female Seychelles Warblers and EPCs

Females engage in extra-pair copulations.

Resident Male Seychelles Warblers

Males guard females during fertile periods until an egg is laid.

False Egg Experiment

Placing a false egg in a nest caused males to stop guarding early.

Mate Guarding and Paternity

The more days females were left unguarded, the greater the chance offspring were sired by extra-pair males.

Mating Plugs

Male appendages block female reproductive openings to reduce future copulations with other males.

Nuptial Gift-Giving

Nutritional gifts exchanged during reproduction, such as food or secretions.

Black-Tipped Hangingfly

Males trade food for mating opportunities.

Black-Tipped Hangingfly Copulation

Mating occurs while females consume the nuptial gift.

Black-Tipped Hangingfly Short Meals

If a meal lasts less than 5 minutes, females leave without accepting sperm.

Black-Tipped Hangingfly Long Meals

If the meal lasts 20 minutes, females accept the full complement of sperm.

Prey Size and Copulation Duration

Larger prey leads to longer copulation duration.

Redback Spider Sexual Suicide

Males flip into females' mouths after mating and are consumed.

Benefits of Sexual Suicide

Females that cannibalize males are less likely to mate again.

Redback Spider Mating Odds

Fewer than 20% of wandering males ever find a mate.

Sexual Suicide Evolution

Sexual suicide evolves when males have little chance of future mating opportunities.

Good Parent Theory

Male signals such as color and courtship behaviors may indicate the ability to provide paternal care.

Female Zebra Finches and Red Coloration

Females prefer males with brighter red coloration.

Carotenoids in Zebra Finches

Extra carotenoids produced brighter red beaks, stronger immune responses, and increased attractiveness.

Zebra Finch Female Investment

Females laid larger eggs for more attractive males.

Blue Tit Paternal Care

Females prefer males with brighter yellow plumage, and offspring of brighter males are healthier.

Blue Tit Cross-Fostering Experiment

Egg outcomes depended on the brightness of the foster father rather than the genetic father.

Plumage and Paternal Behavior

Bright plumage may signal paternal care quality.

Fledgling Size in Blue Tits

Young bird size depended on the brightness of the foster father's plumage.

Great Bower Birds

Males provide genes only and do not contribute parental care.

Long-Tailed Widowbird

Females prefer males with longer tails even though males provide no material benefits.

Long-Tailed Widowbird Experiment

Males with experimentally lengthened tails had greater mating success.

Female Mate Choice Without Material Benefits

Females may choose males based on physical traits rather than parental investment.

Healthy Mates Theory

Females prefer healthy mates with low parasite loads, indicated by displays and appearance.

Good Genes Theory

Female preferences for male traits allow females to choose mates whose genes improve offspring survival.