Animal Behavior Exam 3

study guide for pbsi 311

Section 9

Mating Behavior

What is Mating System?

• Pattern of male-female pairings. Includes monogamu, polygyny, polyandry

Male/Female

• Defined by the relative size of the gametes they produce’This underlying asymmetry between males and females causes them to approach mating with differing and sometimes conflcting interests

Males

• The sex that prodices small motile gametes (sperm)

• Large number of gametes 

• Invests little in each gamete

Females

• The sex that produces large gametes (eggs)

• Relatively small number of gametes

• Invest heavily in each gamete

Why two sexes?

• Natural selction of gametes favored the extremes: small and large

• Smaller gametes were fast and could travel quickly- but the trade off was reduced nutrient content for the zygote

• Balanced by fertilizing larger, nutrient-rich gametes

Hermaphrodites

• Animals that can produce both eggs and spem

• Simultaneous hermaphrodites: male and female at the same time (seas slugs)

• Sequential hermaphrodites: first one sec and then the other (clownfish and wrasse fish)

What is sexual reproduction?

• Process of combining genetic material from two parents through fusion of gametes. Offspring are novel combination of genes

• Genetic recombination from meiosis: process of removing half of genes after mixing chromosome pairs

• Fertilization: gametes fuse to create zygote

What is High evolutionary cost?

• The cost of meiosis is that half the genome is “lost”

• Sexual reproduction- animals pass only half of their genes to each offrpsing

• asexual reproduction- animals pass along all of genes to each offspring

• Benefit: advantages from genetic recombination and genetic diversity among offspring (outweighs the cost)

Asexual Reproduction

• Most common in invertebrates than vertebrates (fish)

• Useful in environments that change little between generations

• Sometimes occurs in pioneering species where single animal migrates to habitat

Switiching between asexual and sexual reproduction

• Some species can perform this strategy

• Sea anemonies alternate between the two

• Stable environment: maintain genetic combinations via asexual reproduction

• Colonizing new habitats (dispersal): use recombination and offspring diversity via sexual reproduction

Mating System Theory (choosy females)

• Much theory is based on the fac tthat an egg is more costly to produce than a sperm

• females should protect their investment by caring for offspring

• Common prediction is that females should be choosy about mate

Mating System Theory (choosy males)

• Sometimes males are choosier 

• Limited male options for mating means equally choosy as females

• Males invest more than females in offspring than they are choosier

Batemans Rule:

• Males generally have higher variation in reproductive success than females (reproductive success increases with number of mates)

• Male limited not by sperm production but by number of mates

• Intensity of sexual selection higher

• Mating can be costly enough to limit male reproductive success

What is sexual selection

• Preference by one sex for certain traits leads to type of natural selection known as sexual selection

• Intersecual selection = mate choice; how mating preferences of one sex affect characteristics of the other sex

• Intrasexual selection = mate competition; how competition within a sex for mates affects characteristics

• Both can result in sexual dismorphism

Secually Selected Traits:

Costs of producing sexually selected traits can be high, these signals are honest signals

Handicap Principle: if the secually selected trait is a handicap for the animal it becomes an honest advertisement of the animals ability 

What is Parental Investment theory:

• Predicts that the sex that pays the higher cost of parental investment should be choosier when it comes to mates

• They can choose from direct material Benefits: food gifts, access to territory with food, parental care

• OR indirect genetic benefits: genetic quality of potential mate “good genes”

Female Mate Choice

• Any trait that is preferred by females will be strongly favored (sexual selection)

• Should choose matye on liklihood of enhancing survival for females offspring

• Some copy other demale choices

• Example: Pronghorn Antelope: seek out males that are good Harem defenders

Courtship

• Gives animals the chance to demonstrate their quality as a potential mate

• Example: Bowerbirds build elaborate bowers with brightly colored objects and perform dances

Sexy Son Principle

• Prefer to mate with males that will father sons that will be moreattractive to females in next generation

• AKA bad boy phenomenon

• More of a driving factor in mate choice than good genes

Good Fathers

• Selection favors femals that can attract social mates that are goodfathers (directbenefit)

• Good fathers often rear some young that are not theirs due to extra-pair copulations

• Most species cant access relatedness to young

Male mate choice

• Less studied

• Male has substancial role in parental care

• Females vary greatly in their quality as mate

• If males of a species are chosy, then females should experience sexual selection and develop secondary sexual characteristics

• Example: Pipefish males invest heavily in parental care

• Males are choosier; femal competition and secondary characteristics (stripes); female courtship dance

Mating system dishonesty in Males

• Strong selection for two types of dishonesty in males:

• Misrepresentation of quality in mate choice

• In species in which male partners in parental care, misrepresentation about whether they already have a mate and young

Dishonesty in females

• Females also show the second type of dishonesty

• Females may be uncertain about mate choice

• Mate with other males but hide this to protect their offspring 

What is mating system? And what are the major mating systems?

• Pattern of male-female pairings

• Monogamy: pairing a single male with a single female

• Polygyny: association of one male with many females

• Polyandry: association of one female with many males

• Polygynadry: association of many males with many females

Social mating systems vs. genetic mating systems

• In many species the socal father may not be the biological (genetic) father of young

• (Extra Pair copulations EPC) are surprsingly frequent

• Most birds species are socially monogamous

• Social father may not be genetic father

Monogamy

• Pairing of one male with one female

• The most common mating systems in bird but rare in most other animals

• Increased chances of future reproduction

• Benefits include: female gains protection from other males that might attempt forced copulation (common reprodcutive behavior in ducks and geese)

Monogamy can evolve when:

• costs of acquiring mates is very high

• Females have ability to restict male behavior

• Offsrpiing siurvival requires intensive care by two parents

Monogamy- EPCs

• Major cost in monogarmy is the entire reproductive investment of an individual depends on the fitness of the chosen mate

• This may be why monogamous animals are often not completelt monogamous 

• Serial monogamy: choosing a new each season

• EPC: hidden extra-pair copulations

• 95% of birds are socially monogamous but extra pair paternity (EPP)

• If male parental involvement is high, then EPP is lower

Polygyny:

• Association of one male withmany females

• The most common mating system in mammals 

• Forms of polygyny: resource defense polygyny, female defence polygyny, Lek polygyny, and scramble polygyny

Resource Defense Polygyny

• Groups of females centered around resources or a male that hold resources (or territory)

• Mate chouice: females may sample and make choices

• Male-Male competition: females may cluster around a resource and then males compete

• Territorial males have more than one mate while others have none

Polygyny threshold model:

• Makes predicitons about when females should choose to be a secondary mate in one territory rather than be the sole female in another

• Sharing a male’s resources provides a greater benefit - despite the cost of sharing

Female defense polygyny

• membership in a harem or defended group of females

• Females might form a her or group based on defense against predators, rather than around a resource

• Males compete for the group

• Females also might compete for dominance in the group

Lek Polygyny

• Aggregation of males that seek to attract a mate by performing competitive courtship displays for visiting females

• The lek attracts females than an individual male

• Only a few dominant males will end up mating with the majority of females

Bachelor herds:

• Groups of males that travel together

• Males that are not chosen for mating or males thatcome together outside the mating system and made up of this

• They benefit from mutual protection and food discovery

Scramble Polygyny

• Males compete to find and mate with as many females as ossible

• Caused by small groups of females being distibuted throughout the environment

• Males travel and search extensively

Polyandry :

• asscociation of one female with many males

• Resource defense polyandry: in some species, where female is terrirotial and males live on territory ( females leaves eggs with males to incubate)

• Cooperative polyandry: femals have several maytes and cooperated with them to raise brood. (honeybees)

Polygandry and promiscuity 

Polygandry: when females mate with several males and males mate with several females, often caring for young of several females

Promiscuity: no pair bonds, males and females seem to mate randomly with multiple partners, mating system theory suggests this should be rare

Hormones and sexual behavior

• Major hormones involved in reproductive behavior include:

• Lutenizing hormone (LH) and follicle stimulating hormones (FSH): produced by the pitituary and act on the gonads to cause release of steriod hormones

• STeriod hormones: testosterone, estrogen, and progesterone

• Oxytocin and Vasopresin: also release from pituitary role in pair bonding

Hormones in Females:

• Hormone are cycilic

• LH peak increases sexual receptivity prior to ovulation

• Progesterone coordinates behavior and physiological changes for pregnancy in mammals and brooding in birds

Hormones in Males:

• Testosterone levels increase with sexual maturity, then reman constant or cycle seasonally

• testosterone also involved in aggression

Precopulatory competition:

Male-male competition prior to mating (including aggression)

Postcopulatory competition:

Male-male competition after mating.

Sperm COmpetition

• occurs with internal and external fertilization.

• Internal fertilization: consists of most territorial animals: offemale mates more than once within short time period

• External fertiliztion (marine animals) sperm competition during spawning most common type

Sperm competition – Mating strategies

• Sperm competition occurs when males use different mating strategies.

• Example: Bluegill sunfish

• A. “Parental” males are territorial and use courtship, building a nest on bottom of lake to court females, who spawn in nest. Parental males then guard the eggs.

• B. “Sneaker” males can dash in and release sperm near the nest.

• C. “Satellite ” males mimic females to come close to eggs.

Sensory cues- avoiding inbreeding

• Animal inbreeding decreases survival and reproductive success

• Thus natural selection has favored mechanisms to avoid mating with relatives:

• Learning identities & using sensory cues like smell

Sensory Cues- choosing good immune genes

• Many mmals detect immune system type of other animals by smell

• Immunocoompetence and immunocompatiability hypothese: mate choice should favor non matching or complementary immunotypes ro increase offspring immune diversity and disease resistance

Visual Cues- choosing good genes

• In many birds and fish, color may be an honest indicator of fitness: 

• Ability to cope with parasites and animals nutritional state

Parental Care

• Can range from choosing a safe place to lay eggs to caring for young for months or years as they mature

Nest

• Often includes construction of a den or nest and its used to

  • keep young safe from harm

  • keep young in the appropriate microclimate

• Evolution shapes architecture and construction strategies

Simple Nests:

• Bat roosts are sheltered spots that do not require modifications

• Downside: less contol of microclimate. Huddle together for warmth

Beaver Lodges:

• Beavers usually construct a dam and a lodge (when trees present)

• Can dig a burrow in the water bank

• Flexibility means they have broad range of habitat

• Submerged entry to lodge provides protection from predators

Prairie dog burrows:

• Praire dogs can occupy up to 100 square miles

• Above ground: they make a mound of scavated soil and clear the surrounding grass (prevents rain from getting in burow and help to watch for predators)

• Below ground: the tunnel leads to a chamber in which young are reared

Magpie Nests:

• Black-billed magpie build nest out of sticks like many birds

• formed in a “cup” style or can be completely enclosed

Paperwasp nests

• Paperwasps, yellowjackets, and hornets form a nest with cells

• Egg laid in each cell

Termite mounds

• Termite construct mounds with feces, saliva, mud, and plants

• Strong enough to support itself

• Needs to be porous enough to allow air exchange

Sand goby nests:

• Many fish including snad goby’s make nests of sand

• Eggs are laid and fertilized in nest

• Male constructs and defends the nest

• Female chooses nests to lay eggs (preferes a nest with fewer eggs)

Parental Investment

• Can be though of as the investment that a parent makes in an offspring that reduces the parents future fitness

• It icludes: provisining gametes, egg guarding and protecting, provisioning and guarding offspring, giarding of nests and territories, and teaching surival skills

Parental investment based on life history traits

• Characteristics that determine the course of a life such as maturation, reproduction, and logetivity

• Age at first reproduction, number of young in a clutch, number of clutches in a lifetime

• Animals with high reproductive rates typically show low investment

• Animals with low reprodcutive rates invest heavily in offspring (stable & highly competitive environments)

Male Parental Care:

• Male parental care is not rare

• The conditions that favor biparental care include greater requirements for producing young that survive and reproduce themselves due to environmental pressures and life history traits

• Djungarian hamster males care for their young and even assist in the birth, likely due to greater environmental changes in temperature

Altricial Animals

• Relatively immature at birth and require lots of parental care

Presocial animals:

• Can move and forage shortly after birth

• needs less investment

Recognition cues:

• Help to identfy individual young

• In species where the young do not wander far, recognition of young is unnessecary

• Certainty of paternity influences male parental care. With external fertilization, males be more certain

Recognition via sounds:

• Auditory cues are used in recognition by many birds

• Goats can recognize the vocalization of their offspring

• Domestic sows that communcation with litters have lower mortality among piglets

Recognition via odors:

• Olfactory cues are important in many land animals

• Cows used odors of calves to identify

Parental Care: External fertilization

• Fish parental care varie by species

• SOme scatter eggs in water, some deposit eggs and guard them, some build nests of bubbles, come keept their small fish in their mouth

• Male participation is common in fish: constructing nests, guarding eggs or fry, and even mouth brooding

Uniparental care: Internal Fertilization

• More common in land animals

• Parental care can mean as little as finding an appropriate clime for egg development anf laying eggs

• Female reptiles may lay their eggs in a protected place

Uniparental care by males

• Male only caregiving is rare, but includes seahorses, pipefish, and sea spiders

• Female mammals gestate and feed younf, making male uniparental care impossibe

Biparental care: internal fertilization

• Common in birds

• Fitness gained by added survival of yound due to males care outweighs fitness gained by other potential matings

Biparental care in seabirds

• In many seabirds, one partner remains with nest while the other forages

• Male emperor penguins fasts >100 days while incubating eggs

Raising other animals’ young: adoption

• Interspecific adoptions: adoption of another females young may occur in shared nests and communal brood care

Raising other animals young: Paratism

• Intraspecific brood parasitism: when birds lay theor eggs in the nest of other bird species

• Interspecific brood parasitism: when bird lay eggs in nests of other species (cowbirds and cuckoos)

Cuckoos and cowbirds

• Cuckoos show rapid changes in eg apearance to match host bird

• Cowbirds: are also brood parasites

Hormones: Prolactin in Birds

• In vertebrates, maternal behavior associated with the hormone prolactin, while paternal behavior is associated with declining levels of testosterone

• In birds, prolactin in females stimulates nesting behavior

Hormones: prolactin in mammals

• In mammals, prolactin during pregnancy stimulates mammary gland development (for milk production) and primes maternal behavior

• Each pregnancy induces more prolactin receptors in the brain

• Prolactin inhibits ovulation

Hormones: Oxytocin in mammals

• In mammals, the hormone oxycotin is involved with milk letdown reflec in milk production and maternal bonding with young animals

Hormones: Naked Mole Rats

• Naked mole rats are eusocial mammals that live in a colony with one dominant, reproductive queen

• When eaten by subordinate females, their estrogen levels rise and they become more responsive to young pups

Parent-offspring conflict

• What is the ideal time that parental care should cease? Parents and offspring likley differ in the ideal time point

• As offspring get older require more resources

• Parent-offspring conflict: increasing demans of the offspring but no added fitness benefit to the parent

Example: Banded Mongoose

• Offspring demand resources based on their need, but also on the liklihood the parent wil provide the resources

• Example: banded mongooses breed communally

• When cared for by escorts that were more likely to provide, the pups begged more

Parent-offspring conflict among siblings

• Siblings in most species do not necessarily want to share resources

• However, sometimes parents benefit from some offspring: not surviving and becoming nonreproductive

Begging and weaning conflict:

• Begging: when young birds and mamals ask for food, sometimes continuously

• Weaning: when the parent determines it no longer needs to feed the young

Begging: Offspring point of view:

• Begging helps the offspring as a way to attract food

• Begging may reflect actual needs (honest signal) or desire

Example: Mimic Poison Frog

• Mimic poison frog provides parental care

• Cared for by father, who carres tadpoles on his back to small pools of water. he attends to them during 2-3 months

• When she arrives, the tadpole stops swiming and begins to vibrate (begging)

• The vibrations are costly to the tadpole and represent an honest signal of need

Begging: Parental POV

• Begging helps the parents: it ensures that parents are feeding the offspring enough

• Begging reduces (risk of waste of time and risk of overlooking nestlings)

Begging in brood parasites:

• When the egg of another bird hatches in the nest, that hatchling has more intense begging than host nestlings

• Dishonest signal

Weaning conflict:

• The offspring benefits from a guaranteed food resource, while the parent benefits from using the food for other offspring or their own nutrition

Orcas need their mothers:

• Often live in family groups and remain with their mothers (cost)

• Long lived sons are valuable to moter’s fitness (benefit)

• Death of a mother orca adversely affects survival of offspring, especially in older male offspring

Sibling conflict:

• Some offspring may seem less likely yo survive and reproduce. Parents may allow for sibling competition (sibling conflict) of resoruces

• Mammals, sibling may compete over access to mother’s milk

• Birds, chicks with bright plumage recieved more food

Sibling conflictL extra offspring

• This might increase the overall odds of sirvivng and provides extra offspring as insurance

• Parents generally do not kiill surplus offspring, Typically death comes from lanourishment or sometimes from older siblings (siblicide)

Infanticide by males:

• Killing of young animals and common amonst mammals

• Infanticide by male: is almost alwasy caused by paternity uncertainty

• Blue footed booby

• In primates: infanticide is thouught to be reduced by: concealed ovulation and pair bonding

Infanticide by females

• May occur when resources for offspring are limited, killing other females young

• Banded mongooses have communal litters which protects young from infanticide

Killer Prairie Dogs

• Prairie dogs will

Dominance conflict:

• Dominance interactions include aggression, threats, and submission

• Example: spciable weavers live in a communal nest. subordianate bird will increase contribution

Sexual Conflict:

• Males can use aggression or threats to ensure females remain with them or the group

Parent-offspring conflict:

• Parents may use mild forms of aggression on offspring to promote safety and assist in shifting parental investment

Antipredatory conflict:

• Includes fighting back against predators and mobbing

Territorial conflict:

• Related to aquiring or maintaing a territory

• Male-male interactions are typically either territorial or dominance

• Territorial conflict includes defense of young or nest; mothers may be particularly aggressive

How do you know if an animal species is territorial?

• Observations that animal shows territory defense

• The spatial distribution of animals must be nonrandom

Territoriality vs. personal space

• Territoriality is different than “personal space” within a social group

Social Groups:

• Inclide gatherings of members of a species

• Common general terms for social groups include: herd, flock, school, pack, colony, and troop