chapter 54 - behavioural ecology

Optimal diet model

• preys are ranked by benefit per unit of undling time

• Top ranked prey are never rejected but lower ranked preys can

Ex. Oystercatcher may reject large mussels because they take too long to open. Medium sized mussels are more profitable because easier to open

Central place foraging

Many animals travel from a central place (nest or den) to catch prey

Prediction of central place foraging theory

States that longer travel times are other worthwhile if you can bring back larger, valuable prey

Ex. Ospreys flying further to forage ring back larger fish to nest

When to forage?

Many animals have foraging schedules to avoid predators

Ex. Deer, mice and kangaroo rats will forage at night to avoid daytime dinural predators like coyotes and foxes

• some predators like owls take advantage of nocturnal foraging prey

Types of mating behaviours

Seeking/attracting mates, choosing among potential mates, competing for mates and caring for offsprings

2 types of mating systems

1. Monogamous - one male one female, usually ave similar external morphologies

Ex. Western gulls

2. Polygamous - one individual of one sex with several individuals of other sex, usually sexually dimorphic and have different external morphologies

3 types of polygamous mating systems

1. Polyandry - one female mate, multiple male

• ex. Phalaropes and angler fish

2. Polygyny - one male, multiple female

• ex. Elephant seals, elk

3. Polygynandrous - both have multiple partners

Ex. Red winged blackbirds

Most common form of mating

Mating is promiscuous, with no strong pair bonds or lasting relationships

• but varies species to species

Expensive offspring favours….

Favours monogamy

• its favoured when offspring need parental care and cant care for themselves

• Males benefit by staying with their partner

Ex. Altricial birds

Cheap offspring

Where Young’s can feed themselves and males have less benefits by staying with their partner

• they can maximize reproductive success by searching for additional mates

Ex. Precocial birds like Ducks and pheasants

What is the second factor affecting mating systems and parental care

Certainty of paternity

2 ways males can increase their reproductive success

1. Helping female raise offsprings

2. Searching for other females

• he gains no evolutionary benefits if another male is the genetic parent of the offspring

Which species is certainty of paternity more common in

when fertilization is external for species

Ex. Fish, amphibians, aquatic invertebrates, giant water bug and plain fin midshipman

• its not common in species with internal dertilization

Midshipman fish in certainty of paternity care

• Males sing to attract females to their nest under a rock. Males guard eggs until they hatch but they dont feed while protecting the kids

2 types of midshipman males

Type 1 - are larger and more vocal when they sing to attract females

Type 2 - smaller, sneakier

2 types of sexual selection

1. Intersexual - member of one sex choose mate based on desirable traits

Ex. Peacocks and peahen

2. Intrasexual - members same sex compete for opposite sex

Ex. Male elephant seals

Female choice

• Type of intersexual competition

• Females can drive sexual selection by choosing males with specific behaviours or features

Ex. Stalking eyed flies females choose males with long eye stalks which correlates to health and vitality

Male competition

• Intrasexual selection

• Can reduce variation among males as it favors evolution of weaponry and large body size

• May involve agonistic behaviour, a ritualized contest that determines which competition gains access to a resource

Intrasexual competition in pacific salmon (dog salmon) and hooknose in chinook salmon

Chum salmon (dog salmon) develop a canine teeth when spawning and hop nose male dont feed on spawning grounds, their cabin teeth are for fighting other males

Genetic basis of behavioural variation

Can be linked to variation in a single gene but most behaviours are governed by many genes (polygenic)

Genetic basis of behaviour in personality

Humans of the big 5 personality traits (Extraversion, agreeableness, openness, conscientiousness and neuroticism) show high degrees of heritability

Mating system in prairie voles vs meadow voles

Prairie voles are monogamous and meadow voles are polygynous

• difference in male behavior is in the receptor for a neuropeptide hormone vasopressin

Vasopressin and oxytocin

Are neuropeptideds that play a key role in social attatchment and affiliation including parental care and pair bonding

How do variations on a gene effect behaviour example

Differences at a single locus have large effects on behaviour

Ex. Male prairie voles pair bond with mates while male meadow voles dont

What determines which behavioural patttern develops

Level of a specific receptor for a neurotransmitter

Variation in prey selection in garter snakes

Natural diet of garter snakes vary by population

• coastal → banana slugs

• Inland → rarely eat banana slugs

This shows that diet differences are genetic Since the two populations differ in ability to detect and respond to specific Oder molecules produced by banana slugs

Importance of monoamine oxidase gene

it codes for enzyme that breaks down neurotransmitters norepinephrine and dopamine

• a single point mutation can disable the gene on the X chromosomes causing males to be cognitively impaired and prone to violence and sexual offences

• Gene affects flight or fight responses

Warrior gene

Slow acting variant of monoamine oxidase that results in individuals more prone to aggression and anti social behaviours

Warrior genes on environmental conditions

The effect of the warrior genes is conditional in early environment, thus having the mutation does not guarantee the behaviour

• those raised in abusive environments show more anti social behaviours than those in nurturing environments

How have twin studies helps with research in nature vs nurture with behaviour

Showed how strong genetics are in behaviour

• monozygotic twins show greater similarity than dizygotic twins

Altruism

Behaviour of organisms where they reduce their individual fitness but increase fitness of others

Ex. Under threat from predators, an individual Beldings ground squirrel will make an alarm call to warm others, despite making its presence more known to the predator

Kin selection

Proposed by Hamilton where animals help close relatives to increase its genetic representation in the next generation rather than direct offsprings

• its the natural selection that favours altruistic behavior by enhancing reproductive success of relatives

Inclusive fitness

Total effect an individual has on proliferating its genes by producing offsprings and helping close relatives produce offspring

• helps explain altruistic behavior

Ex. Workers in ants, bees and wasps dont reproduce, they assist close relatives to raise offsprings

Concept of relatedness

Why the average relatedness of full siblings is ½

• theres a 50% chance youll share an identical copy of a gene received from one of your parents

3 key variables in an altruistic act (Hamiltons rule)

1. Benefit to the recipient ; B

2. Cost to the altruist ; C

3. Coefficient of relatedness (fraction of genes that on average are shared) ; r

Hamiltons rule

rB > C

• shows when natural selection favors altruism

• Kin selection - natural selection that favours this kind of altruism behaviour by enhancing reproductive success of relatives

Inclusive fitness in beldings ground squirrels

Female belding ground squirrels are more likely to call alarm in the presence of a predator than males

• alarm calling attracts predators (dangerous)

But in a group, most females are closely related to each other and males are less related to each other since males tend to leave home

• the kin selection benefit for calling is greater for females than males

Inclusive fitness

Non reproductive individuals increase their inclusive fitness by helping reproductive queen and kinds (close relatives) to pass their genes to the next generation

Ex. Naked mole rats

Human behaviour

Results from interactions between genes and the environment

• our social and cultural institutions may provide the only feature in which there is no continuum between humans and other animals

2 examples of adaptive human behaviours

1. Humans have a language instinct

• we acquire language automatically during an early critical period that lasts into puberty

2. Tongue pushing in new borns

• in their first months of life, infants push out solid objects from their mouth, this behaviour is adaptive because the digestive system isnt ready for solid foods

Why do women gain weight during pregnancy

• lactation is energetically expensive

• Mothers add weight during pregnancy to pay for the cost of lactations

• Thus Mothers of twins gain more weight than mothers of singles

Incest avoidance

Children reared together in the first 30 months off life usually show no sexual interest in one another

• Is an adaptive human behaviour to avoid harmful effects of interbreeding since everyone carry’s at least 2 recessive lethal genes

What behaviour is influenced by genes

in almost all behaviours but no behavior is 100% heritable, theres still some environmental influence

Ex. Alzheimer’s, aggression, intelligence, etc

Parent offspring conflict

Offspring should be more selfish than parents desire

• Parents and offspring have shared but not identical genetic interests

Example of parent offspring conflict in humans

Human pregnancy

• preeclampsia (high blood pressure) and gestational diabetes are both due to embryonic genes manipulating mother to increase food supply to the fetus

• Both involve imprinted genes (dads fault)