-
Territoriality
occurs when an animal lays claim to an area and defends it against other animals
-
Dominance Hierarchy
members of an aggressively organized group coexist with one another within one territory
-
Simplest Dominance Hierarchy
Despotism
-
Visual, Chemical and Auditory signals are important?
because of communication and recognition
-
Special Properties of Dominance Hierarchies
- Xenophobia
- Strong Leadership Means Peace
- The Will to Power
- Nested Hierarchies
- Social Inertia
-
Why Xenophobia?
- Disease
- Competition for Mates
- Competition for Resources
-
Advantages to being Dominant
- Get food
- Get shelter
- Get mates
- Less stress
- Grooming
-
Consequences of being Subordinate
- Less food
- Reproduce less often
- Poorer nesting sites and shelter
-
why stay in a group if you are Subordinate?
- Consequences of being subordinate
- - emigration
- - "sneak copulations"
- - benefits of being in a group
-
What qualities determine the dominance status of an individual?
- - adults are dominant over juveniles
- - bigger animals are usually dominant over smaller animals
- - healthy animals are dominant over sick animals
- - males are dominant over females
- - animals are most dominant on their own territories
- - accidents play a role
- - intensity of status signals
-
Intergroup Dominance
- Slavery, Kignapping, Killing
- - wolfs
-
Consequences of Intergroup
Hierarchies
-
Territory
- any defended area...contra Home Range - recognized 2,300 years ago by Aristotle (2 Falcons will not occupy the same area..) (Formalized by Eliot Howard 1920)
-
Home Range
refers to all space used by an animal
-
Functions of Territorial Defense:
- - To control critical resources (e.g. for breeding): often advantageous to control somewhat more than the minimum amount
- * male might be able to attract >1 female or a higher quality female (polygyny threshold model)
- - To reduce predation (reduces chance of community becoming a popular hunting area)
- - As a sexual advertisement
- - To help with mate-guarding
- - NOT to control popoulation size (Wynne-Edwards, Ardery)
-
Economic Defendability
- a resource attribute
- - consider how large a territory ought to be staked out and maintained
-
When does excluding others ('hogging') pay a higher return than sharing?
Resource quality and spatial distribution ("patchiness")
-
what happends when patch resources get a lot richer? What can we predict should happen to Territory Size?
- The optimal size of territory to defend shrinks
- - richer you get the more you can afford to relax (you no longer need to be desperate)
-
Forming selfish herds
- - animals move to position conspecifics between themselves and predators
- - if predators take nearest animal, moving to center benefits individual
- - result: form tight groups because each individual selfishy seeks middle
- - forming groups does NOT imply cooperation
- - each individual may be selfishly for its own benefit
-
Confusing the Predator
Several prey can flee in unpredictable directions
-
Learning & Social Facilitation
Experiments: John Krebs
- - Birds search for a clumped source of food web more successful in groups of four than in pairs or singly
- - different species can learn where food is from one another
-
Adaptive Value of Being in a Group
For Prey Species
Passive: Thermoregulation, Kin related benefits, grooming, etc.
-
Adaptive Value of Being in a Group
For Predator Species
- Coordinated Foraging
- - makes more food availabe to be hunted
- - reduces path overlap
- - allows species to compete better for food with other competing species
- - enables unsuccessful individuals to learn locations of new food resources from successful individuals in the group
- - reduces energy costs or risks per individual or permits the taking of larger prey
-
"Mixed Bird Parties"
"Beating Hypothesis"
Birds move through a field they flush out insects so all can eat or some leader species (large mammal) disturbs foliage causing insects to fly
-
Hunting in Groups
- reduces energy costs or allows animals to take larger prey
- - weight of four social carnivores and weight of prey species they are able to kill
- - hyena 100lbs/ 660 lbs
- - lion 240 lbs/ 2000 lbs
- - wolf 80 lbs/ 800 lbs
- - hunting dog 35 lbs/ 550 lbs
-
Classcial view of Communication
( mutually beneficial transfer)
-
Selfish model of Communication
- Signal CAN be mutually beneficial, but should always, on average, benefit the signal sender
- - corollary: it may benefit the receiver or it may exploit the receiver ruthlessly, or it may have utterly trivial value to the receiver
- - viewed as coevolutionary 'arms race', in which all players play both roles (signal sender and receiver-- frequently)
-
Each signal can be recognized as a transmission of energy which can be of many forms
sound, light, touch, electrical, and chemical
-
Choice of Energy Channel
Vision-based Signals
- Energy source = usually sun (occasionally bioluminescence)
- Coding Variables
- - Brightness (surface refelectivity)
- - Color (uv of light NOT absorbed)
- - spatial patternine of the above two
- Properties
- - short duration
- - closed channel (receiver must have eyes open & be facing signaler)
- - Long range
- - Light rays don't bend; can be blocked
-
Choice of Energy channel
Acousitic-based signals
- Energy source = Internal
- Coding Variables
- - pitch (= frequency = wavelength)
- - loudness (energy level)
- - temporal patterning is very important
- Properties
- - short-lived
- - sound attenation
- - channel continuously open
- - can circumnavigate objects (esp. long-wave)
- - localizable
-
Choice of Energy channel
Chemical Signals
- Energy source = Pheromones = like hormones between individuals. Universal
- Properties
- - Channel open
- - Amplification principle: tiny investment can elicit expensive response
- - Enormous potential range (wind-borne)
- - fantastic specificity
- - flaw: achingly slow
-
Hyena Social Behavior
- - live in social groups called clans
- - clan members defend a territory and hunt in groups
- - femalse are dominant members of the clan ( clear dominance hierarchy)
-
Major feature of social interaction in hyenas
penis sniffing
-
Pseudopenis
- Females penis
- - enlarged clitoris
-
Pseudopenis is costly
- - 10-20% of females die giving birth first time and 60% of first born pups die
- - pseudopenis must provide big selective advantage to balance this
-
Advantages of pseudopenis
- - hormones increase aggression in females (increase social status, and access to food)
- - sniffing appears to enhance cooperation among hyenas (communication)
- - sniffing enable dominants to monitor hormonal status of other females
- - dominant benefit: know if challenged
- - subordinates benefit: allowed to remain in pack
-
Evolutionary pathways
complex traits evolve from less complex ones as a result of a long sequence of small developemental changes
-
Evolution
- - natural selection can only operate on the material available to it
- - evolutionary intermediates must be improvements over what preceded them
- - intermediate structures can have different functions to their current ones, but should be useful in some way
-
Evolution of insect flight
- - gill plates, retained in the adult, act as sails allows the insect to skim over the surfact of the water
- - increaseing wing size would increase skimming speed
- - beating wings would increase speed still further so adding musculature would be favored by selection
-
Honest Signals
- display signals to be expensive and difficult for smaller/ weaker individuals to imitate.
-
Novel environment hypothesis
(Dishonest signals)
mistake made because environment has changed. response once adaptive.
-
Exploitation hypothesis
(Dishonest signals)
- response adaptive on average, but sometimes expolited
- - risk outweighed by benefits.
-
What mechanisms favour honest communication?
- 1. Common interest
- 2. Handicap/cost
- 3. Index of quality (uncheatable signals)
-
Sexual Selection
- a form of non-random mating
- - selection that arises when individuals of one sex, usually males, gain an advantage over others of the same sex in obtaining mates
- - targets loci that code for mate choice traits and changes allele frequencies
-
Sexual Selection results in sexual dimorphism
- - acts on males much more strongly than females
- - females usually invest much mroe in their offsprint than do males
- - females prefer males with certain characteristics
-
Fundamental asymmetry of sex
- - female fitness is limited by an ability to gain the resource required to produce egges and rear young
- - male fitness is limited by the ability attract mates
-
Two ways sexual selection can happen for males
- - fighting between males
- - attract females
-
two forms of sexual selection
- - intrasexual (fighting)
- - intersexual (epigamic)- attract females
-
Epigamic Selection
females must show a sexual attraction for males that have certain secondary sexual characteristics (ornaments, behaviors, etc.)
-
Sexual Dimorphism
Male advantage and Female advatange
- Males: possessing a character preferred by females is clear - he gets to mate more often
- Females: mating with a male that has that character - character is heritable = more sons = more offspring
-
Sexy Son Hypothesis
- Female preference and male attractiveness evolve together
- - Females that mate iwth males that do not have this character will produc less sexy sons and therefore their choice will be lost over time
-
R.A. Fisher- Evolutionary Biologist
- original character must have been some marker of some other characteristic that increases male fitness
- - once that characteristic become linked to greater male fitness, ti become established simply for its attractive properties
-
Polygamy
more than one mate
-
Polygyny
male mates with more than one female
-
Polyandry
female mates with more than one male
-
Resource Defense Polygyny
- males gain access to female by controlling resource stahat are vital to females
- - ex. bullfrogs ( with the best territories get the most mates)
-
Female Defense Polygyny (Harems)
- males gain access to females by directly defending them against rivals
- - ex. elephant seals (most dominant gets the most mates)
-
Male Dominance Polygyny
Explosive Breeding & "Leks"
- No male defense of females of resources
- - males set up a dominance hierarchy and females choose them
- - explosive breeders (short breeding period) (Cascades Frog)
- - leks (communal display area) (Prairie Chicken)
-
Male-male competition can be
Traditional Combat or Indirect
-
Nuptial feeding
- Scorpionfly
- - female eats while copulating with male
- - copulation last as long as food lasts
-
Do females always have a choice?
- Scorpionfly
- - secrete hard salivary mass/ pheromone induces females to mate
- - disperse pheromone on deat insect after eatin dead insect female mates
- - Forced copulation (rape) : male rushes female
-
Blowfly attraction females
- - attack and get insect to offer to potential female mate
- - steal food from rival male to give to female
- - turn into female, entice male to give you food and fly away and give it to female (transvestite blowflly strategy)
-
Sexual Selection in monogamous species
- Female coyness & mate choice
- - males usually must display to females
- - males ' salesmanship' (display, provide food, make a nest, etc.)
- - females are 'coy'
-
Female Choice Criteria
- - correct species
- - correct sex
- - sexually mature
- - good male genes; survivorship, reproductive ability, complimentarity of genes
- - willingness in male to care for offspring
- - ability to invest
- - complimentarity of parental attributes
-
Proximate Perspective
- Focus on stimuli that trigger and support behavior
- - genetic, physiological, neural, envrionmental
-
FAP
- Fixed action pattern
- - unchangeable sequence of unlearned, innate behaviors
- - once initiated, usually carried to completion
- - sign stimulus
- - external sensory stimulus
-
Organization-Activation Hypothesis
- Hormones and Behavior
- - Organization: permanentmorph change, in early development, critical period
- - Activation: during puberty, changes due to increase, androgens or estrogens
-
Factors affecting physciological mechs
- Physcial Environment ( Day length, temperature)
- Social Environment (Social cues can cause hormonal changes)
-
Behavioral changes due to development exposure
- - exposure to androgen can masculinze females
- masculine: aggressivenss, attacks, mounting and intromission, little parental behavior
- feminine: non-aggressive, attractiveness to males, exhibit parental behavior
-
Sensory system
- part of the Nervous system
- - samples the environment for information
-
Motor system
- part of the nervous system
- - produces action
-
Endocrine system
- - organs produce class of proteins called hormones
- - delivered passively via the circulatory system - relatively slowly
-
Hormones have 2 different scales of operation
organizational & activational effects
-
Organizational effects
- - occur very early
- - influence a subset of neurons
- - shape adult behavioral repertoire a permanent menu change
-
Activational effects
- - require immediate presence of key hormone for the sensitive neurons to function normally. to 'turn on'
- - themporary (short term) menu change
-
RIA
- radioimmunoassay
- - measures concentrations of hormones
-
Challenge Hypothesis
Basic predation = that (T) should be high when males are most aggressive with each other & vice versa
-
True monogamy
bonded for life with no replacement, even if mate dies
-
Natural Selection vs. Sexual Selection
- Natural: reproductive success, rivals = both sexes
- Sexual: mating success, rivals = same-sex
-
Limiting Sex
- one sex becomes a restricted resource for the other (because it has higher costs associated with mating), access to it "limits" what the other sex can achieve
- limiting sex: female
- limited sex: male
-
Parental Investment
any effort toward one offspring that increases the change of that offsprins survival at the cost of the parents ability to invest in other offspring (Trivers)
-
Externally-fertilized species
can be observed
-
Internally-fertilized species
males probability of bieng genetically related to offspring is nearly always lower that of female
-
Cruel Bind
a focal male can either remian with his current mate and contribute to the raising of her young (STAY) or he can go off and seed a second mate (DESERT)
-
Last Custody
one parent departs before the other one has equivalent opportunity, it puts the partner in a cruel bind (depending on the brood's needs)
-
Parental Care and Desertion
- Most animals -- no parental care
- 1. value for staying
- - precocial young, altricial young
- 2. value for deserting
- - often hinges on availability of high-quality alternative mates
|
|