Behavioral Ecology: Evolutionary Basis

Behavioral Ecology

• Focuses on the study of the evolutionary basis for animal behavior due to ecological pressures.
• It looks at how organisms interact with their physical and social environment.

Examined Questions

• Why do animals cooperate?
• What traits and behaviors have animals evolved to avoid being eaten by predators?
• Why do animals show such ornate mating behaviors?
• How do animals talk to one another?
• What are the genetic, physiological, and neuronal mechanisms that cause different behaviors?

Nikolaas Tinbergen

• (1907-1988) outlined four questions on how to study animal behaviors (ethology) which focuses on two levels of answers

Ultimate Explanations

• Evolutionary explanations addressing why and how the individual has evolved a certain behavior

Proximate Explanations

• Physiological or developmental explanations detailing how the individual comes to behave in a particular way during its lifetime

Function (Adaptation)

• Answers the question how the behavior affects an animal's probability of survival or reproduction
• A function doesn't become an adaptation until enough generations pass in and become advantageous to reproduction

Phylogeny (Evolution)

• Study of the evolutionary relatedness among groups of organisms
• Reconstructing a species phylogeny makes it possible to understand their uniqueness

Mechanism (Causation)

• Some prominent classes of causal mechanisms include:
  • The brain: Broca's area is a small area in the human brain, and is critical for linguistic capability
  • Hormones: chemicals used to communicate among cells of an individual organism; testosterone stimulates aggressive behavior
  • Pheromones: chemicals used to communicate among members of the same species; dogs and moths emit pheromones to attract mates

Development (Ontogeny)

• Concerned with genetic and developmental mechanisms
• Considers how behavior changes with age, what early experiences are required for the behavior to be expressed and how the environment interacts with development and behavior

Visual Perception

• Its function is to find food and avoid danger
• The vertebrate eye initially developed with a blind spot
• Adaptive intermediate forms stopped the loss of the blind spot
• The lens focuses light on the retina
• Neurons need the stimulation of light to wire the eye to the brain

Why male starlings sing in the Spring time

• Causation: The increasing length of day triggers changes in their hormones, or because of the way air flows through the vocal apparatus and sets up membrane vibrations
• Development/Ontogeny: Starlings sing because they have learned the songs from their parents and neighbors, and have a genetic disposition to learn the song of their own species
• Adaptive Advantage: Starlings sing to attract mates for breeding, increasing their reproduction success.
• Evolutionary History: The complex songs of starlings and other song birds evolved from simpler ancestral calls

Lion Reproductive Behaviour

• Pride of lions consists of three to twelve related adult females, one to six adult males and several cubs.
• Females reproduce from 4 to 18 years.
• Young males leave the pride, become vagrants and take over a pride when the resident males get old.
• The new males stay in the pride for ~2 yrs and are driven off by a new set of males.

Female Lions and Synchronous Estrus

• Female lions within a pride show synchronized oestrus
• Causal explanation: influence of pheromones on oestrus cycles
• Functional explanations:
  • Synchronous births of different cubs born survive better
  • Possibility of communal suckling because of all the females are lactating and cub can possibly suckle from a different female

Male lions killing cubs they did not sire.

• Causal explanation: unknown but potentially unfamiliar odor of the cubs
• Functional explanation:
  • Females come into oestrus more quickly; they become ready after nine months compared to the 25 months that would take if cubs were left intact
  • Males removes older cubs which would compete with his young

Key Point

• Causal explanations are concerned with mechanisms and functional explanations are concerned with why these particular mechanisms have been favored by natural selection

Innate / Instinctual Behavior

• Rely on response (involuntary and rapid) to stimuli
• Under strong influence of genes

Learned Behavior

• Allows an organism to adapt to changes in the environment and are modified by previous experiences

Kinesis

• Undirected response in which the body's long axis exhibits no consistent relationship to the direction of the stimulus and the direction of locomotion.

Orthokinesis

• The increased or decreased speed of movement of an organism in response to a stimulus
• Sow bugs are more active in dry areas compared to humid areas

Klinokinesis

• Is an increase in turning behaviors
• Exhibited by bacteria like E. Coli which, with Orthokinesis, helps organisms randomly find a more hospitable location

Taxis

• More directed version of kinesis
• Directed movement towards or away from a stimulus.
  • Phototaxis: movement in response to light
  • Chemotaxis: movement in response to chemical signals
  • Geotaxis: movement in response to gravity and can be directed either toward or away from the stimulus.

Fixed Action Patterns

• A series of movements elicited by a stimulus that goes to completion even when the stimulus is removed.
• Male stickleback fish attack other male sticklebacks.
  • Proximate cause: red belly of the intruding male acts as a sign stimulus that releases aggression in a male stickleback.
  • Ultimate cause: By chasing another male away, the resident decreases the chance that his eggs laid will be fertilized by another male.

Migration

• Being genetically programmed
• Long-range seasonal movement of animals
• A response to variation in resource availability and is common in animals
• Some migrate every year which is obligate migration
• Facultative migration is when they choose to migrate or not
• Incomplete migration is when only a portion of the population migrates with the rest remaining behind

Foraging

• The act of finding and exploiting food resources
• Optimal foraging behaviors should favor feeding behaviors that maximize energy gain and minimize energy expenditure

Fruit Fly Larvae

• Two types: Rovers and Sitters
• Caused by a difference in the foraging gene (for)

Rovers

• Traverse a large area while feeding
  • Have the rover allele (for^R)
  • Show high PKG activity
  • Have short term memory for olfactory stimuli
  • Improved at finding new food patches

Sitters

• Cover a small area
  • Have the sitter allele (for^s)
  • Show low PKG activity
  • Have long term memory for olfactory stimuli
  • Optimal with uniformly distributed food and low larval density

Honeybees

• Polyethism is specializing on non-reproductive individuals in a colony of social organisms

Nurse Bees

• Young worker bees that stay at home

Forager Bees

• Adult Workers which are "roving for food"
  • There is increased expression of the for gene
  • There is increased production of the enzyme PKG

Communication

• Animals communicate with each other using known stimuli as signals
  • Chemical signals using pheromones to attract the opposite sex, sound alarms, mark food trails, and begin other more complex behaviors
  • Aural signals using songs to attract an opposite sex bird
• Dolphins communicate with wide amounts of vocalizations
• Visual signals used in courtship and aggressive displays
  • The display must be performed correctly to get the right response with Tactile signals
  • Touch is usually observed in primates (e.g. grooming, embracing, or lip contact)

Altruistic Behavior

• Behaviors that lower the fitness of the individual but increase the fitness of another individual
  • Social insects cannot reproduce, so they maintain the hive with their offspring
  • Wolves and dogs bring meat not there when hunting
  • Emperor penguins migrate miles to bring food

Reciprocal Altruism

• It requires that individuals repeatedly encounter each other.
• If there is a "cheater" they are punished

Sexual Selection

• Has two types: Intersexual and Intrasexual selection

Mating Systems

• Mating systems consist of Monogamous, Polygynous, and polyandrous

Monogamous System

• A male and female are paired for a breeding season and can last a lifetime -"Mate Guarding Hypothesis" state that males stay with the female to prevent other males from mating and prevents where scarce and hard to find
  • "Male Assistance Hypothesis" is where males that stay with a female to provide care will get healthier offspring
  • "Female-Enforcement Hypothesis" the female ensures that a male has to other offspring and interferes with the males ability to attract mates

Polygynous System

• One male mating with multiple females where a female has to provide all parental care without the male's help
  • Resource-based polygyny (e.g. yellow-rumped honeyguide defending beehives)
    • Males try to get prime territories, then mate with the females in the resource rich territory
  • Harem Mating Structure (e.g. elephant seals)
    • The males dominate mating for a territory's resources
  • Lek System
    • Communal courting arena is where several males perform elaborate displays for females to come choose a mate

Polyandrous Mating System

• A female mates with lots of the males and are usually more rare then the other mating systems. -In seahorses, sea dragons, and pipefishes the males receive the eggs from the female, fertilize, protect within a pouch, and even give birth

Imprinting

• A type of behavior that includes learning with innate components, irreversible -There is a limited phase in animals development for the right time to learn

Case

• Baby geese will recognize the first adult they see
  • Proximate cause: Occurs during an early development stage when geese observe their calling mother
  • Ultimate cause: On Average when imprinting on their mother the geese will receive more skilled care for a higher rate of survival

Habituation

• Simple learning which an animal stops responding to being exposed for a long time -Non-associative since there is no punishment or reward

Case

• Prairie dogs sounding an alarm will stop when they get to the foot steps with no harm

Animal Grouping Behavior

• Typical size of each animal SPECIES is important to operate efficiently
• Includes Solitary, Pairs, Family, Harem, Matriarchy, Oligarchy, Caste System

Solitary

• Auldts loving lone and coming together for breeding
  • The male and female will split and do not see each other -The female takes full responsibility - Examples are Caracal, Leopard, and Serval

Pairs

• Parents together with bonded pair
• More then 90 for birds

Family

• Extension of the pair
  • Young stay until fully grown and will move to with family group

Harem

• Consists of one male and a group of females.
  • The females will vary depending on different species and can be up to 20 individuals

Matriarchy

• When a family splits up and forms a new herd with the next matriarch to take over

Oligarchy

When power is invested in elite gang of dominant males.

• Advantage includes efficient means of defending from predators

Caste System

• Insects living in organization
• They add to the provision to efficient division of labor

Classical Conditioning (Ivan Pavlov)

The "conditioned response" is "now associated" with a stimulus which "was not" associated before.

• Also the original response (unconditioned response) to the "unconditioned stimulus"

Operant Conditioning (B.F. Skinner)

• The conditioned behavior is gradually modified by the consequences as the animal responds to the stimulus
  • Positive reinforcement is when a mouse is rewarded for pressing the level
  • With negative when the mouse presses on the level the shocks are turned off

Cognitive Learning

• Type of learning for mental processes
• Individuals process information connecting new and existing knowledge
• Then using reasoning and solve the problem