Transcript Introduction to Behaviors

A Historical Perspective to B.E.
The field of Animal Behavior was fairly
well established in the 1960’s when some
began to look at behaviors with a different
perspective.
Behavioral Ecology is a mixture of
Ethology (Animal Behavior), Ecology, and
Evolutionary Theory.
Historical Perspective cont’d
In Behavioral Ecology emphasis is put on
the value of a behavior to an organism’s
fitness
Function is emphasized as opposed to the
“cause” of the behavior
Fitness – reproductive success, or the number
of your genes that get passed on to future
generations is the criteria used to measure
biological success.
Inclusive Fitness
Fitness is based on “related-ness” (r) or the
number of genes that you share with
another.
The r value is 1 in terms of relatedness to
yourself (an identical twin has ALL your
genes so your relatedness to them would be
1).
Inclusive Fitness cont’d
Your parents each have half the same genes
you do, so for parents r = 0.5
Similarly, your siblings each share half of
your genes, so for siblings r = 0.5
For grandparents, r = 0.25
For first cousins, r = 0.125 (1/8), etc.
Direct vs. Indirect
Organisms can exhibit direct fitness, by
passing genes through their own fitness
Organisms can exhibit indirect fitness by
passing genes on through related children
(helping raise related children).
Ex. Having a child yourself (r = 0.5), and
helping a sibling to have a child (r = 0.125)
increases your fitness to 0.625
Putting it together
So, Inclusive Fitness = Direct Fitness + Indirect Fitness
This idea was first discussed by W.D. Hamilton
He was talking about altruistic behavior (decreases fitness
of actor while increasing fitness of recipient).
Described Hamilton’s Rule: Altruistic behavior will only
occur when the inclusive fitness of the actor will
eventually increase due to the altruistic action.
So if the actor is not related to the recipient the only time
to be altruistic is if there is a reasonable expectation of
getting the same in return. (ex. alarm call in flock of birds)
Back to Historical Perspective
In the 1800’s, Animal Behavior was studied by two very
different groups of researchers.
Europe: Ethology was developed, and emphasis was
placed on the functional aspects of behavior. Field
research and observation were favored.
North America: Practiced by Psychologists, emphasis
was placed on causation. Controlled experiments in
laboratories were favored.
These two schools of thought did not agree on much, but
over time they began to cooperate and synthesize their
ideas into what we know today as Modern Ethology.
History cont’d
In 1973 three famous and very different Animal
Behaviorists jointly shared a Nobel Prize for their
contributions to the modern understanding of Ethology.
They were:
Konrad Lorenz: studied imprinting in Graylag Geese
Karl von Frisch: studied communication in bees (Waggle Dance)
Niko Tinbergen: studied gulls, stickle backs (fish) and wasps and
many topics in Animal Behavior.
Imprinting
Konrad Lorenz carried out famous studies
of imprinting behavior in Graylag Geese.
Young goslings imprint on their mother in
first few days of life, follow her and learn
basic goose behaviors.
Imprinted Canada Geese Goslings
Imprinting cont’d
However, goslings will imprint on a human
substitute (or an object such as a toy truck)
if exposed to the correct stimuli (large
object that moves away slowly).
Imprinting occurs in a short sensitive period
and is irreversible.
Imprinting cont’d
Bee Communication
It was suspected (based on observations) that “scout” bees
could communicate the location of a good food source to
the worker bees of the hive, but no one could understand
how that might happen.
Karl von Frisch worked on that problem.
While observing the behavior of the scout bees when they
returned to the hive, he noticed that they always walked in
circles waggling their abdomens. This he dubbed the
waggle dance, and started relating the attributes of the
dance to the newly found food source. Through hard work
and good record keeping, he discovered how the bees
communicated.
von Frisch
Waggle Dance
So, it turns out that vertical in the hive is the direction of
the sun, and all bees innately understand that.
The angle to vertical that the bee waggles is the angel (to
the sun, outside) that indicates the direction of the food
source.
The length of the waggling indicates the distance to the
food source.
Fixed action pattern (FAP)
Fixed Action Pattern is a sequence of behaviors
that is essentially unchangeable and once begun, is
always completed.
Niko Tinbergen studied FAP in three-spined
sticklebacks. Males have red bellies and defend
territories from other males. But they will attack
any small unrealistic model fish so long as it has a
red belly.
Fixed action pattern (FAP)
Red belly is a “releaser” that causes
stickleback to initiate its defensive
response.
Fig 51.4
Proximate Questions
Proximate questions focus on mechanisms and
development of behavior.
They are “how” questions.
For example: How does a bird learn its species song? Or
How does a plant know when to produce flowers?
Possible hypotheses that address these “how” questions
include:
Males learn their species song by listening to what their
father sings and
Flowering in plants is triggered by increasing daylight.
Ultimate Questions
Are “why” questions.
They ask why natural selection favors a certain behavior
and not others. Ultimate hypotheses generally suggest that
the behavior enhances fitness, through
For example: Why do female birds prefer males with
brighter plumage?
Or Why do birds look up occasionally when they are
feeding?
Ultimate Questions
Ultimate hypotheses that might address
these “why” questions include:
Females prefer males with brighter plumage
because such males possess genes that
confer disease resistance (sickly birds won’t
have bright plumage).
Birds look up to scan for predators, which
enhances their survival.
Tinbergen’s Rules
Niko Tinbergen developed the 4 Questions of behavior that
must be answered for any thorough study of a behavior.
What is the behavior’s function ?
What causes the behavior to occur ?
How does the behavior develop ?
What is the evolutionary or phylogenetic history of the behavior ?
Infanticide among Lions
A researcher notices that when taking over a
pride, the new male lion will kill all the
offspring of the previous male, and asks the
question, why.
Lions cont’d
Background:
Lions live in groups called Prides
• Many adult females and cubs
• All the adult females are related to each other
• All the adult males are related to each other, but not to the females
Males leave the natal pride at about 3 years of age, females do not
leave
Female’s job is to reproduce and feed the pride
Male’s job is to protect the pride and invest in pride fitness (donate
DNA).
Males (sometimes traveling with a brother) become “nomads” until
they can physically take over a pride.
•
•
•
•
Nomads hunt together and search for vulnerable prides (males 7 yrs or older)
The take over precipitates the killing of existing cubs (killed, not eaten)
Females then come into estrous in 9 months rather than the normal 25 months
Male copulates with all adult females, all will get pregnant at same time, so all
births occur at same time. Increase survival from shared care.
• Incoming new male will increase his fitness
Lions cont’d
So, why do males kill the existing cubs?
Animal Behaviorist: The lion kills the cubs
because of the unfamiliar smell.
Behavioral Ecologist: The lion kills the cubs
to increase his own fitness.
What do you say?
Adaptive Significance of Behaviors
Behaviors evolve, and Behaviors with the most positive
influence on fitness will be passed on.
Since natural selection works on behavior, there is
behavioral variation.
Let’s look at migratory behavior in the Blackcaps (Sylvia
atricapilla)
Migratory Orientation in Blackcaps
European Blackcaps migrate to Western Africa. Asian
Blackcaps migrate to Eastern Africa. (so, Blackcaps from
SW Germany migrate in SW direction and those from
Hungary in a SE direction).
Researchers can assess the direction birds choose to
migrate using an Emlen funnel.
Birds spend most time in part of funnel that faces in
direction they want to migrate.
Blackcap Migration Map
Emlen Funnel
Migratory Orientation in Blackcaps
Members of the two populations were crossed and
produced offspring.
Offspring’s orientation was tested in an Emlen funnel.
Mean orientation of offspring south which is strong
evidence that there is genetic control of migration.
Black Triangles: Eastern European Adults (SW)
White Triangles: Western European Adults (SE)
Black Dots: Offspring (S)
So, Behavioral Ecology is…
Behavioral Ecology is the study of an individual’s genetic
fitness on their behavior
The major behaviors involve in an organism’s fitness are
related to:
Predator avoidance
Foraging
Reproduction (including Migration and Territory Selection)
Such behaviors occur within the context of an organism’s
ecology and Life History Strategy.
Life History Strategy
A Life History Strategy is the affect of all decisions
regarding the allocation of time and energy on
reproductive fitness over the lifespan of the individual.
These decisions can be made through Natural Selection or
by Direct Individual Decision
Decision Examples
1. Traditional (Natural Selection based)
 At what age should an organism begin to reproduce
 How many offspring at once
 r – selected (many offspring (generally smaller), little to no parental care)
 k – selected (few offspring (generally larger), lavish parental care)
 How long is the reproductive lifespan
Ex. Iteroparity vs. Semelparity in species of Lobellia (scrub plant).
- Iteroparity is the ability to have several generations in a year
- Semelparity is the ability to have only one generation in a year
Lobellia telekii
semelparous Lives on dry rocky slopes
Lobellia keniensis
iteroparous
Lives in moist valley bottoms
1000’s of seeds
100’s of seeds
Decision Examples cont’d
2. Non – Traditional (Direct Individual based)
a. Foraging decisions: what to eat/where to eat
b. Mate Choice: monogamy vs. polygamy
c. Migration Choice: when, where, or if
d. etc.
Cost vs. Benefit Tradeoffs
Life History Strategy decisions involve a cost/benefit
analysis.
Ultimately, these decisions will be determined by Natural
Selection (one way or the other will be better for fitness)
These decisions result in compromises that ultimately
optimize the reproductive fitness over a lifetime.
The decisions occur on two levels
Evolutionary phylogenetic level (age of reproductive readiness)
Level under direct individual control (where to forage)
Both levels involve exclusively genetic control and control
exerted by the environment or genetic make-up.
Tradeoff’s and Compromises
Since the ultimate idea here is reproductive fitness,
sometimes organisms are required to choose between
future reproductive potential and current reproductive
success.
Ex. Douglas Fir Tree
When conditions are good (plenty of sunlight and water) more
energy goes into growth than reproduction (banking on future
reproductive potential). Fewer cones are produced.
When conditions are poor (usually lack of water or some other
environmental disaster) the trees put more energy into reproduction
and less into growth (focusing on current reproductive success).
More cones are produced.
Examples of some
Different Behaviors
Innate Behavior: Kinesis
Kinesis: strong change in activity or turning
rate in response to stimulus.
Woodlice become more active in dry areas
and less in humid areas. Helps to keep
them in moist areas and move out of dry.
Woodlouse Movement
Innate Behavior: Taxis
Taxis is movement towards or away from a
stimulus.
Cockroaches demonstrate negative
phototaxis (move away from light).
Trout demonstrate positive rheotaxis and
face towards the current in a stream.
Positive Rheotaxis
Environment Modifies Behavior
Habituation
Loss of responsiveness to stimuli that do not convey useful
information (“cry wolf” effect).
Associative Learning.
Many birds learn quickly that Monarch butterflies taste foul and
will avoid them after an initial experience.
Rats will permanently avoid a food if after eating some of it they
subsequently become nauseated.
Spatial learning.
Many animals modify their behavior depending on the
environment they live in.
In stable environments landmarks are useful for navigating.
Minimizing predation risk while
foraging.
There are numerous ways in which
organisms attempt to minimize their risk of
predation.
These include: avoiding habitats that are the
most dangerous, foraging in groups and
spending time looking for predators.
Predation/Avoidance
Many animals group together to avoid
predation.
Grouping increases chances a predator will
be spotted before it can attack. Grouping
also increases time spent foraging as
individuals have to scan less often in a
group.
Experiments by Kenward using a trained
Goshawk showed that as flock size
increased wood pigeons detected an
approaching bird at greater distances.
Kenward Wood Pigeon Study
Kenward Wood Pigeon Study
Enhancing reproductive success
Males and females generally differ in optimal
reproductive strategies.
The sex that invests more in the offspring
(usually female) is the choosy sex.
Hamster egg and sperm
Enhancing reproductive success
Investment includes energy invested in young and
time spent caring for and guarding the young.
Choosy sex has limited capacity to produce more
young.
Enhancing reproductive success
Choosy sex maximizes reproductive success
by requiring other sex to provide resources
(e.g. territory, food) or by choosing the best
possible mate for its genes.
Non-choosy sex maximizes reproduction by
mating more often.
Monogamy
Type of mating system observed influenced
by whether both parents needed to rear
young.
In most birds young need lots of care so
monogamy is common and both parents
participate in caring for young.
Polygamy
When one sex can care for the young
polygamous (many gametes) mating
systems are common (e.g. most insects, elk,
elephant seals, some birds e.g. grouse,
peafowl, jacanas) and individuals mate with
multiple mates.
Polygyny, Polyandry are examples.
Bull Elk with harem
Competition for mates
Generally, members of the non-choosy sex
compete to either control choosy’s by
defending them (e.g. elk, elephant seals,
phalaropes) or to attract females to mate
(peafowl, grouse).
By maximizing number of times they mate
they maximize reproductive success.
Competition for mates
Sperm competition
Males compete not only to mate with females, but
frequently engage in sperm competition as well.
More sperm a male can insert the higher his
chances of fertilizing eggs (like a lottery).
In species with lots of sperm competition males
have proportionally larger testes than males of
monogamous species.
Sperm competition
Males also commonly remove other males’
sperm (e.g. damselflies have a penis with
spines), plug up females’ reproductive tract
(many insects) or guard females against
other males.
Alternative mating strategies
Paracerceis isopods (a type of crustacean)
live inside sponges.
There are 3 genetically different male types.
Alternative mating strategies
Alpha males large and defend harems of
females.
Beta males pretend to be females.
Gamma males are tiny and sneak inside
harems undetected.
Mate choice
Females are very choosy about which male
they mate with.
For example, in polygynous species, such as
sage grouse, a few males obtain almost all
the matings and most males fail to mate.
Sage Grouse Mating Ritual
Birds of Paradise
Female birds assess male
plumage quality
(symmetry and color)
and display quality
(duration and intensity)
in evaluating males.
(Male Raggiana Bird of
Paradise displaying.)
Male display and male quality
Considerable evidence that male’s ability to
grow attractive plumage and engage in
vigorous displays are indicators of males
genetic resistance to disease and parasites.
By choosing such males, females ensure
their young will receive high quality genes.
Similarly, female stalk-eyed flies
prefer males with the longest eye stalks.
Male display and male quality
Various genetic disorders are correlated
with flies inability to develop long
eyestalks. Females who avoid such males
enhance genetic quality of their offspring.
Kin Selection
Natural selection favoring the spread of
alleles that increase the indirect component
of fitness is called kin selection.
Kin selection is expected to operate most
strongly among close relatives
Belding’s Ground Squirrels
Belding’s Ground Squirrels breed in
colonies in Alpine meadows.
Males disperse, but female offspring tend to
remain and breed close by. Thus, females
in colony tend to be related, but males
other than offspring are not.
Belding’s Ground Squirrels
Belding’s Ground Squirrels
Long term study by Sherman of marked
animals of known relatedness.
Analysis of who called showed that females
were much more likely to call than males.
Belding’s Ground Squirrels
In addition, females were more likely to call
when they had relatives within earshot.
Belding’s Ground Squirrels