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Biology 484 – Ethology
Topic 1 – An Evolutionary Approach to
Animal Behavior
What is Ethology?
• Ethology is the scientific and objective study of animal behavior
• Often, ethology has a focus on behavior under natural conditions
• However, laboratory based studies of behavior are also very important for
what is called “proximate understanding” of behavior
• Critical in the study of ethology is the idea that behavior is an evolutionarily
adaptive trait
An example of a laboratory based study that has “natural world”
relevance:
Isopod Behavioral Responses to Moisture
Douglas Spaulding – (1841-1877)
• biologist who first described the idea of
“imprinting”
• overlooked for many decades by
scientists because his writings were
published in rather obscure journals
• his ideas were further developed by
Heinroth and Lorenz
Oskar Heinroth (1871-1945)
• German biologist who was the first to apply
methods of comparative morphology to animal
behaviour
• His extensive studies of behavior in the ducks
and geese showed that instinctive behavior
patterns correlated with taxonomic relationships
determined on the basis of morphological
features.
•He also rediscovered the phenomenon of
imprinting, reported in the 19th century by
Douglas Spalding
Konrad Lorenz
(1903-1989)
Received 1973 Nobel
Prize in Physiology
(along with Tinbergen
and vonFrisch) for their
foundation work in the
field of ethology
• Lorenz studied instinctive behavior in animals.
• The primary animals he worked with were greylag geese and jackdaws
• While working with geese, he rediscovered the principle of imprinting
Karl vonFrisch
(1886 – 1982)
• His work centered on investigations of the
sensory perceptions of the honey bee.
• He was the first to discern and translate
the meaning of the honeybee “waggle
dance.”
• His theory was disputed by other scientists
and greeted with skepticism at the time.
Niko Tinbergen
(1907 – 1988)
well known for originating the four “questions” he
believed should be asked about any animal
behavior relating to:
Causation, Ontogeny, Phylogeny, Adaptation
These shall be a primary focus in this chapter of
our text.
A major body of Tinbergen's research focused on what he termed Supernormal
Stimuli. This was the concept that one could build an artificial object which was a
stronger stimulus or releaser for an instinct than the object for which the instinct
originally evolved.
Tinbergen observed that sticklebacks
perform an elaborate mating ritual that is
carried out the same way each time:
1) First the male stakes out a little area in
its environment which becomes its
territory
2) The male stickleback then digs a little
hole (in loose detritus), shoveling
material with his snout until a hole is
constructed
3) He gathers stringy pieces of algae,
coats them with a sticky substance
secreted from his kidneys, and piles the
algae in the pit, forming a little mound
4) Finally, the male stickleback wiggles
through the mount, leaving a tunnel
B.F. Skinner
(1904 – 1990)
• invented the operant conditioning chamber
• developed and innovated his own philosophy of
science called radical behaviorism
• founded his own school of experimental research
psychology….. the experimental analysis of
behavior from a psychology perspective
The basic design of the
“Skinnerian Operant
Chamber”.
The advantages of this
device are many and have
significantly affected both
psychological and
biological studies of
behavior.
Tinbergen’s four “questions” further expanded and developed by Holekamp
and Sherman describe different perspectives on how to examine behavior.
Kay Holekamp – Researcher at
Michigan State University
Paul Sherman – Researcher at
Cornell University
The monogamous prairie vole
• the Prairie Vole (Microtus ochrogaster) is a
mouse-like mammal that displays a rather rare
type of reproductive behavior for rodents
• this species of vole is monogamous… meaning
it will mate and bond exclusively with a single
other vole and remain bonded for life.
• the vast majority of voles (and rodents in
general) are polygynous (have multiple mating
partners)
The interesting aspect of this rather rare
behavior is why does this behavior arise?
Many answers we shall see combine
information and techniques from the fields of
neurobiology and endocrinology to discern
answers to ethological questions.
• The Ventral Pallidum is a structure within the basal ganglia of the brain.
• The Ventral Pallidum is classified as an output nucleus whose fibers project to
thalamic nuclei, such as the ventral anterior nucleus, the ventrolateral nucleus, and
the medial dorsal nucleus.
• The Ventral Pallidum is a component of the limbic loop of the basal ganglia, a
pathway involved in the regulation of motivation, behavior, and emotions. It is
involved in drug addiction.
The brain of the prairie vole is a complex, highly organized machine
The ventral pallium region of the Prairie Vole brain differs from most other rodent
brains in that there are very high numbers of receptors for the hormone,
vassopressin (or sometimes called anti-diuretic hormone (ADH).
This region of the brain is associated with the reward centers in our brain. Each
time the male Prarie Vole mates with a female it stimulates the release of
vasopressin, which floods and stimulates the brain region causing pleasure and
encourages the pair bond to form.
Most other rodents have significantly lower numbers of these receptors in this
region of the brain.
• Neuroendocrinology is the study of the extensive interactions between the
nervous system and the endocrine system.
• Especially important to neuroendocrinology are the biological features of the cells
and how they functionally communicate.
• Neuroendocrinology originally arose from the recognition that the brain, especially
the hypothalamus, controls secretion of pituitary gland hormones.
• Currently, neuroendocrinology has expanded to investigate all manner of
interconnections of the endocrine and nervous systems.
A gene that affects male pairing behavior in the prairie vole
In a study where Prarie Vole
males were genetically
altered to have MORE of the
gene responsible for
producing the receptor
proteins for vassopressin,
would spend MORE TIME
with the female if these
added genes were in the
ventral pallidum compared to
an alternative brain region
(CP = caudate putamen) or if
an alternative gene were
inserted.
How are phylogenetic trees constructed and what do they mean?
Suggests which species are most closely
related
Suggests which species are more closely
related to a recent ancestor
Common features used in phylogenetic
trees include:
Anatomy
Physiological Features
Behavior
Molecular Relatedness
The evolutionary relationships of the prairie vole and six of its relatives
The possible history behind monogamy in the prairie vole
Potentially, the development of monogamy in the Prairie Vole may be a product
of a multitude of slight behavior shifts over time.
Testing the hypothesis that monogamy in prairie voles is linked to a specific gene
In this experiment, male MEADOW
VOLES (normally polygynous) are
genetically altered to express higher
more of the gene that produces the
protein receptors for vasopressin,
again, specifically in the ventral
pallidum.
The males show considerably more
time spent “huddling” with females if
they are genetically altered than if
they are control males.
Charles Darwin, shortly after returning from his around-the-world voyage on the Beagle
Darwin’s ideas
of evolution
greatly
influence the
studies in
ethology.
The aspects of Darwin’s
theory of evolution and the
role that change plays in
evolution that are especially
valuable to ethology inlcuide:
•
Variation
•
Heredity
and
•
Differences in
reproductive
success
Charles Darwin’s study
A variable species
Ladybugs (Harmonia
axyridis) can exhibit
a wide array of
variation in heritable
features.
Natural selection
Darwin’s idea of natural selection is especially well suited for coupling with
genetic aspects of heritability. If one heritable feature is favored for a given
environment, it will tend to proliferate whereas other forms will be less favored.
A band of Hanuman langur females and their offspring
Natural selection is the likely
reason for the fighting behavior
seen in males as they try to
monopolize access to female
mating partners.
Male langurs commit infanticide
Infanticide is also a behavior that may have
been selected for in an effort to bring
females more quickly back into estrus.
Infanticide by a male lion
Although it is still unclear if infanticide brings a female langur back into estrus
faster or if there are other potential explanations for the behavior, it has been
shown in research by Hrdy (1977) & Sommer (1994) that lion males who engage
in infanticide end up siring a larger number of offspring than males that do not.
An evolved response to the risk of infanticide
Females may
also display
infanticide. Here
is a male who is
guarding
fertilized eggs
from FEMALES
who wish to
replace the egg
clutch with her
own eggs.
Conclusions from Topic 1:
•
Please be aware of the rich role that history and
historical figures play in the development of ethology
as a science.
•
Please know and understand the importance of the
questions posed by Tinbergen and how they have
shaped ethological research.
•
Understand the importance of Darwin and how his
work has been significant in the study of ethology.
•
Know and understand the examples of sexual and
reproductive behaviors described and how they show
some of the rich variation that is seen in the study of
ethology.