Animal behavior
H1: The study of behavior
1.1: What is behavior?
There is not 1 single definition of behavior & definitions differ among scientists. These debates are philosophical, & in
practice researchers use working definitions. Commonly used definition: Behavior = Internally coordinated responses
(actions or inactions) of whole living organisms (individuals or groups) to internal &/or external stimuli, excluding
responses more easily understood as developmental changes. => Key aspects of behavior:
• Behavior is influenced by internal processes within organism.
• It is something performed by whole organism, not just organs or body parts.
• Behavior must be observable, recordable, & measurable.
• Behavior does not always involve movement, it can be freezing, staring, defensive postures.
There are some grey areas => Chameleon changing color when touched is considered behavior because it’s
immediate response to stimulus. While seasonal color change in Arctic fox isn’t considered behavior, because it’s
developmental/physiological change & not immediate response.
Some scientists argue behavior only occurs in animals, but other organisms can also respond to
stimuli & move. => Example: Unicellular organisms (such as Dileptus & Spirostomum) show
predatory behavior, using venom & phagocytosis to capture prey.
1.1.1: Ethology
Ethology = scientific & objective study of animal behavior, usually under natural conditions and by treating behavior
as evolutionary adaptive trait.
Ethology is connected to Ecology, Neurology, Physiology, Sociobiology, Psychology, Evolutionary biology,
Developmental biology, Conservation biology, Global change biology, Toxinology, … This field is expanding &
increasingly integrative, with emerging subdisciplines (such as Cognitive ethology, Neuroethology, and Animal
welfare science).
Behavioral plasticity often provides initial responses to environmental change, which may later be followed by
genetic evolutionary change. => Behavioral evolution & behavioral plasticity can sometimes be confused at short-
term evolutionary timescales.
Early ethology (1870s–1930s):
In 1872, Charles Darwin published ‘Expression of Emotions in Man & Animals’. This work influenced early ethologists,
as it suggested that behavior & emotional expression evolve & have adaptive value.
Early researchers (such as Charles Otis Whitman, Oskar Heinroth, Wallace Craig & Julian Huxley) studied innate
(instinctive) behavior using descriptive methods. During this period ethogram was developed.
Ethogram = inventory of all behaviors exhibited by animal & is based on objective observation => All descriptions in
ethogram should be free of interpretation & interpretation occurs only after analysis.
Modern ethology (1930s–1980):
Modern ethology was founded by Karl von Frisch, Konrad Lorenz & Niko Tinbergen. They combined ethograms,
hypothesis-driven research, experimental testing and quantification of behavior. In 1973, these 3 scientists received
Nobel Prize in Physiology or Medicine for their discoveries about organization & elicitation of individual & social
behavior patterns.
,Karl von Frisch (1886–1982) => Studied behavior of honeybee Apis mellifera & how bees
use sensory systems (vision, smell, taste) during navigation & foraging. Discovered that
they use 2 recruitment dances (AKA Round dance & waggle dance) to communicate about
direction, distance, & quality of food sources. Modern research shows system is more
complex than originally thought.
Konrad Lorenz (1903–1989)=> Focused on innate behavior in birds & studied filial imprinting in birds
• Filial imprinting = Young animals develop social attachment to specific object (usually parent) shortly after
hatching => He showed that animals could imprint on almost any object, including humans.
o Example: Newly hatched geese may follow 1st moving object they see.
• Imprinting (which is rapid, phase-sensitive learning process) is now used in conservation programs, such as
those for endangered Grus americana.
Niko Tinbergen (1907–1988) => studied behavior in birds, fish, & insects. He proposed that animal behavior should
be studied from 4 complementary perspectives/questions. These questions help explain both how behavior works (=
Causation & Development) & why it exists (= Function & Evolution).
1. Function = What is it for? How will it increase fitness? You look at how this behavior improves survival or
reproduction, & how natural selection or sexual selection favors individuals with that behavior. => Focus on
adaptive value & utility of behavior
2. Mechanismsm / Causation = How does it work? Which mechanisms trigger this behavior? It includes:
o Internal factors = Hormones, Neural activity, Physiological processes
o External factors = Environmental stimuli
o Example: In birds, multiple brain regions coordinate song production. Some birds can produce song even
when raised in isolation, showing genetic basis, but normal songs are often learned from parents.
=> Focus on physiological & neurological mechanisms of behavior.
3. Development / Ontogeny = How does it develop during organism’s lifetime? It considers learning processes, life
history, & development of related traits.
o Example: Young birds learn their songs during early life & this behavior may change with age or
experience.
4. Evolution (Phylogeny) = How did it evolve? It investigates evolutionary history of behavior. Involves comparisons
across related species, phylogenetic analyses, identifying genetic & evolutionary mechanisms => Focus lies on
how behavior evolved across species over evolutionary time.
Example 1: Bird songs
1. Function => Birds sing mainly to attract mates & to defend
territories from rivals
2. Mechanism (Causation) => Bird song is produced by specialized
neural network (= song system), consisting of interconnected
brain nuclei controlling learning & production.
3. Development => Young songbirds learn songs early in life during
sensitive period. Experiments show that birds raised in isolation
produce abnormal songs, demonstrating role of learning (such
as Fringilla coelebs).
4. Evolution => Comparative studies show that song characteristics differ among related species, reflecting
evolutionary divergence.
Example 2: Hunting behavior of spider-tailed viper => Snake’s tail structure resembles spider & it moves its tail to
imitate spider movement. It uses its tail to mimic spider & lure prey (such as birds).
1. Function => Behavior lures prey, increasing feeding success & fitness.
2. Causation
o Internal factor = hunger
o External factor = detection of prey
3. Development => Unclear if behavior is fully innate or partly learned.
, 4. Evolution => Behavior likely evolved through co-evolution of morphology (tail shape) & behavior, driven by
natural selection.
Example 3: Mating behavior in crickets => Male attract females using stridulation, producing chirping sounds by
rubbing specialized wings together.
1. Function => Chirping attracts females, increasing reproductive success.
2. Causation
o Internal factor = hormonal changes
o External factor = day length
3. Development => Behavior may be innate, but also depends on development of wing structures enabling sound
production (such as Mirror, Harp, Scraper & Stridulatory file).
4. Evolution => Wing morphology & stridulation behavior evolved together through sexual selection. Comparing
chirps across related species helps to reconstruct evolutionary changes & speciation.
Tinbergen & Lorenz together
• Developed ideas about Sign stimulus (releaser) = specific
feature of stimulus that triggers behaviour.
o Example: Fish Gasterosteus aculeatus => Red color triggers
aggressive behavior in males, while shape of model fish is
less important (AKA Red color = sign stimulus).
• Proposed that certain behaviors are innate neural responses triggered by
specific stimuli => Fixed Action Patterns (FAPs) = Stereotyped behavioral
sequences that are triggered by specific stimulus & are usually completed even
if stimulus disappears.
o Example: Greylag goose Anser anser => Displaced egg triggers egg-rolling
behavior & goose continues motion even if egg is removed mid-action.
Supernormal stimulus = exaggerated artificial stimulus that elicits stronger response than natural one. Examples:
• Gull Larus argentatus => Chicks peck at red spot on parent's bill to beg for food. Red stick with
white stripes can trigger even stronger begging behavior than real parent.
• Australian beetle Julodimorpha bakewelli => Males are attracted to brown beer bottles, because
they resemble large females with similar color & textured surface. This study won
Ig Nobel Prize in 2011.
1.2: Scientific approach to behavior
Studying behavior scientifically follows step-by-step process, starting from simple observations to testing hypotheses.
1) Observation:
Research often begins with observation about something that attracts attention because it is unusual, unexpected, or
raises questions.
Example: Silent crickets in Hawaii => On island of Kauai, populations of cricket became silent within 3–5 years (12–20
generations).
• Cause = Parasitic fly locates male crickets using precise directional hearing. This fly lays maggots on cricket,
which later burrow into & kill host.
• Timeline:
o Since 1991, number of calling males decreased.
o By 2003, crickets were abundant again but most males were silent.
o By 2006, >90% of males on Kauai were silent.
, Silence evolved because calling males attracted parasites. Detailed observations revealed that calling males had ~30%
parasite infection rates, while silent males had <1% infection. Additional observations:
• Silent males often stayed close to few remaining calling males.
• Females were still willing to mate with silent males.
• Silent males still move their wings (stridulate), but sound is inaudible to humans.
• Morphological difference = Silent males have “flatwing” morphology with vestigial sound-
producing structures (mirror, harp, scraper) => This morphology prevents them from
producing audible songs.
2) Ethogram:
= detailed inventory of all observable behavioral patterns of species, either generally or in specific context (such as
feeding, mating, defense, social interaction). => Creating ethogram requires extensive observation of species. Its has
several benefits, as it provides insight into animal’s biology, helps formulate research questions allows definition of
quantifiable behavioral parameters.
Researchers also review existing literature to understand what is already known about species or related species.
Rare behaviors should also be recorded because they can be important for understanding species.
Sampling strategies for building ethogram
• Ad libitum sampling = Record any behavior observed without restrictions => Useful when little is known about
species & helps capture rare behaviors.
• Behavior sampling = Focus on 1 specific behavior or small set of behaviors within
group.
• Focal sampling = Focus on 1 individual (or interacting individuals) & record all
behaviors over time.
• Scan sampling = Quickly scan group & record states or positions rather than
detailed actions.
How to describe behavior in ethogram
• Be objective & avoid interpretation => don’t write “Spider reacts in
frightened way”, but “Spider crawls away from wasp”.
• Describe structure, not consequences => don’t “Wasp kills spider with
sting & paralyses spider”, but “Wasp stabs spider with sting & spider stops
moving”. Actual cause (such as venom paralysis) must be tested
experimentally before concluding.
• Be detailed & precise => don’t “Wasp stabs spider”, but “Wasp stabs
spider 1–5 times for <1 second on dorsal anterior cephalothorax. After 30
à 60 seconds spider curls its legs & stops moving.”
Practical considerations is that observers can influence animal behavior, so
observations should be non-intrusive.
To quantify behavior, behavioral actions are often broken down into measurable
units. Examples:
• Courtship sequence => Ethograms can describe stepwise behavioral
sequences, such as mating stages in snakes or newts.
• Activity budgets = measuring how much time animals spend performing
different behaviors (such as study of stereotypic behavior in captive
Elephas maximus, because these Stereotypic behaviors are often
indicators of poor welfare or stress), & via that researchers can calculate %
of time spent on each behavior. => Activity budget analysis requires
specific mode of recording, different methods exist:
o Continuous recording = Record exact duration of each behavior, is very precise but time-intensive.
H1: The study of behavior
1.1: What is behavior?
There is not 1 single definition of behavior & definitions differ among scientists. These debates are philosophical, & in
practice researchers use working definitions. Commonly used definition: Behavior = Internally coordinated responses
(actions or inactions) of whole living organisms (individuals or groups) to internal &/or external stimuli, excluding
responses more easily understood as developmental changes. => Key aspects of behavior:
• Behavior is influenced by internal processes within organism.
• It is something performed by whole organism, not just organs or body parts.
• Behavior must be observable, recordable, & measurable.
• Behavior does not always involve movement, it can be freezing, staring, defensive postures.
There are some grey areas => Chameleon changing color when touched is considered behavior because it’s
immediate response to stimulus. While seasonal color change in Arctic fox isn’t considered behavior, because it’s
developmental/physiological change & not immediate response.
Some scientists argue behavior only occurs in animals, but other organisms can also respond to
stimuli & move. => Example: Unicellular organisms (such as Dileptus & Spirostomum) show
predatory behavior, using venom & phagocytosis to capture prey.
1.1.1: Ethology
Ethology = scientific & objective study of animal behavior, usually under natural conditions and by treating behavior
as evolutionary adaptive trait.
Ethology is connected to Ecology, Neurology, Physiology, Sociobiology, Psychology, Evolutionary biology,
Developmental biology, Conservation biology, Global change biology, Toxinology, … This field is expanding &
increasingly integrative, with emerging subdisciplines (such as Cognitive ethology, Neuroethology, and Animal
welfare science).
Behavioral plasticity often provides initial responses to environmental change, which may later be followed by
genetic evolutionary change. => Behavioral evolution & behavioral plasticity can sometimes be confused at short-
term evolutionary timescales.
Early ethology (1870s–1930s):
In 1872, Charles Darwin published ‘Expression of Emotions in Man & Animals’. This work influenced early ethologists,
as it suggested that behavior & emotional expression evolve & have adaptive value.
Early researchers (such as Charles Otis Whitman, Oskar Heinroth, Wallace Craig & Julian Huxley) studied innate
(instinctive) behavior using descriptive methods. During this period ethogram was developed.
Ethogram = inventory of all behaviors exhibited by animal & is based on objective observation => All descriptions in
ethogram should be free of interpretation & interpretation occurs only after analysis.
Modern ethology (1930s–1980):
Modern ethology was founded by Karl von Frisch, Konrad Lorenz & Niko Tinbergen. They combined ethograms,
hypothesis-driven research, experimental testing and quantification of behavior. In 1973, these 3 scientists received
Nobel Prize in Physiology or Medicine for their discoveries about organization & elicitation of individual & social
behavior patterns.
,Karl von Frisch (1886–1982) => Studied behavior of honeybee Apis mellifera & how bees
use sensory systems (vision, smell, taste) during navigation & foraging. Discovered that
they use 2 recruitment dances (AKA Round dance & waggle dance) to communicate about
direction, distance, & quality of food sources. Modern research shows system is more
complex than originally thought.
Konrad Lorenz (1903–1989)=> Focused on innate behavior in birds & studied filial imprinting in birds
• Filial imprinting = Young animals develop social attachment to specific object (usually parent) shortly after
hatching => He showed that animals could imprint on almost any object, including humans.
o Example: Newly hatched geese may follow 1st moving object they see.
• Imprinting (which is rapid, phase-sensitive learning process) is now used in conservation programs, such as
those for endangered Grus americana.
Niko Tinbergen (1907–1988) => studied behavior in birds, fish, & insects. He proposed that animal behavior should
be studied from 4 complementary perspectives/questions. These questions help explain both how behavior works (=
Causation & Development) & why it exists (= Function & Evolution).
1. Function = What is it for? How will it increase fitness? You look at how this behavior improves survival or
reproduction, & how natural selection or sexual selection favors individuals with that behavior. => Focus on
adaptive value & utility of behavior
2. Mechanismsm / Causation = How does it work? Which mechanisms trigger this behavior? It includes:
o Internal factors = Hormones, Neural activity, Physiological processes
o External factors = Environmental stimuli
o Example: In birds, multiple brain regions coordinate song production. Some birds can produce song even
when raised in isolation, showing genetic basis, but normal songs are often learned from parents.
=> Focus on physiological & neurological mechanisms of behavior.
3. Development / Ontogeny = How does it develop during organism’s lifetime? It considers learning processes, life
history, & development of related traits.
o Example: Young birds learn their songs during early life & this behavior may change with age or
experience.
4. Evolution (Phylogeny) = How did it evolve? It investigates evolutionary history of behavior. Involves comparisons
across related species, phylogenetic analyses, identifying genetic & evolutionary mechanisms => Focus lies on
how behavior evolved across species over evolutionary time.
Example 1: Bird songs
1. Function => Birds sing mainly to attract mates & to defend
territories from rivals
2. Mechanism (Causation) => Bird song is produced by specialized
neural network (= song system), consisting of interconnected
brain nuclei controlling learning & production.
3. Development => Young songbirds learn songs early in life during
sensitive period. Experiments show that birds raised in isolation
produce abnormal songs, demonstrating role of learning (such
as Fringilla coelebs).
4. Evolution => Comparative studies show that song characteristics differ among related species, reflecting
evolutionary divergence.
Example 2: Hunting behavior of spider-tailed viper => Snake’s tail structure resembles spider & it moves its tail to
imitate spider movement. It uses its tail to mimic spider & lure prey (such as birds).
1. Function => Behavior lures prey, increasing feeding success & fitness.
2. Causation
o Internal factor = hunger
o External factor = detection of prey
3. Development => Unclear if behavior is fully innate or partly learned.
, 4. Evolution => Behavior likely evolved through co-evolution of morphology (tail shape) & behavior, driven by
natural selection.
Example 3: Mating behavior in crickets => Male attract females using stridulation, producing chirping sounds by
rubbing specialized wings together.
1. Function => Chirping attracts females, increasing reproductive success.
2. Causation
o Internal factor = hormonal changes
o External factor = day length
3. Development => Behavior may be innate, but also depends on development of wing structures enabling sound
production (such as Mirror, Harp, Scraper & Stridulatory file).
4. Evolution => Wing morphology & stridulation behavior evolved together through sexual selection. Comparing
chirps across related species helps to reconstruct evolutionary changes & speciation.
Tinbergen & Lorenz together
• Developed ideas about Sign stimulus (releaser) = specific
feature of stimulus that triggers behaviour.
o Example: Fish Gasterosteus aculeatus => Red color triggers
aggressive behavior in males, while shape of model fish is
less important (AKA Red color = sign stimulus).
• Proposed that certain behaviors are innate neural responses triggered by
specific stimuli => Fixed Action Patterns (FAPs) = Stereotyped behavioral
sequences that are triggered by specific stimulus & are usually completed even
if stimulus disappears.
o Example: Greylag goose Anser anser => Displaced egg triggers egg-rolling
behavior & goose continues motion even if egg is removed mid-action.
Supernormal stimulus = exaggerated artificial stimulus that elicits stronger response than natural one. Examples:
• Gull Larus argentatus => Chicks peck at red spot on parent's bill to beg for food. Red stick with
white stripes can trigger even stronger begging behavior than real parent.
• Australian beetle Julodimorpha bakewelli => Males are attracted to brown beer bottles, because
they resemble large females with similar color & textured surface. This study won
Ig Nobel Prize in 2011.
1.2: Scientific approach to behavior
Studying behavior scientifically follows step-by-step process, starting from simple observations to testing hypotheses.
1) Observation:
Research often begins with observation about something that attracts attention because it is unusual, unexpected, or
raises questions.
Example: Silent crickets in Hawaii => On island of Kauai, populations of cricket became silent within 3–5 years (12–20
generations).
• Cause = Parasitic fly locates male crickets using precise directional hearing. This fly lays maggots on cricket,
which later burrow into & kill host.
• Timeline:
o Since 1991, number of calling males decreased.
o By 2003, crickets were abundant again but most males were silent.
o By 2006, >90% of males on Kauai were silent.
, Silence evolved because calling males attracted parasites. Detailed observations revealed that calling males had ~30%
parasite infection rates, while silent males had <1% infection. Additional observations:
• Silent males often stayed close to few remaining calling males.
• Females were still willing to mate with silent males.
• Silent males still move their wings (stridulate), but sound is inaudible to humans.
• Morphological difference = Silent males have “flatwing” morphology with vestigial sound-
producing structures (mirror, harp, scraper) => This morphology prevents them from
producing audible songs.
2) Ethogram:
= detailed inventory of all observable behavioral patterns of species, either generally or in specific context (such as
feeding, mating, defense, social interaction). => Creating ethogram requires extensive observation of species. Its has
several benefits, as it provides insight into animal’s biology, helps formulate research questions allows definition of
quantifiable behavioral parameters.
Researchers also review existing literature to understand what is already known about species or related species.
Rare behaviors should also be recorded because they can be important for understanding species.
Sampling strategies for building ethogram
• Ad libitum sampling = Record any behavior observed without restrictions => Useful when little is known about
species & helps capture rare behaviors.
• Behavior sampling = Focus on 1 specific behavior or small set of behaviors within
group.
• Focal sampling = Focus on 1 individual (or interacting individuals) & record all
behaviors over time.
• Scan sampling = Quickly scan group & record states or positions rather than
detailed actions.
How to describe behavior in ethogram
• Be objective & avoid interpretation => don’t write “Spider reacts in
frightened way”, but “Spider crawls away from wasp”.
• Describe structure, not consequences => don’t “Wasp kills spider with
sting & paralyses spider”, but “Wasp stabs spider with sting & spider stops
moving”. Actual cause (such as venom paralysis) must be tested
experimentally before concluding.
• Be detailed & precise => don’t “Wasp stabs spider”, but “Wasp stabs
spider 1–5 times for <1 second on dorsal anterior cephalothorax. After 30
à 60 seconds spider curls its legs & stops moving.”
Practical considerations is that observers can influence animal behavior, so
observations should be non-intrusive.
To quantify behavior, behavioral actions are often broken down into measurable
units. Examples:
• Courtship sequence => Ethograms can describe stepwise behavioral
sequences, such as mating stages in snakes or newts.
• Activity budgets = measuring how much time animals spend performing
different behaviors (such as study of stereotypic behavior in captive
Elephas maximus, because these Stereotypic behaviors are often
indicators of poor welfare or stress), & via that researchers can calculate %
of time spent on each behavior. => Activity budget analysis requires
specific mode of recording, different methods exist:
o Continuous recording = Record exact duration of each behavior, is very precise but time-intensive.
