1-4- Swift & Marzluff 2015 Flashcards
What happened in the 72 hours after observing novel humans paired with a dead crow, a red-tailed hawk or a hawk with a dead crow?
Crows mobbed and increased the time to approach food
On the day the stimulus was presented, the number of trials that resulted in mobbing and
avoidance of the food was strongest when what happened?
On the day the stimulus was presented, the number of trials that resulted in mobbing and
avoidance of the food was strongest when crows were presented a hawk with a dead crow
Crows use the proximity of a human to predators, to dead conspecifics and to
predators with dead conspecifics as cues to learn to recognize and subsequently scold the associated
human after only one training event, and that this association can last how long?
6 weeks
Which animals congregate around dead conspecifics?
Black-billed magpies, western scrub-jays, chimpanzees, african elephants and bottlenose dolphins
Which animals respond to dead conspecifics in the absence of artificial distress calls?
Western scrub-jays
following carcass removal, what did scrub-jays show?
following carcass removal, scrub-jays show
reduced feeding activity in the area for 24 h.
How can fear be extinguished?
Fear can be extinguished, however, through repeated exposure to the conditioned
stimulus without reinforcing its predictive value of the unconditioned stimulus
what was experiment 1?
To test
danger learning, we conducted three experiments on wild crows. In
experiment 1, we examined (1) whether the sight of a dead
conspecific is sufficient to elicit alarm calling and recruitment, or
whether the presence of an unconditioned predator is also necessary, (2) whether crows learn areas associated with these dangers
and subsequently avoid them, (3) whether crows use dead conspecifics to identify novel predators and, if so, how this process
compares to conditioned learning when novel predators are paired
with unconditioned stimuli (hawks), and (4) whether fear extinction can be achieved with a minimum of three additional exposures.
What was experiment 2?
For experiment 2, we determined whether a dead conspecific
is a more salient source of dangerous information than a similarly
sized, dead heterospecific
What was experiment 3?
In experiment 3, we compared responses of rock pigeons and crows to dead conspecifics.
what were the three phases of each experiment?
conditioning, stimulus presentation and post-exposure
We assumed that no more than ___ adult birds occupied each territory, as helping behaviour occurs infrequently in crow populations
in the northwestern United States
We assumed that no more than two adult birds occupied each territory, as helping behaviour occurs infrequently in crow populations
in the northwestern United States
Crows received a 2:1 mix of what?
Crows received a 2:1 mix of raw, unshelled peanuts and cheese puffs
Pigeons received a 2:1 mix of what?
Pigeons received a 2:1 mix of
birdseed and crumbled white bread.
After providing food, the observer monitored the food pile from ____ m away, for up to ____, and measured the birds’ latency to approach within ___m of
the food pile (‘food discovery time’).
observer monitored the food pile from 15-25 m away, for up to 2.5 h, and measured the birds’ latency to approach within 2 m of the food pile (‘food discovery time’).
What was the conditioning phase?
Once the birds at each site approached the food within the 2.5 h observation period for 3 consecutive days (in most tests, birds met
the criterion in 3 days; in seven tests, birds took up to 10 days to meet the criterion), we began the stimulus presentation phase on the following day (day 4).
During the stimulus presentation phase, we _____ _____ ____ _____, after which a volunteer ______________________
During the stimulus presentation phase, we provided food as normal, after which a volunteer exposed an experimental or a control stimulus 2 m from the food pile
Volunteers
wore one of six ______ _____ with _____ _____
Volunteers
wore one of six realistic facemasks with neutral expressions
Why did volunteers wear a white sign
around their neck that read ‘UW CROW STUDY’?
to limit interruptions by pedestrians or police
During stimulus presentation,
the data collector recorded instances and durations of _____ and
typical crow ____ ____, and the number ____ _____ ____ _____
During stimulus presentation,
the data collector recorded instances and durations of scolds and
typical crow contact calls, and the number of birds present within
25 m of the stimulus
what was mob formation?
the presence of
more than two scolding individuals within 25 m of the stimulus.
what was mob size?
We calculated mob size as the maximum number of individuals
present during the stimulus event.
why did they not determine
whether all individuals within a mob actively scolded beyond the
three-bird minimum?
Because mobs are highly mobile and most birds were not individually marked
The volunteer removed the stimulus ___min after the first bird perched within __ m of the stimulus and was
observed gazing towards the experimental set-up (‘stimulus discovery time’).
The volunteer removed the stimulus 30 min after the first bird perched within 25 m of the stimulus and was
observed gazing towards the experimental set-up (‘stimulus discovery time’).
Following stimulus removal, for up to __h, the
observer recorded the birds’ latency to approach within __m of the
food pile (‘food discovery time’).
Following stimulus removal, for up to 2.5 h, the
observer recorded the birds’ latency to approach within 2 m of the
food pile (‘food discovery time’).
We removed all but a small
amount (_____) of food after ___-h
We removed all but a small
amount (five pieces) of food after 2.5 h
. If birds approached the pile
in the presence of the stimulus, we recorded the food discovery
time as ___s
. If birds approached the pile
in the presence of the stimulus, we recorded the food discovery
time as 0 s.
The observer used ____, ____, ___and ___ ___ to discriminate between hatch-year and older birds
The observer used plumage, profile, voice and mouth
lining to discriminate between hatch-year and older birds
Only birds
older than 1 year of age were counted for what?
Only birds
older than 1 year of age were counted for stimulus discovery time,
food discovery time and mob or group size.
During the post-exposure phase, on days __-__, we split the
experiment into two trial types
During the post-exposure phase, on days 5e7, we split the
experiment into two trial types
what was trial type A
In trial type A, we
continued to provide food (as described above) to test for site
aversion.
what was trial type B?
In trial type B, following standard feeding by the observer
(as during conditioning), a volunteer wearing the same mask as
seen during the stimulus exposure phase arrived and stood 2 m
from the food pile.
What was the difference between A and B?
n trial type B, following standard feeding by the observer
(as during conditioning), a volunteer wearing the same mask as
seen during the stimulus exposure phase arrived and stood 2 m
from the food pile. The experimental procedure during test trial B
otherwise matched that of the stimulus exposure phase, allowing
us to test for novel predator learning and to evaluate the influence
of varying levels of exposure to danger on fear extinction
which experiment used both trial types?
experiment 1
what trial type did experiments 2 and 3 use?
Experiments 2 and 3 used trial
type A during the post-exposure phase.
marked individuals were banded __ years before the
onset of the present experiment.
marked individuals were banded 5 years before the
onset of the present experiment.
Experimental locations were
established ___-___m from nest sites to limit nest disturbance.
Experimental locations were
established 35-45 m from nest sites to limit nest disturbance.
How many sites were there and how many territorial pairs?
In 2013 and 2014, we selected 17 independent sites and, within
each site, identified seven to nine territorial pairs
In
April-June, we used ___ ___ to define the _____ for tests,
and established specific test locations ___-___m from the nest tree
In
April-June, we used nesting areas to define the locations for tests,
and established specific test locations 35-45 m from the nest tree
During July-September, we identified test _____by the presence of ____ ____or the consistent ____ ___ ____ ____ ____
During July-September, we identified test locations by the presence of fledged young or the consistent presence of an adult pair.
American crow territories in the urban core are smaller than what?
American crow territories in the urban core are smaller than their
suburban counterparts
what was the minimum distance between two test locations?
90m
what was the median distance between two test locations
430m
During the stimulus presentation phase of the experiment, birds
received one of five stimuli . what were they?
3 dangerous:
- dead crow + mask
- hawk + mask
- dead crow + hawk + mask
2 control:
- person in mask
- food only
Between sites, why did they vary the
sequence of stimulus presentations ?
Between sites, we varied the
sequence of stimulus presentations so that the order of control and
dangerous stimuli were counterbalanced.
. In 2014, what was not used?
. In 2014, the mask-only
control was not used
what happened because the mask only control was to used in 2014?
. In 2014, the mask-only
control was not used, and thus fewer sites were tested in 2014
than in 2013.
how many taxidermy crows and hawks were there?
We used three identically prepared taxidermy mounts of crows (randomized across trials) but only a single, mounted redtailed hawk.
Because of time constraints, in ___ of cases, birds were present
during the stimulus set-up and witnessed the unmasked volunteer
interact with the avian stimuli.
Because of time constraints, in 43% of cases, birds were present
during the stimulus set-up and witnessed the unmasked volunteer
interact with the avian stimuli.
why did they not believe witnissing the set-up biased the response?
Given that humans were common at
each site and that their presence with or near dangers was already
an element of our experimental design,
what happened (more detail) in trial type A?
in trial type A (N =74, which
included 17 food-only controls), we provided food as during the
conditioning phase.
what happened (more detail) in trial type B?
In trial type B (N =57), after the observer
provided food, a colleague wearing the same mask used during the
stimulus presentation phase immediately arrived and stood 2 m
from the food pile.
how did they test longevity of response?
scolding, diving
or mobbing the masked person, or refusing to approach within 2 m
of the food pile for the full 2.5 h after the masked person’s departure
We administered up to ___ weekly
tests (longevity tests 1-6),
We administered up to six weekly
tests (longevity tests 1-6),
because of time constraints, only ___
of the 17 sites (one each from Redmond and Kirkland, and all nine
Seattle sites; 77 of 114 potential territories) were tested beyond the
first longevity test.
because of time constraints, only 11
of the 17 sites (one each from Redmond and Kirkland, and all nine
Seattle sites; 77 of 114 potential territories) were tested beyond the
first longevity test.
when were tests discontinued?
Tests were discontinued prior to completing all
six tests if the birds became unresponsive.
Tests in trial type A
began __ ____ from the ___ ____ _____ provided that
the birds had responded during the stimulus presentation phase
Tests in trial type A
began 1 week from the stimulus presentation phase provided that
the birds had responded during the stimulus presentation phase
In type A in experiment 1, how many birds did not respond?
24 of 74 did not respond: N =5 mask-only controls, N =17
food-only controls
Birds in trial type B were tested __ ____ from
the last day of the _______ ____ provided they were still
responding at that time
Birds in trial type B were tested 1 week from
the last day of the post-exposure phase provided they were still
responding at that time
in experiment 1 type b, how many birds stopped responding?
20 of 57 stopped responding; of those,
N =5 were mask-only controls
The first four longevity tests followed what?
The first four longevity tests followed the format of the post-exposure phase in trial type B;
If birds remained
responsive during the longevity test in week 4, during the fifth
longevity test, what did they do?
If birds remained
responsive during the longevity test in week 4, during the fifth
longevity test we did not provide food and instead presented either
a person wearing the conditioned mask or a novel, unconditioned
mask followed approximately 6-9 h later by the opposite mask, to
test for recognition of the dangerous mask.
Following the first
encounter with an adult bird, the masked volunteer did what?
Following the first
encounter with an adult bird, the masked volunteer walked around
the approximated home range of the birds (based on observations
by volunteers and the primary observer) for 30 min, and the
observer recorded the number of crows within 25 m and any instances of scolding.
what happened if the birds responded during the fifth test?
. If the birds responded during the fifth test, on
week 6 we presented birds with the dangerous mask at a distance
of 25, 50 or 75 m from the food pile
why did they present birds with the dangerous mask at a distance
of 25, 50 or 75 m from the food pile
to test for
context-dependent learning of the masked volunteer.
The observer
recorded the number of birds within __m of the food pile and the
masked person.
The observer
recorded the number of birds within 25 m of the food pile and the
masked person.
what was stimulus discovery?
the time the first bird came within 25 m of the stimulus
and was observed gazing towards it
what was food discovery?
the first time a bird approached the food pile following stimulus
discovery
The masked person left the area __min following
stimulus discovery.
The masked person left the area 30 min following
stimulus discovery.
when did they do experiment 2?
august-september 2014
what was the distance between sites in experiment 2?
a minimum distance of 400 m from all previous experiments. Sites were 1000 m from each other.
what happened after the conditioning phase in experiment 2?
fter the conditioning
phase, the crows were presented with a masked person holding a
taxidermy-mounted ‘dead’ pigeon 2 m from the food pile
when did they do experiment 3?
December 2013 and AugusteSeptember
of 2014.
why did behavioural differences
due to breeding did not differ between winter and summer tests?
Since pigeons breed year-round, behavioural differences
due to breeding did not differ between winter and summer tests.
what was the distance between sites in experiment 3?
We used six unique sites at least 350 m from previous crow experiments, and 1000 m from each other,
what was the difference between 2013 and 2014 in experiment 3?
Experiments conducted in 2013 used a fresh
pigeon carcass, and experiments in 2014 used a taxidermymounted ‘dead’ pigeon.
Experiment 1
Across years, territorial adults scolded during ___ of trials that
presented dangerous stimuli (N =102 tests),
Across years, territorial adults scolded during 96% of trials that
presented dangerous stimuli (N ¼ 102 tests),
Experiment 1
only __%
scolded during mask-only control presentations (N =12 tests)
only 17%
scolded during mask-only control presentations (N ¼ 12 tests)
Experiment 1
__% scolded during food-only control presentations (N ¼ 17 tests).
0% scolded during food-only control presentations (N ¼ 17 tests).
Experiment 1
Of
those crows that did not scold when presented with a danger, ___
observed a dead conspecific, ___observed a hawk, and ___
observed a hawk with a dead crow.
Of
those crows that did not scold when presented with a danger, two
observed a dead conspecific, one observed a hawk, and one
observed a hawk with a dead crow.
Experiment 1
Neither __-___ nor ___-____ control tests resulted in
mobbing.
Neither food-only nor mask-only control tests resulted in
mobbing.
Experiment 1
what primarily drove the result of the likelihood of mobbing differed between the three
dangerous stimuli
The response of crows that saw a hawk with a dead conspecific
primarily drove this result
Experiment 1
Was hawk + dead crow versus hawk
alone significantly different
hawk þ dead crow versus hawk
alone were not significantly different
Experiment 1
After mob formation, crows spent more time constantly
____ the hawk with a dead crow (mean ± SE =11.1 ± 1.3 min)
than they did the dead crow (7.5 ± 1.3 min) or the hawk
(6.1 ± 1.5 min) alone, but this difference __________
After mob formation, crows spent more time constantly
scolding the hawk with a dead crow (mean ± SE ¼ 11.1 ± 1.3 min)
than they did the dead crow (7.5 ± 1.3 min) or the hawk
(6.1 ± 1.5 min) alone, but this difference was not significant
Experiment 1
The number of birds present
during stimulus presentation depended on the type of stimulus. How?
The number of birds present
during stimulus presentation depended on the type of stimulus
(F4,126 ¼ 8.69, P < 0.001; Fig. 4). More birds were present during
presentation of the hawk þ dead crow than during presentation of
the dead crow (mean difference ¼ 6.35; Tukey HD: P ¼ 0.002) or
the hawk (mean difference ¼ 5.85; Tukey HD: P ¼ 0.005)
Experiment 1
. In trials
that resulted in mobbing, mob size differed with stimulus type
(ANOVA: F2,75 =3.53, P =0.034), but this effect was driven solely
by what?
. In trials
that resulted in mobbing, mob size differed with stimulus type
(ANOVA: F2,75 ¼ 3.53, P ¼ 0.034), but this effect was driven solely
by the difference between hawk þ dead crow versus hawk (mean
difference ¼ 5.25; Tukey HD: P ¼ 0.043).
Experiment 1
There was ______ in mob size during presentations of the hawk + dead
crow versus the dead crow or the dead crow versus the hawk
There was no significant
difference in mob size during presentations of the hawk þ dead
crow versus the dead crow (mean difference ¼ 4.47; Tukey HD:
P =0.13) or the dead crow versus the hawk (mean difference =0.78; Tukey HD: P =0.94).
Experiment 1
During the 2.5 h immediately following presentation of the
stimulus, what % of crows exposed to a dangerous stimulus did not return to the food pile?
17%
Experiment 1
All crows that received a
___ ____ returned to the food
All crows that received a control treatment (N ¼ 29 tests) returned to the food
Experiment 1
Crows
differed in avoidance of particular stimuli . what drove this effect?
Crows’ avoidance of the
hawk þ dead crow primarily drove this effect
however,
dead crow versus hawk + dead crow were not different
Trial type A
During the stimulus presentation phase, __% of birds avoided the
food for the 2.5 h following stimulus removal, whereas during the
post-exposure phase, ___________
During the stimulus presentation phase, 17% of birds avoided the
food for the 2.5 h following stimulus removal, whereas during the
post-exposure phase, most birds eventually approached the food
Trial type A
Regardless of the dangerous stimulus seen during the stimulus presentation phase, crows showed similar increases in what?
presentation phase, crows showed similar increases in latencies to
approach the food pile during the post-exposure phase relative to
the conditioning phase
Trial type A
, birds
exposed to dangerous stimuli showed a larger change in latency to
________
, birds
exposed to dangerous stimuli showed a larger change in latency to
approach the food pile (relative to the conditioning phase) than did
birds in the control treatment
Trial type A
Comparing only the post-exposure phase, birds exposed to danger
took longer to approach food than did who?
control birds
Trial type B
In trial type B, crows’ change in latency to approach the food pile
during the post-exposure phase did not vary with the type of
dangerous stimulus
therefore, what did they do?
we lumped all
dangerous stimuli into a single ‘danger’ treatment and lumped the
two controls into a single ‘control’ treatment.
Trial type B
The difference in latency to approach the food pile during the conditioning phase and
the post-exposure phase was greater for crows that saw a
____ ____than for crows that saw a ____ _____
The difference in latency to approach the food pile during the conditioning phase and
the post-exposure phase was greater for crows that saw a
dangerous stimulus than for crows that saw a control stimulus
also took longer to approach food
Longevity tests
Crows that viewed a dangerous stimulus were equally likely to
respond in the first longevity test to the ____ ____ ___ ___ regardless of the type of unconditioned stimulus
or the trial type
Crows that viewed a dangerous stimulus were equally likely to
respond in the first longevity test to the previously conditioned
masked person regardless of the type of unconditioned stimulus
or the trial type
Longevity tests
Even after 6 weeks of
additional weekly exposures, birds in trial type B showed no
significant difference in ____ ____ compared to those in trial
type A and they were no more
likely to respond to ____
Even after 6 weeks of
additional weekly exposures, birds in trial type B showed no
significant difference in fear extinction compared to those in trial
type A and they were no more
likely to respond to the person associated with any one of the three
dangers
Longevity tests
During the fifth longevity test
(where crows saw a dangerous stimulus or a person wearing a
neutral mask, then a dangerous mask), birds were more likely to
scold the _____ than the ______
During the fifth longevity test
(where crows saw a dangerous stimulus or a person wearing a
neutral mask, then a dangerous mask), birds were more likely to
scold the dangerous mask than the neutral mask
Longevity tests
. During the sixth longevity test,
where crows saw the masked person previously associated with
danger either 25 m (N ¼ 13), 50 m (N ¼ 10) or 75 m (N ¼ 8) from
the food pile, the crows were no more likely to stop responding
than they had been during _____ ___
. During the sixth longevity test,
where crows saw the masked person previously associated with
danger either 25 m (N ¼ 13), 50 m (N ¼ 10) or 75 m (N ¼ 8) from
the food pile, the crows were no more likely to stop responding
than they had been during week 4
Longevity tests
crows’ failure to respond to the masked
person did not differ with ________
crows’ failure to respond to the masked
person did not differ with distance to the food pile
Seasons & carryover
did the season the brids were tested in effect the likelihood of scolding
The season (AprileJune, N ¼ 65; JulyeSeptember, N ¼ 37) in
which birds were tested did not influence the likelihood of scolding
the dangerous stimuli
Seasons & carryover
The
proportion of birds that mobbed during AprileJune tests (N ¼ 47 of
65) was _____ ____ than those tested during JulyeSeptember
(N ¼ 31 of 37), however,____________
The
proportion of birds that mobbed during AprileJune tests (N ¼ 47 of
65) was slightly lower than those tested during JulyeSeptember
(N ¼ 31 of 37), however, this difference was not significant
The same trend could be seen with respect to
changes in latency to approach food in both type A (repeated
measures ANOVA: F1,49 ¼ 1.48, P ¼ 0.23) and type B
Seasons & carryover
Of 24 marked individuals, how many birds were
recruited to mob at a different test site during stimulus presentation?
f 24 marked individuals, only one previously tested bird was
recruited to mob at a different test site during stimulus presentation, although six marked birds were seen on other days.
Seasons & carryover
did proportion of brids that mobbed during first and last week of testing differ between sites?
proportion of birds that mobbed the dangerous stimulus during the
first week of testing (N ¼ 7 of 12 birds) and the last week of testing
(N ¼ 9 of 13 birds) did not differ across sites
Seasons & carryover
Crows tested first within a site tended to take longer to approach
food after exposure to danger than those tested last, but _________________________-
Crows tested first within a site tended to take longer to approach
food after exposure to danger than those tested last, but this difference was not significant
Seasons & carryover
Furthermore, crows in control territories that
were either greater than (N ¼ 8) or less than (N ¼ 8) 400 m from a territory where a dangerous stimulus had previously been
deployed___ ___ ____ in their change in latency to approach food
between the conditioning phase and the post-exposure phase
territory where a dangerous stimulus had previously been
deployed did not differ in their change in latency to approach food
between the conditioning phase and the post-exposure phase
Experiment 2
While 94% of the crows scolded when they saw a dead
conspecific (N ¼ 34 tests), only ___% of the crows scolded in
response to a dead pigeon
40%
Experiment 2
Even in cases where crows scolded in response to
the dead pigeon, they did so _____ times
than in response to a dead conspecific
Even in cases where crows scolded in response to
the dead pigeon, they did so far fewer times (mean ± SE ¼ 7 ± 1.26)
than in response to a dead conspecific (63.74 ± 9.89).
Experiment 2
Crows
exposed to a dead pigeon did not ____, unlike the majority of those
that saw a dead crow
Crows
exposed to a dead pigeon did not mob, unlike the majority of those
that saw a dead crow
Experiment 2
Following exposure to a
dead conspecific, crows in trial type A took longer to approach the
food during the post-exposure phase relative to the conditioning
phase, more than did crows confronted with __ _____ ____
Following exposure to a
dead conspecific, crows in trial type A took longer to approach the
food during the post-exposure phase relative to the conditioning
phase, more than did crows confronted with a dead pigeon
Experiment 2
During the post-exposure phase,
crows that saw a dead conspecific took longer to ____ _____
than crows that saw a dead pigeon
During the post-exposure phase,
crows that saw a dead conspecific took longer to approach food
than crows that saw a dead pigeon
Experiment 3
Pigeons flocked to food in the presence of a masked person
holding the dead pigeon in ___% of cases (N ¼ 6 tests)
66%
Experiment 3
crows never ____________________
crows never approached the food in the presence of a masked
person holding a dead crow
Experiment 3
Sight of a dead conspecific had
different effects on the ____ __ ______ to approach the food pile
in pigeons relative to crows
Sight of a dead conspecific had
different effects on the change in latency to approach the food pile
in pigeons relative to crows
Experiment 3
crows delayed their approach to the food pile after stimulus
exposure, pigeons ____________
crows delayed their approach to the food pile after stimulus
exposure, pigeons approached the food pile faster during the postexposure phase than during the conditioning phase
wild
crows use the bodies of dead conspecifics as an indication that _______
wild
crows use the bodies of dead conspecifics as an indication that an
area is dangerous
we show that crows make inferences about ____ _____ based on a novel predator’s _________
we show that crows make inferences about novel predators based on a novel predator’s proximity to dead conspecifics and to hawks.
how long do inferences about novel predators last?
up to 6 weeks
what are the purposes of mobbing?
chastising the predator , displaying dominance
, or social learning of the dangerous person
or place
Our finding that crows scolded and mobbed people holding dead
crows, without playback of conspecific alarm vocalizations, supports the assessment that dead crows represent ____ _____ ____
Our finding that crows scolded and mobbed people holding dead
crows, without playback of conspecific alarm vocalizations, supports the assessment that dead crows represent a salient danger.
control presentations of people or food rarely elicited
_____ by individual crows and never escalated to ____,
control presentations of people or food rarely elicited
scolding by individual crows and never escalated to mobbing,
like ____
______, the discovery of a dead conspecific is effective at triggering typical antipredator behaviours
like western
scrub-jays, the discovery of a dead conspecific is effective at triggering typical antipredator behaviours
Crows were more likely to mob and to avoid the food pile more
consistently over the next ___h in response to a hawk with a dead
crow than in response to either a hawk or a dead crow alone.
Crows were more likely to mob and to avoid the food pile more
consistently over the next 2.5 h in response to a hawk with a dead
crow than in response to either a hawk or a dead crow alone.
In crows, exposure to a
hawk results in activation of the___ _____
In crows, exposure to a
hawk results in activation of the caudal nidopallium
Our finding
that crows were less likely to mob if a hawk was observed without
conspecific prey supports the conclusion of what?
Our finding
that crows were less likely to mob if a hawk was observed without
conspecific prey supports the conclusion that crows are sensitive to
predator behaviour (with or without prey) and subsequently adjust
the aggressiveness of their mobbing response
After exposure to a human with a dead crow, or a hawk, or a
hawk with crow remains, the crows in both trial types A and B took
longer to _________ than they did during the ____
After exposure to a human with a dead crow, or a hawk, or a
hawk with crow remains, the crows in both trial types A and B took
longer to approach food in the locations associated with these
events than they did during the conditioning phase.
When we
compared differences only in the post-exposure phase between
control stimuli and dangerous stimuli, we again found that crows
exposed to danger ________ with the event, although this difference was more highly
significant in trial type __
When we
compared differences only in the post-exposure phase between
control stimuli and dangerous stimuli, we again found that crows
exposed to danger look longer to approach food locations associated with the event, although this difference was more highly
significant in trial type B
When we
compared differences only in the post-exposure phase between
control stimuli and dangerous stimuli, we again found that crows
exposed to danger look longer to approach food locations associated with the event, although this difference was more highly
significant in trial type B.
what does this suggest
suggesting that the ongoing presence of
the ‘conditioned person’ may have exaggerated the fear response to
the place.
Our findings
indicate that crows learn the spatial context associated with a brief (30 min) dangerous event and that changes in latency to approach
food in these areas can last for up to __ h after the cadaver and/or
predator is removed
72 h
crows’ change in latency
to approach food before and after stimulus presentation did not
differ with what?
crows’ change in latency
to approach food before and after stimulus presentation did not
differ with the type of danger stimulus
One week following presentation of a novel human paired with
a dangerous stimulus, more than half of birds in each trial type
_____or ___ ____ the person or refused to approach food for
___ h after the person had left.
One week following presentation of a novel human paired with
a dangerous stimulus, more than half of birds in each trial type
scolded or dove towards the person or refused to approach food for
2.5 h after the person had left.
in __% of cases, the crows in sites eligible for all longevity tests
continued to respond for up to 6 weeks
in 38% of cases, the crows in sites eligible for all longevity tests
continued to respond for up to 6 weeks
Our finding that the type of
dangerous stimulus associated with a person did not influence the
crows’ response to the person 1 week later, or up to 6 weeks later,
suggests what?
that dead crows and predators are equivalent at triggering
fear conditioning.
Fear extinction of crows that received three additional exposures to the _____ did not differ from that of _____
Fear extinction of crows that received three additional exposures to the conditioned human stimulus without the unconditioned stimulus (trial type B) did not differ from that of crows that
received no additional exposure (trial type A).
Fear extinction of crows that received three additional exposures to the conditioned human stimulus without the unconditioned stimulus (trial type B) did not differ from that of crows that
received no additional exposure (trial type A). T
what does this suggest
This suggests that
subsequent exposures to conditioned stimuli alone do not immediately lead to fear habituation in wild crows.
a dangerous person
positioned 25, 50 or 75 m from the food during week 6 did what?
a dangerous person
positioned 25, 50 or 75 m from the food during week 6 did not
result in a higher number of extinctions than was observed during
week 4, when the food and the person were last paired together
ws there a difference in extinction between the differences
a dangerous person
positioned 25, 50 or 75 m from the food during week 6 did not
result in a higher number of extinctions than was observed during
week 4, when the food and the person were last paired together
experiment 2 was in contrast to what other species?
western scrub-jays
In our experiments, __% of crows
remained wary of the person or the place associated with death of a
conspecific for 6 weeks.
38%
