Chapter 9: Antipredator Behaviour Flashcards
crab colouration research question:
why do juvenile crabs have a complex body colour
crab colouration hypothesis:
the body colourant of juvenile crabs is cryptic on a heterogenous shell-hash substrate
crab colouration prediction
juveniles on shell hash will have higher survival
crab colouration methods
tethered individual juvenile crabs on ceramic tiles in ocean that were uniform white or heterogenous shell hash
record survival of all individuals over time
crab colouration results
few crabs on white tiles survived, over 60% on shell hash survived.
crab colouration conclusion
juvenile body colouration is cryptic on shell hash substrate and reduces predation risk
crab anti predator research question
can crabs select cryptic shell hash substrate?
crab anti predator hypothesis
crabs will move to cryptic backgrounds when they are available
crab anti predator prediction
crabs prefer a shell hash background to one that is uniform in colour, especially when predation risk is high
crab anti predator methods
place small and large juvenile crabs in aquarium with 2 types of tiles: white and shell hash
manipulate predation risk for 1/2 of crabs by adding water from tank with predatory fish
record proportion crabs on each tile
crab anti predator results
in comparison to large crabs, small crabs preferred shell hash regardless of treatment
large crabs preferred shell hash when risk was high
lizard anti predation research question
how does the presence of predators affect prey behaviour
lizard anti predator hypothesis
activity level of prey influences risk of being killed by a predator
lizard anti predation prediction
activity level of prey will be lower when predators present
lizard anti predation methods
whiptail lizards in experimental pens, add 2 predator lizards to half.
record behaviour of whiptails
lizard anti predation results
whiptails in predator present were less active
lizard anti predator conclusion
lizards reduce their activity level when predators are nearby
what is a reason a prey may take evasive action?
they may be too slow to flee from predator. some moths will just drop before being attacked
evasive action
a range of maneuvers or strategies employed by prey animals to escape or avoid capture when they are detected by a predator. these actions are part of prey’s defence mechanisms to increase chances of survival.
fleeing
running away from predator to create distance and reduce likelihood of capture.
some prey are adapted to swift, agile movements to escape
hiding
seeking cover or concealing themselves to make it difficult for predator to locate them.
find shelter, burrow into ground, blend into environment
camouflage
some prey have evolved to blend into surroundings, making it harder for predators to spot them.
includes colouration and patterns that match environment
deception
using tactics to confuse or distract the predator
false alarms, changes in direction, vocalization meant to startle or confuse
group defence
prey animals may band together in groups for safety. larger numbers make it more challenging for predators to single out and capture an individual
defensive weaponry
some prey species have evolved physical defences (horns, spines, etc) to deter predators. used to defend themselves when cornered.
mimicry
some prey mimic appearance or behaviour of other organisms that are unpalatable, toxic or dangerous to predators to deter them
freezing
prey will freeze in place, hoping that their lack of movement will make them less conspicuous
vigilance behaviour
scanning the environment for predators
elk research question
what affects vigilance levels of prey
elk hypothesis
animals will trade off feeding time for vigilance based on level of risk
elk prediction
vigilance will be higher and feeding time will be lower when predation risk is high
elk methods
quantified vigilance and feeding behaviour of elk living in areas with and without wolves
elk results
females with calves were more vigilant
males were least vigilant
squirrel research question
how often should animals carry food to safety for consumption
squirrel hypothesis
food carrying behaviour represents a trade off between feeding in safety and obtaining high energy intake
squirrel prediction
large items should be carried to safety more than small
as distance to safety increases, carrying behaviour should decline
squirrel methods
offered different sized food items at varying distances from trees
recorded proportion of items carried to safe cover
squirrel results
proportion of items carried increased with food size and decreased with distance to cover
squirrel conclusion
food carrying represents a behavioural trade off between predation risk and feeding efficiency
nocturnal or crepuscular activity
some species are primarily active during night (nocturnal) or during twilight (crepuscular) to avoid diurnal predators
vigilance and alertness
animals may remain vigilant and alert to detect predators early, allowing them to free or take defensive action
breeding synchronization
some species time their reproductive activities to coincide with periods of abundant resources, so they dont need to expose themselves to predation often
hiding and shelter use
animals seek refuge in burrows, nests or dens to avoid predation during vulnerable times, like when giving birth or molting
escape behaviour
rapid and agile escape behaviours, like flight or fleeing, help animals evade predators
warning calls or signals
many animals use alarm calls or signals to warn others in their group about the presence of a predator
social groups
live near individuals to reduce predation risk via dilution effect. probability of dying in a successful predator attack is reduced by presence of others
killifish research question
how does predation risk affect schooling behaviour in fish
killifish hypothesis
socialite reduces predation risk via dilution effect
killifish prediction
fish should prefer to associate with larger rather than smaller groups
killifish methods
high predation risk treatment: diluted killifish skin extract added to tank to simulate predation event
control:water added
recorded school size
killifish results
median school size in high predation risk treatment was max. (10)
medial school in control was 2.
killifish conclusion
killifish prefer to associate with other fish when predation risk is high, as predicted by the dilution effect
benefits of group living
group acquisition of food
access to mates
shelter
protection from predation
social thermoregulation
predation reduction:
improved vigilance for predators
cheating
not an ESS.
cheaters get kicked out
and it isn’t evolutionarily stable, as if it were, all animals would be cheaters
negates benefit of group living if theyre all cheating
cheetahs vigilance
individuals that are more vigilant due to alarm calls depart faster than non vigilant individuals
lion pride
adult males often related, called “coalitions” which control the territory and its associated lionesses
cooperative hunting in lions
individuals specialize their hunting strat, wings or centre
wings stalk prey, tend to be smaller
centre are larger, and tend to run in and jump the prey
optimal group size
the optimal number of individuals where benefits of group living are maxed, but the costs of group living are minimized
skew theory
models that consider the effect of group size on an individual’s reproductive success
considers potential costs and benefits of group living
Warkentin lab
studies tree frogs and connects them to social issues
tree frog transformation
they can go from a cell sac to a developed tadpole in 7 days
tree frog challenges in environment
eggs attach to vegetation overhanging ponds and swamps
tree frog ongoing threats
predation
dehydration
drowning
tree frog defence mechanism
can hatch early to escape threats
tree frog trade off
early hatching exposes them to dangers in water
what can trigger early hatching in tree frogs
predators
pathogens
oxygen availability
bad parenting
environmental cues- vibrations
warkentin tree frog study
how do eggs differentiate predation vibrations vs harmless vibrations?
recorded vibrations in wild to play to clutches in lab
found frog eggs picked up on vibrations over time: rain and wind batter the egg less and are constant, but snakes take a break to chew
selfish herd hypothesis
a predator is more likely to kill a member on the outside of the group
individuals can reduce predation risk by moving to middle
group size effect
vigilance behaviour of individuals declines as group increases
doves research questions
- do doves exhibit group size effect
- are doves on the edge exposed to higher predation risk?
doves hypotheses
- vigilance decreases as group size increases
- individuals can reduce predation risk by moving into middle
doves prediction
- individual scan rates will decline as flock size increases
- individuals at edge of flock will have higher vigilance levels than those at centre
doves methods
record group size
used focal animal sampling to record position, scan rate/duration and feeding time
doves results
as flock size increases, the scan rate declines and feeding rate increased.
mobbing research question
why do prey harass predators
mobbing hypothesis
harassment causes predators to move away from an area (the move on hypothesis)
mobbing prediction
after being harassed, predators move away from an area
mobbing methods
observed mobbing behaviour by birds
noted frequency of owl predation on bird species that mobbed and those that didnt
recorded response to mobbing
mobbing results
mobbing over time led to the owl leaving
pursuit deterrence
advertisement behaviour informs a predator it lost the element of surprise and pursuit will not be successful
alarm signal hypothesis
advertisement behaviour functions to warn nearby conspecifics
deer tail research question
why do deer exhibit tail flagging behaviour after seeing a predator
deer tail hypothesis
1: tail flagging deters predator pursuit
2: tail flagging warns conspecifics
deer tail prediction
1: tail flagging should occur more often as distance between predator and deer increases
2: solitary deer should exhibit less tail flagging than deer in social groups
deer tail methods
slowly stalked focal deer
record number of deer nearby
recoded tail flagging behaviour during stalk and distance to deer
deer tail results
no difference in tail flagging between solitary and social deer
tail flagging was more frequent as distance to deer increased
brown thornbill calling
mimics warning call of many birds to scare off predators. mimics by pretending bigger bird is near
