Slideshow 8 Flashcards
What is the Manly-Chesson index
measure selective feeding or resource preference by a consumer when multiple resource types are available. It accounts for changing resource availability, which makes it especially useful in experiments where resource abundance decreases due to consumption.
What is the Manly Chesson index formula
Alpha i= (di/Ni)/ksum (dj/Nj)
What does k represent in the Manly-Chesson Index
number of prey categories
What does di represent in the Manly-Chesson Index
is the proportion if prey of type i in the predators diet
What does Nirepresent in the Manly-Chesson Index
Ni is the proportion of the prey type i in the environment
What does alpha i = 1/k mean
No preference
What does alpha i > 1/k
Positive preference
What does alpha i < 1/k
Negative preference
What is the optimal foraging theory
What foraging decisions lead to the most efficient
energy capture
What is the formula for the optimal foraging theory
En/T = E/Th + Ts
What does E represent in the Optimal foraging theory
energy gained during feeding
period of length T
What does Ts represent in the Optimal foraging theory
search time
What does Th represent in the Optimal foraging theory
handling time
What does En/T represent in the Optimal foraging theory
net rate of energy gain
What are 2 predictions about the Optimal diet model
1) Foragers should prefer the
most profitable prey
2) An efficient forager should broaden its diet to include more low value prey as the abundance of high value prey decreases
How was should Foragers prefer the
most profitable prey represented
crab feeding on mussels graph,
shows optimal size of muscles to be middle of the pack in size.
How was An efficient forager should broaden its diet to include more low
value prey as the abundance of high value prey decreases
Great tits feeding on mealworms. and bluegill graph
What are 2 predictions about prey selection
1) The zero one rule: Prey are either always eaten when encountered
(Pi = 1) or they are never eaten when encountered (Pi = 0)
2) Inclusion of a prey type in a diet depends only on its own
profitability and that of higher profitability prey types.
i.e. it doesn’t depend on its own encounter rate
What are some limitations of the optimal diet theory
- Mobility of prey had a negative effect on the ability of ODT to
predict observed diets
- Prey handing time increases with the ratio of prey size to
predator size - Prey energy value is positively related to prey size
- Predators prefer the most energetically rewarding prey
yes
What percentage of predator-prey links in 4 real-world food webs
65%
What are 3 probabiliets of predation
encountered – attacked – consumed
What happens when the density of the prey decreases
predators diet should
broaden to include more prey types
What is an example of Consequences of selective predation
Periwinkle Littorina littorea
How is Periwinkle Littorina littorea food chance between habitats
- In tidal pools its preferred food is competitively dominant
- On emergent substratum its preferred food is inferior
What is a Consumptive effects
predator kills and eats prey
What is a Non-consumptive effects
non lethal effects
1. Habitat shifts
2. Life history evolution
3. Activity levels
4. Morphological changes
how are Paramecium aurelia affected in presences of Stenostomum
virginianum
wider and
swim slower in the
presence predator
what happends to Paramecium aurelia and Stenostomum
virginianum when undefended and defended
undefened, Stenostomum
virginianum lags behind its prey Paramecium aurelia
Defended , Paramecium aurelia thrives and Stenostomum
virginianum slowly increases
How does Temporary habitat shift affect population
No real impact on
population dynamics
How does Population consequences habitat shift affect population
Predation risk can change with body size
* Ontogenetic niche shift – changes in pattern of resource use as
an animal grows to maturity
What is an example of a habitat shift
- Small size-class bluegills are at high
risk of predation by large mouth
bass - The largest individuals are not
susceptible to predation - In the absence of bass habitat use was similar across size-classes
- In the presence of bass smaller-size classes were restricted to sub
optimal habitats
How can habitats shifts affect populations
Habitat with a lower predation rate may be less good quality
* ‘Safe’ areas may have higher competition for fewer resources
* Trade-off between reduced mortality and energy gains
How does Zooplankton experience habitat shift
Daylight - zooplankton
stay in deeper, colder
darker areas to avoid
visual predator
Night - zooplankton move
to the surface where
phytoplankton (prey) is
more abundant at a time
when predation risk is
lower
What type of effect is Vertical diel migration of zooplankton
Non-consumptive effect - reduction in birth rate due to time
spent in the colder, deeper parts of the lake
How can predation of Tadpoles effect life history
Metamorphose when fitness in larval
habitat drops below achievable fitness
in the terrestrial habitat
When does the optimal life history evolution switch happen
μ1/g1 > μ2/g2
where μ is size-specific mortality rate
and g is size-specific growth rate
What is Gilliams rule
Life history evolution rule
* Only applies to stable populations with
no time constraints
* Useful tool to understand behavioural decisions under predation
What is the example of Life history evolution in mayflies
- Adult mayflies are short lived (2 days ) and can’t feed
- Must maximise energy gain for reproduction in their larval phase before
metamorphosis - Trade-off between remaining a larva and maximising energy and avoiding
predation - Adults emerge earlier and at a smaller size if trout are present in the
stream
How was the mayfly experiment conducted
- Were changes in metamorphosis due to the presence of the trout or could
that be induced by chemical cues - Streams that were treated with tank water had earlier metamorphosis of
smaller adult mayflies compared to controls - 13% - 20% reduction in size and 24%-35% loss of fecundity
Non-consumptive effects on population growth
were larger than the effect of being consumed by
the predator
How does predation effect activity levels
- If you’re hiding you’re
generally not feeding and
gaining energy - Trade-off between growth rate
and predation - Species will differ in how to
prioritise and resolve these
issue
How was activity level of green frogs experiemnt created
- Green frog larvae prefer pools where the bullfrog is absent, but
will inhabit a full range of temporary to permanent pools - The presence of bluegill was experimentally manipulated
- A series of choice experiments using 3 known larva predators:
bluegill, dragonfly larva Anax junius, the salamander Ambystoma
tigrinum - Bullfrogs survived in the presence of bluegill, but did not survive
when it was absent - Green frogs survived both , but did better when bluegills were
absen - Bullfrog have higher activity levels result in higher predation risk
- Bluegills predate both dragonfly larva and salamanders and
reduce this predation risk - Bluegills also predate green frog larvae which reduces
competition with bullfrog - Bulldogs are limited to bluegill pools as they trade-off lower
predation risk for a faster growth rate - Neither bullfrog or green frog are able to dominate the
environmental gradient due to these trade-offs
How does predation effect morphological traits
Changes traits to allow for better survival
how was Morphological changes in carp changed by predation
- In the absence of predator it is narrow bodied and
lives in dense populations - In presence of predators (pike) there are fewer
individuals and have a deep body
How do carp reeduced
their predation risk
changing body shape
What is the tradeoff of carp changing body size for predation
Deep bodied fish expended
30% more energy when
swimming
