Topic 19 -Predation Flashcards
Fitness depends on an individuals ability to grow, survive and reproduce it requires…
suitable environmental conditions (abiotic factors)
sufficient resources to acquire appropriate quantities of energy and acquire energy efficiently (gain>loss)
Predation
an individual of one species (predator) consumes all or part of a living individual of another species (prey)
Predation does not include
but includes
scavengers or decomposers
blood feeders
What are the 3 predation categories
Herbivory
Carnivory
Parasitism
herbivory
prey is plant or algae
carnivory
prey is an animal, predator is typically also an animal
parasitism
for those parasites that feed on host tissues
Specialist
an individual takes one or a few prey items
Generalist
an individual takes many prey items
preference
proportion of a prey type in the diet is higher than in the environment
what does preference depend on
Energy content of prey
Nutritional content of prey (vitamins and minerals)
switching of preference depends on
the abundance of different prey types
“Prey switching”
may not occur right away if….
switching to increased consumption rates of a more abundant prey type
may not occur right away if predator still operates on search image of the prey type that used to be abundant
Profitability
net energy gained after energy is spent capturing and consuming the prey
Search time
search efficiency for prey
Handling time
time to pursue, subdue and ingest prey
Increased search and handling time both operate to
reduce consumption rate of predators
Increased size of prey population decreases
search time and in some cases can decrease handling time
Passive and filter feeders functionally have a handling time of
zero (spider web)
in general consumption rates and prey population size have a
linear relationship until saturation
at very low population sizes consumption rates will decrease disproportionately which means
need to learn new capture strategies
prey switching has not occurred yet
Refuges exist -hiding spots for prey
what is the goal of Optimal foraging theory
What is it based on
What does it offer
predict the optimal foraging strategy under certain conditions
based on mathematical models derived from economics
offers a powerful way to understand foraging decisions of predators
Assumptions for optimal foraging theory
foraging behaviour enhances fitness (i.e. foraging strategy= a behavioural trait favours by natural selection in the past)
animals maximize net energy gain ensures high fitness
predators must expend energy to obtain prey
energy loss:
energy gain:
searching and handling time
consumption
