Topic 5 Flashcards
Evolution and Behaviour
Environment & genetics can both influence behaviour
relationships between organisms and between organisms, and their environment are mediated by behaviour.
Foraging theory
How organisms make decisions on foraging.
Influenced by natural selection
OFT:
Behaviour of optimally, foraging individuals in patchy environments.
QUANTIFY HOW AND WHY THE FORGE THE WAY THEY DO.
NATURAL SELECTION SHOULD FAVOURITE INDIVIDUALS THAT ARE MORE EFFECTIVE AT ACQUIRING LIMITED RESOURCES .
What kind of trade offs are they making? Ex; foraging and predators.
If Doing it in the best way you should see natural selection act on that behavior, and see it be passed down from generation to generation
OFT: deer example
What might influence this Deers forging behavior?
Lives in patchy environment, organisms have access to limited resources —> influences there, fitness.
Deer would, act different in zoos, compared to in the wild. Might not look up as much.
What kind of trade-off might face?
Eating shrubs and stopping to look around and move years around to look for predators. Fair amount of time with their head up. This is a trade off of eating s being alert.
OFT: owl example
What might influence this owls, foraging behavior?
What kind of trade-offs might it face?
How much time and energy is needed? And what type of prey is available.
Optimal forging theory: diet composition
Prey attributes that may affect predator energy intake rates
• Abundance of prey: # prey encountered per unit time, Ne
• Search cost: time & energy spent searching for prey, Cs
• Handling time: time spent processing prey, H
• Energy in each prey, Ex
E / T = Ne1E1-C1 / 1 + Ne1H1
E / T is the energy (per unit time) a predator requires by forging on a specific pray item.
Ne1E1-C1 is the Energy gained - energy consumed
1 + Ne1H1 is the time spent
Foraging Behaviour for Mustelids Hunting
Abundance of prey was high
Catching the rabbit, has to be worth it.
The size type abundance of prey hasta be worth it.
Explains why there may be preference in prey.
Which prey species should a predator choose?
Not a lot of energy gained from prey, easy to catch, not a lot of time to consume.
E / T = Ne1E1-C1 / 1 + Ne1H1
> or <
Gain more energy from prey, more energy to catch, takes more time to eat.
E / T = Ne1E1-C1 / 1 + Ne1H1
Energy intake for prey one species
E / T = Ne1E1-Cs / 1 + Ne1H1
Energy intake for 2 prey species.
E / T = (Ne1E1-Cs) + (Ne2E2-Cs) / 1 + Ne1H1 + Ne2H2
Should’ve predator forage on just one prey species, or include more than one species is a diet?
Should the species, be a specialist or a generalist?
Prediction: predator will prey exclusively on one species if:
E / T = Ne1E1-Cs / 1 + Ne1H1 > E / T = (Ne1E1-Cs) + (Ne2E2-Cs) / 1 + Ne1H1 + Ne2H2
Prediction: predator will add second prey species if:
E / T = Ne1E1-Cs / 1 + Ne1H1 < E / T = (Ne1E1-Cs) + (Ne2E2-Cs) / 1 + Ne1H1 + Ne2H2
Wolf hunting different pray
Tundra wolf
Caribou, huge herd animals never stops travelling
Environment is tundra
Wolves will die if they don’t find Caribou.
- Panicked heard and pick out the week, young and old out from the herd. Then the single one of them.
Ne1 low abundance, in terms of energy to find the Caribou.
E1
Can lots of energy looking and catching.
H1 may not need to handle as long
More “specialist “
Sea wolves
- Live in families live in coastal environments there a good swimmers and they find food from the sea. Unique hunting grounds when the tide is low and they used to eat many smaller animals, though they do look for bigger when they can. More generalist species
Optimal Foraging in Bluegill Sunfish
Available prey:
- The most abundant pray in the environment or approximately 1 mm long.
Optimal diet:
- Optimal foraging theory predicts that to maximize rate of energy intake, blue gill should feed on prey 4mm or longer.
Observed diet:
- As predicted the most abundant pray in blue gill diets are 4 mm in length.
Optimal Foraging By Plants
They have different decisions to make because they can’t move.
Ratio between shoots and leaves to roots
Shoots and leaves - acquire light to produce sugars
Roots - acquire minerals and water.
Environment, impact growth in order to get enough materials for survival.
Light limiting environments:
- Invest in shoots and leaves because not a lot of light and should maximize amount of light received.
Water limiting environments:
- Invest in roots, because want to maximize the amount of water absorption.
Fitness, Inclusive Fitness, Kin selection, Altruism
• fitness: contribution individuals make to future generations
• Inclusive fitness: fitness determined by individual survival & reproduction plus the survival & reproduction of its relatives.
• Kin selection: evolutionary strategy that favours reproductive success of an organism’s relatives (even at a cost).
— trade-off, less foraging time behaviour is a strategy that increases survival of all relatives.
• Altruism: an act that benefits the recipient but harms the donor.
Altruism and Inclusive Fitness
Altruistic behaviour expected if:
Inclusive fitness gains > inclusive fitness costs
Coefficient of relationship: relatedness of 2 individuals
0.50 parent-offspring
0.50 full siblings (0.25 half-siblings)
0.25 grandparent-grandchildren
0.125 first cousins
“I would jump into a river to save two brothers, but not one. Or to say eight cousins, but not seven.” — J.B.S Haldane
How much you’re gaining for sacrificing yourself.
Brothers are each 50% of your own genes. Saving two brothers is like saving your self. 100% vs 50% 50%
But only saving one brother is 50% 100% versus 50%
Altruism and Inclusive Fitness With squirrels
With squirrels
- Knew the parent died and would take some kids that werent theirs.
- Found out that it was her relatives either a sister or a mom that died.
- So they would adopt relatives.
- A large litter = larger cost
— so they wouldn’t take all of the children, but they would take some. - They would take the amount of relatives that would actually give them a Gain in Fitness, so they would balance the cost and benefits.
