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Lecture 10

Lecture 10 (Chapter 11) - March 23 - PSYCH 2TT3

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McMaster University
Margaret Fahnestock

PSYCH 2TT3 2013 Lecture 10 Chapter 11: Antipredatory Behaviour Tradeoffs associated with Predation  Ethologists who study antipredator tactics focus on “tradeoffs” more than on any specific behaviour  Think of the value of fighting behaviour Predation  The central challenge for most animals – staying alive; want to grow to the age and size that they can reproduce  Eg/ video – turtles after hatching; large amount of predation risk  Small proportion of animals reach sexual maturity Antipredatory behaviour in humans  Few large predators – bears, mountain lions  Large animals – bison, elk  Poisonous spp – snakes, scorpions  Anti-car accident behaviour in humans o Avoidance in space – avoid car “habitat”; walk on sidewalks or left side of road o Avoidance in time – cross roads at green peds light o Visual inspection – watch both sides before and during crossing What Does Antipredator Behaviour in Animals Look Like?  Eg/ Squid – ejects ink that can distract predator enough that they cannot rely on split-second instinct; ink also serves as a chemical cue that alarms other squids in proximity  Graphs o Left – Pre-exposure to Predator o Right – After exposure to Predator  Eg/ Ground Squirrel – group upon, mob, bite harass, yell, shove dirt, throw sticks at snakes to alarm other squirrels; snakes tend to rely on being sneaky o Squirrels physiology is well adapted to fighting a snake; snakes have venom  Serum-to-venom binding levels (antidote to being bitten by snake) o Measure of immunological defense against snake bites o Rapid rise until 30 days of age o Corresponds to leaving their burrows  At 30 days of age, squirrels begin to emerge from next 1 PSYCH 2TT3 2013 Prey approaching their predators  Paradoxical behaviour has advantages  Eg/ Gazelle only approach lions and cheetahs, but never approach wild dogs and hyenas o Gazelle jumps up and down in front of cheetah as if to entice a chase o Cheetahs and lions rely on the element of surprise – short and fast chases  >60 km/hr for a limited time  Break element of surprise, break how they capture prey o Hyenas and dogs are “marathon runners” that work in groups  Flankers, draw prey into specific area o Gazelles on their own do not approach predators – only if in group will the approach predator o Dogs hunt in groups; element of surprise would not work  Split up and take positions around their prey  Dog has great stamina – run long distance  Costs o More conspicuous to predators o Increased risk of mortality o Graph – as group size increases, probability of approaching predator increases – dilution of risk in group  Cheetahs respond to inspection by moving away sooner and travel further during rest periods o Cheetahs element of surprise less probable with larger group of gazelles o Graph – distance walks away depending on gazelle group size 2 PSYCH 2TT3 2013 Balancing Feeding and Anti-Predatory Behaviour  Fat stores – vary with predation risk, food and patch choice (safety)  Eg/ birds; how much to forage vs. how much to watch out for predators  Eg/ African crown eagle; can kill prey over 4x own weight; preys on vervet monkeys -  Questions o Food and patch choice – should an animal prefer lesser quality food at a safer place? o Feed (head down) or scan for predators (head up)? o Keep feeding or flee? o Stay in a shelter or resume feeding? o What is the optimal amount of fat? Optimal Amount of Fat  Benefits – insurance, insulations  Can measure the cost based on mobility  Decreased mobility  increased predation risk  How long does it take them to get up in the air – angle of ascent (steepness of takeoff), speed and latency between poin
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