BIOL1003 Lecture Notes - Lecture 21: Siberian Jay, Natural Selection, Amplexus
Example: Siberian Jay
• Builds well hidden nests in the winter
• Flying to the nest will give away location to predators
• Optimum time: when predators are not looking for prey
Experiment 1:When predators are in the environment:
• Predict: more jay feeding early in the morning (less predators in the morning)
Experiment 2: To prove predators where the influence: when predators aren’t in the
environment
• Predict: even pattern throughout the day
Experiment 3: broadcast calls of ravens in the afternoon
• Predict: more feeding in the morning
When inserting behavior traits some flexibility may be offered: the rule may be inherited
i.e. don’t fly to nest when there are predators, rather than the time of day
The Jay’s dilemma
Safe, but starve - grow well but get eaten
• Prediction: happy medium
Example: prey selection in crabs
• Should choose size that results in greatest rate of energy —> feed for shorter period of
time —> less risk of predation (also short period between tides)
• Profitability= energy/time
◦ Small mussel= little energy
◦ Big mussel= lots of time
Experiment 1: using calorimeters (finding maximum profitability)
• Happy medium —> weighted towards smaller mussels
Experiment 2: smog’s board of mussels
• Happy medium —> weighted towards smaller mussels
Example: Mating time in dungflies
• Longer mating —> more eggs fertilised
• Optimal mating time: mate briefly with each female: manu females, but few
eggs fertilised per female
• Mate a long time with each female: all eggs fertilised, but few females, maximise: total
eggs fertilised/total time (guarding + searching + copulation)
• Measured rate of fertilisation during copulation
• 10 minutes-50%
• 90 minutes- 100%
• Predicted: 41 minutes
• Observed: 36 minutes
Do animals really make decisions?
Natural selection for behaviors that increase survival or reproduction
If genetic variation in mating, males with the ‘best’ mating time will sire more off spring
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Document Summary
Example: siberian jay: builds well hidden nests in the winter, flying to the nest will give away location to predators, optimum time: when predators are not looking for prey. Experiment 1:when predators are in the environment: predict: more jay feeding early in the morning (less predators in the morning) Experiment 2: to prove predators where the influence: when predators aren"t in the environment: predict: even pattern throughout the day. Experiment 3: broadcast calls of ravens in the afternoon: predict: more feeding in the morning. When inserting behavior traits some flexibility may be offered: the rule may be inherited i. e. don"t fly to nest when there are predators, rather than the time of day. Safe, but starve - grow well but get eaten: prediction: happy medium. Example: prey selection in crabs: should choose size that results in greatest rate of energy > feed for shorter period of time > less risk of predation (also short period between tides, profitability= energy/time.
