ENWC424 Lecture Notes - Lecture 18: Fossorial, Alger Hiss, Natural Selection
2 May 2018
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ENWC Lecture 18 Defense
• Vulnerability to Predation
o Eggs most vulnerable
▪ Natural selection favors fast development or well concealed nests
o Depends on size of herp and size and type of predator
▪ Vulnerability decreases with increased size
o Foraging and reproduction expose herps to predators
▪ mode of foraging
▪ habitat used
▪ time of day
o Defense against predation
▪ Feeding strategies and defense related
▪ Specialized adaptations
▪ Selection stronger on prey for enhanced defense capabilities
• Defensive Mechanisms
o Passive Defense
▪ Location and timing of activity
▪ Crypsis
o Active Defense
▪ Sprinting away, posturing, struggling, hissing, screaming, biting, urinating,
defecating, musking
▪ Mechanism employed depends on
• Age/size
• Physiological state
o E.g., body temperature, reproductive status, energy level
o Type of predator
o Distance from retreats
• Employed in hierarchical manner
o Avoiding detection
o Avoiding attack or capture
o Preventing consumption
• Avoiding Detection
o Location and timing of activity
▪ Forage in concealed areas or areas predators cant access
• e.g. fossorial species
• e.g. anoles become more arboreal in areas with ground predators
▪ Nocturnal activity
• e.g. most amphibians
o Crypsis
▪ Coloration and morphology
• Disruptive patterns or structures
• Countershading
• Hiding the eyes
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