antipredator strategies and warning coloration

lecture exam 2

Predator Escape

Detection and Avoidance

– Vigilance (e.g. lots of lizards)

– Burrow or refuge escape

– Immobility – run and stop

– Active at times when predators are inactive

Detection and Avoidance: Coloration

Crypsis: background matching (camouflage)

• Many herps brown, gray, rusty, green, etc…

• Blotches and lines may help

• Lack of movement, flattening also helps

Startle reactions / flash coloration

• Inguinal color patches of hylids

• Movement of a banded animal (blurs unicolor in motion;

converts to bands when stopped

Predator Escape: Coloration

– Misdirection of attack site (Tadpole tails, Blue skink tails, Juvenile Agkistrodon tails)

– Disruptive coloration

– Aposematic coloration (Salamandridae, Dendrobatidae, Unken response, Coral snakes)

Physical deterrence

• Biting and striking (Lizards and snakes, Sirens)

• Skin modifications (spines, horns, Turtle shells, Crocodilian “armor”, Spiky tails)

• Death feigning

• Blood squirting in Phrynosoma

Tail Autotomy

Lizards, Salamanders, some snakes

often brightly colored tails that twitch

fracture planes

tail can regenerate

Skin may “autotomize” in some species

Chemical Defense

• Poison glands of amphibians (Paratoid glands in toads, tail in some plethodontids, Newt toxins)

• Snake venoms

• Kinosternidae: stink!

• Snake musk from cloacal scent glands

Batesian Mimicry

palatable species (mimic) evolves to resemble unpalatable/dangerous species (model)

Elapidae mimicry

example of batesian mimicry

Best example of a coral-snake mimic is harmless milk snake

milk snakes outside of coral snake range are not brightly colored

Mullerian mimicry

unpalatable/dangerous species evolves to resemble another unpalatable species

predator-prey coevolutionary arms race

Western Newts (Taricha) have been used in classic study of co-evolution of predator and prey and of “geographic mosaic theory of coevolution”

• Geographic mosaic theory: Basic Idea 

  • Strength of co-evolution varies geographically; such that there are “hotspots” and “coldspots” 

• Rough skinned newt (Taricha) 

  • Has deadly venom called tetrodotoxin (TTX) in some populations 

  • One adult newt can drop 25,000 white mice 

• Garter snake 

  • Only predator species that eats newt, found through US 

  • Resistance to TTX in some populations where sympatric with newts 

  • Snakes that eat newts cannot move for 30 minutes to 7 hours (have to “detox”) 

• Co-evolution of newts and snakes 

  • Study by Brodies tested garter snake resistance in 40 populations

  • Found resistance is high where newt is present and toxic 

  • Resistance is low where newt is absent or non-toxic (British Columbia) 

  • Some obvious coldspots also

• Geographic mosaic theory

Strength of co-evolution varies geographically; such that there are “hotspots” and “coldspots” 

ex. Rough skinned newt and garter snakes