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aviodingpredators05

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Published on December 30, 2007

Author: avsar

Source: authorstream.com

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Escape & Defense:  Escape & Defense Interactions with predators Predation Survivorship Against the odds Body size Escaping predation Avoidance Escaping Detection Identification to be left alone Escaping approach Escaping capture Chemical defense Death feigning Tail displays & autotomy Schooling I. Interactions with Predators:  I. Interactions with Predators A. Predation:  A. Predation Various types of predators, selective pressure: predation in response, many prey have developed strategies to avoid being eaten or to be able to escape once captured Predator-prey relationships, ever evolving -back and forth battle between the two Amphibians & reptiles are important components of the diets of many kinds of predators, thus they have a profound regulatory effects on populations of these prey species B. survivorship:  hypothetical survivorship curves – Type III, large portion of the population is lost in the juvenile stages (characteristic of most amphibians and reptiles). Intense predation of young causes a major decrease in the number of individuals in a cohort through time – therefore the majority do not reach sexual maturity. B. survivorship 1) Against the odds – herps have many predators:  1) Against the odds – herps have many predators Fungus & Bacteria (amphibian eggs) Predation on amphibian & reptile eggs: (amphibians) Insects, spiders, leeches, fish, other herps (reptiles) Mammals, birds & ants Juvenile prey Larvae prey of fishes, turtles, wading birds, small mammals, insects, spiders, centipedes, other amphibians Reptiles prey of all vertebrate groups Adult amphibians Fish, turtles, crocodilians, snakes, birds & mammals Some anurans feed on other frogs (i.e. Rana catesbeiana) 2) Adults – Body size = immunity:  2) Adults – Body size = immunity Crocodile Komodo dragon Anaconda Tortoise II. Escaping Predation:  II. Escaping Predation Requires: interference with a predator’s ability to detect or identify an individual as prey, or the successful escape of a potential prey once detected A. Predator Avoidance:  A. Predator Avoidance Escaping Detection Limiting activity Crypsis Identification to be left alone Aposmatic coloration Mimicry Escaping approach Escaping capture 1) Escaping Detection:  1) Escaping Detection Interfering w/a predator’s ability to use cues Not being present when a predator might be searching for prey Limiting activity to time periods when predators are unlikely to be active Crypsis & Catalepsis:  Crypsis & Catalepsis Camoflauge & immobility – allow for the organism to blend in with the environment Slide11:  Crotalus lepidus, grey near Boquillas which has limestone outcroppings in microhabitat, more orange in Big Bend w/sandstone substrate. Disruptive coloration:  Disruptive coloration Visual search image of a predator can be confused by color patterns that don’t conform to the outline of the prey. 2) Identification to be left alone:  2) Identification to be left alone Aposmatic Coloration Bright coloration associated with life-threatening defense mechanisms (toxins) Chinese fire-bellied toad Slide14:  Mimics take advantage of an aposematically colored species: Batesian mimicry = nontoxic species mimics toxic species Mullerian mimicry = one or more toxic species resemble each other (each is both the model & mimic) Slide15:  BATESIAN MIMICRY harmless mimic of venomous model Slide16:  MULLERIAN MIMICRY mildly venomous mimic of a venomous model © Salamanders of Kentucky Pseudotriton montanus diastictus - Midland Mud Salamander Notophthalmus viridescens - Red Spotted Newt - eft Salamandridae Plethodontidae Slide17:  M. fulvius M. limbatus M. diastema M. mipartitus M. diastema, M. elegans M. diastema Pliocercus (right of each pair, middle of “E”) mimics the species or morph with which it is sympatric, at “E” it has elements of both models Pliocercus euryzonus (Central America) & P. wilmarai (Mexico) (rear-fanged colubrid) mimic Micrurus (Elapidae) Pough et al. 2001. Herpetology. Prentice Hall, Upper Saddle River, NJ Mimicry – an evolutionary force 3) Escaping approach:  3) Escaping approach Locomotion away from predator high tail it outta there when predator moves within a critical distance or makes a dash for the prey use crevices or burrow when predators approach (snakes/lizards) jump away into water (frogs) Chuckwalla lizard 4) Escaping capture:  4) Escaping capture Skin, armor, spines Slide20:  BLUFFING Slide21:  UNPALATABILITY Slide22:  Chemical defense Amhibians: Granular glands & Parotid glands Biogenic amines Peptides Bufodienolides alkaloids Fire salamander Marbled treefrog Slide23:  Phyllobates terribilis Batrachotoxin: A .00001 gram dose is enough to kill an adult human. Effect the permeability of selective ions, resulting in depolarization of the nerves and muscles, arrhythmias, ventricular fibrillation, and possible cardiac arrest. Slide24:  Reptile chemical defense Musk glands Blood squirting Musk turtle Diplodactylus spinigerus Slide25:  Death feigning Plains western hognose snake Slide26:  D. Tail displays & autotomy Slide28:  large school is perceived by some predators as something other than many individual tadpoles, and is thus avoided E. SCHOOLING

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