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Topic 20: Predators

� Who eats herps?

� Variation in predators across taxa

� Variation in predators through ontogeny

� How do herps avoid being eaten?

� Introduction to the diversity of anti-predator defenses

Who eats herps?

� Many animals

� Depends on the prey’s _______ and ________

� Birds are a major predator

� _________ – especially lizards

� Secretary birds – snake specialists

� __________ –amphibians, snakes

� Road runners -Squamates

Photos: J Dickson; www.sweetand bitter.com; wikipedia; Pough et al. 2004, Fig 15-14

Who eats herps?

� ________ are also important

� Frog-eating bat

� Honey badger

� ______________ – cobra specialists

� Rodents

Photos: C & K Begg; P Koch; Pough et al. 2004, Fig 15-14

Who eats herps?

� Invertebrates

� ____________

� ____________

� Size is particularly important

� Anolis are small

and abundant

� Many small frogs

are also vulnerable

Photos: R Keegan; Pough et al. 2004, Fig 15-14

Who eats herps?

� Other herps

� Some are generalist predators

� Some are specialists

� ______________

� Lialis

� ______________

� Heterodon

Photos: N Kley; J McDonald; Pough et al. 2004, Fig 15-14

Who eats herps?

� Predation pressure changes through ______________

� Turtles� Change size over

orders of magnitude� Shell rigidifies with age� Influence on survivorship

� High predation, broad range of predators

� Low predation, few predators

� Crocodylia� Similar pattern

Pough et al. 2004, Fig 15-15, P Richardson, ??

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Who eats herps?

� Predation changes through ontogeny

� ________________ are important

� Predators may select prey with a certain _____________

� Metamorphosing frogs may be poor at swimming and jumping…

� Thamnophis predation on Pseudacris regila �

G Nafis; Pough et al. 2004, Fig 15-16

Who eats herps?

� Different life cycle stages have different predators

� Agalychnis callidryas oviposit on leaves overhanging water

� Each life cycle stage has a different suite of predators

Photos: K Warkentin; P Weish

� Eggs � Tadpoles � Adult� Metamorphs

Who eats herps?

� Agalychnis callidryas oviposit on leaves overhanging water

Photos: K Warkentin

� Egg predators

� Snakes

� Wasps

� Ants

� Eggs can ___________ in response to vibrations from predator

� Will hatch prematurely

� http://people.bu.edu/kwarken/KWvideo.html

� Wasps target _______

� More likely to hatch prematurely and escape

� Easier to open and carry off tadpole

Who eats herps?

Photos: K Warkentin

� Tadpole predators

� Fishes

� Water striders

� Fresh water shrimp

� Early-hatched tadpoles are ____________ premature

� Can hatch after 4 days of development

� Fully developed at 7 days

� Premature tadpoles are poorer swimmers

� More difficult to escape predators

Who eats herps?

� Tadpoles can also metamorphose prematurely when predators are abundant

Photos: K Warkentin

� Metamorph predators

� Water bugs

� Spiders

� Again, decreased performance if:

� _________________

� _________________

Who eats herps?

� Adult Agalychnis callidryas are terrestrial and mobile

Photos: K Warkentin; Furrer; Pough et al. 2004 Fig 15-14

� Adult predators

� Bats

� Snakes

� Tarantulas

� Etc.

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How do herps avoid

being eaten?

� What kinds of anti-predator defenses do

you know of?

Photos: PJB

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Defenses

� _____________

� Easiest way to deal with predators is not to bump into them

� _______________

� A form of avoidance

� Camouflage

� Includes many adaptations

� Color

� Pattern

� Mimic environment

� Eliminating or enhancing shadows

Photos: T Hakonsen; M Fogden; Pough et al. 2004, Fig 15-18

Defenses

� Crypsis can also occur while ____________

Photos: Pough et al. 2004, Fig 15-14

Moving Stationary

Nerodia sipedon on

different backgrounds

Defenses

� _______________

� _____________

� Chuckwalla in crevices

� Adaptations against being pulled out

� _____________

� Jumping from danger

� All-out running away

� Running for a hiding spot

Photos: CJ Hamilton, PJB

Defenses

� ___________________

� Spines

� Can be weapons

� Can show that

something is inedible

Photos: PJB, ??

Defenses

� Signaling inedibility

� _________________

� ________________

� Frills

� Crests

� Inflating

� Opening mouth

� Flattening out

� ______________

� Hissing

� Barking

Photos: PJB; T Gamble; ER Pianka; wikipedia; Pough et al. 2004, Fig 15-24

Defenses

� Signalling inedibility

� ________________

� May be repellent to Canids

� ________________

� ________________

� All of these signal some sort of distaste

Photos: PJB; J LeClere; Pough et al. 2004, Fig 15-17

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Defenses

� Signaling inedibility

� ___________________

� Warns of toxicity

� Sometimes associated with behavior to show and hide the warning

� Unken reflex

Photos: G Nafis; DH Cummins; BP O’Connor; Pough et al. 2004, Fig 15-22

Defenses

� Mimicry� Looking like a venomous

species to signal inedibility

� _______________ mimicry� A harmless species mimics

a noxious one

� Predators should avoid both

� _______________ mimicry� Same coloration in a

number of noxious species

� Greater density of noxious individuals more effectively educates the predators

Photos: P Coin; L Brook; M Tegges

Model: Eft of Notophthalmus viridescens

Batesian Mimic

Plethodon cinereus

Mullerian Mimic Pseudotriton ruber

Defenses

� Mimicry

� Many Micrurus* are sympatric or parapatric

� Are _______________ mimics

� Pliocercus* are opisthoglyphs

� Far less toxic

� _____________ mimics of Micrurus

Pough et al. 2004, Fig 15-19

* *

*

*

* *

*

* *

*

*

*

*

Defenses

� Mimicry

� Does it work?

� Brodie (1993) used a clay model approach

� Brown snake models were attacked much more despite being more camouflaged

� Tested many different Micruruspatterns

Photos: Pough et al. 2004, Fig 15-20, 15-21

Defenses

� Force

� ___________________

� Armor

� Spines

� Teeth

� Claws

� Tail

� Some have evolved for defense

� Others evolved for other purposes

Photos: PJB, M O’Shea

� ______________

� ______________

� ______________

Mechanical Defenses

� Shrike predation on Phrynosoma mcallii

� Lizards with relatively longer horns suffer less predation

� Higher expected survival with longer horns

Young et al. 2004

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Defenses

� Implications of mechanical defenses

� Bergmann et al. 2009 on Phrynosomatinae

� Losos et al. 2002 on Cordylidae� Species with longer spines

� ___________________

� Are more terrestrial

� ___________________

� Run shorter distances

Losos et al. 2002; Pough et al. 2004, Fig 4-27

Defenses

� Toxins

� ______________________

� Amphibia

� ______________________

� Viperidae

� Elapidae

� Both are often associated with behaviors

� Squirting poison

� Rattling to warn

� Various postures

Photos: Getty Images; Australian Government

Autotomy

� ____________ dropping of a body part to escape from a predator

� Can be spontaneous

� Can occur when grasped

� Salamanders

� Limbs (rare)

� Tails

� Lizards

� Tails

� All of these are ___________ after autotomy

Photos: M Thompson; AB Sheldon; Wikipedia

Autotomy

� There are costs to autotomy

� _____________________

� Loss of fat stores

� _____________________

� Change in sprint speed

� There is also considerable variation in how readily different species autotomize

Photos: K Bergmann, PJB