8/19/2013. Who eats herps? Topic 20: Predators. Who eats herps? Who eats herps? Who eats herps? Who eats herps?

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1 Topic 20: Predators Variation in predators across taxa Variation in predators through ontogeny How do herps avoid being eaten? Introduction to the diversity of anti-predator defenses 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; bitter.com; wikipedia; Pough et al. 2004, Fig are also important Frog-eating bat Honey badger _ cobra specialists Rodents Invertebrates Size is particularly important Anolis are small and abundant Many small frogs are also vulnerable Photos: C & K Begg; P Koch; Pough et al. 2004, Fig Photos: R Keegan; Pough et al. 2004, Fig Other herps Some are generalist predators Some are specialists _ Lialis _ Heterodon 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 Photos: N Kley; J McDonald; Pough et al. 2004, Fig Pough et al. 2004, Fig 15-15, P Richardson,?? 1

2 Predation changes through ontogeny are important Different life cycle stages have different predators Agalychnis callidryas oviposit on leaves overhanging water Each life cycle stage has a different suite of predators Eggs Tadpoles Metamorphs Adult 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 Photos: K Warkentin; P Weish Agalychnis callidryas oviposit on leaves overhanging water Eggs can in response to vibrations from predator Will hatch prematurely rken/kwvideo.html Wasps target More likely to hatch prematurely and escape Easier to open and carry off tadpole Egg predators Snakes Wasps Ants 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 Photos: K Warkentin Photos: K Warkentin Tadpoles can also metamorphose prematurely when predators are abundant Metamorph predators Water bugs Spiders Adult Agalychnis callidryas are terrestrial and mobile Adult predators Bats Snakes Tarantulas Etc. Again, decreased performance if: Photos: K Warkentin Photos: K Warkentin; Furrer; Pough et al Fig

3 How do herps avoid being eaten? What kinds of antipredator defenses do you know of? Photos: PJB 1

4 8/19/2013 Crypsis can also occur while Easiest way to deal with predators is not to bump into them Moving Stationary Nerodia sipedon on different backgrounds A form of avoidance Camouflage Includes many adaptations Color Pattern Mimic environment Eliminating or enhancing shadows Photos: Pough et al. 2004, Fig Photos: T Hakonsen; M Fogden; Pough et al. 2004, Fig Chuckwalla in crevices Adaptations against being pulled out Spines Can be weapons Can show that something is inedible Jumping from danger All-out running away Running for a hiding spot Photos: CJ Hamilton, PJB Photos: PJB,?? Signaling inedibility Signalling inedibility Frills Crests Inflating Opening mouth Flattening out May be repellent to Canids All of these signal some sort of distaste _ Hissing Barking Photos: PJB; T Gamble; ER Pianka; wikipedia; Pough et al. 2004, Fig Photos: PJB; J LeClere; Pough et al. 2004, Fig

5 Signaling inedibility Warns of toxicity Sometimes associated with behavior to show and hide the warning Unken reflex Mimicry Mullerian Mimic Pseudotriton ruber 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 Model: Eft of Notophthalmus viridescens Photos: G Nafis; DH Cummins; BP O Connor; Pough et al. 2004, Fig Batesian Mimic Plethodon cinereus Photos: P Coin; L Brook; M Tegges Mimicry Many Micrurus* are sympatric or parapatric Are mimics ** * * * * ** Mimicry Does it work? Brodie (1993) used a clay model approach Pliocercus* are opisthoglyphs Far less toxic mimics of Micrurus *** ** Brown snake models were attacked much more despite being more camouflaged Tested many different Micrurus patterns Pough et al. 2004, Fig Photos: Pough et al. 2004, Fig 15-20, Force Armor Spines Teeth _ Claws _ Tail _ Some have evolved for defense Mechanical Shrike predation on Phrynosoma mcallii Lizards with relatively longer horns suffer less predation Higher expected survival with longer horns Others evolved for other purposes Photos: PJB, M O Shea Young et al

6 8/19/2013 Implications of mechanical defenses Bergmann et al on Phrynosomatinae Losos et al on Cordylidae Toxins Amphibia Species with longer spines Are more terrestrial Run shorter distances Viperidae Elapidae Both are often associated with behaviors Squirting poison Rattling to warn Various postures Losos et al. 2002; Pough et al. 2004, Fig 4-27 Photos: Getty Images; Australian Government Autotomy Autotomy dropping of a body part to escape from a predator There are costs to autotomy Can be spontaneous Can occur when grasped Limbs (rare) Tails Lizards Salamanders Loss of fat stores Change in sprint speed There is also considerable variation in how readily different species autotomize Tails All of these are after autotomy Photos: M Thompson; AB Sheldon; Wikipedia Photos: K Bergmann, PJB 3