F&W ECOL 306 - Reptiles

Notes and flash cards on the ecology, life history, and characteristics of Wisconsin reptiles and reptile orders of the world.

Reptilia

Class of Reptiles

• ~11,940 Known Species Worldwide

• 36 Species in Wisconsin

Reptile Characteristics

• Epidermal Scales of Keratin

• Amniotic Eggs with Leathery or Calcified Shells

  • Non-Reliant on Water for Reproduction

• Non-Aquatic Larvae

• Internal Fertilization

• Toes with Claws (Except in Legless Members)

• Exothermic

• 3-Chambered Heart in Most Orders

Reptile Skulls

• Single Inner Ear Bone

  • The Stapes

• Several Lower Jaw Bones

• Single Occipital Condyle

Amniote Skulls

• Anapsid: Solid Skull with No Opening, Turtles

• Synapsid: One Opening in Skull, Mammals

• Diapsid: Two Openings in Skull, All Reptiles & Birds minus Turtles

Anapsid Skull

Solid Skull with No Opening

• Turtles

Synapsid Skull

One Opening in Skull

• Mammals

Diapsid Skull

Two Openings in Skull

• All Reptiles except Turtles

• Birds

Advantages of Exothermy

• Lower Energy Demands

• More Efficient

• Better Adapted to Environments with Sparse Food

• Can Survive in Larger Range of Temperatures

Disadvantages of Exothermy

• Activity Limited to Warmer Seasons & Times of Day

• Cannot Sustain Long Activity

• Absent from Colder Environments

Thermoregulation

• Basking

• Move Between Sun & Shade

• Postural Adjustments

• Activity Temperature: ~30 to 37 ^oC, Body Temperature required for Locomotion, Foraging, Etc.

• Majority of Wisconsin Reptiles Limited to Southwestern Corner

  • The Driftless Area

Functions of Reptile Skin

• Defense

• Concealment

• Mate Attraction

• Locomotion

Epidermal Layer

Layer of Reptile Skin made of Keratinous Scales

Dermal Layer

• Connective Tissue

• Blood Vessels

• Nerves

• Pigment Cells

Skin Glands of Reptiles

• Relatively Few Compared to Other Classes

• Musk/Scent Glands in Some Turtles, Snakes, & Crocodilians

  • Defense or Sexual Recognition

• Salt Glands for Osmotic Regulation

Reptile Scales

• Composed of Keratin

• Arise from Folds in Epidermis

• Thin & Overlapping in Lizards & Snakes

• Large Scutes Underlain by Bony Osteoderms in Turtles & Crocodilians

Bones & Skeletons of Reptiles

• Wide Variation in Number of Vertebrate & Degree if Rigidity

• Scleral ossicles around eyes in some groups support eye & assist in focusing.

• Absence of bony epiphyses in crocodiles & giant tortoises allow growth throughout life.

Teeth & Dentition of Reptiles

• Several Bones on Each Side of Lower Jaw

• Thecodont: Rest in Sockets

• Acrodont: Attach Directly to Bone Surface

• Pleurodont: Arise from Groove in Maxilla/Dentary

• Lifelong Continuous Tooth Replacement

• No Teeth in Turtles

Thecodont

Teeth Resting in Sockets

Acrodont

Teeth Attached Directly to Bone Surface

Pleurodont

Teeth Arising from Groove in Maxilla/Dentary

Reptile Senses

• Good Color Vision in Most Species

• Similar hearing to mammals, but no pinnae & only single inner ear bone.

• Nasal Olfactory System: Detects Aerial Odors

• Vomeronasal/Jacobson’s Organ: Detects Non-Aerial Particulate Odors in Roof of Mouth

• Parietal Eye

Vomeronasal/Jacobson’s Organ

• Organ in Roof of Mouth

• Detects Non-Aerial Particulate Odors

• Most Developed in Snakes

Parietal Eye

• “3rd Eye”

• Associated with Pineal Gland

• Maintains Circadian Rhythms & Seasonal Activities

• Primarily Only in Tuataras

Sexual Dimorphism in Reptiles

• Males Larger in All Crocodilians & Many Lizards + Tortoises

• Females Larger in Most Snakes & Some Aquatic Turtles

• Males More Brightly Colored in Some Lizards

Reptile Reproduction

• Single Penis in Turtles & Crocodilians, Paired Hemipenes in Snakes & Lizards

• Fertilization through Cloacal Contact in Tuataras

• Parthenogenesis: Asexual Reproduction in Lizards & Snakes

• Oviparity: Reproduction through Laying Eggs

• Ovoviviparity: Eggs Hatch Internally & Yong Born Live

• Genotypic or Temperature-Dependent Sex Determination

Parthenogenesis

• Form of Asexual Reproduction

• Females produce Eggs that develop without Fertilization

• Results in Genetically Identical All-Female Population

Ovoviviparity

• Eggs Hatch in Mother’s Body

• Young are Born Live

• Occurs in Many Snake & Lizard Species

  • Occurs in Several Wisconsin Species of Snake

• Likely helps keep Young Warm in Colder Climates

Genotypic Sex Determination

• Sex Determined at Conception by Sex Chromosomes

• All Snakes

• Most Lizards

• Some Turtles

Temperature-Dependent Sex Determination

• Sex Depends on Temperature During Development

• All Crocodilians & Tuataras

• Most Turtles

• Some Lizards

• Concern of Potential Effects from Climate Change

Order Testudines - Turtles & Tortoises

• 369 Species Worldwide in 14 Families

• Bony Shells

• No Teeth

• Low Adult Mortality & Extreme Longevity (Type III)

  • Shell Defends Against Predators

• Marine, Freshwater, Semi-Aquatic, or Terrestrial

• Hotspot in Southeastern U.S.

Bony Shells of Turtles

• Carapace on Top

• Plastron on Bottom

• Carapace & Plastron Connected by Bridge

• Made of Scutes

• Attached Part of Body

  • Vertebrate Fused to Bottom of Carapace

Suborder Pleurodira

Suborder of Side-Necked Turtles

• 3 Families

• Mostly in Southern Hemisphere

Suborder Cryptodira

Suborder of Hidden-Necked Turtles

• 11 Families

• Includes All North American, European, & Mainland Asian Turtles

Aquatic Turtles

• Flat & Stream-Lined Shell

• Webbed Feet

• Long Claws

Terrestrial Turtles/Tortoises

• High-Domed Shell

• Short & Sturdy Feet

• Bent Legs

Male Turtles

• Concave Plastron

  • Easier to Mount

• Longer & Thicker Tails

• Vent Beyond Posterior Edge of Shell

• Longer Claws

• Smaller in Most Aquatic Species

Female Turtles

• Flat or Slightly Convex Plastron

• Shorter & Skinnier Tails

• Vent Even with Posterior Edge of Shell

• Shorter Claws

• Larger in Most Aquatic Species

Respiration in Turtles

• Lungs

• Cutaneous: Breathing through Skin

• Buccopharyngeal: Breathing through Lining of Throat

• Cloacal Bursae

• Able to Survive Underwater for Long Periods of Time

Winter Behavior of Turtles

• Spent Underwater for Most Wisconsin Species

• Able to Tolerate Long Periods without Oxygen

• Some undergo torpor, others remain semi-active under ice.

• Terrestrial Species Burrow & Hibernate

Diet & Foraging in Turtles

• Most are Opportunistic & Generalist Omnivores

• Eat Sedentary Prey or Plants

• Varies with Age

• Sea Species Often Specialize in Jellyfish

• Use Ambush, “Gape & Suck”, or Luring to Catch Fish

Basking in Turtles

• Elevates Body Temperature & Metabolic Rate

  • Promotes Digestion

• Improves Growth Rate

• Removes Ectoparasites

• Accelerates Egg Development

• Can Increase Exposure to Predation

Ecological Benefits of Turtles & Tortoises

• Clean-Up Detritus as Scavengers

• Egg & Young are Food Source for Predators

• Facilitate Seed Germination & Dispersal

• Burrowing species are keystone species that create habitats/shelter for other species.

Societal Benefits of Turtles & Tortoises

• Popular Ambassador for Reptiles

• Easy to Raise in Captivity

• Products Formerly Made from Shells

• Food Source

Conservation Threats to Turtles & Tortoises

• Wetland Loss & Shoreline Development

• Habitat Fragmentation

  • Easily Become Isolated due to Poor Dispersal

• Roadkill

• Overharvesting: Food, Shells, Medicine, Pet Trade

• Predation of Eggs & Hatchlings

  • Especially from Human Commensal or Invasive Species

Wisconsin Turtles

• 11 Species: 1 Fully Terrestrial, 2 Semi-Terrestrial, 8 Primarily Aquatic

• Mostly Diurnal

• Active from About April to October

• Breed in Spring or August

• Eggs Laid in Self-Dug Nests

• No Parental Care: High mortality of young but long lifespan for survivors.

• All Overwinter Underwater except for Ornate Box Turtle

Chelydridae

Family of Snapping Turtles

• 1 Wisconsin Species

• Common Snapping Turtle

Kinosternidae

Family of Mud & Musk Turtles

• 1 Wisconsin Species

• Stinkpot

Emydididae

Family of Pond & Box Turtles

• 7 Wisconsin Species

• Wood Turtle, Blanding’s Turtle, Ornate Box Turtle, Painted Turtle, & The Map Turtles

Trionychidae

Family of Softshell Turtles

• 2 Wisconsin Species

• Smooth Softshell Turtle & Spiny Softshell Turtle

Common Snapping Turtle (Chelydra serpentina)

• Largest Wisconsin Turtle

• Lives in All Aquatic Habitats

• Bottom Forager

• Commercially Harvested

• Common Statewide but Declining Populations

• Primarily Midwest & Eastern U.S. Distribution, Some of Central America

• Reduced Plastron

• Aggressive Behavior, Especially on Land

Common/Eastern Musk Turtle or Stinkpot (Sternotherus odoratus)

• Smallest Wisconsin Turtle

• Emits Foul-Smelling Musk

• Bottom-Dweller

• Lives in Slow Current & Soft Bottom Habitats

• Southeast U.S. Distribution, Southern Third of Wisconsin

• Reduced Plastron

Wood Turtle (Glyptemys insculpta)

• Growth Rings on Shell

• Semi-Terrestrial

• Lives in Forested Areas along Rivers

• Norther Two Thirds of Wisconsin

• Small Range, Northeast U.S. & Northwest of Great Lakes Region

• Threatened Status in Wisconsin

Blanding’s Turtle (Emydoidea blandingii)

• Yellow Chin & Hinged Plastron

• Semi-Terrestrial

• Live in Shallow Wetlands with Submerged Vegetation

• All but Northernmost Wisconsin, Primarily Great Lakes Region Distribution

• Special Concern Status in Wisconsin

  • Formerly Threatened

Ornate Box Turtle (Terrapene ornata)

• Small with Hinged Plastron

• Strictly Terrestrial

• Lives in Dry Prairies & Oak Savannas

• Shelters & Hibernates in Burrows

• Only in Lower Wisconsin Floodplain in Driftless Area

• Primarily Midsouth U.S. Distribution

• Endangered in Wisconsin

  • Most Threatened Turtle Species in Wisconsin

  • Abundant Elsewhere

Painted Turtle (Chrysemys picta)

• C. p. belli = Western Subspecies Statewide

• C. p. marginata = Midland Subspecies in Southeast

• Aquatic

• Live in Shallow Water with Slow Current

• Abundant Throughout Wisconsin

Common/Northern Map Turtle (Graptemys geographica)

• Patterning on Carapace Resembles Map

• Low Keeled Carapace

• Highly Aquatic

• Live in Large Rivers

• Distributed in Southwest Two Thirds of Wisconsin

Ouachita/Southern Map Turtle (Graptemys ouachitensis)

• Strongly Keeled Carapace

• Yellow Spot on Chin

• Highly Aquatic

• Lives in Large Rivers like Mississippi & Lower Wisconsin

False Map Turtle (Graptemys pseudogeographica)

• Strongly Keeled Carapace

• No Chin Spot

• Highly Aquatic

• Lives in Large Rivers

• Special Concern Status in Wisconsin

Smooth Softshell Turtle (Apalone mutica)

• Flat & Scuteless Carapace with Smooth Front Edge

• Aquatic

• Lives in Large Rivers like Mississippi & Lower Wisconsin

• Special Concern Status in Wisconsin

Spiny Softshell Turtle (Apalone spinifera)

• Flat & Scuteless Carapace with Spines on Front Edge

• Aquatic

• Lives in Rivers, Lakes, & Ponds

• Common in Most of Wisconsin & Midwest

Order Crocodylia - Crocodilians

• 27 Species in 3 Families

• Largest Living Reptiles

• Semi-Aquatic with Pantropical Distribution

• Exclusively Carnivores

• 4-Chambered Heart

• Ambush Predators

• Provide Parental Care

Crocodilian Hunting Strategy

• Ambush Predators

• Rely on Concealment

• Opportunistic

• Often Drown Prey

• Typically Swallow Prey Whole

Crocodilian Parental Care

• Nest Attendance & Defense

• Excavation of Hatchlings

• Transport Young in Mouth

• Care for Young

American Alligator

• 1 of 2 American Members of Crocodylia

• Live in Southeast Coast of U.S.

American Crocodile

• 1 of 2 American Members of Crocodylia

• Live in Southern Most Florida, Central America, & Northern South America

Crocodilian Families

• Alligators & Caimans

• Crocodiles

• Gharial

Alligators & Caimans

• Family in Order Crocodylia

• Broad & Blunt Snouts

• Teeth Lie Inside Closed Mouth

Crocodiles

• Family in Order Crocodylia

• Narrow Snouts

• Lower Teeth Visible in Closed Mouth

• Salt-Excreting Glands

• More Aquatic Lifestyle

Gharial

• Family in Order Crocodylia

• Only 1 Species

• Elongated & Slender Snout

• Lives in Indian Subcontinent

Crocodilian Adaptations for Aquatic Life

• Raised Nostrils & Eyes

• Palatal Flap: Prevents water from entering throat when mouth is open.

• Partially Webbed Hind Feet

• Long & Muscular Tail for Swimming

Order Rhynchocephalia - Tuataras

• Once diverse group, now only one species.

• Limited to Small Islands Off New Zealand

• Living Fossils: Diverged much earlier than other reptiles & haven’t changed much.

• Dorsal Spines on Neck & Head

• 2 Rows of Teeth in Upper Jaw

• Live in Burrows

• Nocturnal

• Tolerant of Cool Temperatures

• Long Living & Slow Reproduction (k-Selected)

• Eat Invertebrates, Vertebrates, & Eggs

• Parietal Eye: Sensory Patch on Head

Order Squamata

Order of Lizards, Snakes, & Amphisbaenians

• Largest Order of Reptiles

• Hemipenes in Males

• 3 Suborders: Lacertilia, Serpentes, & Amphisbaenia

Suborder Amphisbaenia - Amphisbaenians or Worm Lizards

• 203 Species in 6 Families

  • 1 U.S. Species in Florida

• Only Completely Fossorial Group of Reptiles

• Legless or Forelimbs Only

• Scales Arranged in Rings

• Reduced Eyes & No External Ears

• Eat Arthropods, Worms, & Small Vertebrates

• Push Skull through Soil to Burrow

  • Require Loose Substrate

Suborder Lacertilia - Lizards

• 7739 Species in 37 Families

• Generalized Tetrapod Body Form in Most Species

• Smooth & Dry Skin

• Claws on End of Toes

• Movable Eyelids

• External Ear Openings

• Halves of Lower Jaw Joined in Front

• Primarily Carnivorous

• Many Lifestyles: Terrestrial, Fossorial, Arboreal, Semi-Aquatic, Marine, Human Commensal

• Global Distribution except for Northern Poles & Canada

Diets & Foraging in Lizards

• Most (~98%) Species Carnivorous

• Mostly Insects & Other Invertebrates in Smaller Species

• Often Vertebrate Prey in Larger Species

• Foraging Techniques: Active Foraging or Sit-&-Wait

Reproduction in Lizards

• Paired Hemipenes in Males

• Internal Fertilization

• Less Frequent Ovoviviparity

• Little or No Parental Care

• Annual Breeding in Temperate Species, Continuous in Tropics

• Parthenogenesis in Some Species

Communication in Lizards

• Communicate Territory, Dominance, Courtship, Etc.

• Flash Brightly Colored Dewlap of Belly Skin

• Push-Ups, Tail Flicking, & Head Bobbing

• Vocalizations in Geckos

• Pheromones

Adaptations of Lizards for Arid Environments

• Use Basking, Burrowing, & Postural Adjustments to Thermoregulate

• Low Demands for Energy & Nutrients

• Able to Withstand Large Fluctuations in Electrolyte Balance

• Uric Acid Excretion Conserves Water

Defense Strategies of Lizards

• Tail Autotomy: Most species have the ability to shed their tail as a defense against predation.

  • Energetic Cost for Regeneration

• Change Color to Match Environment

• Intimidating/Startling Predator

  • Gaping & Hissing

  • Squirting Blood

• Playing Dead

• Venom

Wisconsin Lizards

• 4 Species in 3 Families

• All Oviparous

• Carnivorous: Eat Mostly Arthropods

• Live in Dry, Open, Sandy Habitats

• Patchy Distribution & Rarely Seen

• Active from Late April/Early May to Early September

• Hibernate Underground during Winter

Anguidae

Family of Glass & Alligator Lizards

• 1 Wisconsin Species

• Slender Glass Lizard

Teiidae

Family of Whiptails & Racerunners

• 1 Wisconsin Species

• Six-Lined Racerunner

Scincidae

Family of Skinks

• 2 Species

• Five-Lined Skink

• Prairie Skink

Slender Glass Lizard (Ophisaurus attenuatus)

• Legless with Relatively Rigid Body

• External Ears & Eyelids

• Lateral Grooves

• Provide Parental Care

• Lives in Oak Savannas & Sand Prairies

• Isolated Population in Central Wisconsin

• Primarily Distributed in Southeast

• Endangered Status in Wisconsin

Six-Lined/Prairie Racerunner (Aspidoscelis sexlineatus)

• Long & Thin Tail

• Rough Scales

• Active & Fast

• Lives in Dry Prairies

• Wisconsin Distribution through Mississippi & Lower Wisconsin Floodplains

• U.S. Distribution through Central South to Southeast U.S.

• Special Concern Status in Wisconsin

Five-Lined Skink (Plestiodon fasciatus)

• Shiny & Smooth Scales with Vertical Stripes

  • Primarily Black with Orange Stripes

• “Y” Pattern on Head

• Bright Blue Tail in Young Individuals

• Live in Oak & Pine Barrens, Forest Edges, & Openings

• Distributed through Central Wisconsin & Much of Southeastern U.S.

Prairie Skink (Plestiodon septentrionalis)

• Shiny & Smooth Scales with Vertical Tan Stripes

  • Brown & Black Pattern

• Orange Chin in Males

• Live in Pine Barrens & Bracken Grasslands

• Distributed through Northwestern Wisconsin & Central Line of U.S.

• Special Concern Status in Wisconsin

Suborder Serpentes - Snakes

• 4038 Species in 30 Families

• Limbless but Some have Slight Girdles

• No External Ears or Eyelids

• Elongate Body with Extra Vertebrae

• Exclusively Carnivorous

• Global Distribution except for Northern Most Regions

Skeletons of Snakes

• 200 to 400 Vertebrae each with Attached Pair of Ribs on Body & Neck

• Loosely Articulated to Allow Bending & Coiling

• Pectoral Girdle Absent & Pelvic Girdle Absent or Vestigial

• Flexible Skulls to Take Large Prey

  • Halves of Lower Jaw Unconnected at Front

Snake Senses

• Poor Eyesight in Most Species

• No External Ear Openings

• Inner Ear can sense Sound Waves & Vibrations

• Primarily Rely on Smell

  • Aided by Vomeronasal Organ in Palate

  • Flicking Tongue

• Pit Organs

Pit Organs

• Sensory Organ

• Used by Boas, Pythons, & Pit Vipers

• Detect Warm-Blooded Prey

Locomotion in Snakes

• Scales allow sliding in only one direction.

• Mix of Friction & Weight Distribution

• Types: Serpentine, Rectilinear, Concertina, & Sidewinding

Serpentine Locomotion

Movement by Pushing Off of Sides

Rectilinear Locomotion

Movement in a Straight Line

Concertina Locomotion

Movement through Contracting & Expanding like an Accordion

Sidewinding Locomotion

Movement through Parallel Sliding that Requires Loose Substrate

Feeding in Snakes

• Exclusively Carnivorous

• All Swallow Prey Whole

• Able to Catch & Eat Large Prey

• Two Halves of Lower & Bones of Upper Jaw can Move Independently

• Eat prey headfirst, then “walk” it into esophagus.

• May Subdue Prey with Constriction or Venom

Snake Venom

• Produced & Stored in Glands on Sides of Head

  • Causes Broad & Triangular Head

• Used to Immobilize & Digest Prey or For Defense

  • Can Begin to Break Down Tissue

• Injected through Hallow Fangs

Constriction

• Used Mostly by Non-Venomous Snakes to Kill or Subdue Prey

• Snake wraps loops of body around prey, then squeezes intermittently.

• Cuts-Off Circulation & Causes Cardiac Arrest in Prey

  • Does Not Typically Kill through Suffocation

Defense Strategies of Snakes

• Cryptic Coloration to Camouflage

• Aposematism to Show Venomous

• Batesian Mimicry to Trick

• Foul-Smelling Musk

• Hissing, Rattling, Rearing Up, & Striking

• Playing Dead