WALLACE RESOURCE LIBRARY Lecture 07 – Mexican Herpetofauna and Adaptation

1. WALLACE RESOURCE LIBRARY Lecture 07 – Mexican Herpetofauna and Adaptation This is an ‘example’ of a lecture that is given to A level students as part of their academic lecture series whilst on their expedition. It has been produced for the exclusive use of the lecturer conducting the series and is solely intended for educational purposes. Most of the material comes from Operation Wallacea sources and any other material that has been used has been credited (as far as is possible) to the appropriate author wherever possible. This lecture is only to be used for EDUCATIONAL purposes.

2. WALLACE RESOURCE LIBRARY Lecture 07 – Mexican Herpetofauna and Adaptation

3. Lecture overview • Herpetofauna • Amphibians • Reptiles • Survey methods for Herpetofauna • Adaptations • Adaptation activity

4. Two types of herpetofauna • Amphibians • Salamanders (tailed) • Caecilians • Frogs and toads (without tail) Reptiles • Lizards and snakes • Crocodiles • Turtles, tortoises and terrapins

5. Herpetofauna of the Yucatan • 188 species of amphibians and reptiles known or presumed to occur in the Yucatán Peninsula

6. Amphibians • Salamanders, caecilians, frogs and toads • Wet, thin skin, some produce toxins. • Developed legs (except caecilians) • Some have webbed feet • Adults are carnivorous

7. Amphibians of Calakmul Mexican Salamander 2 species of Salamander Mexican Caecillian 1 species of Caecillian known in Yucatan – not known if at Calakmul Red-eyed treefrog 17 species of frogs and toads Of which 8 are treefrogs

8. Reptiles • Snakes, lizards, turtles, crocodiles • Tough, scaly skin • Heart divided into more chambers than amphibians • Oviparous reproduction

9. Snakes • Snakes can sense other animals approaching through detecting faint vibrations in the air and on the ground • Prey are killed by constriction or venom • Snake venom is modified saliva called Zootoxin • Most snakes can be placed into one of four groups.

10. Snakes • Snakes can be classified into four main groups based on the structure of their teeth • Aglyph • Opisthoglyph • Proteroglyph • Solenoglyph

11. Snakes Aglyphous snakes • These snakes do not have fangs with a grooved channel which is necessary to transport venom • They tend to have many teeth of relatively similar shape and size • Some have lost their venom apparatus and fangs

12. Snakes Opisthoglyphous snakes • ‘Rear-fanged’ group • Fangs at the back of the mouth that are grooved to channel venom into the puncture • The snake must move the prey to the back of the mouth to envenomate • Most venom is too weak to affect humans, the boomslang and the twig snake are two notable exceptions

13. Snakes Proteroglyphous snakes • Known as ‘front-fanged’ snakes • Short jaw bones with few teeth except for the front fangs which are still small • The fangs point downwards and are completely folded around the venom channel to form a hollow needle • Most toxic venom, neurotoxic • Classic example is the cobra

14. Snakes Solenoglyphous snakes • ‘Piped grooved’ long hollow fangs • The snake can control the fangs, keeping them folded against the roof of the mouth • The fangs swing into a biting position when the jaw is opened • They can then stab their prey and inject large quantities of venom • Seen in vipers and adders e.g. The Mexican jumping viper (Atropoides mumifer)

15. Snakes Different venoms attack different biological systems: • Cytotoxic – attack cells e.g. • Myotoxin – damage muscle cells • Haemotoxin – damage red blood cells • Neurotoxic • Attack the nervous system causing paralysis leading to respiratory and heart failure

16. Lizards • Large and widespread group with close to 3800 speciesworldwide • Ecologically successful due to efficient predation techniques • Lizards typically have limbs and external ears, while snakes lack both these characteristics Dwarf Gecko

17. Crocodiles • Two families: • Crocodilidae – ‘true’ crocodiles and gharial • Alligatoridae – alligators and caiman • Large predatory carnivores • Inhabit shores of lakes & rivers • Remains found in Mayan ruin sites

18. Tortoises and Turtles • Turtles, tortoises and terrapins belong to the order – Testudines • Charatcterised by a special bony or cartilaginous shell developed from their ribs • Some are terrestrial and some aquatic Scorpion Mud Turtle Kinosternon scorpiodes Furrowed Wood Turtle Rhinoclemmys areolata)

19. Reptiles of Calakmul Snakes - 23 species Lizards – 14 species Crocodiles – 1 species Turtles, Terrapins and Tortoises – 7 species Morelet’s Crocodile Slider Milk snake Yucatan Banded Gecko

20. Herpetofauna Survey Methods Sampling can be active or passive Transect surveys • Distance sampling • Fixed-width sampling Trapping surveys • Active trapping (larger species) • Pitfall traps (smaller species)

21. Fixed-width Searches Pros • Good for both reptiles and amphibians • Can be used along transects or in specific areas (e.g. along streams or around lakes) • Effort and time regulated searches of the undergrowth, capturing any specimens found • Captures more cryptic species Cons • Scares many away so capture rate not necessarily high

22. Pitfall traps • Pros • Can be placed along transects or in specific locations • Does not scare away animals like active searching • Cons • Labour intensive and not always successful • Size of bucket influences species captured

23. Concept of Adaptation • ‘The adjustment or changes in behavior, physiology, and structure of an organism to become more suited to an environment.’ • The word adaptation is normally reserved for inheritable genetic changes developed in a population over a long period of time. • This is Evolution through Natural Selection

24. Adaptations in Herps Aposematism • In latin apo = away and sematic = sign or meaning • Some organisms are brightly coloured advertising that they are ‘nasty’ tasting or dangerous to be near as they can sting or bite. • .

25. Types of Mimicry Batesian mimicry • Mimic resembles a model that is poisonous or unpleasant to eat • Mimic thus benefits because predators have learned to avoid the model • Usually based on appearance, but also calls, scents etc Mullerian mimicry • Two or more equally poisonous or distasteful species have a similar colour pattern • Reinforces the warning each gives to predators

26. Examples mimicry Mimicry in coral snakes is complicated. There are a number of species of New World coral snakes belonging to two separate families, some poisonous (Elapidae) and some non-poisonous (Colubridae). Which is the poisonous one? ‘Red bordered by yellow – kills a fellow’!

27. Adaptation Activity Herp Quiz Red –eyed Leaf Frog Agalychnis callidryas Milk snake Lampropeltis triangulum Yucatan Banded Gecko Coleonyx elegans

28. Lecture overview • Herpetofauna • Amphibians • Reptiles • Survey methods for Herpetofauna • Adaptations • Adaptation activity