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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.
WALLACE RESOURCE LIBRARY
Lecture 07 – Mexican Herpetofauna and
Adaptation
Lecture overview
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Herpetofauna
Amphibians
Reptiles
Survey methods for Herpetofauna
Adaptations
Adaptation activity
Two types of herpetofauna
• Amphibians
– Salamanders (tailed)
– Caecilians
– Frogs and toads (without tail)
Reptiles
– Lizards and snakes
– Crocodiles
– Turtles, tortoises and terrapins
Herpetofauna of the Yucatan
• 188 species of amphibians and reptiles known or presumed to
occur in the Yucatán Peninsula
Group
Families
Genera
Species
Caecillians
1
2
2
Salamanders
1
2
6
Frogs and Toads 7
15
36
Crocodiles
1
1
2
Turtles
6
13
16
Lizards
11
23
52
Snakes
6
48
74
Total
33
104
188
Amphibians
• Salamanders, caecilians, frogs and toads
– Wet, thin skin, some produce toxins.
– Developed legs (except caecilians)
– Some have webbed feet
– Adults are carnivorous
Amphibians of Calakmul
Mexican Salamander
2 species of Salamander
Red-eyed treefrog
17 species of frogs and
toads
Of which 8 are treefrogs
Mexican Caecillian
1 species of Caecillian
known in Yucatan – not
known if at Calakmul
Reptiles
• Snakes, lizards, turtles, crocodiles
– Tough, scaly skin
– Heart divided into more chambers than amphibians
– Oviparous reproduction
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.
Snakes
• Snakes can be classified into four main groups
based on the structure of their teeth
– Aglyph
– Opisthoglyph
– Proteroglyph
– Solenoglyph
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
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
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
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)
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
Lizards
• Large and widespread group
with close to 3800 species
worldwide
• Ecologically successful due
to efficient predation
techniques
• Lizards typically have limbs
and external ears, while
snakes lack both these
characteristics
Dwarf Gecko
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
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
Furrowed Wood Turtle
Rhinoclemmys areolata)
Scorpion Mud Turtle
Kinosternon scorpiodes
Reptiles of Calakmul
Snakes - 23 species
Lizards – 14 species
Crocodiles – 1 species
Turtles, Terrapins and Tortoises – 7 species
Morelet’s Crocodile
Slider
Yucatan Banded Gecko
Milk snake
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)
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
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
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
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.
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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
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’!
Adaptation
Activity
Herp Quiz
Yucatan Banded Gecko
Coleonyx elegans
Red –eyed Leaf Frog
Agalychnis callidryas
Milk snake
Lampropeltis triangulum
Lecture overview
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Herpetofauna
Amphibians
Reptiles
Survey methods for Herpetofauna
Adaptations
Adaptation activity