Reptiles are a diverse group represented today by
lizards, snakes, and turtles. Many consider crocodiles as reptiles
for convenience, but crocodiles are more closely related to dinosaurs
and birds, than to snakes, lizards, and turtles. Fossils also show
that turtles are unrelated to snakes and lizards. So the reptiles
may just be a collection of "scaly things", rather than
a naturally related group of animals. Reptiles have several adaptations
for terrestrial life not generally found in amphibians including the
shelled egg and a waterproof skin.
Scales
Scales containing the protein keratin, which waterproofs the skin
of a reptile, help to prevent dehydration in dry air. Keratinized
scaly skin is the vertebrate equivalent of the chitin cuticle
of insects and the waxy skin of land plants. Because reptiles cannot
breathe through their dry skin, they obtain all of their oxygen
with its lungs.
Reproduction
Although viviparous reptiles exist (reptiles that give birth to
live young), most species lay eggs on land; parchment-like shells
prevent them from drying out. The embryo develops in the fluid of
an amniotic sac within the egg. The evolution of the amniote egg,
a shelled egg with a self-contained "pond" of amniotic
fluid, enabled vertebrates to complete their life cycles on land
and sever their last ties with their aquatic origins. Fertilization
in reptiles must occur internally, before the shell and certain
membranes are secreted as the egg passes through the reproductive
tract of the female.
Cold-blooded Animals
Reptiles are sometimes labeled "cold-blooded" animals
because they do not use their metabolism to control body
temperature. But reptiles do regulate body temperature by using
behavioural adaptations. Many lizards can maintain an internal temperature
of about 37°C by basking in the sun when the air is cool and
seeking shade when the air is too warm. Since they absorb external
heat rather than generating much of their own, reptiles are said
to be ectothermic, a term more appropriate than "cold-blooded."
The leatherback turtle of British Columbia's coastline maintains
a stable body temperature because of its sheer mass, which resists
rapid temperature changes.
By heating directly with solar energy rather than with food, a reptile
can survive on less than 10% of the calories required by a mammal of equal
size. Having relatively modest food requirements and being adapted to
dry conditions, many reptiles thrive in the deserts.
Reptiles in British Columbia
There are 44 species of turtles, lizards, and snakes that occur
in Canada as a whole; 20 of these (7 turtles, 4 lizards, 9 snakes)
have been recorded in British Columbia, although not all of the
introduced species that have appeared here persist to present day.
While the number of species is small, British Columbia has a fairly
rich diversity of reptiles compared to other parts of Canada, due
to the different habitats and mild climate in this province.
Endangered Species
Several species of reptiles are endangered in interior regions
of the province for various reasons, but mostly from the loss of
suitable habitat because of urban development and agricultural.
Two species of Reptiles known from the dry Thompson-Okanagan region
of southern British Columbia: the endangered Night
Snake (Hypsiglena torquata) and the extirpated,
Short-horned Lizard (Phrynosoma
douglassii).
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