For an animal to be classed as a reptile it must have scales, be cold blooded and obtain its oxygen from the air [air breathing]. All three requirements are necessary. For example a bird has scales [on the legs] is air breathing but is warm blooded while a frog is cold  blooded and in the main air breathing has no scales and a fish is scaled and cold blooded but obtains its oxygen from the water.
   The term cold blooded refers to the fact that reptiles do not have the internal mechanism to regulate their body temperature to one that will allow their bodies to function effectively. Mammals and birds can do this but the cost is high, about two thirds of the energy produced from the food they eat is used to maintain a suitable body temperature. Reptiles must find a warm place for basking to raise their body heat and some cooler spot to move to from time to time to prevent overheating.  This means they must spend some time lying in the open and exposed, especially the smaller ones, to possible predators.  To protect themselves against this most reptiles are able to blend in with their surroundings and by keeping quite still can be hard to detect.
     With the exception of some livebearing lizards and snakes reptiles lay eggs which are usually buried in warm sand, soil etc and left to hatch. The livebearers also produce eggs but they are retained within the body of the female and develop there allowing her to have some control of the hatching temperature by moving them around.
      Reptiles living at the present time are classified in four orders, Crocodilia [crocodiles and alligators]  Squamata [lizards and snakes] Chelonia [tortoises and turtles] and Rhynchocephalia [tuataras].
 With the exception of snakes [forbidden by law in New Zealand] and sea turtles the Reptile Park has representatives from all four orders.

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