Colouration in Relation to Concealment

In both L. hochstetteri and L. archeyi, the almost invariable first reaction of a frog to the removal of a covering log or stone is to remain perfectly still. After a time, however, it leaps suddenly to a darker spot. This movement is apparently mainly a reaction to light and, possibly, desiccation. It has been shown (Czopek, 1955, 357) that in L. hochstetteri at any rate, the skin capillaries are very much more important than the lungs in effecting gaseous exchange.

Because of their initial immobility, specimens of Leiopelma are sometimes difficult to recognise, and this is especially the case with L. hochstetteri when it is found in a stream. With its colouring resembling that of the gravel and mud, and in its typical, flattened, crouching position, with its angular head merely lifted to free the nostrils and eyes from the water, it can easily be overlooked when one is searching in the shaded stream bed. If, however, it is accidentally touched, the frog quickly discloses its presence by leaping away.

On brown earth, under the same log, specimens of L. archeyi of all types of colour pattern (Table I) may be found together. The colour patterns of different specimens of L. archeyi do not therefore appear to be adapted to the individual environment except that L. archeyi, and to some extent lighter-coloured specimens of L. hochstetteri, show a type of disruptive colour pattern which Cott (1940) has called “coincident disruptive colouration”. If the hind limbs are considered in relationship to the normal crouching attitude of rest (E. M. Stephenson, 1955, Pl. I), it is seen that the oblique black bands on the parts of the hind limb coalesce—i.e., when the leg is folded up the dark bands on the thighs mainly coincide with those on the leg, the latter forming in turn a continuation of those on the foot. Also, the bands on the thighs often form a continuation of black patches on the sides of the body. This type of pattern accentuates a superimposed structure, built up by black bands, passing across the true structure, which is made less obvious.