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Tuatara: Volume 8, Issue 3, April 1961

The Introduced Frogs of New Zealand

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The Introduced Frogs of New Zealand

Among the animals which have been successfully introduced to New Zealand are three species of Australian frogs. Attempts have also been made to introduce a fourth frog (Rana temporaria) and a toad (Bufo vulgaris) from Europe, but without success. It might well be asked why anyone should wish to have these animals in New Zealand, for, generally speaking, they are looked upon as loathsome. The reasons for their introduction fall into two categories: (a) their usefulness to man, and, (b) as possible ‘ reminders ’ of the homeland of the colonists.

New Zealand has its indigenous frogs, but they are comparatively small and rare and accordingly need protection. Incidinetally, the existence of the indigenous species was barely known at the time the exotic species were introduced. Frogs and toads are needed in the pursuit of academic studies and biological research, and for certain medical tests. For these purposes a call on the indigenous, slow-breeding species would soon write ‘finis’ to the existence of these unique creatures. Under the circumstances suitable substitutes had to be imported which would not have too great an impact on the natural fauna. This was achieved with a fair amount of success, resulting in the acclimatisation of three species of the genus Hyla from Australia. In addition, a supply of toads (Bufo) required for medical tests is maintained by some hospitals by periodical consignments from Fiji and some of the other Pacific Islands. Toads are occasionally accidentally imported in cargoes of fruit but, as far as I am aware, no toads appear to have established themselves in a feral state.

The three species that were successfully introduced are Hyla aurea, the Green Frog; H. ewingi, the Brown Tree Frog or Whistling Frog; and H. caerulea, the Great Green Tree Frog. Of these Hyla aurea is common and widespread. H. ewingi is common on the west coast of the South Island and Southland, while in recent years it was successfully introduced into the North Island. H. caerulea is present in parts of the North Island, but has rarely been found.

The following account is an attempt to cover in brief form the main aspects of the biology and natural history of the introduced frogs. It includes also a description of each species, and a literature list giving the main items of the synonymy and New Zealand references.

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Family: Hylidae

The Hylidae includes the true tree frogs and may be described as bufonids with intercalary cartilages and usually with dilated sacral diaophyses. There are sixteen genera of hylids and these are placed in two subfamilies. All, except Hyla, are confined to the New World. Two genera, Hylella and Nyctimystes have been described from East Indian and Australian regions, but these are scarcely distinct from the genus Hyla. Hyla is almost cosmopolitan in its distribution, except for an hiatus in the Indomalayan (including Borneo), Polynesian. Ethiopian and Madagascan regions. One species, perhaps erroneously, has been recorded from the Gulf of Guinea, and two have been recorded from Java. Hylids may be arboreal, terrestrial or aquatic and some are fossorial.

Subfamily: Hylinae

The Hylinae include hylids which lay their eggs in or near water; possess dilated sacral diapophyses and terminal claw- or T-shaped phalanges. Usually twelve genera are recognised but this number may be increased to fifteen according to some authorities. Many of the hylids closely resemble members of the sub-order, Diplasiocoela, particularly of the genus Rana.

Genus: Hyla Laurenti

Pupil horizontal; tongue entire or slightly nicked, adherent or more or less free behind. Vomerine teeth present. Tympanum distinct or hidden. Fingers free or slightly webbed; toes webbed, the tips dilated into larger or smaller discs. Outer metatarsals united or slightly separated. Omosternum cartilaginous; sternum a cartilaginous plate. Diapophyses of sacral vertebrae more or less dilated. (After Boulenger, 1882.)

Key to the Species of Hyla in New Zealand

A. Fingers free.
Digital discs hardly visible; snout acute; vomerine teeth between choanae. Male, 60-65 mm.; female, 80-92 mm. H. aurea
B. Fingers webbed.
a. Fingers much less than one-third webbed; digital discs small; snout rounded; vomerine teeth between choanae. Male, 30-35 mm.; female 40-45 mm. H. ewingi
b. Fingers one-third webbed; digital discs large; snout rounded; vomerine teeth on a level with hinder edge of choanae. Male, 65-70 mm.; female, 80-90 mm. H. caerulea

Hyla Aurea (Less): Green or Golden Bell Frog

Plate I, figs. 1-2; text-fig. 1, fig. 1

Rana aurea Lesson, 1830. Voy. ‘Coquille’, Zool., p. 60, pl. 7, fig. 2 (Syst.).

Hyla aurea Guenther, 1858. Cat. Tailless Batr. Brit. Mus., p. 114 (Syst.); Steindachner, 1869. ‘Novara’ Amphib., p. 161 (Syst.); Boulenger, 1882. Cat. Batr. Sal. s. Ecaud. Brit. Mus., 2nd Edit. p. 140 (Syst.); Fletcher, 1889. Proc. Linn. Soc. N.S.W. 2nd ser. 4: 384 (Breeding); Gadow, 1901. Amphib. page break
PLATE I Fig. 1: Breeding female of Hyla aurea with numerous small ova. Fig. 2: Breeding male of Hyla aurea. Fig. 3: Breeding female of Leiopelma hochstetteri with few large ova. Photos by courtesy of Dominion Museum; Figs. 1 and 2 by F. O'Leary. Fig. 3 by C. Hale.

Fig. 1: Breeding female of Hyla aurea with numerous small ova. Fig. 2: Breeding male of Hyla aurea. Fig. 3: Breeding female of Leiopelma hochstetteri with few large ova. Photos by courtesy of Dominion Museum; Figs. 1 and 2 by F. O'Leary. Fig. 3 by C. Hale.

page 110 and Rept. Cambr. Nat. Hist. Ser., 8:201 (Gen. Biol.); Marriner,* 1907. and Rept. Cambr. Nat. Hist. Ser., 8: 201 (Gen. Biol.); Marriner,* 1906. Trans. N.Z. Inst., 38: 27 (Anat.); Marriner,* 1907. Trans. N.Z. Inst., 39: 144 (Introd.); Benham and Hutton,* 1907. Trans. N.Z. Inst., 51: 30 (Anat.); Thomson,* 1922. Naturalised Anim. and Plants N.Z., p. 179 (Introd.); Thomson,* 1926. Wild Life in N.Z., 2: 75 (Gen. Biol.); Archey,* 1935. Bull. Auck. Zool. Soc., 2: 5 (Gen. Biol.); Richardson,* 1943. Copeia, 122 (Hernia.); Martin,* 1947. N.Z. Nat. Study, p. 227 (Gen. Biol.); Richardson.* 1947. Copeia, 4: 255 (Hernia.); Richardson.* 1952. Trans. Roy. Soc. N.Z., 80: 579 (Hernia.); Class Project,* 1953. Tuatara, 5: 12 (Parasites); Richardson and Barwick,* 1957. Trans. Roy. Soc. N.Z. 84: 941 (Abnorm. Develop.).


Habit raniform. Tongue suboval, nicked and free behind. Vomerine teeth between the choanae, in two slightly oblique series convergent posteriorly. Head as long as broad, or a little longer than broad, resembling in shape that of Rana esculenta; snout longer than the diameter of the eye: canthus rostralis moderately distinct: loreal region slightly concave; interorbital space narrower than the upper eyelid. Fingers free; no distinct rudiment of pollex; toes entirely webbed, or nearly so; digital discs small, about half the diameter of the tympanum; subarticular tubercles moderate; a distinct fold along the inner edge of the tarsus. The tbio-tarsal joint of the hindlimb breaches the eye, occasionally less or slightly beyond. Skin smooth or warty above, granulate beneath; a more or less distinct glandular lateral fold. Male with two internal vocal sacs. Brown rugosities on inner side of first finger developed during the breeding season. (After Boulenger, 1882.)

Size and Dimensions

Adult males are about two-thirds smaller than adult females; females up to 92 mm.

Male: Snout to vent 62 mm.; hindleg 91 mm.; foot 42 mm.; longest toe 26 mm.; snout to nostril 4.5 mm.; snout to tympanum 15 mm.; snout to eye 9 mm.; eye 6 mm.; tympanum 4 mm.; distance between eyes (anterior corner) 7 mm.; testes (breeding) 10 by 2 mm. (Dom. Mus. 83.)

Female: Snout to vent 92 mm.; hindleg 227 mm.; foot 69 mm.; longest toe 36 mm.; snout to nostril 7 mm.; snout to tympanum 22 mm.; snout to eye 13 mm.; eye 9 mm.; tympanum 7 mm.; distance between eyes 13 mm. (Dom. Mus. 84.) Ova almost mature.


The colour and colour pattern of this species is very variable and is largely dependent on its immediate surroundings. Commonly it is a brilliant pea-green above and purplish beneath with longitudinal bands of golden yellow on the back; a black dorso-lateral line is often present. The forelegs are green mottled above with yellow, the hind legs are bluer green with

* New Zealand references.

page 111 the hinder part of the thighs and feet a rusty orange (breeding male) or bluish as in the female. This brilliance may change to brown or almost black over the dorsal surface with a lighter underside.


Australia, widely distributed through the greater part of the continent except in the desert regions. Introduced into New Zealand and is now found in most streams and pools throughout the Dominion and on some of the off-shore islands.


In the tadpole stage frogs are generally herbivorous, rasping off algae and other vegetable matter with the beak and the labial horny teeth. They will also feed on animal tissue in the same way. In the adult stage the diet is entirely carnivorous. They will take almost any animal life that they can overpower and conveniently swallow, from insects to lizards and even their own species when opportunity arises. Lengthy or large objects are ‘shovelled’ into the mouth by the alternate use of the ‘hands’.


The enemies of frogs are numerous. As eggs and tadpoles they are devoured by aquatic insect larvae, fish and lacustrine birds. As adults they are eaten by lacustrine birds such as herons and bitterns, etc., while wekas, pukekos and kingfishers possibly account for a number also. On land some of the smaller mammals will also eat frogs when available.

Normally females are voiceless for they are not provided with vocal sacs, but they are capable of emitting short grunts by way of protest when handled, or a piercing shriek when caught by an enemy. The male of H. aurea is provided with a pair of internal vocal sacs which normally come into play during the breeding season. The voice is a loud castanet-like call which can be heard over a considerable distance. In concert the call has been described as deafening.


H. aurea is usually found in the vicinity of streams, lakes and pools. Garden ponds have a special attraction for them, and during the breeding season they will congregate in large numbers in such places.


This species is essentially terrestrial and aquatic. Under cover of darkness or in dull weather it will wander far and wide. During the day it remains in the vicinity of water and may be seen sitting on floating leaves and branches where it can quickly return to the water and submerge on the slightest sign of danger.


A frog's life may be divided into two periods: one of active feeding, and the other of rest or hibernation during the winter. Between the two a short breeding period intervenes during which the eggs are laid and left to their fate.

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Undoubtedly, the breeding and developmental cycles may be accelerated or retarded according to the locality and the prevalent climatic conditions. During the active period of vigorous feeding, frogs accumulate sufficient reserve fat, in special fat-bodies, to tide them over the winter and to build up the gonads in readiness for the next breeding cycle. The gonads develop considerably during the winter sleep and after breeding is over they become greatly reduced.

In the spring the frogs emerge from hibernation looking none the worse for their long fast. Normally, the first impulse on emergence is to breed. A large female taken on August 29, 1952, near the Hutt River, contained maturing ova close on the time of being voided. Some observers believe that the general mating or spawning season is towards the end of October each year, but, as indicated above, the period may vary according to locality. Age may also cause variation for older animals generally spawn earlier than young animals. A smaller female than the Hutt River individual, from Taupo, taken on October 10, 1956, had smaller ova and less enlarged oviducts and would accordingly lay later.

When ready to mate and spawn the pairs engage in amplexus, the male clasping the female dorsally in a firm embrace behind the armpits. The pair remain in this embrace till egg-laying is completed. During amplexus the male exerts considerable pressure, thus assisting in the passage of the ova to the exterior. At the same time the male exudes the spermatoza into the water, as fertilisation is external. The male also’ ‘paddles’ his hind legs from time to time as though he were making an effort to maintain his position, but this action, I believe, is partly to stimulate the female and partly to churn up the surrounding water to disseminate the products of both sexes and enhance the chances of fertilisation. With the decrease of the ova the male's grasp moves back on the abdomen of his mate till finally amplexus ceases.

The ‘puddling’ action of the male during amplexus has been described as ‘then kicking the female vigorously in the ribs he induces her ova into the water’. (Martin, 1947.) This figurative expression is partly true, but contains an inaccuracy insomuch that frogs possess no ribs.

After deposition of the eggs in water they hatch in a few hours (or perhaps a few days) according to the temperature of the water. The duration of the tadpole stage and metamorphosis, as far as I am aware, has not been recorded for this species. However, as I have seen metamorphosis completed (around Wellington) by summer, it seems reasonable to suspect that it lasts about two to three months. Undoubtedly, the period varies according to locality, temperature and food supply. Nevertheless, it seems almost certain that metamorphosis must be completed before the onset of winter. Under normal conditions it is doubtful whether the tadpoles, not possessing a great surplus of reserve fat, could survive a period of hibernation.

Thomson (1926) states: ‘Tadpoles which are unable to leave the water in which they have been born— as, for instance, those confined in page 113 tanks with smooth sides— may grow to as much as 6 in. in length without developing into frogs. Probably such undeveloped specimens cannot survive the first winter.’ Normally, the tadpole of each species attains a certain optimum size by which time metamorphosis must be completed; thus, I fail to understand the enormous growth attributed to the tadpole of this species as stated above by Thomson. During the tranisition period from tadpole to frog, the animal must leave the water from time to time and rest out of water till it is completely adjusted to the air breathing state. It has been my experience that, once the animals having reached the frog stage, they will eventually drown if they are not able to leave the water to rest. Much remains to be studied of the life cycle of this species.

TEXT-FIGURE I Beaks, teeth and circumoral papillae of tadpoles of New Zealand species of Hyla. Fig. 1: Hyla aurea, 70 mm. total length. Fig. 2: Hyla ewingi, 33 mm total length. Fig. 3: Hyla caerulea (Inglewood specimen), 134 mm. Total length. Fig. 4: Hyla caerulea (Puketaha specimen), 111 m. total length. Fig. 5: Hyla caerulea (Inglewood specimen), 134 mm. total length. del. C. McCann

Beaks, teeth and circumoral papillae of tadpoles of New Zealand species of Hyla. Fig. 1: Hyla aurea, 70 mm. total length. Fig. 2: Hyla ewingi, 33 mm total length. Fig. 3: Hyla caerulea (Inglewood specimen), 134 mm. Total length. Fig. 4: Hyla caerulea (Puketaha specimen), 111 m. total length. Fig. 5: Hyla caerulea (Inglewood specimen), 134 mm. total length. del. C. McCann

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The specific determination of tadpoles is difficult as they present few reliable morphological characters. Optimum size, i.e. the linear dimensions attained just before the completion of metamorphosis, is a good character but allowance must be made for limited variation. The structure and configuration of the lips and the arrangement of the horny teeth in relation to the beak are considered of systematic value, but, again, due allowance must be made for slight variation according to the age of the individual tadpole and damage to the series.

A tadpole collected at Palmerston North in March, 1960, with the hindlimbs just appearing measures, in total length, 60 mm. (tail 37 mm. by 15 mm. at its deepest point, including membrane). Another, taken at the same time as the above, with the hindlimbs fully developed, measures 70 mm. (tail 44m., by 15 mm. at the deepest point); hindlimb 26 mm.; foot 12 mm.; longest toe 5 mm. This specimen probably represents the optimum size attained by the tadpoles of H. aurea before assuming the frog stage.

The lips of both specimens are papillate (text-fig. I, fig. 1), the second showing a certain amount of reduction at this stage. There are two series of horny teeth above the beak and three below; the uppermost of the lower series is interrupted at the centre by a short interval.

Introduction to New Zealand

The introduction of H. aurea to New Zealand has been the most successful of all three species. Probably the first attempt to introduce it was that of the Auckland Acclimatisation Society which, in 1867, introduced two specimens and augmented its efforts in the following year by several more consignments from Sydney. Australia. These frogs soon established themselves.

About the same time as H. aurea was introduced into the North Island, the Southland Acclimatisation Society, in 1868, introduced some spawn from Tasmania(?), but this attempt evidently did not meet with success, for no signs of the frogs were seen in 1890. In 1888, some of the successful ‘northern colonists’ were transported from Napier to Southland and liberated in a marsh, but evidently the new environment did not suit them and the attempt failed once more. However, not discouraged by failure, the importations were repeated from the North Island to the areas of Otago and Southland and eventually proved successful. Today H. aurea is common in suitable localities throughout the Dominion. It serves an useful role in biological studies in this country and an addition to the menu of some of the local fauna.

Hyla Ewingi Dumeril and Bibron: Brown Tree Frog or Whistling Frog

Text-fig. I, fig. 2

Hyla ewingii Dumeril and Bibron, 1841. Erp. Gen., 8: 597 (Syst.).

Hyla ewingi Steindachner, 1869. ‘Novara’ Amphib., p. 62 (Syst.); Boulenger, 1882. Cat. Batr. Sal. s. Ecaud. Brit. Mus., p. 406 (Syst.); Fletcher, 1889.

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Proc. Linn. Soc. N.S.W., 2nd ser., 4: 383 (Breeding); Gadow, 1901. Amphib. and Rept. Cambr. Nat. Hist. Ser., 8: 201 (Breeding); Marriner,* 1907. Trans. N.Z. Inst., 39: 144 (Gen. Biol.); Thomson,* 1922. Naturalised Anim. and Plants, N.Z., p. 181, (Introd.); Thomson,* 1926. Wild Life in N.Z., 2: 79, (Gen. Biol.); Waite,* 1929. Reptiles and Amphib. S. Austr., p. 260, figs. 186-188 (Breeding); Archey,* 1935. Bull. Auck. Zool. Soc., 2: 5 (Gen. Biol.); Martin,* 1947. N.Z. Nat. Study, p. 227 (General); Falla,* 1957. Proc. N.Z. Ecol. Soc., 5: 30 (Distrib.); Wilson,* 1959. Bird Islds, N.Z., p. 150 (Introd.).


Tongue heart-shaped, free behind. Vomerine teeth in two small transverse or slightly oblique series between the choanae. Head moderate, a little broader than long; snout rounded, as long as the diameter of the eye; canthus rostralis distinct; loreal region not or but slightly concave; interorbital space as broad as, or a little broader than, the upper eyelid; tympanum distinct, half or three-fifths the diameter of the eye. Fingers with a slight rudiment of web; no distinct rudiment of pollex; toes two-thirds webbed; digital discs smaller than the tympanum; subarticular tubercles moderate; a distinct fold along the inner edge of the tarsus; tibio-tarsal articulation reaches the tympanum or eye. Upper surface smooth or with small scattered tubercles; lower surfaces granulate; a fold above the tympanum. Male with an external subgular vocal sac; during the breeding season the inner side of the first finger is covered with blackish rugosities. (After Boulenger, 1882.)

Size and Dimensions

The males are considerably smaller than the females which may reach 45 mm.

Male: Snout to vent 34 mm.; hind leg 50 mm.; foot 22 mm.; longest toe 13 mm.; snout to nostril 2 mm.; snout to tympanum 7 mm.; snout to eye 4 mm.; eye 3 mm.; tympanum 2.5 mm.; distance between eyes (anterior angle) 5 mm.; testes 5 by 1 mm. (breeding), (Dom. Mus. 51).

Female: Snout to vent 43 mm.; hind leg 68 mm.; foot 30 mm.; longest toe 19 mm.; snout to nostril 2 mm.; snout to tympanum 10 mm.; snout to eye 6 mm.; eye 4 mm.; tympanum 3 mm.; distance between eyes (anterior angle) 7 mm.


The general colouring varies considerably from a uniform dark brown with or without markings to almost creamy white without markings or with minute blackish flecks. In some specimens a dark brown pattern extends from the snout down either side of the vertebral column to the vent, the flanks being lighter. A characteristic blackish band stretches from the nostril through the eye (broader behind the eye) to the insertion of the forelimb or slightly beyond; another dark streak margins the uper jaw as far as the angle of the gape; between the two dark bands the colour is a greyish-white. Eye brown, lighter above; pupil oval, black (the

* New Zealand references.

page 116 pupil forms a continuous ‘line’ with the dark band passing through the eye). Underside whitish, granulate, undersurface of thighs orange yellow in both sexes. (Colours from living specimens in breeding condition.)


Australia: It is spread over south-west and south Australia, New South Wales, Victoria and Tasmania.


The males are provided with vocal sacs which produce a shrill piping sound, hence the popular name, Whistling Frog.


The general habitat of this species appears to be bushclad country of a swampy nature where the humidity and herbage afford it a suitable environment.


Marriner (1907), who studied the habits of this species in New Zealand, states that it is strictly nocturnal, seldom emerging during the day. It is arboreal, often ascending several feet above the ground. Thorny bushes are easily negotiated.


According to Marriner (1907), who kept specimens under observation, this species spawns in the autumn, and eggs deposited on the 1st of March hatched out on the 11th and 12th of the same month. The tadpoles from these eggs did not mature, not even by the following autumn, but it seems likely that the artificial conditions under which the tadpoles were kept may have retarded their growth. It is doubtful whether under normal conditions the metamorphosis would have been so delayed.

Waite (1929), writing on the breeding of this species in Australia and Tasmania states: ‘The eggs are laid in water and are attached to submerged weeds in small bunches (fig. 188), which encircle the stems of the plants and may be found at almost any time of the year.’ My observations are confined to some specimens obtained for me by Capt. Ainsworth at Greymouth, West Coast, and on a small series of tadpoles collected by Mr. J. H. Sorensen at the mouth of the Waiau River, Southland, in January of 1939. Most of the specimens in this series were at the frog stage and would have left the water in about a week.

On November 7, 1959, I dissected a pair from the Greymouth set which I had kept alive. The female contained a large number of eggs, almost mature and deeply pigmented. The size of the ova suggested that they would have been voided within a fortnight or less. Compared with H. aurea the ova of H. ewingi are comparatively larger and considerably fewer in number, which in itself suggests a different breeding habitat to H. aurea.

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If we may take the size of the ova in the Greymouth specimen and the estimated time of laying, November, and couple it with the tadpoles from the Waiau River area, January, it would appear that this frog completes its tadpole stage and metamorphosis in about two to three months time, that is, before the onset of winter.


A tadpole from the Waiaua set, with the hind limb buds just showing, measures 33 mm. in total length; another with the hind limbs fully developed 36 mm. (tail 22 mm.); a third with all limbs developed and the tail being absorbed, 33 mm. A young frog with the metamorphosis complete measures 14 mm. from snout to vent.

The lips of the tadpole are papillate (text-fig. I, fig. 2). There are two series of teeth above the beak, the upper continuous, but with a downward loop at the centre; the lower is formed of a series interrupted in the centre. Below the beak there are three continuous series. The upper portion of the beak is feebly denticulate; the lower markedly so. All teeth are shed at the time the mouth is assuming its final form.

Introduction to New Zealand

Apparently the introduction of H. ewingi to New Zealand was an individual effort. A Mr. W. Perkins brought some frogs in a bottle from Tasmania in 1875, and liberated them in a drain in Alexander Street, Greymouth, South Island. They soon spread to the southern bank of the Grey River as far as Aharua and a few miles further southwards, but apparently did not succeed in crossing over to the north of the river. About 1900, Mr. James King introduced some of the Greymouth individuals into the Hokitika area where they survived and increased for a time, but as they are believed to be extinct in the area today, it is presumed that the larger and more voracious H. aurea was responsible for their extermination. H. ewingi is still prevalent in Westland.

H. ewingi is present in the Waiau River area (Southland) and is breeding. Recently Dr. C. A. Fleming sent me a specimen obtained by him in this area on January 12, 1960. Just how this species arrived so far south is not known, but it seems more than likely that it had been transported into the area and possibly other areas by human agency.

In 1946 Major R. Wilson attempted to introduce living individuals of H. ewingi from Westland into the North Island. This effort proved a failure. About two years later another attempt was made, this time using spawn from Barrytown. The experiment proved successful and the species has now spread northwards for about twenty miles from Himatangi, the original site of this liberation.

Hyla Caerulea (Boulenger): Great Green Tree Frog

Pelodryas caeruleus (part) Guenther, 1858. Cat. Tailless Batr. Brit. Mus., p. 119, pl. ix, fig. B (Syst.).

Hyla caerulea Boulenger, 1882. Cat. Batr. Sal. s. Ecaud., 2nd Edit., p. 383 (Syst.); Fletcher, 1889. Proc. Linn. Soc. N.S.W., 2nd ser., 4: 381 (Breeding);

page 118

Gadow, 1901. Amphib. and Rept. Cambr. Nat. Hist. Ser., 8: 198, fig. 39 (Gen. Biol.); Thomson,* 1922. Naturalised Anim. and Plants N.Z., p. 181 (Introd.).


Tongue circular, free and very slightly notched behind. Vomerine teeth in two slightly oblique series on a level with the hinder edge of the choanae. Head broader than long; snout rounded, truncate; canthus rostralis distinct; loreal region slightly concave; interorbital space broader than the upper eyelid; tympanum very distinct, two-third the diameter of the eye. Fingers one-third webbed; no projecting rudiment of pollex; toes nearly entirely webbed; subarticular tubercles well developed; digital discs large, those of the fingers as large or somewhat larger than the tympanum, of toes a little smaller; a slight cutaneous fold along the inner side of the tarsus; tibio-tarsal articulation reaches hardly to the eye. Skin smooth, above, much thickened and studded with large pores on the back of the head and on the scapular region as far laterally as the strong curved fold bordering the eye; belly and lower surface of the thighs granulate. Male with an internal subgular vocal sac; during the breeding season brown rugosities appear on the inner side of the first finger. (After Boulenger, 1882.)

Size and Dimensions

Males are smaller than females, the latter often exceeding slightly over 100 mm.

Male: (a) Snout to vent 68 mm.; hind leg 96 mm.; foot 42 mm.; longest toe 26 mm.; snout to nostril 4.5 mm.; snout to tympanum 19 mm.; snout to eye 10.5 mm.; eye 6 mm.; tympanum 4.5 mm.; distance between eyes (anterior corner) 13 mm.

(b) Snout to vent 83 mm.; hind leg 106 mm.; foot 51 mm.; longest toe 29 mm.; snout to nostril 5 mm.; snout to tympanum 21 mm.; snout to eye 13 mm.; eye 7 mm.; tympanum 4.5 mm.; distance between eyes (anterior corner) 18 mm. (Wanganui Mus.)


Upper surface a bright pea green, lower white, unspotted. (Colour from a fresh male specimen.) The upper surface of the male is similar to the female, but the flanks are spotted with white dots surrounded with dark haloes; armpits, groins and outer portions of thighs mushroom or mauve. Eye brassy.


Spread over the warmer parts of the Australian continent, but does not occur in the colder parts of Victoria nor in Tasmania. Specimens from the plains and drier regions are smaller than those which enjoy a more liberal supply of water.

* New Zealand reference.

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Gadow (1901) gives a good account of the habits of this species. According to him, these frogs live well in captivity, and become confiding enough to take food from one's fingers. They are nocturnal, hiding by day and emerging at dusk. In hiding they simulate the colour of their surroundings; dark brown when resting in hollow logs or a tone of green to harmonise with the surface of the foliage they may be resting on. When at rest the limbs are tucked close under the body. In broad daylight the pupil, when at rest, is reduced to a tiny slit, but at night it enlarges to the full extent of the eye.


The food consists of earthworms, snails, insects and spiders. The food is generally lapped up by a flick of the tongue, but large or lengthy objects are ‘shovelled’ into the mouth by the aid of the forefeet in a ludicrous manner. The shells of snails are ejected through the mouth after their contents have been digested, much in the same way in which some birds of prey eject pellets of undigested parts of their prey.


Both sexes are said to have a voice, but that of the female is merely a grunting sound. The male is provided with internal vocal sacs. He inflates his throat and emits a sharp cracking sound, which can turn into a ‘regular bellowing like the gruff barking of an angry dog‘. They croak at any time of the year, particularly on the approach of showers of rain. Certain noises will induce them to bark. Once one has commenced others will join in the chorus.


In Australia breeding takes place in August and September, but abnormally dry conditions may result in the postponement of egg-laying to January. The eggs are laid in foamy masses which float on the surface of the water. The tadpoles pass their early development within the mass and enter the water from beneath.

Nothing is known of the breeding of this species in New Zealand, but I have seen a tadpole taken at Inglewood about June 26, 1952, and two from Puketaha, eight miles from Hamilton, on March 10, 1957. In both cases buds of the hind limbs were just visible.


A tadpole collected at Inglewood (text-fig. I, fig. 5) about June 26, 1952, with the hind limbs just appearing measures, in total length, 134 mm. (tail 89 mm. by 31 mm. at the deepest point, including membrane). Another two, taken at Puketaha on March 10, 1957, also had the hind limbs just appearing. The larger of the two specimens measures 112 mm. (tail 75 mm. by 28 mm. at the deepest point). These tadpoles give some page 120 idea of the size they attain for this species. They are considerably larger than the tadpoles of either H. aurea or H. ewingi.

The lips are fringed with papillate processes. In the Inglewood specimen no horny teeth are visible above the beak, but this may be due to delayed or poor preservation. The imperfection of the series below the beak is probably due to the same cause (text-fig. I, fig. 3). In the Puketaha specimens two series are visible above the beak, the lower series being interrupted in the centre; below the beak there are three series (text-fig. I, fig. 4), the uppermost interrupted at the centre.

Introduction to New Zealand

In 1897 the Agricultural Department received a consignment of six dozen of this species from Mr. J. Stein of Sydney. According to Mr. T. W. Kirk, some of these frogs were liberated at Greenmeadow Vineyards and Orchards, some on Frnley Estate and a few on the Hastings Racecourse, all in the Hawke s Bay area. Others were released in the Wellington Botanical Gardens and at Paraparaumu. These were augmented by another consignment imported in 1899.

The island of Motuihi in the Auckland area was also stocked with them. In the South Island, Mr. Kingsley liberated some on behalf of Dr. G. M. Thomson in the Queen's Garden at Nelson. A further number was freed on the Government Experimental Station at Moumahaki. Dr. Thomson remarks that although he especially sought them some years later in the area, he did not find any and surmises that in all probability they perished.

There has been much speculation as to the survival of the species in the North Island. Mr. J. Moreland, at that time Curator of the Wanganui Public Museum, brought me a specimen which had been found dead in the town. Of this specimen Mr. Moreland remarked, ‘Picked up freshly dead in a gutter, in Wanganui City area on the 17th February, 1949 after a warm showery night.’ This record of the species is of interest although there is the possibility that the specimen in question may have been accidentally imported. Enquiries by Mr. Moreland led to no results.

Although no further adult specimens of H. caerulea have been obtained in the North Island, there is good reason to believe that the species still survives there, for on about June 26, 1952, a large tadpole was obtained at Inglewood and another two of about the same size at Puketaha on March 10, 1957. It is more than likely that this highly camouflaged, arboreal frog has so far escaped attention and still survives in suitable localities.


I wish to express my thanks to Dr. R. A. Falla, Director, Dominion Museum, Wellington, for the opportunity of undertaking the work; to Dr. J. C. Yaldwyn and Mr. J. A. F. Garrick for going through the manuscript and making several useful comments and suggestions; and, last but not least, to Messrs. C. Hale and F. O'Leary for the fine photographs accompanying this article.