The Owl That Fell from the Sky (11 page)

The mystery of the banjo frogs

Most enquiries from members of the public are of only transitory interest but occasionally they can be momentous. So it proved when my telephone rang in October 1999. A young man said he had found some unusual tadpoles. He was familiar with the common tadpoles in the Auckland area that belonged to the introduced green and golden bell frog,
Litoria aurea
. The ones he had were different and he felt someone should know about them.

Three species of Australian frogs were deliberately established in New Zealand in the late nineteenth century: two large green species—the green and golden bell frog and the southern bell frog,
L. raniformis
—and the small brown whistling frog,
L. ewingii
. These are the frogs New Zealanders are most likely to encounter: they call noisily during the breeding season and produce tadpoles. However, the native frogs are seldom seen. Of the genus
Leiopelma
, they are restricted to a few forested parts of the northern North Island and to some small islands in the Marlborough Sounds. They have no loud breeding calls and their eggs hatch directly into tailed froglets without a tadpole stage.

I asked the caller to bring in a few tadpoles so I could
see them for myself. At the appointed time he arrived, placed a container of water on the bench in my workroom, and opened it up. The tadpoles were certainly not the pale, uniformly coloured ones I was used to. As they swam about, there was an indication of a faint pattern of blotches on their dark upper surfaces, and their body shape was different.

I asked if I could raise some of the tadpoles into froglets to see what developed. Later that day I blanched some lettuce leaves in boiling water to serve as tadpole food. As the tadpoles grew it was soon clear they were turning into brown-coloured froglets and not the green ones to be expected. I advised the finder that I was going to ring the Ministry of Agriculture and Forestry's biosecurity hotline.

The ministry's telephonist took my details and I was very promptly contacted by Davor Bejakovich, a herpetologist at the ministry. Bejakovich asked me to send preserved samples to Michael Tyler, a frog expert in Adelaide: all indications were that the frog was an Australian species not previously recorded in New Zealand. After Tyler had studied the specimens and photographs, he advised us we were dealing with the banjo frog
Limnodynastes dumerilii
. A laboratory in Queensland later analysed DNA from the samples, confirmed this identification, and found the New Zealand specimens belonged to a subspecies of banjo frog that inhabited coastal New South Wales.

 

 

Soon after I sounded the alarm, field investigations—a “delimiting survey” as it is known in biosecurity circles
—began. I joined Bejakovich and another herpetologist,
Tony Whitaker, as they visited the house of the young man who had discovered the tadpoles. As a form of supplementary income the man collected and raised frogs and tadpoles to sell to pet shops. In the garden of his parents' home there were a series of large, free-standing aquariums containing hundreds of tadpoles.

He told us he had collected spawn of the mystery frog at a remote bush-clad stream on the road to Whatipu, an isolated beach in the Waitakere Ranges west of Auckland city. We all travelled to the site and a search of the stream revealed further tadpoles, and two emerging from the water as froglets. Next day torrential rain scoured the creek, and on subsequent inspections ministry staff found no more tadpoles or frogs. The existing tadpoles and froglets were destroyed and the aquariums at the man's home sterilised with sodium hypochlorite.

In the following months, staff from the ministry, the Department of Conservation and Auckland Regional Council searched likely sites across west Auckland. At night they listened for the banjo frog's loud and distinctive “bonk” calls, which are nicely evoked by the creature's other name, pobblebonk. Recorded frog calls from Australia were played to see if there was any response.

Michael Tyler was brought to New Zealand to view potential habitats for the frog in Auckland and advise on the likelihood of its establishing there. The news was not encouraging: there seemed a good chance the frog could survive where there was suitable habitat. As an aggressive and reasonably large predator it might then eat, or compete for food with, certain native animals, with detrimental impact on the environment.

I killed and preserved some of the banjo frog tadpoles and froglets at various stages of growth so Auckland Museum would have a good range of reference samples against which to compare any future suspicious tadpoles. While on holiday in Fiji, I also took the opportunity of collecting samples of the dark tadpoles of the introduced Central and South American cane toad
Bufo marinus
, which is a serious pest in several Pacific countries and a significant threat to native species in northern Australia. Cane toads were once brought live into New Zealand as laboratory animals, and have been found alive in cargo arriving in the country. In 1997 I was given a specimen for the museum: it had been found hopping about in a South Auckland ditch near a cargo warehouse.

 

 

It appeared the banjo frog had been deliberately introduced: spawn, or perhaps tadpoles, had been smuggled in from Australia. To this day it remains a mystery as to who did this and why the spawn was placed at such a remote and unlikely location. No further banjo frogs were found in west Auckland in 1999 or during monitoring over the next two years, and none has been reported since.

Accidental introduction of pest animals is as much a hazard as deliberate introduction. With Davor Bejakovich and Tony Whitaker, I embarked on a study of the potential for amphibians and reptiles to arrive by accident in cargo coming into New Zealand. We compiled records of interceptions of foreign species, based on specimens in museums and records held by the Ministry of Agriculture and Forestry. For the period from 1929 to 2000 we were able to document more than fifty species of frogs and reptiles among 189 incidents: most were from Australia, south-east Asia and the south-west Pacific. In more than eighty percent of cases animals were alive when detected, and nearly half the animals were intercepted after the cargo had passed through border controls. This showed the importance of having reference material in museum collections to help biosecurity officers quickly and easily identify unknown animals—the first and fundamental step in any action against an unwanted intruder. Interestingly, despite the potential for accidental introduction, only one frog or reptile—the Australian rainbow skink
Lampropholis delicata
—has so far established in this way in New Zealand.

 

Captain Cook's tortoise

One of Auckland Museum's more esoteric claims to fame is that it is mentioned at the beginning of Philip K. Dick's classic 1968 science fiction novel
Do Androids Dream of Electric Sheep?
—the book that inspired the 1982 Hollywood movie
Blade Runner
. The novel begins with a dispatch from Reuters news agency, dated 1966, reporting that the tortoise Captain Cook gave the King of Tonga in 1777 had just died at the age of nearly 200 and its body would be sent to Auckland Museum in New Zealand.

A tortoise named Tu'i Malila that lived in the grounds of the Royal Palace at Nuku'alofa did indeed die in May 1966, and at the request of the Tongan Government was sent to Auckland—frozen and presumably by sea—to be stuffed.

When it arrived the museum's preparator, Leo Cappel, set about the laborious task. He had to remove the tortoise's flesh and internal organs, clean the skin and carapace—the domed shell—and put inert material in place of what had been taken away. A framework of connected internal rods was needed to strengthen the attachment of head and limbs. Then, while the skin was still soft and supple, it had to be sewn up and the animal arranged in a life-like position before it dried rigid. It was a big job on such a bulky animal.

During the preparation Joan Robb, a reptile specialist at Auckland University's zoology department, examined the body, and with the help of books and articles determined it was a radiated tortoise native to southern Madagascar. Its carapace was about forty-one centimetres long and twenty-four centimetres high, full-sized for the species; its weight would have been about thirteen kilograms.

According to Tongan tradition, James Cook presented a pair of tortoises to a chief in the Ha'apai group in May 1777, during his third voyage to the Pacific. However, Cook would almost certainly have recorded such an important chiefly presentation in his journals and there is no corroboration there, which casts some doubt on the matter. The chief is said to have given the tortoises to the Tu'i Tonga, or king, as a plaything for his daughter at Mu'a on the island of Tongatapu. The female tortoise eventually died and the male passed into the care of Catholic priests and nuns until 1920, when it was transported to the main town of Nuku'alofa, presumably to take up residence in the palace grounds.

If it were indeed presented by Cook (or another officer or seaman) on that voyage, Tu'i Malila would have been at least 189 when it died. Even if it had come to Tonga during the period of whalers and traders in the early 1800s, or later, in the mid 1800s, it was still at least a century old. Its dented and scarred carapace testified to its great age, and to the trials and tribulations of its long residence in the “Friendly Islands”, which included being kicked by a horse and run over by the wheels of a dray. The tortoise had also gone blind, and hampered by this impediment had wandered into a grass fire in the palace gardens and been badly singed.

Tu'i Malila was a great curiosity for dignitaries visiting the Tongan royal family. Admirers included Queen Elizabeth and Prince Philip during their 1953 Commonwealth tour and the governor general of New Zealand, Sir Bernard Fergusson, on an official visit in 1964.

During taxidermy the sex of Tu'i Malila could not be determined from internal organs because the soft tissues had deteriorated before the body reached Auckland. However, the plastron, the section of shell covering the belly, was flat, suggesting Tu'i Malila was a female, not a male as had always been thought: male tortoises have a concave plastron to facilitate the juxtaposition of their shell with the shell of the female during copulation.

The taxidermy job completed, Tu'i Malila was exhibited in Auckland Museum for a while before being shipped back to Tonga, where it was displayed in the lobby of the International Dateline Hotel in Nuku'alofa.

In 1988 I went to Tonga for fieldwork and chanced upon Tu'i Malila in a display case at the new Tongan National Centre. It was not a pretty sight. The head and a limb or two had fallen to the floor of the case, insects had damaged the skin and stuffing was tumbling out. Just as sad were the robes that Sālote Tupou III, the Tongan queen from 1918 to 1965, had worn to Queen Elizabeth's coronation. These were upright on a mannequin in a tall case but were peppered with large holes, as if they had been raked up and down by heavy machine-gun fire. The holes were presumably the work of insect larvae when the robes had been folded away in storage. The tropics are a difficult environment for many museum objects. In New Zealand “borer” beetle larvae make pinhead-sized holes in wooden framing and furniture, but at Nuku'alofa the dining table in the house where I stayed had woodworm holes into which you could poke a pencil. It was no doubt these sorts of larvae that had played havoc with the queen's robes, and something similar had eaten away at Tu'i Malila's skin.

The state of the tortoise eventually led to its return to Auckland in 1997. This time things were not so easy: Tu'i Malila was impounded for two months at Auckland Airport pending fumigation, issuing of agricultural quarantine permits, and production of paperwork to clarify its position under CITES (Convention on the International Trade in Endangered Species) regulations. After Auckland Museum conservators finally took delivery of the tortoise and assessed its condition, a preparator undertook remedial work to make the tortoise again presentable for display in Tonga.

Tortoises are renowned for their longevity, and some individuals have lived so much longer than humans it has proved difficult to keep accurate records of just how old they are. A tortoise taken from the Seychelles to Mauritius is thought to have lived at least 152 years, and another in the garden of the residence of the governor of Saint Helena may have lived more than 175 years.

A Galápagos giant tortoise named Harriet died in 2006 at a zoo in Queensland, Australia. It had supposedly been a passenger on HMS
Beagle
with Charles Darwin. Because England had been too cold for the tortoise, it was said to have been sent to Brisbane in 1842. DNA tests showed that the zoo's Harriet belonged to a population from the Galápagos island of Santa Cruz, which the
Beagle
never visited, but that did not stop a celebration of her 175th birthday taking place in 2005. Another Galápagos giant tortoise, Lonesome George, who lives at the Charles Darwin Research Station on Santa Cruz and is the last survivor of his race from Pinta, a remote island in the Galápagos group, is thought to be between sixty and ninety years old.

 

 

During my 1988 visit to Tonga, in a display of old photographs at the Tongan National Centre I saw a picture of a man standing astride a tortoise that seemed much larger than Tu'i Malila. At that time, Tongan friends got me entry to a feast in the royal palace grounds, where I was surprised to see a small tortoise wandering about. All this raised the question of just how many Tu'i Malilas there had been. I wrote to the Tonga Traditions Committee and received a copy of a newspaper clipping showing that the small tortoise was a gift to the king, Tāufa'āhau Tupou IV, from America's National Geographic Society. A senior editor, while visiting Tonga, had seen Tu'i Malila, identified the species, and arranged for another individual to be sent by sea from Madagascar to the United States. From there it had been flown to Tonga, arriving on a Fiji Airways plane.

The tortoise was intended to be a mate for Tu'i Malila but alas it arrived in September 1966, four months too late. At the opening of the International Dateline Hotel soon afterwards, the king had the new tortoise brought along. In the presence of a large gathering he named it Tu'i Malila II.