Varanus salvadorii

Salvadori's monitor, Crocodile monitor

Varanus salvadorii  Peters & Doria 1878

Salvadori's monitor is one of the world's most magnificent animals. Often cited as being "the longest lizard in the world" virtually nothing is known of its ecology and the species remains one of the world's greatest zoological enigmas. This species was first described from a specimen 50cm SVL (165cm TL) caught by Dr Odoardo Beccaris, supposedly at  Dorei in northwestern New Guinea. It was described by Wilhelm Peters (the owner of the Zoological Museum in Berlin) and Marchese Giacomo Doria (later the owner of the Natural History Museum in Genoa) and named after Conte Tommasso Salvadori, an eminent Italian ornithologist.

Salvadori's monitor does not appear to live anywhere other than the magical island of New Guinea. According to Whitaker et al (1982) it is found in Western, Gulf, East and West Sepik provinces of Papua New Guinea. Mertens (1958) records it from the Fly River whilst Mertens (1971) and/or Brandenberg (1983) examined specimens from Aird Hill, Kikori, Kokoni River, Kwari (Dore), Hollandia Bivak, Lake Sentani and the Jamoer River. According to MacKay (pers. comm.) they are found in mangrove and other estuarine swamps as well as drier forest from Port Moresby westward along the coastal regions as far as the Vogelkopf in Irian Jaya. Because they are restricted to the southern coast he considers records from Lake Sentani and other parts of northern New Guinea to be incorrect.

Salvadori's monitor is an excellent climber, able to support itself on vertical surfaces by hanging on with the hind feet alone. The tail is extremely long (up to 200% of the snout-vent length) and surprisingly prehensile; able to curl round branches to support the lizard when descending. It is also a formidable whip. Murphy & Mitchell (1974) describe how an adult male used the tail to make well-aimed strikes at its keeper's eyes. On the ground Salvadori's monitors tend to keep the tail tightly curled up in a spiral (Mertens 1960). In captivity males tend to be much bulkier than females, but there are no clear external differences. Indeed, several animals identified as males on the basis of hemipenal eversion have subsequently laid eggs (Madsen, pers. comm.).

According to the record books, Salvadori's monitor is indeed the longest lizard in the world. The record appears to be held by a specimen examined by Dr Michael Pope, a zoologist of Port Moresby, which measured 475cm from the tip of its nose to the tip of its tail (Wood 1982). Unfortunately neither the lizard nor Dr Pope can be traced. However reliable sources suggest that some very large monitor lizards do occur there. According to Menzies (pers. comm.) the largest ever seen at the University of Port Moresby could have been 500cm long, but it escaped before it could be measured. Another specimen of 427cm has been reported from the area of Kikori, Gulf Province, Papua New Guinea (MacKay, pers. comm.) and a captive specimen circa. 300cm TL was reported to be kept at Moitaka (Allison, pers. comm.). Despite these claims the specimens available for inspection are all much smaller. The largest known example measured 244cm TL (Mertens 1962).

Furthermore, long-term captives that appear to be in old age never attain a greater length. Even if much longer specimens do exist, Salvadori's monitor is a slightly built species compared with the Komodo dragon and there is no possibility that any will be found to compete with these giants in terms of bulk. About two-thirds of a Salvadori's monitor's length is made up of tail (Mertens (1960) cites tail length of 250-260% of SVL), and so even the largest of the supposed giants cannot have a body length of much more than 130cm. Females reach sexual maturity at less than 45cm SVL and the only known hatchling measured 11.5cm SVL, 45cm TL and weighed 55g (Hairston Adams, pers. comm.). Geographical differences in tail length have been described in many species of monitor lizard (e.g. Storr 1980) and it is not inconceivable that specimens with head and body lengths similar to those of known specimens could sport very long tails, thus accounting for the apparently incredibly long specimens that have been reported from many reliable sources. There are undoubtedly still many undescribed monitor lizards in New Guinea and the possibility remains that the real giants belong to a species as yet unknown to science.

Salvadori's monitor is often known as the tree crocodile, in reference to its arboreal habits, great size and large, bulbous snout. A description of the skull is given in Mertens (1950). The teeth of this species are particularly long and straight. As in the white-throated monitor the snout becomes particularly bulbous and prominent in old males.  The toes are long and equipped with massive, curved, shiny-black claws.  Observations in captivity tend to suggest that males spend less time above ground than females, but this is probably due to the fact that most specimens have lost at least a couple of toes by the time they are imported. The long tail lacks any sign of lateral compression and is reminiscent of the tails of dwarf monitors such as V.gilleni, but they are definitely found along rivers and are said to be good swimmers (McKay, pers. comm.). In defence the tail is often curled up in a manner very similar to that of  the smaller New Guinea tree monitors (prasinus group).

Records of prey eaten by this extraordinary animal in the wild are sadly lacking. The only definite report appears to be that of Brandenberg (1983) who found a bird's egg in the stomach of a preserved specimen. Mertens (1960) believed that their diet consisted of small mammals, birds and their eggs, frogs and reptiles and Auffenberg (1981) claims that birds and their eggs form part of the diet. Suggestions that these lizards prey on children can be dismissed as utter nonsense, although they would probably consume them as carrion. According to MacKay (pers. comm.) the lizards feed largely on birds and often lie on branches overhanging trails to ambush small mammals (such as rats and bandicoots) by dropping on them as they pass by.

Salvadori's monitors are often very nervous in captivity. They need to be kept warm and with high humidity and provided with a huge enclosure that allows them ample opportunity to climb. Plenty of hiding places on and above the ground will help them feel secure. They seem to appreciate regular hosing downs with tepid water. They appear unfussy in their diet and will accept birds and small mammals, but larger specimens are prone to obesity Salvadori's monitors kill rats by shaking them very violently before swallowing them.  The lizards are best kept apart except when breeding is attempted because there are several known cases of animals killing or maiming each other. Most of the damage is caused by the claws. The long teeth of these lizards can inflict horrific injuries on their keepers (Anon, pers. comm.) but long-term captives can become tame enough to feed by hand and have been described as "observant and curious" by several keepers who are not usually inclined to spout anthropomorphisms. Copulation has been observed in enclosures as small as 8m2 (and at least 3m high) and often occurs during periods of short day length. Up to 12 eggs (weighing 40-50g and measuring about 8 X 3.5cm) may be produced in a single clutch (Philippen 1994). Females prefer to nest above the ground and up to three clutches (total of 17 eggs) have been laid over a year.  Only one successful breeding is known, with a single youngster hatching after 176 days at 28-29oC (Hairston Adams, pers. comm.). In captivity they can live in excess of 20 years (Mitchell, pers. comm.).