Mertens 1957
Rosenberg's goanna
Rosenberg's goanna is among the best studied of the
Australian monitor lizards. They are found throughout
southern Australia; in Western Australia, South Australia,
New South Wales and possibly the western edge of
Victoria and are also present on a large number of islands
including Thistle. Reevesby. Boston. Louth. Spilsby, Taylor's and Kangaroo Islands. It has been suggested that
the goannas were purposely introduced to some of these islands (e.g. Reevsby Island) in
order to reduce the numbers of dangerous snakes. On these islands Rosenberg's goanna is
said to be very rare (believed extinct on Ainder's Island), whilst on Kangaroo Island they are
abundant and seen more often than any other lizard. They inhabit a range of habitats,
including woodlands, heathlands, scrublands and farmlands, but appears to be restricted to
sandy soils (Ehmann 1976; Tyler
et al 1979; Robinson
et al l985; Schwaner 1985; Maryan &
Robinson 1987; Shea 1994).
Rosenberg's goanna is similar in appearance to
V.gouldii and
V flavirufus but is darker in
colour (those from islands tend to be darkest), has a less distinct pattern and usually has a
plain. dark tail tip. rather than a light or banded tip as is found in the other species. On some
islands (including Kangaroo Island) the tail tip is banded rather than plain (Houston & Tyler
1979).
In areas of Western Australia where they are sympatric with
V.flavirufus the two races do
not interbreed. prompting Storr (1980) to elevate them to a separate species. Hatchlings of
Rosenberg's goannas are far more colourful than the juveniles of closely related species. They
have an almost blue ground colour, with bright orange markings on the sides of the head,
flanks and tail (see Green & King 1993). Rosenberg's goannas may reach a larger size than
V.flavirufus, and tend to be more bulky. Maximum size in Western Australia is given as
103cm TL (Storr 1980). According to Tyler et at (1979) they can reach a length of 150cm
on Kangaroo Island. The artimals are significantly larger on Kangaroo, Reevesby and Spilsby
Islands than on the mainland. In all populations males grow about 12% longer than females
(Storr 1980; Case & Schwaner 1993). Around Sydney they reach at least 50cm SVL (Shea
1994).
Rosenberg's goanna eats a wide variety of animals. They will take larger mammals such as
adult possums (either alive or as carrion) (Waite 1927 in Houston & Tyler 1979). Overton
(1987) reports an attack on a young echinda. Usually they are said to feed on insects, spiders,
scorpions frogs, snakes, lizards, small birds and small mammals (Houston & Tyler 1979).
King & Green (1979) found that mammals (especiaUy rodents) and invertebrates (roaches,
orthopterans, spiders, scorpions, beetles, centipedes and moUuscs) account for two-thirds of
all food taken on Kangaroo Island. The remainder of the diet is made up of frogs, reptiles,
lizard eggs and birds. A 770g specimen examined by Losos & Greene (1988) contained
orthopterans, lepidopterans and the remains of a mammal.
Rosenberg's goanna appears to do a lot of digging. They encounter much of their food below
ground and dig enormous burrows. Tubb (1938) describes very long (over 9m), shallow (less
than 30cm), forked burrows dug on the Banks Islands. Green & King (1979) found that
burrows used in the surruner on Kangaroo island were much shallower than those used
during the winter but shallower than those on the mainland. On Kangaroo Island the goannas
may remain active throughout the winter, whilst the activity of those on the mainland is
greatly reduced. Males are more active than females, and therefore encountered more often.
Breeding occurs during early summer. Where tennite mounds are available they are used as
nests. Eggs laid in February hatch 6-7 months later (King & Green 1979; King 1980).
Ehmann
et al (1991) provide an account of nesting behaviour and incubation conditions.
Several years ago there were proposals to eradicate Rosenberg's goanna from Reevsby Island
to allow reintroduction of the almost extinct sticknest rat. It was claimed that the goannas
had been introduced to several of the Banks Islands in the 1920s or 1950s to destroy the
tiger snake population (Mirtschin 1982; Minschin & Jenkins 1985). This was refuted by
Schwaner (1985) who suggested that the claims that the goannas were not native to the
island were entirely speculative. Robinson
et al (1985) argued that early visits to the islands
had shown no evidence of goannas and that their removal was essential to allow the
reintroduction of sticknest rats. Permission was given to destroy the goannas, but in the
event the population proved so small that it was not worth eliminating and the scientists
contented themselves with the extermination of feral cats (Schwaner pers.comm. Robinson
pers. comm.).
I can find no published reports of captive breeding in this species. They should be housed in
the same manner as for other large, burrowing goannas. An extremely informative and
engaging account of Rosenberg's goanna is given by Green & King (1993).
