Acrochordus
arafurae Mcdowell 1979: Type locality: Lake Daviumbo, western Province.
Distribution Coastal regions of northern
Australia and New Guinea. McDowell (1979) gave a more detailed discussion of its distribution. I have edited this slightly.
Distribution. In New Guinea, known
from the Mimika and Lorentz Rivers (Irian Jaya), the Fly-Strickland River
system, including Lake Daviumbo and Lake Murray, the smaller rivers (Bensbach,
Binaturi, Oriomo, Pahoturi) of southwestern Western Province, Papua New Guinea,
and the Aramia River drainage (I can find no records from east of Balimo on the
Aramia). In Australia, I know of definite records from the Daly, Alligator,
Koolatong, and McArthur River systems, Northern Territory, and the Leichardt,
Gilbert, Mitchell, Lukin, Edward, and Archer River systems, Queensland. Cogger
(1975) maps the Australian distribution as along the coast from the Kimberly
region of Western Australia to the eastern (Coral Sea) coast of the Queensland
Peninsula. Cogger (pers. comm.) notes that this apparent Coral Sea coast distribution
in Queensland is a result of the small scale of the map used, and neither
Cogger nor Covacevich (pers. comm.) know of any records
from Queensland that are not from rivers draining into the Gulf of Carpentaria;
Thomson (1935) reported aborigines claim this species does not occur on the
eastern coast of Queensland. It should be noted that although the Fly and Aramia
Rivers of New Guinea open into the western end of the Coral Sea, they are connected
by swampy lowlands to the rivers draining into the Arafura Sea. This species
thus seems confined to the freshwater drainages of New Guinea and Australia
connected to the Arafura Sea (including the Gulf of Carpentaria). I have not
found any records from the Aru Islands or from the islands of Torres Strait.
Size
Maximum length may be 2.5 meters, with
1.5 meters being the average length. Young average about 360 mm SVL. Sexual
maturity is reached by males at about 85 centimeters SVL, and at about 115
centimeters SVL in females.
McDowell (1979) provided the following diagnosis:
McDowell (1979) provided the following diagnosis:
Differs from other species of Acrochordus
in each of the following features: 1) nasal bones fused anteriorly; 2) hemipenes
forked only at extreme tip, without spines or papillae; 3) pattern with
intricate network of dark markings that are connected with one another but
isolate spots of the brown or tawny ground color. Additionally differing from A.
javanicus (but resembling A. granulatus) in 1) absence of coronoid
process on lower jaw; 2) posterior dentary teeth resembling other teeth in
form; 3) scales of sides with one main cusp, flanked by much smaller cusps; 4)
nasal bones tapering to a median anterior point; 5) maxillary teeth fewer (16-19);
6) dentary teeth fewer (13-17). Additionally differing from A. granulatus (but
resembling A. javanicus) in: 1) nostrils directed forward, without
upward inclination, separated from eye by 11-14 scales (against 5-7); 2) labial
scales less enlarged, with more rows (8-11, against 5-7) between eye and edge
of lip; 3) long pterygoid row of 11-16 (against 5-7) teeth; 4) no transversely
enlarged scale behind nasal; 5) less compressed tail, its vertical diameter
much less than twice its horizontal diameter. (The hemipenial characters of
this diagnosis checked on all males of material listed above; external, osteological,
and dental characters checked on all material listed above, except nasal bones
not checked for MCZ 118668, 118669, 118765, and 129121. In addition, vertebrae
in region of heart checked on AMNH 86182 [Borroloola, Northem Territory and
found to have short neural spine confined to posterior edge of neural arch,
essentially as in A. granulatus but unlike the high neural spine that
arises from most of the length of the neural arch in A. javanicus and the
Miocene-Pliocene A. dehmi Hoffstetter [1964]).
Although this species has
previously been confused with Acrochordus
javanicus, its resemblances to that form would seem to consist largely of a
common lack of the peculiarities of A.
granulatus. If special weight is given to the hemipenis, A. arafurae is the most distinct species
of the genus; if special weight is given to dentition and cranial structure, A. javanicus would seem the most
distinctive and peculiar; and if external features, such as upward inclination
of the nostrils, comparatively smooth texture of the scales, compression of the
tail, and strong definition of the belly fold, are given special weight, then A. granulatus would seem the most
distinct species of the genus.
Acrochordus
javanicus
and A. arafurae agree in being
freshwater forms, whereas A. granulatus
is found most often in salt water. This is not an absolute difference, for A. granulatus enters fresh water
extensively in New Guinea, reaching Lake Murray in the Strickland-Fly River
system and ascending the Sepik River as far as Brugnawi and Ambunti. Conversely,
Cogger (1975:362) says of A. "javanicus" [=A. arafurae], "Largely restricted to fresh-water streams and
lagoons, wherever monsoonal floods permit them to enter permanent waters;
however, they freely enter estuarine waters and the sea." Perhaps A. granulatus is the stronger swimmer
(as hinted by its compressed tail) and better able to cope with surf and fast water,
whereas A. arafurae is more efficient
in quiet ponds and lagoons, where its large size allows it to capture larger
prey than is utilised by A. granulatus.
Most accounts of the behavior and ecology of Acrochordus arafurae are so thoroughly permeated with observations
on A. javanicus that it is very
difficult to determine how much is really known about A. arafurae.
External Morphology
They are sexually dimorphic with females
generally the larger sex. File snakes are aquatic snakes with small, but very
strongly keeled scales, which give them the texture of a file. The skin of file
snakes is very loose and baggy. Colors vary slightly, but most are light brown
or gray with dark brown or black reticulations extending from a broad vertebral
band that gives a cross-banded, or a blotchy appearance on the dorsal surface
of the body. File snakes are somewhat lighter underneath, and the dark
reticulations usually extend onto the ventral surface of the body (Vincent,
1999).
Reproduction
File snakes are viviparous with
litter sizes of 6-27 young. Females may reproduce
only every eight to ten years in the wild. High population density, low
metabolic rates, and poor feeding efficiency are thought to be possible causes
for such low reproductive rates. Males are also able to store sperm in their
bodies for a number of years (Vincent, 1999). Captive individuals have been
reported to live for 8.8 years
Food Habits
File snakes feed almost
exclusively on fish. They forage at night, exploring cavities in mangroves and
riverbanks. Larger snakes ingest fish up to one kilogram. These snakes have
extremely low metabolic rates, thus feed less (about once a month) than many
other snake species. File snakes capture prey using their teeth, body scales,
and tail.
File snakes are an important food
source for Aboriginal communities in northern Australia. Aboriginal people,
usually the elder women, still hunt for File snakes by wading into the water
and feeling under submerged logs and overhanging banks. Pregnant female snakes
are a valuable source of calories to the Aboriginal people.