M. Serena et al., Effect of food availability and habitat on the distribution of platypus (Ornithorhynchus anatinus) foraging activity, AUST J ZOOL, 49(3), 2001, pp. 263-277
While the diet of the platypus (Ornithorhynchus anatinus) is known to inclu
de a wide range of benthic macro-invertebrates, little is known about how t
he animals distribute their feeding behaviour along a waterway. This radio-
tracking study aimed to determine whether the spatial distribution of platy
pus foraging activity varied in relation to habitat attributes and/or the a
mount of food present along a southern Victorian stream. Five O. anatinus w
ere tracked nocturnally for a total of nearly 95 h in March and April 2000.
Attributes of the channel and bank were described both in the area used by
the animals and adjoining unused sections of stream, and macro-invertebrat
es were sampled quantitatively in six substrates that varied in abundance i
n the used and unused areas. Eleven habitat variables showed a significant
positive relationship with the occurrence of platypus activity (including t
he number of medium and large Eucalyptus, Acacia and Populus trees growing
along the bank; presence of gravel, pebbles, cobbles, large rocks and coars
e particulate organic matter in the channel substrate; amount of riffle hab
itat; amount of large woody debris in the channel; and amount of undercut b
anks). Six habitat variables showed a significant negative relationship wit
h platypus activity (including the number of medium and large Salix trees g
rowing along the bank; the presence of silt, solid clay and Salix roots in
the channel substrate; the amount of pool habitat; and the maximum channel
depth). Substrates that were relatively abundant in the area used by O. ana
tinus (gravel/pebbles, Eucalyptus litter, Populus litter) did not consisten
tly support more macro-invertebrates than substrates that dominated the unu
sed area (silt, Salix roots, Salix litter). This may reflect the fact that
the platypus population was not food-limited (and hence not under pressure
to optimise foraging) at the time of the study, that platypus feeding patte
rns were influenced by habitat features that were not considered in relatio
n to invertebrate abundance, or that the choice of foraging areas by O. ana
tinus may be influenced by factors other than the total abundance of food i
tems, e.g. the nutritional quality and/or accessibility of prey.