On Macquarie I. it rains daily and abundantly; whether the habitat is flooded
or not determines whether the tick Ixodes uriae and the flea Pavapsyllus magellanicus
heardi can survive and breed. The principal hosts of these ectoparasites are penguins;
the degree of infestation of the four species of penguins that breed on Macquarie I.
differs because of differences in their breeding and moulting behaviour.
Royal penguins, Eudyptes chrysolophus schlegeli, form large colonies which are
surrounded by tussock, Poa foliosa. Rock stacks covered with vegetation may be
within the colony. The drier conditions within the tussock and on the rock stacks are
necessary for oviposition and egg development of I. uriae although larvae, nymphs,
and adults can survive submersion in water for many weeks. Royal penguins are
present in the colony from September to April, and consequently a blood meal is
readily available close to the breeding area of the tick for half of the year. In these
circumstances the life cycle of I. uriae can be completed within 2 yr. The other
penguin species do not afford such favourable opportunities for population growth of
I. uriae.
Only the rockhopper penguin, Eudyptes chrysocome, nests in sheltered situations
such as caves, or under overhanging rocks. In these drier nests the larval and adult flea,
P. magellanicus heardi, can survive, and the larvae can overwinter.
Bats were killed between 1963 and 1973 during surveys in Australia, Papua New Guinea and Bougainville Island. Results are given as number of stomachs containing particular food items, or as number of items in a stomach. Insect remains on the floor of bat caves were examined also. There were 42 species of bat examined, of 16 genera; stomachs of 36 species had Lepidoptera, 29 had Coleoptera, 27 had Hymenoptera and 23 had Hemiphera. Twelve bat species ate wingless insects and 7 ate aquatic insects, though those may be found away from water. Results are discussed in relation to foraging behaviour of bats.
The eastern water rat, Hydromys chrysogaster, lives in inland waters, estuaries, sea beaches and islands from Queensland to South Australia and Tasmania. It is adapted to semiaquatic life and changes in its molar teeth may be an adaptation to diet of crustaceans and molluscs. The present study was of 408 stomach contents and 316 contents of caecum with rectum, collected in New South Wales in 1970-73 from permanent Typha swamp. From elsewhere there were 12 other stomach and 11 gut contents and live rats were observed. At any time of day but particularly in evenings the rats swam along the bank or between logs or reed clumps, foraging and catching fish. Captive rats crushed small mussels and left large mussels to open by exposure. Diet varied with season and included crustaceans, mostly the yabbie, a crayfish (Cherax destructor), spiders, all Araneida with one identified as of the suborder Pisauridae, a fishing spider. Insects were the main food and were eaten in all seasons, and included larvae, nymphs and adults. Only 1% of rats had the freshwater mussel Veksurio ambiguus but the flesh was difficult to identify and empty shells were often found. Fish were eaten all the year, and were found in up to 35% of rats in autumn and winter; fish may be underestimated because flesh is not easily recognised and hard parts are not much eaten. Several species of fish, mostly introduced, were identified, their ages estimated from their scales, and length was calculated to be up to 36 cm. Frogs and macquaria tortoise (Emydura macquarii) were eaten. Birds were eaten all the year and were in up to 10% of stomachs in winter. Personal communications are quoted, from persons having seen H. chrysogaster capture large adult birds including duck and mutton bird (Puffinus tenuirostris). Captive rats were able to open cracked hen's eggs but left intact eggs. Plant material was eaten as food and possibly also in stomachs of prey. For 3 rats half the starch content was plant; 3 other stomachs had 5, 40 and 50% plant material, Azolla fuliculoides. Differences in diet with age are described. H. chrysogaster was an adaptable and opportunist feeder, making use of transient plenty of insects, exploiting plagues among other species and using plants during shortage of food. They may control introduced pests such as perch, or control yabbies in irrigation ditches.
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