MURIDAE RECORDED FROM VICTORIA 
83 
The Black and Alexandrine Rats have spread throughout 
almost the length and breadth of Victoria. They are met with 
in uninhabited bush, and in the centre of the busiest cities. 
Though they sometimes construct burrows, they are not essen- 
tially fossorial but often live in trees, where they make nests 
or take over those originally built by birds. In buildings they 
live in walls and ceilings. They prefer a vegetable diet, play 
havoc in grain warehouses, and in orchards often climb trees 
to eat the growing fruit. They are also ships’ rats and are the 
hosts of the plague flea. 
In the towns of Northern Europe the Black Rat has been 
driven out and largely replaced by the Brown or Norway Rat, 
but, strangely, the exact opposite has taken place in Mel- 
bourne. Thirty years ago the rat population of this city was 
composed entirely of R. norvegicus, and the Black Rat was of 
such rarity that any specimens captured were considered 
worthy of preservation in the museum. About four years ago 
the writer investigated the present-day rat population of Mel- 
bourne, and, through the kindness of the City Health Officer, 
Dr. Dale, examined all rats caught by the City ratcatchers for 
a period of several weeks. About 500 adult specimens were 
individually examined, measured, and variation noted. Only 
the general facts are quoted here as an illustration of the 
present-day dominance of the smaller species. 
Of the rats caught within the City area of Melbourne, 87 5 
per cent, were R. rattus; of R. rattus the black form was 
represented by only 10 per cent, the remainder being grey. 
The colour forms do not grade, though the fact of interbreed- 
ing was verified, the two forms being present in a single litter 
of young. 
In Europe and America the colour forms remain more or 
less true to geographical conditions. The black form is 
northern (cool climate), the grey southern (warm climate). 
In Australia the two forms intermingle, though in view of the 
great percentage of greys in the cooler south it would be 
interesting to know whether, if at all, the percentage varies 
in the warmer climate of northern cities. 
Victoria has not been greatly troubled with rat plagues, 
though other States, principally northern, have had many 
occurrences. 
Mus musculus Linnaeus 1758. 
The European House Mouse has invaded every part of 
Victoria, and is usually known in the bush as the Field Mouse. 
