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There are many factors to be considered, such as environment and the pattern of behaviour,
embracing the general feeding habits and ability to subsist without water, plus the acceptance of
harbourage and food supply which would be quite inadequate for rats.
Mice, unlike both species of rats which are fairly stable in behaviour, are best described as
mercurial. They are on average about 25 grammes in weight when mature, and the food intake in
24 hours is consequently very small - between 3 and 5 grammes, so that very small quantities of
food are sufficient for their welfare. They are erratic in their feeding habits and may eat a very
small amount at a number of places - not necessarily the same each day. This means that very
many small baiting points are necessary when applying control measures with poison. This factor
also limits the use of the more acute poisons.
Where there is unlimited harbourage, structural and incidental, as found in warehouses with
large bulk stowages of varying commodities, and a reasonable food supply, there appears to be a
very diminished range of activity from the nesting quarters. Therefore, a high percentage of an
infestation living and breeding therein do not emerge to accept the baits at the baiting sites,
which are limited by the size of the stowages or by congestion often found in other types of
premises.
The nucleus of mice infestation is often imported into premises and, in the case of catering
establishments, many instances have been seen where this has occurred via sacks of vegetables,
crates of eggs, and cartons.
Many of the complaints of mice infestation are received from offices, and the cause can
usually be traced to the careless or thoughtless disposal by the staff of food scraps. It is a common
occurrence to find food wrappers, fruit paringp, odd scraps, and milk bottle tops with cream
adhering, thrown down in inaccessable places. Alternately, it is put into waste paper baskets
where, as a rule, it remains all night, to attract and provide the subsistence for mice.
During the year, three direct poison treatments for the destruction of rats in sewers were
carried out. These control measures were proceeded by an overall test bait control and comprised
the third series of four quarterly controls by direct poisoning with Fluoracetamide '1081'.
The first of these treatments was applied in December 1956 and the final treatment of the
series will be carried out in March 1960.
On completion a comprehensive report will be written giving the full details of each treatment,
and test controls applied between each series.
These control measures, unique to the City, have been carried out in conjunction with the
Scientific Officers of the Infestation Division, Ministry of Agriculture, Fisheries and Food.
Prior to the institution of these control measures, a similar series of 17 treatments at quarterly
intervals, interspersed with overall test bait controls was applied, the toxic agent being
Mono Sodium Fluoroacetate '1080'.
These treatments, the first to be carried out in this country, appeared to be very successful,
and it was decided to apply the present series, now nearing completion, in an endeavour, as far
as reasonably practicable, to ascertain if the low level of rat infestation believed to have been
achieved, could be maintained by Fluoracetamide '1081'.
From the information collated so far, and the similarity of the results obtained with these
poisons, it does appear that Fluoracetamide is comparable in effect with sodium Fluoroacetate.
By reason of its more granular texture, the former is safer to dispense, and owing to its lower
toxicity to rats, and presumably to man, is less hazardous in distribution.
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