Studies on the Feeding and Neophobic Behaviour in Norway Rats (Rattus norvegicus Berkenhout, 1769) from Farms in Germany (English shop)

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Studies on the feeding and neophobic behaviour of Norway rats (Rattus
norvegicus) have been done in 1998 – 2000 at the Institute for Nematology and
Vertebrate Research, Federal Biological Research Centre for Agriculture and Forestry,
Münster. The results of these previous studies showed that there were some differences
in the consumption of baits and rodenticides by rats from several farms in the
Münsterland. This phenomenon was presumed to be caused by the differences in the
feeding and neophobic behaviour of the rats. Therefore, some experiments were
conducted in the laboratory, to examine these possible causes using rats from different
farms.
Studies on the feeding preference and rodenticides acceptance were done in
separate cages. Among cereals, rolled oats was the most palatable feed while intact oats
was the least one. There were some differences in the preference of rats from several
farms to cereals and to the feed from one farm, except to maize silage. Previous
experiences at the particular farm could affect the feeding behaviour in the laboratory.
Newly caught rats consumed feed in an equal amounts compared to long adapted rats
from the same farm. Comparing all feed offered, rolled oats was the most palatable
feed while soybean coarse meal was the least one.
Preference to attractants was studied in a choice test. Rats preferred bait bases
with attractants compared to those without attractants. There were some differences in
the preference to several attractants between rats from different farms. However, there
were no differences in the preference to vanilla-sugar and egg as attractants. Comparing
the consumption of rats differing in sex and body weight, it could be shown that female
rats consumed more than males, while small rats did more than the bigger ones.
Several rodenticides were tested, with three bait bases and in several batches.
There were some differences in the preference of rats to some rodenticides. However,
there were no differences in the rodenticides consumption by rats from different farms.
Some, but not significant, differences were observed between the results of laboratory
and field trials.
Experiments to study the neophobic behaviour were carried out in an
experimental room to that the rats had to be adapted. Then, a lamp which was
automatically switched on-off and producing a noise as a new object was placed inside
that box where more of the feed was consumed. The rats were afraid of the new object
when it was used for the first time. The consumption and time spent inside both boxes
were recorded. The experiments were conducted both at groups and individuals level,
using the same and different feed (at individuals level). Different sample of rats from
two farms were tested in individuals level following the study at groups level.
In the tests on groups and individuals rats, rats from farm no. 4 showed the
lowest level of neophobic behaviour, while rats from farms no. 3 and 5 showed the
highest one. Rats tested as individuals or in groups showed in most cases identical
responses. Comparing different feed it was shown that rats preferred to consume the
most palatable feed over the least one, although there was an interference (new object)
around the feed. The highest level of neophobic behaviour was found in rats stemming
from very quiet locations, without disturbance, and from frequently controlled areas.
The lower the level of neophobic behaviour in rats is, the easier the rats accept several
kinds of feed and taste.
There was a correlation between the time interval within two trials and the
adaptation time on one hand and the neophobic response on the other hand. The shorter
the interval and the longer the adaptation time were, the more familiar the rats were with
the new object, showing higher feed consumption and longer time spent inside the box
with device. Feeding and neophobic behaviour must be taken into consideration in the
chemical control of rats. Experiences at the different farms can affect the preferences to
the feed and levels of neophobia in rats. There were three factors at the farm that could
affect the feeding responses and levels of neophobia, i. e. disturbance, effectiveness of
rat control, and feed availability. The differences in the behaviour of rats resulting from
these factors are also detectable in laboratory studies and can be decisive for the
effectiveness of rodenticides.