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Rodent infestation is considered as one of the major pest problems since it is not only acting as a health hazard, but also causes damages to household, agricultural fields and even transportation business. The use of rodenticides is a common approach to rodent control, however, most rodenticides are poisonous to man. Therefore, using natural extracts as a rat repellent may be a better alternative. In the current study, various natural extracts were experimented whether they could repel a rat when testing in the behavioral model, a circular open field. The tested substances were wintergreen oil, chilli, peppermint oil, bergamot oil and geranium oil either being applied as singly or in combination. For the natural behavior of the rats in the apparatus, the rats had the highest activity rate during the beginning of the nocturnal phase (light offs) as shown by total number of line crossed during 30 min. Therefore, this period was used for testing the efficacy of rat repellents. We found that the number of visit to the tested core and the time rat spent near the tested core significantly lowered compared to blank control. We can therefore conclude that these natural extracts can repel the rats as determined by rat's behaviors in the circular open field. However, more studies need to be done to see whether these extracts are of practical in real environment.
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Thai J. Vet. Med. 2010. 40(4): 411-418.
The Efficacy of Pure Natural Repellents on Rat Responses
Using Circular Open Field
Sarinee Kalandakanond-Thongsong1* Suwaporn Daendee2 Boonrit Thongsong3
Vivat Chavananikul3
Abstract
Rodent infestation is considered as one of the major pest problems since it is not only acting as a health
hazard, but also causes damages to household, agricultural fields and even transportation business. The use of
rodenticides is a common approach to rodent control, however, most rodenticides are poisonous to man. Therefore,
using natural extracts as a rat repellent may be a better alternative. In the current study, various natural extracts were
experimented whether they could repel a rat when testing in the behavioral model, a circular open field. The tested
substances were wintergreen oil, chilli, peppermint oil, bergamot oil and geranium oil either being applied as singly
or in combination. For the natural behavior of the rats in the apparatus, the rats had the highest activity rate during
the beginning of the nocturnal phase (light offs) as shown by total number of line crossed during 30 min. Therefore,
this period was used for testing the efficacy of rat repellents. We found that the number of visit to the tested core and
the time rat spent near the tested core significantly lowered compared to blank control. We can therefore conclude
that these natural extracts can repel the rats as determined by rat’s behaviors in the circular open field. However,
more studies need to be done to see whether these extracts are of practical in real environment.
Keywords: Circular open field, natural repellent, rat
1Department of Physiology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand.
2Interdisciplinary Program of Physiology, Graduate School, Chulalongkorn University, Bangkok 10330, Thailand.
3Department of Animal Husbandry, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand.
Corresponding author E-mail: Sarinee.Ka @chula.ac.th
Original Article
412 Kalandakanond-Thongsong S. et al. / Thai J. Vet. Med. 2010. 40(4): 411-418.


Circular open field
   1*   2   3   3
  
   
  
     
  Circular open field 
 24   (
)  30   

  Circular open field

:  circular open field  
1ภาควชาสรรวทยา คณะสตวแพทยศาสตร จุฬาลงกรณมหาวทยาลัย กรงเทพฯ 10330
2สหสาขาวชาสรรวทยา บัณฑตวทยาลัย จุฬาลงกรณมหาวทยาลัย กรงเทพฯ 10330
3ภาควชาสตวบาล คณะสตวแพทยศาสตร จุฬาลงกรณมหาวทยาลัย กรงเทพฯ 10330
* E-mail: Sarinee.Ka@chula.ac.th
Introduction
Rodent infestation is one of the major pest
problems since it is not only considered as a health
hazard but also causes damages to household,
agricultural fields and even transportation business.
On a ship, rats can cause extensive damage to cargo
and food and rat-droppings contain organism that
produce intestinal diseases (WHO, 1988). It has been
estimated that the total cost of destruction by rats in
the United States may be as high as $19 billion per
year (Pimentel et al., 2005). In India, analysis of the
information available on the damage and economic
losses caused by rodents in various crop fields,
horticulture and forestry, poultry farms, and rural
and urban dwellings and storage facilities showed
that chronic damage ranging from 2% to 15%
persisted throughout the country and up to 100% loss
of the field crop was not rare in severe damage
(Parshad, 1999). Several approaches to control rodent
infestation are being used such as environmental,
cultural, biological, mechanical and chemical
methods. In a ship, mechanical method like trapping
is a good method of keeping down the rat population
in which snap trap is more effective and practical than
cage type (WHO, 1988). However, the use of
chemicals like rodenticides is the common approach
in South Asia (Parshad, 1999). The rodenticides can be
classified into slow-acting and fast-acting rodenticides
(WHO, 1988). The former such as warfarin and
diphenadione are anticoagulants and must be
ingested for several consecutive days before they
become effective. The latter such as zinc phosphide
and bormethalin are also known as acute rodenticides
and often kill with a single dose. However, most
rodenticides are poisonous to man and the
effectiveness of rodenticides depends upon the
selection of an appropriate compound and its
formulation as bait. Moreover, the method and timing
of application are needed to be considered. One
problem of using bait is that if the rats have taken an
initial non-fatal dose, it can discourage the rats from
taking additional bait known as bait shyness. The
chemical usages are not limited to rodenticides but
chemical repellents like copper oxychloride, thiram,
beta-nitrostyrene, cycloheximide and tribotyltin had
been effectively tested in laboratory (Tigner, 1966;
Parshad, 1999). Major factors that limit the usage of
chemical repellent are possibly handling hazard and
food contamination if apply on individual boxes or
sacks containing food for human (Tigner, 1966). Due
Kalandakanond-Thongsong S. et al./ Thai J. Vet. Med. 2010. 40(4): 411-418. 413
to possible chemical toxicity, the alternative like
natural extracts should be considered. The interested
substances are chilli, wintergreen oil, bergamot oil,
peppermint oil and geranium oil as it had been
reported that these substances had insect repellent
properties. Lale (1992) had shown that powders
prepared from ground chilli can repel the bruchid
beetle or the cowpea weevil (Callosobruchus maculates).
White et al. (2009) reported that wintergreen oil could
kill bee (Osmia cornifrons) or bee’s cleptoparasitic mite,
Chaetodactylus krombeini Bakerbee, depending on
concentration and duration of fumigation. Moreover,
wintergreen and peppermint oils were found to be the
two most effective essential oils at reducing
attractiveness of the Japanese beetle (Youssef et al.,
2009). In addition, larvicidal activity was shown with
bergamot oil (Melliou et al., 2009) or peppermint oil
(Ansari et al., 2000). In water buffaloes, Khater et al.
(2009) reported that peppermint oil could be used to
control lice and flies infestation as it contained
lousicides and insect repellents activity. Geranium oil
was shown to repel mosquitoes (Ixodes ricinus)
(Jaenson et al., 2006), chigger (Leptotrombidium
chiggers, larvae), the carrier of scrub typhus
(Eamsobhana et al., 2009), and stable flies (Stomoxys
calcitrans) (Hieu et al., 2010).
In order to evaluate the efficacy of rat
repellents, there is a number of laboratory testings
such as food acceptance test, barrier test and graded
strip test (Weeks, 1959). In food acceptance test, the
repellent is mixed with food and the effectiveness is
based on the amount of food eaten by a rat in a period
of time. Unfortunately, in this test, some chemicals
were able to make the food unacceptable but were
failed to repel the rat. In barrier test, hungry rats must
be trained to gnaw through repellent-coated paper
barrier and time required to penetrate the paper are
recorded. In graded strip test, a rat has to gnaw
through the paper strip coated with varied
concentration of repellents to get to palatable food like
peanuts which are placed under each strip and then
the repellent activity is calculated based on numbers
of obtained peanuts. For the latter two tests, the rats
must be hungry and trained; moreover the
instruments must be specially made and analyzed
with care. The open field is a behavioral model
usually used for analysis of locomotor activity or
anxiety. In this test, the rats are allowed to explore
freely in the apparatus for a period of time, then the
number of line crossed or time spent in each segment
of the apparatus are analyzed according to types of
tests. Circular open field is also used for measuring
locomotor activity in rats. In this study the circular
open field was adapted in order to observe 24-hour
activity of the rats exposed to various repellents.
The objectives of this study were, therefore,
to observe the natural behavior of rats in the circular
open field when exposed to various natural repellents
and whether these repellents were as effective as seen
in other species.
Materials and Methods
Animals: Adult male Wistar rats weighing 210-220 g at
the beginning of the experiments were obtained from the
National Laboratory Animal Center, Mahidol University
(NLAC-MU), Thailand. All animals were housed 2 per
cage and maintained at 25±2oC on 12-hrs light/dark cycle
with lights on at 0600 am and given standard rat chow
and water ad libitum. All procedures were done under the
approval of the Animal Use Committee, Faculty of
Veterinary Science, Chulalongkorn University.
Repellents: The repellents and cardboard paper were
supplied by Interink Co. Ltd. They were wintergreen
oil+chilli, wintergreen oil+peppermint oil, bergamot oil,
wintergreen oil+peppermint oil+bergamot oil and
bergamot oil+geranium oil, designated as F1-F5. These
substances had been registered for patent number
0901002635. The repellents were freshly sprayed on the
cardboard paper before being placed into the apparatus.
Behavioral model: The circular open field was
constructed as previously described by Itoh et al. (1994)
with some modification (Figure 1). The apparatus was an
aluminum tub-shaped enclosed with a circular base 75
cm in diameter. The top opening had a diameter of 85 cm
and the wall had a height of 85 cm. On the bottom, two
concentric circles with diameters of 25 and 50 cm were
drawn resulting in 3 circular fields, inner, middle and
outer zones. In the middle of the inner part, a stainless
rod with the diameter of 1 cm was installed for the
application of repellent-paper roll. The middle zone and
the outer zone were further divided into eight and
sixteen equal parts by lines, respectively.
Figure 1. The circular open field, an aluminum tub-shaped
apparatus with a based-diameter of 75 cm, an
opening-diameter of 85 cm with a height of 85 cm
(A). The water bottle hanger and a metal testing
core are installed for water dispensing during 24-
hour test and for cardboard paper placer,
respectively (B). The base of the apparatus was
divided into 3 zones; inner zone, middle zone and
outer zones as shown in C.
Behavioral test: The test composed of a 3-day training
and the tests were done on the following day and
then 7 days later. This training period was done in
order to reduce the fear and anxiety of the rats when
exposed to a new environment. This was done by
placing each pair of rat from the same cage into the
apparatus and allowing them to freely explore the
open field arena for 30 minutes for 3 consecutive
days. The next day, each pair of rats was placed in the
apparatus at 06.00 pm and their behaviors were
observed for 24 hrs using closed circuit video recorder
414 Kalandakanond-Thongsong S. et al. / Thai J. Vet. Med. 2010. 40(4): 411-418.
for further analysis. During this time, rats had free
access to water. Seven days later, each pair of rats was
exposed to the same repellent or control (blank). The
behavioral analysis was done every six hours for 30
min, at 06.00-06.30 pm, 12.00-12.30 am, 06.00-06.30 am
and 12.00-12.30 pm designated as P1, P2, P3 and P4,
respectively. The parameters were numbers of visits
and time spent in the inner, middle and outer zones.
If the tested substances could repel the rats, the
numbers of visits and time spent would be fewer in
the inner zone and higher in the outer zone.
Moreover, the total number of line crossed during 30
min was also recorded and considered as locomotor
activity of the rats. In order to test the efficacy of
potential repellent, the fear of novelty as being
exposed to a new environment was reduced by the
training period and by placing the rats in pair as rats
are social animals. Because it had been shown that
memory could last for at least 5 days following
learning (Rossato et al., 2006), a 7 day post-exposure
was then used to test whether the rats could
remember the substances. For each substance, 3 pairs
of rat were used and the behavioral data were
analyzed and scored by 2 experimenters blinded to
the experiment.
Statistical analysis: Data are presented as mean+SE.
Two-way analysis of variance (ANOVA) with
treatments or periods (P1-P4) as the independent
factor and days (day 0 and 7) as the dependent factor
were used. In order to test the significant effect of
treatments or periods of time in the same day, data
were analyzed by one-way ANOVA followed by the
Duncan post hoc test. In all cases, a value of p < 0.05
was considered significant.
Results
The effect of time on rat behavior in the circular open
field: In this study, rats were placed in the circular
open field for 24 hrs (06.00 pm–05.00 pm of the
following day) then the numbers of visits, time spent
in the inner zone, middle zone and outer zone of the
apparatus and total number of line crossed during 30
min were counted, which were done for 4 periods (P1,
P2, P3 and P4). The same procedures were repeated
again on day 7.
For the numbers of visits, the two-way
analysis of variance (ANOVA) with the periods of
time (P1-P4) and days (day 0 and 7) as the variables
were used. There was no significant effect of days (p =
0.6406) nor an interaction of day x period of times (p =
0.3362). However, we found that different period of
time had significant effect on numbers of visits (p =
0.0255) in that rats visited the testing core more
frequent during 06.00-06.30 pm (P1) on both day 0
and day 7 (Figure 2).
Figure 2. The effect of time on numbers of visits to the
testing core in circular open field, Data presented
as mean+SEM, different letters denoted significant
difference at p<0.05, ANOVA followed by
Duncan’s multiple range test, n= 6.
Figure 3. The effect of time on the time the rats spent in each part of the circular open field, A. Inner zone, B. Middle zone and C.
Outer zone. Data presented as mean+SEM, different letters denoted significant difference at p<0.05 between each time
point (P1-P4) in the same day (Day 0 and Day 7), ANOVA followed by Duncan’s multiple range test, n= 6.
For the time spent in each part of the
apparatus, there was no significant effect of days on
the time spent in the inner zone (p = 0.9240), the
middle zone (p = 0.4053) nor the outer zone (p =
Kalandakanond-Thongsong S. et al./ Thai J. Vet. Med. 2010. 40(4): 411-418. 415
0.5046). Similarly, there was no significant effect of
different periods of time on the time spent in the inner
zone (p = 0.2143), the middle zone (p = 0.4673) nor the
outer zone (p = 0.3377). Moreover, there was no
significant effect of interaction of day x period of
times on the time spent in the inner zone (p = 0.4454),
middle zone (p = 0.5255) nor the outer zone (p =
0.4519). However one-way ANOVA revealed that on
day 0, the rats spent more time in the inner zone and
less time in the outer zone during 06.00-06.30 pm (P1)
than other periods (p < 0.0001 and p = 0.0009 for inner
and outer zone, respectively). The time rats spent in
the middle zone tended to be different across times (p
= 0.0712). On day 7, periods of time had no effect on
time that the rat spent in the inner (p = 0.8703), middle
(p = 0.6126) and outer zone (p = 0.7229) (Figure 3).
For the total number of line crossed during
30 min, there was no significant effect of days (day 0
vs. day 7, p = 0.8727) nor the interaction of days and
periods of time (p = 0.1277). However, different
periods of time had significant effect on the numbers
of lines crossed during 30 min (p < 0.0001). One way
ANOVA revealed that the rats had more activity as
indicated by higher numbers of lines crossed in 30
min during 06.00-06.30 pm (P1) than other periods (p
< 0.0001 and p < 0.0001 for day 0 and day 7,
respectively) as shown in Figure 4.
All of above indicated that rats had highest
activity for the first 30 min in the circular open field as
shown by the numbers of visits and the total numbers
of lines crossed. Since time spent in each part of the
apparatus could be affected by lack of activity of the
rat and could have led to misinterpretation of the
data, the collected parameters from the time between
06.00-06.30 pm were selected and analyzed in the
further experiments to test the efficacy of various
repellents.
Figure 4. The effect of time on the total numbers of lines
crossed during 30 min in the circular open field.
Data presented as mean+SEM, different letters
denoted significant difference at p < 0.05 between
each time point (P1-P4) in the same day (Day 0
and Day 7), ANOVA followed by Duncan’s
multiple range test, n= 6.
The effect of various repellents on rat behavior in the
circular open field: In this study, the rats were
exposed to various repellents: blank cardboard paper,
or the cardboard paper sprayed with either
wintergreen oil+chili (F1), wintergreen
oil+peppermint oil (F2), bergamot oil (F3),
wintergreen oil+peppermint oil+bergamot oil (F4) or
bergamot oil+geranium oil (F5) in the circular open
field for 24 hrs (06.00 pm–05.00 pm of the following
day) then the numbers of visits and time spent in the
inner zone, middle zone and outer zone of the
apparatus were counted during 06.00-06.30 pm. The
same procedures were repeated again on day 7.
For the numbers of visits, the two-way
analysis of variance (ANOVA) with treatments and
days (day 0 and 7) as the variables were used. There
was no significant effect of days (p = 0.2909) nor an
interaction of treatments x days (p = 0.8406).
However, we found that different repellents had
significant effect on the numbers of visits (p = 0.0227)
in that rats visited the testing rod less frequent in all
repellents compared to control on both day 0 and day
7 (p = 0.0227). One way ANOVA revealed that on day
0, all repellents had a significant effect on the numbers
of visits (p < 0.0001) and the rats exposed to F2, F3 and
F4 had fewer visits than F1 and F5. Similarly, on day
7, all repellents had a significant effect on the numbers
of visits (p < 0.0001) and the rats exposed to F2, F3, F4
and F5 had fewer visits than F1 (Figure 5).
For the time spent in each part of the
apparatus, the two-way analysis of variance
(ANOVA) with treatments and days (day 0 and 7) as
the variables were used. There was no significant
effect of days on the time spent in the inner zone (p =
0.6271) nor the outer zone (p = 0. 3201). Similarly,
there was no significant effect of the interaction
between treatments and days on the time spent in the
inner zone (p = 0.6039) nor the outer zone (p = 0.1828).
However, there were significant effects of days and
the interaction between treatments and days on the
time spent in the middle zone (p = 0.0007 and 0.0007,
respectively) in that on day 7, F3 spent more time in
the middle zone when compared to day 0 (Figure 6B).
Figure 5 The effect of various rat repellents on numbers of
visits to the testing core in the circular open field,
Data presented as mean+SEM, different letters
denoted significant difference at p < 0.05 between
substances in the same day (day 0 and day 7),
ANOVA followed by Duncan’s multiple range
test, n= 6 in each treatment.
Moreover, we found that repellents had a
significant effect on the time the rats spent in the inner
zone (p = 0.0197), middle zone (p < 0.0001) and the
outer zone (p = 0.0079). One-way ANOVA revealed
that the rats spent less time in the inner zone when
exposed to repellents compared to the control on both
day 0 (p < 0.0001) and day 7 (p < 0.0001) (Figure 6A).
416 Kalandakanond-Thongsong S. et al. / Thai J. Vet. Med. 2010. 40(4): 411-418.
The time the rats spent in the middle zone was
significant only on day 0 (p < 0.0001) in that the rats
exposed to F2, F3 and F4 spent less time than the
control and F1 and F5 spent less time than F1 but not
different from the control but more than F2, F3 and
F4. This effect was not seen on day 7 (p = 0.1289)
(Figure 6B). For the time spent in the outer zone, the
rats exposed to all repellents spent more time in the
outer zone than the control (p < 0.0001) on day 0. On
day 7, it tended that the rats exposed to repellents
would spend more time in the outer zone than the
control (p = 0.0724) (Figure 6C).
Moreover, it was worth looking at the
cardboard after 24-hrs exposed to the rats in the
circular open field, it was quite cleared that the
cardboards sprayed with F1 were still intact
compared to the others (Figure 7B). For other groups,
the bitten and chewed marks varied between each rat;
however, we noticed that the F4- and F5- treated
cardboards were less likely to be destroyed especially
when compared to blank.
Figure 6. The effect of rat repellents on the time the rats spent in each part of the circular open field, A. Inner zone, B. Middle zone
and C. Outer zone. Data presented as mean+SEM, different letters denoted significant difference at p < 0.05 between each
substance (blank, F1-F5) in the same day (Day 0 and Day 7), ANOVA followed by Duncan’s multiple range test. * denoted
significant different at p < 0.05 between day 0 and day 7, two-way ANOVA, n= 6 in each treatment.
Figure 7A. The rat repellents B. An example of paper
cardboard sprayed with various repellents after
24-hour-exposed to the rats in the circular open
field.
Discussion
Rodent infestation is considered as one of the
health hazards; therefore, many methods have been
adopted such as the used of trapping, rodenticides or
repellents. However, there are limitations to these
methods including chemical toxicities. The alternative
to chemicals was therefore of interested since there
were numbers of reports claiming that some natural
extracts like winter green oil, chilli, peppermint oil,
bergamot oil or geranium oil contained insect
repellent properties (Lale, 1992; Ansari et al., 2000;
Jaenson et al., 2006; Eamsobhana et al., 2009; Khater et
al., 2009; Melliou et al., 2009; White et al., 2009;
Youssef et al., 2009; Hieu et al., 2010). In this study,
these natural extracts were tested whether they were
potential rat repellents using modified circular open
field. The circular open field was modified so that the
test substances could be installed in the middle of the
apparatus (testing core). In this test, the numbers of
visits to the testing core and time the rats spent in
each part of the apparatus were analyzed. If the
repellents were able to repel the rats then the numbers
of visits to the testing core and the time the rats spent
Kalandakanond-Thongsong S. et al./ Thai J. Vet. Med. 2010. 40(4): 411-418. 417
in the closed perimeter to the testing core (inner zone)
would decreased and the time the rats spent away
from the testing core (outer zone) would increased.
Additionally, if the rats could remember the
repellents, then the analyzing parameters would be
differed on day 7.
In order to evaluate the efficacy of repellents
in the circular open field, the natural behavior was
observed for 24 hours from 18.00 hr. (the beginning of
the dark phase) to 17.00 hr. of the following day.
Then the numbers of visits to the testing core and the
time the rats spent in each part of the apparatus were
analyzed every 6 hours for 30 min. during 06.00-06.30
pm, 12.00-12.30 am, 06.00-06.30 am and 12.00-12.30
pm designated as P1-P4. We found that the rats
visited the testing core more frequent and spent more
time in the inner zone and less time in the outer zone
during the first 30 min (P1) after being placed in the
apparatus. However, the time spent in each part of
the apparatus i.e. inner, middle and outer zones may
be confounded by the lack of the rat’s activity, then
the numbers of total line crossed during 30 min. were
taken into account. Similarly, the numbers of total line
crossed was highest during the first 30 min (P1). It
was thus likely that the rats had the highest activity
during the first 30 minutes in the apparatus as it was
the beginning of the nocturnal phase (lights off) of the
rat’s circadian rhythm. During the nocturnal phase of
the circadian cycle in terms of natural behavior, rats
were usually active, inquisitive and more responsive
compared to diurnal phase (lights on). Therefore, in
order to test the efficacy of rat repellents in the
circular open field, the time of highest activity (06.00-
06.30 pm) was used for analysis.
When the rats were exposed to potential rat
repellents i.e. wintergreen oil+chilli, wintergreen
oil+peppermint oil, bergamot oil, wintergreen
oil+peppermint oil+bergamot oil or bergamot
oil+geranium oil, we found that the numbers of visits
to the testing core and the time spent in the inner zone
were lower in all repellent groups compared to blank
on both day 0 and day 7 indicating that the rats were
most likely trying to avoid the closed contact to these
substances. Although previous studies have claimed
that these substances were potential insect repellents
(Lale, 1992; Ansari et al., 2000; Jaenson et al., 2006;
Eamsobhana et al., 2009; Khater et al., 2009; Melliou et
al., 2009; White et al., 2009; Youssef et al., 2009; Hieu
et al., 2010), this current study is the first report
claiming these substances as potential rat repellents.
Since the rats were left exposed to the substance for 24
hours in the circular open field, it was then worth
looking at the cardboards sprayed with various
substances. We found that although the analyzed
parameters showed no different in repellent activity,
the cardboards somehow differed in the degree of
tearing and chewing (Figure 7B). Inconsistent degree
of cardboard destruction were found, which may be
accounted by the rat’s behaviors; some may be more
tolerant to the substances’ odor than others and
resulting in various results. However, we found that
the cardboards sprayed with wintergreen oil+chilli or
wintergreen oil+peppermint oil+bergamot oil
consistently showed no sign of tearing or chewing;
however, some footprints may be evident. For the
cardboard sprayed with bergamot oil+geranium oil,
there was less tearing or chewing than the cardboards
sprayed with wintergreen oil+peppermint oil,
bergamot oil and blank. It is thus likely that for a
longer period of exposure both behavioral data in the
circular open field and the cardboard appearance
after 24-hour exposure should be taken into account
as these potential repellents may be further applied
on packaging and shipping supplies to prevent rat’s
destruction. Moreover, it should be noted that in
terms of application, the wintergreen oil+chilli may be
a little hard to be applied as a spraying product due to
its viscosity.
From these data, we can conclude that these
natural extracts i.e. chilli, wintergreen oil, bergamot
oil, peppermint oil and geranium oil can repel the rats
as shown by the lower numbers of visits to the tested
core and less time spent near the tested core seen in
the circular open field. However, more studies need
to be done like stability and period of protection to
see whether these extracts are of practical in real
environment.
Acknowledgement
This study was financially supported by
InterInk Co., Ltd. We would like to thank Ms.
Massupha Wiyaporn, Ms. Suchawadee Tongta and
Ms. Sureerat Suthongsa for their helps.
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... Rats showed movement in both zones but the activities of rat and distance moved was less in the treated zone as compared to the untreated zone (Table 6). Kalandakanond-Thongsong et al. (2010) reported a decrease in the number of visits of rats in response to repellents to the treated side as compared to untreated side. ...
... Parshad et al. [17] reported repellent effect of two fungicides against R. rattus. Kalandakanond-Thongsong et al. [18] evaluated the efficacy of chilli, wintergreen oil, bergamot oil, peppermint oil, and geranium oil as repellents in the circular open field against adult male Wistar rats. Pine needle oil inhibits feeding in vertebrate species through sensory cues [19]. ...
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