Behavioural Processes, 5 (1980) 173-183 0 Elsevier Scientific Publishing Company,
Amsterdam
-
Printed
FEEDING BEHAVIOUR OF DOMESTIC CHICKS IN A NOVEL MENT: EFFECTS OF FOOD DEPRIVATION AND SEX
R.B.
JONES
and A.J.
23 October
ENVIRON-
BLACK
Agricultural Research Council’s Poultry Research Centre, King’s Buildings, Road, Edinburgh EH9 3JS (Great Britain) (Accepted
173
in Belgium
West Mains
1979)
ABSTRACT Jones, R.B. and Black, A.J., 1980. Feeding environment: Effects of food deprivation
behaviour of domestic chicks in a novel and sex. Behau. Processes, 5: 173-183.
Sex differences in responses to novelty with particular reference to feeding activity were examined in the present study. Male and female domestic chicks (7- and &days-old) were observed in a modified home cage and in an open field or novel environment after experiencing either deprivation of food or continuous access to food. Previous reports that females show more activity and vocalisation and less sitting and eye-closure than males in fearful situations were confirmed in the tests with no deprivation but these sex differences were distorted in the deprivation tests by high feeding activity. Following deprivation of food, females fed sooner and fed more than males both in the home cage and the open field. These results provide further evidence that the female chick is less fearful than the male. The relevance of the hypothesis that behavioural persistence is increased by testosterone and its theoretical implications regarding normal sex differences in behaviour are questioned because, in fact, females showed longer feeding bouts than males. It is suggested that persistence, of feeding at least, in young chicks is not influenced by natural levels of androgens.
INTRODUCTION
Previous work has revealed marked sex differences in the responses of domestic chicks to a novel environment or open field (Jones, 1977a,b), males were less active and less vocal than females and showed longer durations of immobility, sitting, lying and eye-closure. These findings represent a real dichotomy between the responses of males and females and do not merely reflect sex differences in their levels of general activity (Jones, 1978). Repeated exposure of the domestic chick to an open field increases activity and decreases sitting, lying and eye-closure (Jones, 1977b). Faure (1975) suggested that a fearful bird in the open field is characterised by low activity and few jumps and Murphy and Wood-Gush (1978) equated lying and eye-closure with intense fear. These reports, together with the
174
finding that males showed longer emergence latencies in a hole-in-the-wall timidity test (Jones, 1979) suggest strongly that the male chick is more fearful than the female. Fear responses conflict with and nearly always overcome those of other systems such as feeding (Murphy, 1978). Rajecki et al. (1975) argued that “animals will consume more food in any sort of situation that contains familiar components, as opposed to one that is completely novel, insofar as the familiar components can reduce fear or stress”. The presence of familiar objects facilitated feeding in ducklings (Hoffman et al., 1969) and in domestic chicks (Wilson, 1968; Jones, 1977c). There is evidence that females feed more than males when placed in a novel environment (Jones, 1978). Andrew (1972a, b) has suggested that testosterone increases behavioural persistence, decreasing distractability by irrelevant stimuli, and increasing the ability to sustain attention on a particular localised stimulus. Exogenous testosterone increased persistence of search for both types of food and location (Andrew and Rogers, 1972) and sustained responsiveness to the appropriate stimulus (Andrew, 197 5). Testosterone !evels are similar in both sexes during early embryonic development but female levels fall below those of males after 7 days of incubation (Woods and Podczaski, 1974; Woods et al., 1975). Thus, females should show less persistence of attention than males and it has been found that females were less persistent feeders (Rogers, 1974) and searchers (Andrew, 1972b) than males. Two hypotheses were tested in the present study. Firstly, if male chicks are indeed more fearful than females they would be expected to take longer to start feeding in a novel, fear-inducing situation. Secondly, if the persistance phenomenon holds true under endogenous levels of testosterone, males would be expected to feed longer than females once they had started feeding and this effect should be reflected in the durations of their feeding bouts. These hypotheses were tested in two situations, a modified home cage and an open field or novel environment. The object of the study was to observe feeding responses in males and females under conditions likely to induce fear, following either food-deprivation (Experiment 1) or ad libitum feeding (Experiment 2). EXPERIMENT
1
Materials and methods Newly-hatched male and female chicks were housed in same-sex groups of ten in wooden boxes measuring 850 X 380 X 300 mm high; wire mesh lids prevented escape. A wire-mesh divider was positioned 170 mm from one end wall of the home box to provide a holding area and the chicks were housed in the larger (680 X 380 mm) living area. A dull-emitter heater was suspended above each box and the floor was covered with wood litter. Food and water
175 were provided ad libitum until the 6th day when a deprivation regimen was begun (see below). The photpperiod extended from 04.00 to 18.00 h. The chicks used were all “T” strain (derived from a Rhode Island Red and Light Sussex cross). Each chick was clearly marked on its back with indelible ink for identification. Little attention was paid to the marking by its companions. Two test situations were used: the home cage (HC) and a novel environment or open field (OF). Each chick was tested in both situations.
Home cage tests. Each chick was individually
tested, it remained in the large living area of the home cage while its nine companions were placed behind the wire partition in the smaller holding area. Thus, the chick could see and hear but not touch the others in the group. Handling of the birds was thus unavoidable but was relatively constant for each box. Because the chicken can detect olfactory cues (Stattelman et al., 1975; Tolhurst and Vince, 1976) soiled litter from the living area had been scattered over the holding area to reduce distress due to differences in olfactory properties. A 2-min acclimatisation period was allowed before testing began. Several behaviour patterns, some of which have proved useful indices of fear (Jones, 1977b, c, 1978) were observed and recorded over a 15-min period. The latency to feed, accumulated time spent feeding, number of pecks at the food, feeding bouts and duration of bouts were measured as were latency to drink and number of drinks. It was not possible to measure peeping (distress calls) in the home cage because of the difficulties involved in identifying the peeps of the test chick.
Open-field tests. The open field consisted of a wooden box of similar dimensions to the living area of the home cage. Food and water were provided and other features such as temperature and illumination were similar to the home environment. Each chick was individually tested; it was picked up gently, carried 5 m from its home cage and placed in the centre of the open field. The rest of the group received approximately the same amount of handling as that involved in home-cage testing. The behaviour patterns measured in the home cage, with the addition of peeping or distress calling, were also recorded over a 15-min period in the open field. Three separate batches of chicks were used (one batch of ten males and ten females per week for 3 weeks) but all came from the same parent stock, were incubated in the same incubator and were reared under similar environmental conditions. The chicks were housed in groups of ten to conform with previous work but, because of limited time, only five chicks from each of the two groups were tested. These birds were chosen at random. Ten chicks (five male and five female) received home cage tests first at 7 days of age and open field tests on day 8, while ten were first tested in the open field on day 7 and in the home cage on day 8. The order of testing was randomised. This procedure was repeated for 3 weeks so that 15 males and 15 females were tested. All tests were performed by the same observer.
I
and
(s)
bouts
* =
0.02;
males
15 15 15 15 15
353.9k46.0 11.2k1.5 499.7t59.4 31.6t3.6 823.5k33.0
=
and
analysis
1 2
0.8’0.6
15
females (no)
from = number.
and are derived
1.5kO.7
3
15
n = the number
of birds
showing
by the Mann-Whitney
l.OtO.6
15
46.4i4.1**
3
a53.7t30.5
15
871.1t14.6
27.8t4.0
15
12.211.0 745.9+45.8**
each
7
15
15
15
15
15
15
6
1
8
13 15
0
0”
13
14
”
pattern.
(two-tailed). behavior
U test
1.9to.a
792.7t45.2
48.9S3.6***
10.7+0.9 701.2+52.5*
14 14
ll.li1.5 472.3t78.6
15
565.9+32.2***
14
11.1*3.3** 523.7+36.6**
15 14
84.0258.8 337.5t55.1
7 15
22.3A5.9
3.4t1.3
1.3to.5 1.2t1.2
11
2.9il.l O.l-rO.1
2
O.l?O.l
249.1i37.8
15 0
94.4+14.0***
15 15
646.7i92.5
235.7*54.2*** 109.3?18.4**
0
0
0” 0
1
0.5kO.5
3.5*1.2
0
-
0
3.2tO.8
4.9?-1.4*
Female
? SEM)
1 0
15
15
n
(Means
6.3t6.3
8.9A2.4 4.7r0.9
0 0”
Male
field
of food
Open
deprived
0
n
chicks
0
and female
0
0
Female
male
P < 0.002.(s)= seconds:
between ***
5
15
1.3tO.6
13
2
0.2fO.l 8.8k2.6
3
0.550.3
42.0+12.9
15
238.1k38.8
0
2
0 -
0
n
a-day-old
;
8.8+4.0
0.5kO.4
cage
of 7- and
0
0
Male
Home
respcmses
to comparisons
P < 0.05:** = P
Amsterdam
-
Printed
FEEDING BEHAVIOUR OF DOMESTIC CHICKS IN A NOVEL MENT: EFFECTS OF FOOD DEPRIVATION AND SEX
R.B.
JONES
and A.J.
23 October
ENVIRON-
BLACK
Agricultural Research Council’s Poultry Research Centre, King’s Buildings, Road, Edinburgh EH9 3JS (Great Britain) (Accepted
173
in Belgium
West Mains
1979)
ABSTRACT Jones, R.B. and Black, A.J., 1980. Feeding environment: Effects of food deprivation
behaviour of domestic chicks in a novel and sex. Behau. Processes, 5: 173-183.
Sex differences in responses to novelty with particular reference to feeding activity were examined in the present study. Male and female domestic chicks (7- and &days-old) were observed in a modified home cage and in an open field or novel environment after experiencing either deprivation of food or continuous access to food. Previous reports that females show more activity and vocalisation and less sitting and eye-closure than males in fearful situations were confirmed in the tests with no deprivation but these sex differences were distorted in the deprivation tests by high feeding activity. Following deprivation of food, females fed sooner and fed more than males both in the home cage and the open field. These results provide further evidence that the female chick is less fearful than the male. The relevance of the hypothesis that behavioural persistence is increased by testosterone and its theoretical implications regarding normal sex differences in behaviour are questioned because, in fact, females showed longer feeding bouts than males. It is suggested that persistence, of feeding at least, in young chicks is not influenced by natural levels of androgens.
INTRODUCTION
Previous work has revealed marked sex differences in the responses of domestic chicks to a novel environment or open field (Jones, 1977a,b), males were less active and less vocal than females and showed longer durations of immobility, sitting, lying and eye-closure. These findings represent a real dichotomy between the responses of males and females and do not merely reflect sex differences in their levels of general activity (Jones, 1978). Repeated exposure of the domestic chick to an open field increases activity and decreases sitting, lying and eye-closure (Jones, 1977b). Faure (1975) suggested that a fearful bird in the open field is characterised by low activity and few jumps and Murphy and Wood-Gush (1978) equated lying and eye-closure with intense fear. These reports, together with the
174
finding that males showed longer emergence latencies in a hole-in-the-wall timidity test (Jones, 1979) suggest strongly that the male chick is more fearful than the female. Fear responses conflict with and nearly always overcome those of other systems such as feeding (Murphy, 1978). Rajecki et al. (1975) argued that “animals will consume more food in any sort of situation that contains familiar components, as opposed to one that is completely novel, insofar as the familiar components can reduce fear or stress”. The presence of familiar objects facilitated feeding in ducklings (Hoffman et al., 1969) and in domestic chicks (Wilson, 1968; Jones, 1977c). There is evidence that females feed more than males when placed in a novel environment (Jones, 1978). Andrew (1972a, b) has suggested that testosterone increases behavioural persistence, decreasing distractability by irrelevant stimuli, and increasing the ability to sustain attention on a particular localised stimulus. Exogenous testosterone increased persistence of search for both types of food and location (Andrew and Rogers, 1972) and sustained responsiveness to the appropriate stimulus (Andrew, 197 5). Testosterone !evels are similar in both sexes during early embryonic development but female levels fall below those of males after 7 days of incubation (Woods and Podczaski, 1974; Woods et al., 1975). Thus, females should show less persistence of attention than males and it has been found that females were less persistent feeders (Rogers, 1974) and searchers (Andrew, 1972b) than males. Two hypotheses were tested in the present study. Firstly, if male chicks are indeed more fearful than females they would be expected to take longer to start feeding in a novel, fear-inducing situation. Secondly, if the persistance phenomenon holds true under endogenous levels of testosterone, males would be expected to feed longer than females once they had started feeding and this effect should be reflected in the durations of their feeding bouts. These hypotheses were tested in two situations, a modified home cage and an open field or novel environment. The object of the study was to observe feeding responses in males and females under conditions likely to induce fear, following either food-deprivation (Experiment 1) or ad libitum feeding (Experiment 2). EXPERIMENT
1
Materials and methods Newly-hatched male and female chicks were housed in same-sex groups of ten in wooden boxes measuring 850 X 380 X 300 mm high; wire mesh lids prevented escape. A wire-mesh divider was positioned 170 mm from one end wall of the home box to provide a holding area and the chicks were housed in the larger (680 X 380 mm) living area. A dull-emitter heater was suspended above each box and the floor was covered with wood litter. Food and water
175 were provided ad libitum until the 6th day when a deprivation regimen was begun (see below). The photpperiod extended from 04.00 to 18.00 h. The chicks used were all “T” strain (derived from a Rhode Island Red and Light Sussex cross). Each chick was clearly marked on its back with indelible ink for identification. Little attention was paid to the marking by its companions. Two test situations were used: the home cage (HC) and a novel environment or open field (OF). Each chick was tested in both situations.
Home cage tests. Each chick was individually
tested, it remained in the large living area of the home cage while its nine companions were placed behind the wire partition in the smaller holding area. Thus, the chick could see and hear but not touch the others in the group. Handling of the birds was thus unavoidable but was relatively constant for each box. Because the chicken can detect olfactory cues (Stattelman et al., 1975; Tolhurst and Vince, 1976) soiled litter from the living area had been scattered over the holding area to reduce distress due to differences in olfactory properties. A 2-min acclimatisation period was allowed before testing began. Several behaviour patterns, some of which have proved useful indices of fear (Jones, 1977b, c, 1978) were observed and recorded over a 15-min period. The latency to feed, accumulated time spent feeding, number of pecks at the food, feeding bouts and duration of bouts were measured as were latency to drink and number of drinks. It was not possible to measure peeping (distress calls) in the home cage because of the difficulties involved in identifying the peeps of the test chick.
Open-field tests. The open field consisted of a wooden box of similar dimensions to the living area of the home cage. Food and water were provided and other features such as temperature and illumination were similar to the home environment. Each chick was individually tested; it was picked up gently, carried 5 m from its home cage and placed in the centre of the open field. The rest of the group received approximately the same amount of handling as that involved in home-cage testing. The behaviour patterns measured in the home cage, with the addition of peeping or distress calling, were also recorded over a 15-min period in the open field. Three separate batches of chicks were used (one batch of ten males and ten females per week for 3 weeks) but all came from the same parent stock, were incubated in the same incubator and were reared under similar environmental conditions. The chicks were housed in groups of ten to conform with previous work but, because of limited time, only five chicks from each of the two groups were tested. These birds were chosen at random. Ten chicks (five male and five female) received home cage tests first at 7 days of age and open field tests on day 8, while ten were first tested in the open field on day 7 and in the home cage on day 8. The order of testing was randomised. This procedure was repeated for 3 weeks so that 15 males and 15 females were tested. All tests were performed by the same observer.
I
and
(s)
bouts
* =
0.02;
males
15 15 15 15 15
353.9k46.0 11.2k1.5 499.7t59.4 31.6t3.6 823.5k33.0
=
and
analysis
1 2
0.8’0.6
15
females (no)
from = number.
and are derived
1.5kO.7
3
15
n = the number
of birds
showing
by the Mann-Whitney
l.OtO.6
15
46.4i4.1**
3
a53.7t30.5
15
871.1t14.6
27.8t4.0
15
12.211.0 745.9+45.8**
each
7
15
15
15
15
15
15
6
1
8
13 15
0
0”
13
14
”
pattern.
(two-tailed). behavior
U test
1.9to.a
792.7t45.2
48.9S3.6***
10.7+0.9 701.2+52.5*
14 14
ll.li1.5 472.3t78.6
15
565.9+32.2***
14
11.1*3.3** 523.7+36.6**
15 14
84.0258.8 337.5t55.1
7 15
22.3A5.9
3.4t1.3
1.3to.5 1.2t1.2
11
2.9il.l O.l-rO.1
2
O.l?O.l
249.1i37.8
15 0
94.4+14.0***
15 15
646.7i92.5
235.7*54.2*** 109.3?18.4**
0
0
0” 0
1
0.5kO.5
3.5*1.2
0
-
0
3.2tO.8
4.9?-1.4*
Female
? SEM)
1 0
15
15
n
(Means
6.3t6.3
8.9A2.4 4.7r0.9
0 0”
Male
field
of food
Open
deprived
0
n
chicks
0
and female
0
0
Female
male
P < 0.002.(s)= seconds:
between ***
5
15
1.3tO.6
13
2
0.2fO.l 8.8k2.6
3
0.550.3
42.0+12.9
15
238.1k38.8
0
2
0 -
0
n
a-day-old
;
8.8+4.0
0.5kO.4
cage
of 7- and
0
0
Male
Home
respcmses
to comparisons
P < 0.05:** = P
