JOURNAL OF APPLIED ANIMAL WELFARE SCIENCE, 2(3), 169-186
Copyright @ 1999, Lawrcnce Erlbaum Associates, Inc
Influences on the Feeding Behavior of
Three Mammals in the Maruyama Zoo:
Bears, Elephants, and Chimpanzees
Naruki Morimura
Hayashibara Museum of Natural Sciences
Yoshikazu Ueno
Center for Experimenml Plants and Animals
Hokkaido University
Modifications of feeding conditions are essential to the establishment ofenvironmental enrichment in zoos In this study, we attempted to increase the duration offeeding
by varying fetding conditions, such as the spatial or temporal distribution of foods,
while kerping the solts and amounts of food the same Subjects included nonhumar
animals reared at the Maruyama Zoo in Sapporo, Japan: 3 bears ( Urs us arctos),2 elephafis (Elephas taxim6), and 5 chimpanze€s (Pan troglod)tei) Considering that
the feeding ccologies of these animals differed a great deal f.om those in the wild, we
used the focal animal sampling method Consisting of the spatial dispersive and
massed feeding conditions, the experiment with bears found feeding time increased
more in the dispersive condition In addition, the b€havioral rhythm of altemate feeding and sleeping appeared The experiment with elephants, consisting of the temporal
dispersive and massed condition, increased fe€ding time under the massed condition
The experiment using chimpanzees reversed conditions used in the elephant study
and increased feeding time under the dispersive condition Results indicated that
these simple modifications both influenced an increasing duration of feeding and af-
fected behavioral pattems in a day
Environmental enrichment has created considerable interest worldwide in recent
years, especially in Westem zoos concerned about nonhuman animal welfare
and species preservation Environmental enrichment seeks to approximate the
Requesls for reprints should be sent to Naruki Morimura, Hayashibara Museum of Natural Sciences,
Shimoishii l-2-3, Okayam4 700-0907, Japan E-mail: narukim@rc4 so-net nejp
170
MORIMURA AND UENO
behavioral repertoires and activity budgets of animals in a zoo with that of animals in the wild We observed nine mammalian species at three zoos in Japan
and compared behaviors among species, seasons, and exhibit conditions Tbese
observations suggested that large differences in behavior existed between these
zoo animals and their wild counterparts (Morimum & Ueno, 1998) Zoo animal
behavior, lacking much of the natural behavioral repertoire and/or distorted in
the time budget, appears monotonous, especially with respect to feeding Generally, wild animals spend more than half the day feeding Thus, to accomplish
environmental enrichment in zoos, it is important to make the time budgets of
feeding behavior similar to those of the wild
Significant efforts were made to promote feeding enrichment in zoos Foraging boards and puzzle boxes were developed, and their effectiveness in feeding-time prolongation for nonhuman primates was examined (Reinhardt &
Roberts, 1997) Attempts were also made to reduce the level of abnormal behaviors in bears, by modifying the presentation of foods (Fonhman et al , 1992)
Few studies, however, referred to the effectiveness of enrichment on other behavioral repertoires and activity budgets during the day The aforementioned
studies emphasized the effectiveness of modifying feeding conditions on stereotyped behavior Because few studies direcdy compared the behaviors of zoo animals with that of their wild counterlarts, what is more important in making the
feeding behavior of zoo animals similar to that of wild animals-food type vari-
ation or presentation-is unclear.
Many zoos carry out food provisioning once or twice a day, and the variety of
foods is limited Day to day, the time of such provisioning usually remains the
same In the wild, however, food resources are usually dispersed over the animals'
habitat Diurnal species frequently engage in feeding and exploration activities
during the day In general, feeding behavior has several peak periods during the
daytime, and some species have a feeding rhythm These differences in feeding
conditions between the zoo and the wild very likely affect not only the features of
feeding behavior itself, but also those of other behaviors These experiments attempted to €xtend the length of time zoo animals engage in feeding and foraging
behavior by modifying various feeding conditions Examples included changing
the spatial distribution of foods in the exhibits (dispersive vs massed), and the
temporal distribution of food provisioning (small amount-high frequency vs. large
amount-low frequency), while keeping the food types and the amounts constant
We examined quantitatively the influences on behavioral repertoires and activity
budgets in a day
At the Maruyama Zoo, we observed three species whose respective feeding
ecologies are different in the wild: bears (Ursus arctos\, elephants (Elephas
maximus), zndchimpatzees (Pan toglodyres) Bears, whose exhibit sizewas relatively large (306 m2), were surveyed for the influence of the spatial distribution of
food Elephants and chimpanzees, whose exhibits were relatively small (68 m2 and
FEEDING BEHAV:ORS
171
42 m2, respectively), were surveyed for the effects of food provisioning frequency
(temporal food distribution).
EXPERIMENT 1. BEARS
The experiment consisted of the spatial dispersive feeding eondition (D condition) and the spatial massed feeding condition (M condition) In the D condition,
cloter (Trifulium repens), one of the conyentional food items of summer, was
scattered over the entire area ofthe exhibit In the M condition, the same amount
of clover, to be shared among three individuals, was laid out in three locations
By comparing the animals' behavior in the two conditions, we examined the effectiveness of the modification on various behaviors and on the prolongation of
feeding time
Method
Subjects. Subjects included 3 brown bears one male bear designated "No
1," 38 years old, and 2 female bears designated "No 2" and "No 3," 24 years old
and 15 years old, respectively, housed together at Maruyama Zoo They were kept
in an outdoor exhibit (306 m2) thoughout the year, except for periods of food
provisioning in the moming The outdoor enclosure was an open-field style exhibit
with a concrete surface During the summer, when this experiment was conducted,
vegetables, fish, and meats were provided in the moming at the indoor cage At the
outdoor exhibit, each bear received a whole chicken In the aftemoon, clover was
provided at the outdoor exhibit
Procedure. The l8-day experiment was conducted in 1996 between September 20 and October 9, excepting October 4 and 6 Only the way that clover was
provisioned was modified between the two conditions All other conditions were
k€pt constant In the D condition, cloverwas scattered over the entire exhibit In the
M condition, clover was provided at three locations only The experiment was conducted for five l-hr periods per day Periods began at 9:30 a m , 12 00 p m , l:15
p m,2:30p m ,and3 45p m Each condition wascontinued for 3 consecutivedays
We began the experiment with the D condi tion and repeated the two conditions alternately thrce times (D, Ml D,M; D, M), yieldingarotal of 18 sessions Duringtheexperiment, food provisioning occuned in the morning between 10:00 and l l:00 a m
Clover (5 kg) was proyided in the afternoon between 3 @ and 4 00 p m Indoor and
outdoor distribution of food was 527o (12 kg) and 48Vo (1 I kg), respectively
172
MoRTMURA AND uENo
We used a focal animal sampling method (Altmann, 1974) and categorized behavior by using the ethogram from a former study (Morimura & Ueno, 1998) The
ethogram corsisted of 47 behavioral categories based on the posture of animals
and the function estimated by motor patterns such as feeding, resting, attack, and
play (see Table 1) The data included these 47 behavioral categories and the times
wher each appeared and disappeared Based on higher functional aspects of the
animals' behavior, such as survival, reproduction, and social interacti.on, the 47
behavioral units were divided into six behavioral pattems:
I
2
3
4
5
6
Primary behavior (PB)
Locomotion
Social interaction
Search (SR)
Comfort behavior
Context-free behavior (CFB)
Data were analyzed for the time budgets of each behavioral pattem in a day, the
types of behavioral units that each behavioral pattern contained, and the temporal
pattems of these behaviors during a day
TABLE
1
Definilion of gehavior Types and Repe.toires
Delnition (Behavior Repe oites)
Behlrviot Tlpe
Primary
behavior
Behaviors that sustain life and r€prcduction (e I , feeding, drinking,
resting, sle€ping, sexual behavior, excretion, disorder, seating, rearing
offspring)
Incomotion
Social
inreraction
Se.rching
Comfort
behavio
Context-free
behavior
Spatial change from ooe place lo anoth€r place (e g , walking, ruoning,
moving backwards, jumping, climbing, hanging, swimming)
Relationships among t*o or more iodividuals (e g , socia.l grooming, social
play, attack-I., attack-2b, avoidance, body contact, keeper interaclion,
visitor interaction, social vocalization, social consp€cific exploration,
social heterospecifi c exploration)
Using of sense orgaDs (e g , direct objec( searching, listeniog, sniffing,
staring, fixation)
Self-dirccied behavior (e g , self-grooming, body maDipulation, checking,
strEtching, shaking, licking, yawning, involuttary rcaction, bathing)
Behavior with no clear function (e g , obFct rnanipulation, body
manipulation, stereolypic locomotion, stereotypic action, impulsive
moverne[t, vocalizdion)
.Attack- I is an aggre.ssive intemction which does not clear the dominance-subordinrnce rElationship
bAttack-2 is an aggressive interaction which does clear that reladonship
FEEDINC BEHAVIORS
173
Results
In the D condition, some cloyer was still ayailable, after more than 4 hr, until the
end of the fifth period-at least from the third period, when the clover was pro_
vided On the other hand, in the M condition, bears consumed almost all of the
clover during the founh period, only about l% hr after food provisioning. By the
end of the fifth period, all remaining clover was eaten This tendencv was observed in every session
In the case of the duration ofPB and CFB, the difference between the two con_
ditions markedly appeared at and after the third period Individual differences in
behavior were small. The duration of PB in the third and fourth periods in the D
condition was 83 ad 96Vo, respectively In the M condition, the corresponding
figures were 52 and 59% The total duration ofPB in the D condition was I 3 times
longer than in the M condition (Figure I ) CFB in the D condition had almost disappeared at and after the third period In the M condition, CFB appeared during all
five periods, an average of l6Ea pet day. CFB in the D condition tended to be of
shorter duration than in the M condition, No l:r(9)=2591 ,p= O!|Z;No 2 t(9)
=3 238, p = .0122;No.3i t19) =3 628, p = 0055 The differences between the two
conditions were also evident in the behavioral units, feeding and sle€ping, that
constituted PB (Figure 2) The duration offeeding per day was l3Zo in the D condi_
lion and 4Vo in the M condition Thus, the dispersive way of food provisioning
made feeding time longer than did the massed provisioning In the D condition, the
feeding time significantly increased at the third period, and intermittent feeding
was observed until the fifth period In the M condition, however, feeding had almost completely disappeared by the fifth period (an average of I 6Zo). In the D
condition, the duration ofsleeping significantly increased in the fourth period, No
l:(16)=5174,p< 0001;No 2tt('16)=49(f,,p= 0002; No. 3: ( l6) = 4 47 t, p =
0004 This indicated that the dispersive way of food provisioning not only prolonged the feeding time, but also brought about the spontaneous appearance of a
in which feeding and sleeping occurred alternately This
rhythm continued to be observed until the fifth period
behavioral rhythm
Discussion
Dispersive food provisioning accounted for three main features of the bears' behavior: (a) The amount of feeding time increased, (b) CFB disappeared after the
clover provisioning, and (c) an alternating rhythm of feeding and sleeping spon_
taneously appeared This rhythm continued for a number of hours until the end
of the fifth period It is noteworthy that the rhythm of fe_eding and sleeping occuned spontaneously. In the D condition, an increase in duration was observed
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174
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176
MORIMURA AND UEN0
not only in feeding but also in sleeping The decrease in the duration ofCFB re-
sulted from the modification of the way that food was provided, which in turn
transformed the time budgets of each behavior Craighead, Sumner, and MitcheU (1995) pointed out that brown bea$ in the wild remain in favorable habitats
for a few days at a time and enter a cycle of feeding and resting
The behavioral rhythm of feeding and sleeping that appeared in this expedment
may be assumed to be similar to that found in the wild With regard to the prolongation of feeding time and the appearance of a feeding and sleeping rhythm, the
dispersive food provisioning method allowed us to approximate the behavior of
captive beals to the behavior of bears in the wild Even in the D condition, however, the duration of feeding was a third or less of that in the wild Moreover, the
behavioral change in the D condition did not carry over to the next morning The
behavior before moming food provisioning did not differ significantly between
the two conditions To make the duration of feeding time as long as possible-and
preferably close to tiat of the wild-we should consider aspects of the feeding
condition other than the spatial distribution of food
EXPERIMENT 2: ELEPHANTS
The experiment consisted of the temporal massed feeding condition (M condition) and the temporal dispersive feeding condition (D condition) In the M condition, all food was provided at one time. In the D condition, food was provided
twice a day without changing the sort and the amount of food between the two
conditions In comparing behaviors observed in the two conditions, we examined the effectiveoess of this modification on zoo animal behavior and on the
prolongation of feeding time
Method
Subiects.
Subjects included two adult female Asian elephants, 29 and 41
Zoo In the summer, they were kept in the
outdoor exhibit (233 m'?) from 9 0O a m to 3 0O p m without food provisioning
During the winter, when this experiment was conducted, they nonnally remainedin
the indoor exhibit (68 m,) almost all day, excepting about I hr from 9:00 to 10:00
a m Both exhibits were in an open-field style with a concrete surface Hay, comrnercial biscuits, and bran were provided once a day when individuals entered the
indoor exhibit at 10 00 a m
years old, housed together at Maruyama
FEEDING
BEHAVIORS 177
Procedure. The experiment was conducted for l5 days in 1996, fiom February 6 to 20 In the D condition (food provision twice daily), the fint provisioning
took place between 9 30 and 10:30 a m (first period) and the second between 3 00
and 4:00p m (fourth or fifth period) Food provided in the first provision was 667o
of the total weight and included 38 kg of hay, compound feed, and bran, leaving
34% ofthe total weight,20 kg ofhay only, for the second provision In the M condition (food provision once daily), all foods were provided at one time, sometime between 9:30 and 10:30 a m We began the expe ment with the D cordition and repeated the two conditions alternately for a total of l5 sessiols: D condition repeated
three times, M condition repeated two times The ethogram and the procedure of
obseryation and data analysis were the same as those in Experiment l, except for
the starting time of each period (9:30 a.m, 10:45 a m, I :00 p m, 2:15 p m, and
3:30pm)
Results
In the D condition, all foods were completely consumed by the start of the third
period (1:00 p m ), about 3 hr after the first food provisioning Subsequently, until the time of the second food provisioning (3:00 p m ), elephants ate nothing
for approximately 2 hr In the M condition, however, elephants had food available to them at all times, from directly after food provisioning (10 00 a m ) until
the fifth period (3:30 p m ) Foods were completely consumed by the end of the
fifth period, about 6y2 tr after food provisioning This tendency was observed in
every session
The marked differences in behayior between the two conditions concemed the
duration of PB (feeding), SR (gazing and sniffing), and CFB (stereotyped action)
at and after the third period (Figure 3) The behavior of both groups showed this
tendency In the third and fourth periods ofthe D condition, the average duration of
PB decreased 47 and 26Vo, respectively The duration of SR, 5l and 587o, and
CFB,25 and 387o, increased In the M condition, however, PB occupied an average of gzqo of the animals' time at and after the second period Other behaviors
represented only a small proportion, an average of 1070 combined for all five behavioral types except PB Overall, the duration of PB was 647o in the D condition
and 857o in the M condition Feeding time decreased in temporal disprrsive food
provisioning where the amount of food per food provisioning was decreased and
the frequency of food provisioning increased In the D condition, when the second
food provisioning was carried out at the fifth period, the time of PB increased
again, and the time of SR and CFB decreased Furthermore, even in the M condition the duration of PB continued to decrease, and the duration ofSR and CFB continued to increase as time elapsed from the first period to the fifth At the same
time, the behavioral repenoire ofCFB in the fifth period was different from that in
all other periods In the fifth period, the behavioral repertoire of CFB included
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Comparisons of behavioral pattems between two conditions for the Asian ele-
FEEDING BEHAV10RS
179
striking one's own legs or body with hay that served as food (body manipulation)
During all other periods, CFB was characterized by swinging one's own head,
body, or both from side to side (stereotyped action).
Discussion
The increase in the frequency of food provisioning caused changes in the elephants' behavior We drew two conclusions: (a) To increase the total duration of
feeding in a day, decrease the frequency of the food provisioning; and (b) PB
appears mainly during periods when animals have access to food, whereas SR
and CFB are most prominent, and PB disappears almost completely, during
times offood unavailability In the D condition, no food was available for about
2 hr from the third period until the end ofthe fourth At the same time, the duration of SR and CFB incrcased in the third and fourth periods Based on this,
times of food unavailability, hought about by decreasiDg the amount of food per
each round of food provisioning, affected the increase of SR and CFB time For
elephants, the fluctuations of SR and CFB time correlated closely with that of
PB. This study showed the importance of maintaining the consumption of foods
for elephants rather than increasing the frequency of feeding, which results in
derreasing the amount of food per food provisioning
Even in the M condition, the same behavioral change in the case of food unavailability occu[ed toward evening. The duration of PB decreased, and that of
SR and CFB increased In the fifth period in the M condirion, animals had consumed almost all the food We may consider the possibility that rhe lack of food
primarily affects the behavioral change During times when the duration ofPB was
maintained at over 807o per period, the types of behavioral units ofCFB were different ftom those observed during other periods Based on these results, we may
say that the elephants' attention to fod became weaker They were satiated Feeding behavior in zoos where animals eat foods off the ground includes only simple
consuming Feeding behavior in the wild, however, includes a large behavioral
repertoire, especially the detailed manipulation of objects for feeding such as
breaking the trunk off a tree, picking leaves off a branch, and removing soil from
the roots ofa plant (Sukumar, 1989) Compared with feeding behavior in the wild,
the fading repertoires ofthe captive animals were poor For this reason, it may be
necessary to conduct further €xperiments that focus on bringing out new repertoires of feeding behavior by modifying feeding conditions and also to examine
the effectiveness of these modifications on the behavior of zoo animals
EXPERIMENT 3: CHIMPANZEES
The experiment consisted of the temporal massed feeding condition (M condition) and the temporal dispersive feeding condition (D condition) In the M con-
180
MORIMURA AND llENO
dition, same as the animals' summer food provisioning routine, all food was provided at one time, sometime during the afternoon In the D condition, which
corresponded to winter food provisioning, food was given twice a day, once in
the moming and once in the aftemoon By comparing the animals' behavior in
the two conditions. we examined the effectiveness of this modification on zoo
animal behavior and on the prolorgation of feeding time
Method
Subjects. Subjects included 5 chimpanzees, selected from a group of 10,
who were housed together at the Maruyama Zoo: one 23-year-old male chimpanzee designated No l, and four female chimpanzees designated No 2, No. 3, No 4,
and No 5, ages 23, 18,20, and 18, respectively Dudng the winter, when the experiment was conducted, they were kept in an indoor exhibit (42 mr) all day long This
exhibit was cage style The ceiling and the wall on the visitor's side were covered
with grid, and the floor and the walls on all other sides were covered with concrete
Furthermore, a glass partition separated the visitors from the chimpanzees During
the summer, they were kept in an outdoor exhibit ( 177 mr) from 9:30a.m until3:30
p.m In winter, food provisioning was normally carried outtwice aday Vegetables
(carrots, cabbages, and greens) and grains (wheat) were supplied in the morning
Fruits (oranges and apples) and vegetables (greens) were given in the evening
Prccedure. The experiment was conducted for 15 days in 1996, from De9 to 23. In the D condition (food provision twice daily), the first
provisioning took place between 10:00 and I I 00 a m. and the second at about 3:00
cember
m Food proyided in the first provision was 45% oftotal weight (10 kg), leaving
5570 ofthe total weight (12 kg) for the second In the M condition (food provision
once daily), all food was provided at one time in the afternoon, 3:00 p m As the
p
conventional frequency of chimpanzee food provisioning in winter was twice a
day, a routine opposite of that used for Asian elephants, we began this experiment
with the M condition and repeated the two conditions altemately for a total of 15
sessions: M condition repeated three times, D condition repeated two times The
ethogram and the procedure ofobservation anddataanalysis were the sam€ as those
used in Expedment 1 Only the starting time of each period varied (9 :30 a m, I 0:45
a.m, 12:00 p m, l:15 p m,
and 2:30 p m )
Results
In the D condition, food was available for about 5 hr after the fint food provision, until the end of the observation In the M condition, some food remained
FEEDING BEHAVIORS
181
for about % hr, at least during the period when foods were supplied The same
tendency was observed in all sessions, Marked differences in behavior between
the two conditions occurred only in the third pedod (Figure 4) Moreover, these
differences varied among individuals In the case of two individuals, No 2 and
No 3, CFB duration decreased significantly in the third period of the D condition, No 2 ,(13)=3.028,p< 001;No 3: t(13)=21't5,p< 05 Two more in_
dividuals, No 4 and No 5, showed the same tendency, even though in their
cases the differences were not significant For No l, the difference in behavior
between the two conditions was marked for the behavioral repertoire of pB In
the D condition, sleeping time significantly decreased in the third period, (13)
=
3 308, p < 01 (Figure 5). On average, among the five individuals feeding time
was 77o in the M cor,dition and 24Vo in the D condition As a result of the modification, feeding time increased when the frequency of food provisioning was increased and, at the same time, the amount of food per provision was decreased
In all sessions of the D condition, feeding behavior appeared in all four periods
following the beginning of the second period (Figure 5) The chimpanzees did
not completely consume all the food at one time but fed on it intermittently In
the D condition, feeding time in each period differed from individuat to individual There was a general tendency, however, for feeding time to decrease after
the first food provision in the second period and to incrcase again after the second provision
Discussion
The modification of increasing the feeding frequency determined three main influences on the chimpanzees' behavior:
I
2
‐
3
Feeding time increased along with the increase in the frequency offeeding
Differences in behavior that appeared as aresult ofincreasing thefrequency
of feeding continued to be observed for about 2 lII after the first food provision
Differences in behavior between the two conditions varied among the five
individuals
The main change in behavior in the D condition occurred in the third period
only. However, feeding behavior was observed in all periods following food provision This indicates that chimpanzees continued to eat intermittently. In other
words, at times they engaged in behaviors other than feeding, even though food
was readily available Thus, the modification ofactivity budgets as a whole, due to
a change in duration of single bouts offeeding behavior, caused the differences in
behavior in the D condition, not a decrease in sleeping or CFB time and not a
straightforward increase in feeding time
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132
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183
184
MORIMURA AND UEN0
On the other hand, the failure of the animals to pay attention to food despite
its availability indicates the difficulty in increasing feeding time by simply increasing the opportunity to feed Yanagihara, Matsubayashi, and Matsuzawa
(1994) pointed out that, although controlling a maximum food intake is relatively easy, elevating the food intake of animals in captivity should be more difficult Several studies demonstrated that numerous species readily gather food
for eating, process food for eating, or both (R€inhardt & Roberts, 1997) A lack
of opportunities to engage in these behaviors is conducive to the development of
behavioral disorders (Hediger, 1955) Moreover, the preserce of another indi
vidual might play an important role in stimulating an individual to eat (social facilitation). We may, therefore, encourage individuals to eat by controlling the
social situation during feeding. In addition, we need to examine the effectiveness of the provisioning methods----considered an aspect of food gathering or
food processing-and to adjust social relationships indirectly to promote social
facilitation in feeding
GENERAL DISCUSSION
These results, although gathered from a small sample of individual animals under conditions present only at the Maruyama Zoo, suggest that the modification
of feeding conditions (spatial and temporal food distribution) increases the duration of feeding, at least in the case of these three mammalian species As feeding
time inoeased, the duration of CFB in bears, that of SR and CFB in elephants,
and that of CFB or sleeping in chimpanzees decreased After a food provision,
elephants continued to eat until all food was completely consumed This suggests that increase in feeding time resulted in a decrease of SR and CFB time
Bears and chimpanzees did not continuously eat food when it was availabl€ In
the case of bears especially, the rhythm of alternate feeding and sleeping appeared
spontaneously That is, the duration ofCFB in bears and chimpanzees decreased
because of a tendency not to engage in a behavior such as CFB or sleeping----even
at times when the animals were not feeding-not from simple replacement by the
increase in feeding time
In this study, the modification of feeding conditions affected not only the target behavior but also a variety of other behaviors This frnding indicates the im-
portance of considering animal behavior from a discerning viewpoint to carry
out environmental enrichment The effectiveness of our modiltcations on feeding behavior differed considerably among the tluee species The modification
resulted in a change of feeding patterns in bears and chimpanzees from a "consuming all food at one time" to an "intermittent feeding with several peak times"
scheme Field studies
of
bears (Craighead
et
al
,
1995) and chimpanzees
(Goodalt, 1986) observed that feeding and some other behavior are repeated pe-
FEEDING
BEHAVIORS 'I85
riodically In this study, the cyclical rhythm of feeding and sleeping in bears occuned yoluntarily under the condition in which foods were dispersed around the
animals'exhibit
Another study reported that Japanese macaques (Macc ca fuscata) in captivity
showed a rhythm of feeding under the condition in which individuals could feed
freely (Mori, 1979) In our study, chimpanzees and bears repeatedly shifted between feeding and another behavior such as resting Hence, when frequency of
food provisioning was increased and accompanied by cyclically repeated bursts of
feeding, the weakness of feeding drives probably caused the prolongation of feeding time in chimpanzees and bears On the other hand, Asian elephants in the wild,
similar to other herbivores, especially grazers, spend about 12 to 19 hr a day on
feeding, although some studies reported that a peak time of feeding appears in the
evening (McKay, 1993) The duration of feeding was longer in the continuous
feeding condition, where individuals could continue eating while keeping a low
rate ofconsuming, than it was in the condition where the increase in friquency of
food provisioning compelled individuals to eat at intervals The animals' specific
feeding rhythm should, therefore, be an essential factor considered when seeking
to improYe feeding conditions
In addition, the effectiveness of prolongation on feeding differed among the
three species Elephants spenr 8170 of the daylight hours feeding (M condition)
Bears and chimpanzees spent only 14 atd Z4Vo, respectively (D condition) For
chimpanzees and bears, feeding time was sti below the levels observed in the
wild In regard to feeding in the wild, the behavior can be divided into three
steps
I
.
2
3
Individuals initially forage for food Even when food is encountered. some
of it may be covered with a hard shell or be hiding underground or behind
rocks
Individuals, therefore, have to process food
Individuals can proceed to ingest the food acquired through the two previ_
ous steps (consuming)
Feeding behavior in zoos includes the third step
only consuming For ele-
phants, continuing to feed might, in itself, be important Bears in the wild, however, show a rhythm of feeding and exploring for food around their habitat
Addressing and modifying the thee phases of feeding separately may be neces_
sary to iDcrease their time of feeding It is not enough to increase the frequency of
food provisioning, to create a rhythm of feeding, or both On the basis of these re_
sults, we are carrying out experiments designed to encourage captive animals,
time budgets offeeding behavior to approximate those ofthe wild, fiom the viewpointofthe specific characteristics of feeding and the thLree feeding phases: exploring, processing, and consuming
186
MoRIMURA AND uENo
ACKNOWLEDGMENTS
This study was supported by Sasagawa Scientific Research Grant 8-190 to
Naruki Morimura
We thank the Maruyama Zoo staff for their kind help, and give sPecial thanks to
Kitamura, chief of the animal management section
Mr Ken'ichi
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