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Investigation of the functions of coprophagy in juvenile rats



Five experiments examined possible functions of the ingestion of maternal anal excreta by juvenile rats. Ss were 24 recently parturient Long-Evans rats and their 440 pups. No strong support was found for hypotheses suggesting that (a) maternal excreta serves as a major transition diet from mother's milk to solid food, (b) ingestion of maternal excreta influences pup diet selection at weaning, or (c) ingestion of maternal excreta is a necessary condition for inoculation of pups with enteric bacteria. Some support was found for the hypothesis that maternal excreta can serve as a short-term emergency food supply for rat pups after weaning. It is proposed that pup ingestion of maternal anal excreta may not be a functionally meaningful unit of behavior in preweaning rats. Allocoprophagy may be one facet of a broader pattern of oral exploration in which functional significance resides. (23 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Journal of Comparative and Physiological Psychology
1979, Vol. 93, No.2, 295--305
Investigation of the Functions of Coprophagy
in Juvenile Rats
Bennett G. Galef, Jr.
McMaster University, Hamilton, Canada
A series of experiments were undertaken to examine possible functions of the
ingestion of maternal anal excreta by juvenile rats. No strong support was
found for hypotheses suggesting (a) that maternal excreta serves as a major
transition diet from mother's milk to solid food, (b) that ingestion of maternal
excreta influences pup diet selection at weaning, or (c) that ingestion of mater-
nal excreta is a necessary condition for inoculation of pups with enteric bacte-
ria. Some support was found for the hypothesis that maternal excreta can
serve as a short-term emergency food supply for rat pups after weaning. It is
proposed that pup ingestion of maternal anal excreta may not be a functional-
ly meaningful unit of behavior in preweaning rats. Allocoprophagy may be
one facet of a broader pattern of oral exploration in which functional signifi-
cance resides.
During the 17-day period when newborn
rats are totally dependent on their dam's
milk for sustenance (Babicky, Parizek, Os-
tadalova, & Kolar, 1973), they mouth and
possibly ingest samples of most of the solid
objects with which they come in contact.
Under standard laboratory maintenance
conditions the anal excreta of the dam are
one of the substances samples of which are
frequently contacted, chewed, and appar-
ently swallowed by juvenile rats. Although
there are reports in the literature of mouth-
ing and chewing of maternal excreta by the
young of numerous mammalian species
(Ewer, 1968, p. 274), including the rat (see,
e.g., Bolles & Woods, 1964). Leon (1974)
was, to my knowledge, both the first to re-
port stomach content analyses indicating
that rat pups actually ingest maternal ex-
creta and the first to consider systematically
This research was supported by National Research
Council of Canada Grant AP-307 and a McMaster
University Research Board grant to the author. I would
like to thank Rod Pelchat, Carol Edwards, Sheelagh
Kemp, Pat Muskus, Merry Kaner, and Sue Johns for
their technical assistance, and Evelyn Thoman for re-
minding me that Experiment 5 needed to be done. The
comments of J. R. Alberts and M. M. Clark on earlier
drafts of the manuscript are gratefully acknowledged.
Requests for reprints should be sent to Bennett G.
Galef, Jr., Department of Psychology, McMaster Uni-
versity, Hamilton, Ontario, Canada L8S 4Kl.
possible functions of coprophagy in the
growth and development of young rats.
Leon suggested four possible functions of
ingestion of maternal excreta by rat pups:
(a) Ingestion of maternal excreta may inoc-
ulate young rats with maternal enteric bac-
teria which facilitate digestion of solid food
at weaning (Ewer, 1968, p. 274). (b) Ma-
ternal excreta may be utilized by weanlings
as a "baby food," an important transition
diet from mother's milk to solid foods, as
seems to be the case in koala (Minchin, cited
in Gewalt, 1972, p. 125). (c) Excreta de-
posited in or near the nest site may serve as
an emergency food supply which can sustain
weanlings in the absence of their dam. (d)
Ingestion of maternal excreta may serve to
familiarize pups with the flavor of maternal
diet and direct pups to their mother's diet at
weaning (Galef, 1977; Galef & Henderson,
Although the role of autocoprophagy (the
ingestion by an organism of its own excreta)
in the maintenance of intestinal flora and the
prevention of vitamin deficiencies in rats has
been an area of active inquiry (see, e.g.,
Barnes, 1962; Gustafsson & Fitzgerald,
1960), little information is available on the
significance of allocoprophagy (the ingestion
of the excreta of conspecifics). Hence, the
adequacy of the Leon (1974) hypotheses to
account for the phenomenon of allocopro-
Copyright 1979 by the American Psychological Association, Inc. 0021-9940/79/9302-0295$00.75
phagy in
juvenile rats remains open to
Experiment 1
In the present experiment systematic
observation ofthe behavior of infant rats was
undertaken to establish the age of initiation
and the relative frequency of occurrence of
mouthing and chewing episodes directed
toward the various solid objects present in
the environment. The collection of such
des~riptiv~ dB:ta is a necessary first step in
the mvestigatIOn of hypotheses concerning
the functions of allocoprophagy. If, for ex-
ample, rat pups began to chew on solid food
prior to initiating ingestion of maternal ex-
creta, it would be difficult to maintain that
allocoprophagy is a transitional stage be-
tween nursing and ingestion of more usual
foods. Similarly, temporal precedence of
ingestion of 801id food over coprophagy
wouid render difficult the maintename of
hypo(be8es propoaing that pups use adult
ex~ as a supplementary diet when their
dams Me absent. Thus, a descriptive study
of the time of onset of ingestion of the vari-
ous solids available in the environment is a
necessary pfeCUrsor to any analytic investi-
Subjects. Subjects were eight recently parturient
female Long-Evans rats obtained from Canadian
Breedin« Farms (St. CQnatant, Quebec), and their lit-
ters, cldled to ei(ht pups/titter on the day of birth.
Proudure. Each mother and litter was establiahed
38 X 31 X 17 em polycarbonate cace the ftoor of
which was covered with wood chips (Beua-<:hip,
N~tem Products Corp., Warrensburg, New York)
and IIftD ad lib access to food (Purina Laboratory Chow
pellets) and w~ter. The eight litters were kept in a
soun~-att~nuatm? room on a 12:12 hr light/dark cycle.
IllummatlOn durmg the dark period was provided by
two 40- W red light bulbs suspended above the cages.
Eac~ of the eight litters was observed for .5 hr/day
durmg each of the !ight and dark portions of the cycle,
t~e observer recordmg every object mouthed by all eight
htter members.
The results of Experiment 1 are presented
m Figure 1, which indicates the percentage
of observation periods during which one or
more members of each of the eight litters was
seeI? to mouth various objects in its cage
durmg 2 hr of observation on two consecu-
tive days. As is clear from examination of
the figures, prior to weaning, pups regularly
mouth everything available in the environ-
meJ?t-themselves, wood chips, other pups,
their dam, food pellets, mother's fecal pel-
lets, mother's cecotrophe; pup fecal pellets,
and objects not reported in the figures (i.e.,
water spouts, cage walls, etc.). These de-
scriptive categories are obviously somewhat
arbitrary in that while chewing on a wood
chip, its own foot, or its mother's tail, a pup
may actually be tasting fecal material, urine,
or cecotrophe. Further, the fact that pups
mouth an object gives no indication of
whether or not it is ingested.
In spite of their limitations, the present
observations do indicate, for example, that
~a) the range of objects mouthed by pups
m~reases with increasin~ age, (b) there is a
faIr degree of consistency in the ages at
~ 60
f :
PlPFECES ~ ... Ir"''''~--'''
=--:-==~s ~
% 101"
'7,7 '8/'920/21 22/23
Figure 1. Percentage of eight pup litters in which
mouthin~ of various objects was observed during four
consecutive .5-hr observation periods.
which different items are first introduced by
pups into their mouths (Day 1, nipples of
mother and fur of mother's ventral surface;
Days 9-11, own feet, fur of other pups, and
substrate material; Days 13-15, feces of
mother, nonventral surface of mother, and
food pellets; Days 17-21, mother's ceco-
trophe, water, and pup feces), and (c) once
mouthing of a class of objects begins it con-
tinues through the weaning period.
The results of Experiment 1, though not
conclusive because of the difficulty of de-
termining by visual inspection whether or
not chewed samples are ingested, suggest
that ingestion of maternal excreta, particu-
larly dried fecal pellets, is an extremely
common pattern of behavior in laboratory-
maintained juvenile rats. The data, though
not sufficient to exclude any ofthe hypoth-
eses briefly described above, cast serious
doubt on interpretations of maternal fecal or
cecal material as an important transition diet
from mother's milk to solid food. Pups did
not reliably initiate chewing on maternal
excreta prior to chewing on Purina pellets,
in spite of the fact that the former objects
were far more common on the floor of the
cage than the latter.
It is, however, clear that decisive tests of
hypothesized functions of allocoprophagy
require determination of the substances ac-
tually ingested by pups of various ages.
Experiment 2 provides relevant data.
Experiment 2
To determine the substances actually in-
gested by rat pups of various ages, I directly
examined their stomach contents. The re-
sults of a series of pilot studies revealed that
pups 10 days of age were not sufficiently
mature to ingest solid foods. When 10-
day-old pups were force-fed a mash con-
sisting either of ground Purina chow and
water or ground dried excreta (deposited by
a lactating female rat) and water, it was not
possible to reliably discriminate excreta from
chow in the stomachs of pups. However,
lactating female rats fed a diet of powdered
Purina Laboratory Chow adulterated with
.2% by weight alcohol-soluble eosin (Telle,
1966) produced a bright orange anal excreta
(both feces and cecotrophe) which, when
dried, ground, sieved, and force-fed to pups,
was readily discriminable from powdered
Purina chow in pup stomachs. In blind ex-
periments, as little as .01 g of ground, dyed
powdered feces could be reliably detected in
pup stomachs as long as 5 hr after force-
To determine the age of onset of ingestion
by pups of both solid food and excreta, it was
necessary to design an apparatus in which
mothers ate eosin-dyed food at a location
inaccessible to pups and pups had access to
undyed food at a site inaccessible to their
dam. Although the procedure described
below was sufficient for this purpose, it has
certain inevitable disadvantages which I
consider in discussing the results of the
present experiment.
Subjects. One-hundred twenty Long- Evans rat pups
from 15 litters, culled to eight pups/litter at birth, served
as subjects.
Apparatus. A few days prior to parturition each
female was established in a .9 X .9 X .9 menclosure like
that illustrated schematically in Figure 2. The enclo-
sure was divided by a barrier, the height of which (12 in.;
30 cm) was such as to permit an adult rat, but not a ju-
venile, to cross from one side of the cage to the other.
The juveniles were invariably delivered and maintained
on the side containing a .3 X .3 X .15 m nest box, water
bottle, and pup feeder. The pup feeder was a small box
mounted on the cage wall with an entrance hole (1 in.
Figure 2. Enclosure for feeding dams eosin-dyed food
separate from their young and young undyed food
separate from their mothers (Experiments 2 and 3).
[2.54 em] in diameter) sufficiently large to permit ready
access by pups but too small for the mother to enter.
The floor of the pup feeder was kept covered with
powdered Purina chow. Daily inspection of the feeder
revealed no disturbance of the food surface until pup
footprints were found on it.
Food for the dam (powdered Purina Laboratory
Chow, adulterated 2% by weight with alcohol-soluble
eosin) was available ad lib on the far side of the barrier.
Daily inspection of the enclosure revealed no transport
of the bright orange food from one side of the enclosure
to the other. Review of periodic time-lapse videotapes
of the enclosure revealed no instance of a pup crossing
the barrier.
Procedure. Each of six dams and litters were left
undisturbed in one of six enclosures until the pups were
11 days of age. On Day 11 and every 2 days thereafter,
two pups were taken from each litter and sacrificed, and
their stomach contents were examined for the presence
of food particles and orange maternal excreta. The
remaining nine litters were treated identically to the
first six except that sacrifice of litter members was ini-
tiated on Day 19.
Pups 11 or 13 days of age invariably had
stomachs containing a pure white milk curd
of rubbery consistency which could be re-
moved intact from the stomach. As can be
seen in Figure 3, no particulate matter was
f(nVt~ i.Qthe stoma~h.s of either 11- or 13-
daX<;~~ though"th~ turds from the stom-
achs of the latter animals invariably exhib-
--+-- FECES
ited a uniform very pale orange color, which
I attributed to leakage of the eosin dye into
maternal milk during the later stages of
lactation for two reasons. First, if one pup
in a litter had a pale orange stomach curd, all
pups in that litter did, and, second, these
curds contained no particulate matter at
Orange particles began to appear in the
stomachs of pups at 15 days of age and were
detectable thereafter in the stomachs of
many animals. Although the present
method did not provide a means of quanti-
fying the amount of maternal excreta in-
gested by pups, the amounts found in pup
stomachs throughout the study were in-
variably small. Comparison with the
stomach contents of pups force-fed known
amounts of ground, eosin-dyed feces indi-
cated that voluntary feces intake rarely ex-
ceeded .1 g.
Greenish food particles (undyed Purina
chow) were first detected in small quantities
on Day 17, were invariable present in mod-
erate or large quantity on Day 21, and vir-
tually filled the stomach on Day 23.
In summary, our results indicated that
pups initiated ingestion of excreta prior to
feeding on Purina chow but that they in-
15 17
Fi#ure .5. Percentage of pup stomachs observed to contain particles of Purina chow or maternai excreta
as a function of pup age (Experiments 2 and 3).
gested very little of the former material and
increasing amounts of the latter.
The results of the present experiment do
not provide support for the suggestion that
in the rat, mothers' excreta serve as a major
transition diet from milk to solid food. We
could find no case in which a significant
portion of a pup's stomach contents con-
sisted of maternal excreta.
The data do offer limited support for the
hypothesis that ingestion of maternal ex-
creta is necessary to inoculate juveniles with
enteric bacteria which facilitate digestion of
solid food. Small quantities of excreta were
observed in the stomachs of many pups in
the absence of particles of Purina chow, but
Purina chow was rarely observed in the ab-
sence of feces prior to Day 21 when the pups
had weaned. These observations are con-
sistent with the hypothesis that ingestion of
small quantities of excreta precedes inges-
tion of solid food and that such ingestion of
maternal excreta may be a necessary condi-
tion for the transmission of specific enteric
bacteria to juveniles, facilitating their in-
gestion of solid food. It should, however, be
kept in mind that the relative age of onset of
allocoprophagy and ingestion of solid food
found in the present experiment may well be
specific to the experimental situation em-
ployed. My co-workers and I (Galef, 1971;
Galef & Clark, 1972) hav03previously found
that age of onset of weaning in rats is af-
fected by such variables as distance from the
nest to the feeding site and the presence or
absence of conspecifics at the feeding site.
In the present experiment, pups and dam
were prevented from exploiting a common
food source, and one would expect an arti-
factual delay in the weaning of the pups to
solid food.
In addition, there are several reasons for
questioning the necessity of explicit inges-
tion of maternal excreta for the development
of a functional gastrointestinal flora in the
rat. First, even pups reared artificially
(without any direct contact with conspecifics
or their excreta) exhibit normal growth fol-
lowing weaning to standard laboratory diets
(Hall, 1975; Thoman & Arnold, 1968). AI-
though it is impossible, in the absence of
bacteriological examination of the gut flora
of weaned, artificially reared pups, to know
if such animals have a normal enteric popu-
lation, they certainly possess an intestinal
flora both acquired without direct contact
with conspecifics or their excreta and ade-
quate for normal growth in some environ-
Second, available evidence strongly
suggests that although most of the organisms
colonizing the alimentary tract of the neo-
nate probably derive from the anal excreta
of the dam (Smith, 1965a), active ingestion
of feces is not a necessary condition for pup
inoculation with a normal bacterial flora.
The infant rat, sterile at birth, has a rich
bacterial flora as early as 24 hr following
birth, when the pup is insufficiently mature
to locate and chew maternal feces. Strep-
tococci, lactobacilli, and E. coli are all
present in the gastrointestinal tract of young
rats within 72 hr of birth (Raibaud, Dickin-
son, Sacquet, Charlier, & Mocquot, 1966;
Smith, 1965a). Bacteriodes and Clostridi-
um welchii are, respectively, first observed
in the rat gut between Day 4 and Day 10 and
at 18 days neonatally and might enter the
gut as the result of allocoprophagy by.pups.
However, the fact that both Bacteroides and
C. welchii invade the gut of a number of
other altricial species (e.g., man and cat) on
the day of birth (Smith & Crabb, 1961)
suggests that these bacteria may also be
transmitted from dam to young without ex-
plicit ingestion of excreta by the infant. The
fact that C. welchii are not found in the ex-
creta of the dam (Smith, 1965a) and that the
ability of C. welchii to successfully colonize
the rat alimentary tract is largely dependent
on the diet of the host (Smith, 1965b)
suggests that the appearance of C. welchii in
the gut is the result of weaning from moth-
er's milk to solid food on Day 18 and not pup
ingestion of anal excreta. The evidence re-
garding the role of allocoprophagy in pup
inoculation with Bacteroides is less clear, but
the fact that some infant rats are colonized
by Bacteroides as early as Day 4 (Smith,
1965a) again suggests that explicit copro-
phagy is not a critical factor in inoculation.
In general, the literature does not provide
strong support for the view that allocopro-
phagy functions to inoculate young rats with Experiment 3, lacking access to s.olid fo.od
maternal enteric bacteria. rations, invariably had stomachs fIlled wIth
orange particles.
Experiment 3
In discussing the results of Experiment 2
with Leon, it became clear that the data
which he collected on the ingestion of ma-
ternal excreta by weaning rat pups was at
variance with our own. Leon (1974) found
substantial quantities of maternal excreta in
the guts of 93% of the 20-day-old pups he
examined, whereas I found only traces of
maternal excreta in less than 80% of the pups
I examined at the same age (Day 21 in my
system). Consideration of differences be-
tween Leon's experimental design and my
own revealed that although they were very
similar there was a major difference in the
access to food provided pups. In Leon's
study, pups had no possible source of food
other than maternal milk or excreta, whereas
in Experiment 2 above they could ingest
milk, maternal excreta, or Purina chow.
If the failure of pups in Experiment 2 to
ingest large quantities of maternal excreta
resulted from the availability of other solid
food then one would expect pups to ingest
larg~ quantities of mat~rnal excreta if no
other foods were available to them. The
present experiment, which examines th~
possibility, bears directly on the hypothesIs
that maternal excreta may serve as an
emergency food ration for weanlings.
Subjects. Subjects were eight litters of Long-Evans
rat pups born in the McMaster colony and culIed to
eight pups/litter on the day of birth.
Procedure. The procedure was identical to that of
Experiment 2 except no food was present in the pup
feeder and sacrifice of pups was initiated in half of the
litters at Day 13 and in half at Day 23.
As can be seen in Figure 3, pups without
food available initiated ingestion of maternal
excreta at about the same time as those with
food available. Stomach content analyses
revealed small quantities of orange granules
in the stomachs of a steadily increasing
proportion of pups on Days 13, 15, and 17.
However, on Day 21 and thereafter, pups in
The results of the present experiment
strongly suggest that rat pups make us~ of
maternal excreta as an emergency ratIOn
when mother's milk ceases to be a source of
adequate nutrition and no other food .is
available to them. If, as was the case In
Experiment 2, adequate foo~ is available in
the vicinity of the nest, pups mgest that food
in preference to maternal excreta. These
data support the hypothesis that maternal
excreta is available to the young as an
emergency ration in the event that no f?Od
is to be found in the environment at the tIme
of compulsory weaning.
Experiment 4
The results of Experiments 1 and 2 indi-
cate that pups initiate ingestion of maternal
excreta well before weaning occurs. The
results of Experiment 2 further indicate that
so long as mother's milk or regular food is
available to pups in adequate quantity, they
ingest only small quantities of maternal ex-
creta. In the present experiment, I exam-
ined the effects of removal of the dam and
food on the ingestion of maternal excreta by
pups of various ages to determine the .r~ge
of ages at which pups are capable of utl.hzu!,g
maternal excreta as an emergency ratIOn m
the absence of alternative rations.
Subjects. Subjects were 18 litters of Long-Evans rat
pups, culIed to eight pups!Iitter on the day of birth.
Procedure. Six litters of pups were examined at each
ofthree ages (Days 16, 19, and 23) to determine the ef-
fects of both maternal and food deprivation on ingestion
of maternal excreta. Each litter of pups was randomly
divided into two groups of four pups/group, and each
group was placed together in a polycarbonate cage (37
X 31 X 17 cm) with wood chip bedding and a water
source. Pups assigned to the Excreta condition were
given very large rations of fresh maternal excreta (both
feces and cecotrophe) at the time they were removed
from their dam and every 12 hr thereafter. Pups in the
Deprivation condition were treated identically to t~ose
in the Excreta condition except that they were not gIven
access to maternal excreta. Each pup was weighed at
the time of removal from its dam, and 24 and 48 hr
thereafter. To assure independence of groups, I treated
the mean weight loss of each group of four pups as a
single data point in calculating means and standard
Results and Discussion
The main results of Experiment 4 are
presented in Figure 4 which shows the mean
weight loss of pups in Excreta and Depriva-
tion conditions following 24 and 48 hr of
isolation from their dam. As is clear from
examination of the figure, weight loss over a
48-hr period, but not a 24-hr one, was sig-
nificantly reduced in 19- and 22-day-old
pups by the presence of maternal excreta in
their cages. The presence of maternal ex-
creta had no comparable effect on pups 16
days of age at the onset of testing. Thus,
pups of postweaning age are able to utilize
maternal excreta as an emergency food
supplement in the absence both of their dam
and of other rations, but pups of preweaning
age are not.
Of course, the fact that young rats ingest
maternal excreta in the absence of their more
usual sources of nutrition does not mean that
such coprophagy provides a meaningful
source of nutrients. However, in an exper-
iment in which the longevity of seven 22-
day-old rat pups left in a clean cage with ad
lib water was compared with that of seven of
their littermates left in cages provisioned
with maternal excreta and water, it was
found that although all pups succumbed
within 24 hr of one another, the latter ani-
mals lived significantly longer than the for-
mer (Mann-Whitney U = 1,P < .001), which
indicates that mothers' excreta is a partially
adequate diet.
Although allocoprophagy may postpone
death, its long-term value is not clear. The
situation in which the pups in the present
experiment were examined is, of course, far
removed from that experienced in the nat-
ural environment. In particular, the pups
in our study were prevented from dispersing
from a location in which the only available
food was inadequate for long-term survival.
It might be argued that following prolonged
absence of the dam, weanling pups in a nest
site lacking food would be better advised to
disperse from the nest site in search of ade-
quate rations than to remain in the natal site
16 19 22
Fiuure 4. Mean weight loss by pups following 24 and 48 hr of isolation from the dam, in the presence
or absence of maternal excreta.
feeding on an inadequate diet. Humans lost
in the wilderness are advised not to linger in
locl;lls in which inadequate food is available
in that further movement is necessary and
the greater the period of subsistence on an
inadequate diet the less the energy reserves
available for further exploration (Angier,
1962, p. 52). By analogy, the utilization by
rat pups of maternal excreta as an emergency
ration, while providing some short-term
benefit, might not, in the long run, be a use-
ful strategy for weanling pups in the absence
of both their dam and conventional foods.
Experiment 5
The final hypothesis to be examined
suggests that the ingestion of maternal ex-
creta by pups serves as a mechanism for the
transmission of food preferences from a dam
to her offspring. The results of studies in a
number of laboratories (Bronstein, Levine,
& Marcus, 1975; Capretta & Rawls, 1974;
Galef & Clark, 1972; Galef & Henderson,
1972) indicate that at weaning, rat pups ex-
hibit enhanced intake of the diet of their
dam, and it i~ possible that allocoprophagy
by the pups function to introduce the young
to undigested particles of diet in the excreta
of their dam. In a series of studies under-
taken to determine the means by which pups
become familiar with their mother's diet,
Henderson and I (1972) found evidence of
flavor cues in mothers' milk (see also Galef
& Sherry, 1973) but found no evidence that
pup ingestion of feces played a role in the
transmission of food preferences from
mother to young.
The results of studies published after
Henderson and I completed our work (Leon,
1974) suggest that our experiments may not
have been an adequate test of the hypothesis
that maternal excreta is utilized by pups to
determine their food choice at weaning
(Galef, 1977). Leon presented data indi-
cating the following: (a) Lactating female
rats deposit two types of anal excreta, feces
and cecotrophe, and virgin female rats re-
ingest the latter and deposit only the former.
(b) Feces is less attractive to rat pups of
weaning age than cecotrophe. (c) Some
maternal diets, among them one of the diets
Henderson and I used, do not permit syn-
thesis of attractive cecotrophe by lactating
females of some strains (Galef & Heiber,
1976), and (d) food-deprived lactating fe-
males exhibit reduced cecotrophe deposi-
tion. All four of these findings cast some
doubt on the adequacy of the experiments
Henderson and I carried out to test the hy-
pothesis that flavor cues in maternal excreta
influence pup diet choice at weaning. The
present experiment was undertaken to cor-
rect the methodological deficiencies of Galef
and Henderson (1972).
Subjects. Subjects were 16 pregnant Long-Evans
rats obtained from Canadian Breeding Farms. Eight
females and their litters, culled to six pups!litter on the
day of birth, were assigned to experimental groups, and
eight were used as sources of excreta.
Maintenance apparatus. Each female assigned to
serve as an experimental animal was placed in a stan-
dard plastic laboratory cage (37 X 31 X 17 em) with ad
lib access to water. Each female assigned to serve as a
source of excreta was placed in a modified standard
laboratory cage like that depicted in overhead schematic
in Figure 5 and was maintained on ad lib food and water.
A modified laboratory cage containing a source animal
and her litter was suspended above each standard lab-
oratory cage containing an experimental animal and her
litter. Two thirds of the bottom of each modified cage
was removed and replaced with hardware cloth (1.2 X
2.5 em) to permit excreta to fall to the cage below it.
The hardware-cloth-floored section of each source fe-
male's cage was separated from the remaining one third
of her cage by a sealed transparent partition. Entrance
to the third of the cage behind the partition was through
a single 5-cm-diam. hole. A nesting area of aluminum
sheet metal (10 X 10 X 17 em) and a food source were
located behind the partition.
Testing apparatus. The apparatus used to deter-
mine the food preferences of individual pups, described
Figure 5. Overhead schematic view of the modified
standard laboratory cage containing a source-group
female and litter in Experiment 4. (This cage was
suspended directly above a standard laboratory cage
containing an experimental group female and litter.)
in detail in Galef and Henderson (1972), consisted of a
plastic dish (22 cm in diameter, 6.6 cm deep) with two
detachable food cups mounted 1800 apart on its exte-
rior. Water was available throughout testing in a
shallow bowl placed in the center of the apparatus.
Intake of diet from each food cup was determined by
Procedure. Three to four days prior to parturition,
each female was assigned one of two maintenance diets
and was given ad lib access to either powdered Purina
Laboratory Chow (Diet P) or a powdered diet whose
main constituents were potato starch and casein (Diet
PSC).l Both diets are known to allow dams to syn-
thesize cecotrophe highly attractive to young rats (Leon,
1974). On the day of parturition each female was as-
signed to either an experimental or a source cage. To
ensure that pups born to experimental females ingested
solid food for the first time when tested for theirJood
preference in the test apparatus, each experimental
female was fed for 3 hr/day (9-10 a.m., 3-4 p.m., 10-11
p.m.) in a cage separate from her young on the diet on
which she had been maintained prior to parturition.
Each female serving as a source of excreta was paired
with an experimental female whose time of parturition
was within 24 hr of her own and was provided ad lib
access in her home cage to the diet on which she had
been maintained prior to parturition.
Pups in experimental litters were reared in one Of
three conditions: (a) Both their dam and the dam
overhead were eating Purina Laboratory Chow (P/P),
(b) both darns were eating the potato-starch-casein diet
(PSC/PSC), or (c) the dam overhead was eating Purina
Laboratory Chow while the dam of experimental pups
was eating the potato-starch-casein diet (P/PSC).
Cages containing source females were examined daily
and were cleaned if any spillage was detected in the
feeding area. Source mothers invariably kept their
young in the nesting area and kept the area behind the
partition relatively free of anal excreta, more than 90%
of which fell to the cage below.
Testing was initiated when experimental pups were
21 days of age. Each experimental pup was placed in-
dividually in a test apparatus and was offered the choice
of Diet P and Diet PSC. Intake of each diet was de-
termined 3, 6, 12, and 24 hr follo~g placement of a pup
in the test apparatus.
Results and Discussion
I expected on the basis of previous work
that pups in Groups PIP and PSCIPSC
would exhibit a preference for the diet of
their dam and the source female living above
them. As can be seen in Figure 6, which ip-
dicates the amount of Diet PSC ingested by
pups in Groups PIP and PSCIPSC as a per-
centage of total intake, my expectations were
confirmed. Pups exposed to females eating
Diet PSC ingested a considerably greater
percentage of that diet during the test period
than did pups exposed to females eating
Diet P.
-Q- (P)/(PSC) (3 LITTERS)
Figure 6. Amount of Diet PSC eaten by experimental
group pups during 24-hr testing as a percentage of total
intake. '
I expected that if pups were influenced in
their choice of diet at weaning by maternal
excreta, then pups in Group P IPSC, which
were exposed to the excreta of a lactating
female eating Diet P during ontogeny, would
exhibit less of a preference for Diet PSC
during testing than pups in Group PSCIPSC
which lacked such exposure. As can also be
seen in Figure 6, pups in Group P IPSC did
not exhibit any effect of exposure to the ex-
creta of source females eating Diet P. The
feeding preference of pups in Group P IPSC
was not different from that of pups in Group
The results of the present experiment
confirm those found previously (Galef &
Henderson, 1972) and do not offer support
for hypotheses implicating exposure to ma-
ternal excreta in the determination of pup
feeding preferences at weaning. It might, of
course, be argued that the reason why pups
in Group P IPSC failed to exhibit any effect
of exposure to the excreta of females eating
Diet P is that pups in Group P IPSC did not
ingest any of the excreta from the female
eating Diet P and therefore the present ex-
Diet PSC was compounded (in g/kg) of 584.5
potato starch, 211 g of casein, 104.5
g of cellulose, 50.0
g of corn oil, 40.0 g of salt mix VSP XIV, and 10.0 g of
Vitamin Fortification Mix.
periment does not adequately test the hy- orally explore their environment and, per-
pothesis. It should be kept in mind that the haps, learn the adequacy of various sub-
question addressed in the present experi- stances as dietary constituents before serious
ment was not whether pups could utilize weaning begins. In support of the latter
information in maternal excreta ifforced to view, the data presented in Figure 1 indicate
do so but rather whether they would utilize that sawdust is the substance first and most
such information if allowed to do so. The frequently mouthed by pups 8 to 19 days of
results of the present experiment suggest age. Perhaps sawdust chewing is in itself
that the answer to the latter question is functional, perhaps not. Similarly, alloco-
negative, but they provide no evidence prophagy by young rats may be a functional
bearing on the former. unit of behavior, or it may be one aspect of
a broader pattern of oral exploration in
which functional significance resides. The
present studies fail to provide strong evi-
dence supporting the former view.
General Discussion
The results of the present series of ex-
periments are in a sense disappointing. The
hypotheses under study concerning the
function of allocoprophagy in young rats
seemed at the outset readily testable and
likely to be confirmed. However, the ex-
periments and literature review presented
above offer support only for the view that
ingestion of mothers' excreta may serveas a
short-term emergency diet when weaned
pups are starving and no other food is
available. Such data does little to explain
the frequent gnawing of maternal feces to be
observed in 12. to 18-day-old pups which are
both adequately maintained by their dams
and have access to an adequate diet of solid
There seem to me to remain two possible
classes of answer to the question of the
function of allocoprophagy in preweaning
rats. First, future studies may reveal some
as yet unknown benefits accruing to pups
from the ingestion of their dam's excreta. In
particular, it is possible that bacteriological
investigations, beyond the capacity of our
laboratory to perform, might reveal an im-
poverished intestinal flora in rats reared
without access to maternal excreta, which
would leave pups vulnerable to diets defi-
cient in specific vitamins (Barnes, 1962).
Alternatively, it is possible that the question
What is the function of allocoprophagy in
weanling rats? is unanswerable in that form.
Nibbling on and ingestion of maternal ex-
creta by young rats may not be the appro-
priate unit of behavior in which to seek
functional significance. It is possible that
allocoprophagy may simply be one expres-
sion of a general tendency of young rats to
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... There are two types of coprophagy: autocoprophagia, the act of ingesting self-produced feces, and alocoprophagia, the act of consuming the feces of other animals, both of which have been observed in dogs [5,6]. Some possible causes for this habit are the presence of one or more cohabiting coprophagic animals, stress, the punishment carried out by a pet's owners when they see them eating feces, the provision of only one meal a day, and a supply of unbalanced foods, although there is no scientific evidence for the latter [3,5,7]. ...
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Coprophagia is a common and undesirable behavior observed in dogs; however, little is known about its causes or possible consequences when analysis of the animal’s feces is needed for experimental purposes. Therefore, this study evaluated the effect of coprophagy on digestibility, fecal pH, and fermentative metabolites. Twelve healthy dogs with a mean age of 3.50 ± 1.45 years were included and divided into two groups: coprophagic (COP) and non-coprophagic (NCOP). The study lasted 30 days, the last 6 days being used to collect feces for the analysis of the apparent digestibility of coefficients (ADC), fecal pH, and the concentration of short- and branched-chain fatty acids, ammonia, and fecal lactic acid. Statistical analysis was performed using the SAS software. No differences were observed for most variables, except for the ADC of nitrogen-free extract (NFE), which presented the highest average for the COP. This result should be interpreted with caution, as the NFE is estimated from calculations and was not determined in the laboratory; in addition, the results represent not only starch and sugars but also some parts referring to fibers. Therefore, coprophagy seemed not to influence the fecal variables analyzed.
... Coprophagy is a terminology that is used to describe the behavior of eating feces in small herbivores (Garcia et al., 2004;Ferreira et al., 2018). Two types of coprophagy behavior have been observed: the ingestion of own feces (autocoprophagy) or ingestion of excrements of another animal of the same species (allocoprophagy) (Galef and Bennett, 1979). This behavior allows hindgut-fermenting mammals to recover the nutrients that were liberated in the hindgut and aids the absorption of essential amino acids, vitamin B, vitamin K, and trace elements, thereby avoiding the loss of these nutrients (Savage, 1986). ...
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Coprophagy is an instinctive behavior in rabbit with important effects on growth and reproductive performance. The underlying mechanism of this effect in rabbit is unknown. Here, we used Elizabeth circle as a coprophagy preventing model in female rabbits and assess feed intake, growth, and reproductive performance. We found that preventing coprophagy did not affect feed intake but decreased body weight and weight of several organs and tissues and resulted in complete reproductive failure during the late pregnancy period, accompanied by reduced levels of plasma progesterone. RNA-seq analysis of rabbit ovarian tissues revealed that preventing coprophagy affected significantly 241 genes (DEGs), with the large majority being downregulated. Bioinformatic analyses revealed that those DEGs are mostly involved in apoptosis, immune response, and metabolic pathways. Among DEGs, the lysosomal cysteine protease cathepsin B ( CTSB ) was significantly downregulated in the coprophagy prevention group. Further studies using siRNA and adenovirus overexpression systems revealed that CTSB promotes the proliferation of rabbit granulosa cells (GCS) and prevents apoptosis. Measurement of transcripts coding for proteins related to apoptosis revealed a minor transcriptomic effect of CTSB, indicating that its effect is likely post-transcriptional. Overexpression of CTSB increased secretion of progesterone and estradiol, partly via upregulation of CYP19A1 while inhibition of CTSB decreased progesterone secretion partly via downregulation of the StAR gene. In conclusion, our study demonstrated the detrimental effect on reproduction by preventing coprophagy with a main role for this response played by CTSB on the granulosa cells of the ovary.
... In pigs, during the suckling period up to day 14, the nursing dam influences the fecal bacterial community which shows progressive changes, with specific bacteria taxa associated with the nursing sow (Bian et al., 2016). Besides parent/nurse-offspring contact, in some species such as pigs (Soave and Brand, 1991), rabbits , horses (Crowell-Davis and Houpt, 1985), and rats (Galef, 1979), early coprophagia behavior is also likely to play an important role in parent/nurse-to-offspring transmission of the microbiota. It has been demonstrated that, in rabbits, preventing coprophagia delays microbiota maturation . ...
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Evolutionary biologists studying wild species have demonstrated that genetic and non-genetic sources of information are inherited across generations and are therefore responsible for phenotypic resemblance between relatives. Although it has been postulated that non-genetic sources of inheritance are important in natural selection, they are not taken into account for livestock selection that is based on genetic inheritance only. According to the natural selection theory, the contribution of non-genetic inheritance may be significant for the transmission of characters. If this theory is confirmed in livestock, not considering non-genetic means of transmission in selection schemes might prevent achieving maximum progress in the livestock populations being selected. The present discussion paper reviews the different mechanisms of genetic and non-genetic inheritance reported in the literature as occurring in livestock species. Non-genetic sources of inheritance comprise information transmitted via physical means, such as epigenetic and microbiota inheritance, and those transmitted via learning mechanisms: behavioral, cultural and ecological inheritance. In the first part of this paper we review the evidence that suggests that both genetic and non-genetic information contribute to inheritance in livestock (i.e. transmitted from one generation to the next and causing phenotypic differences between individuals) and discuss how the environment may influence non-genetic inherited factors. Then, in a second step, we consider methods for favoring the transmission of non-genetic inherited factors by estimating and selecting animals on their extended transmissible value and/or introducing favorable non-genetic factors via the animals’ environment.
... Interestingly, coprophagy is found in many animal species including pigs (Orland and Brand, 1991), rabbits (Combes et al., 2014), termites (Rosenberg and Zilber-Rosenberg, 2011), horses and rats (Galef, 1979;Crowelldavis and Houpt, 1985). For example, piglets reportedly ingest 20 g of their mother's feces daily (Orland and Brand, 1991). ...
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Reducing antibiotic use is a necessary step toward less antibiotic resistance in livestock, but many antibiotic resistance genes can persist for years, even in an antibiotic-free environment. In this study, we investigated the potential of three fecal complex microbial communities from antibiotic-naive does to drive the microbiota of kits from antibiotic-exposed dams and outcompete bacteria-carrying antibiotic-resistant genes. The fecal complex microbial communities were either orally delivered or simply added as fresh fecal pellets in four to five nests that were kept clean from maternal feces. Additionally, four nests were cleaned for the maternal feces and five nests were handled according to the common farm practice (i.e., cleaning once a week) as controls. At weaning, we measured the relative abundance of 26 antibiotic resistance genes, the proportion of Enterobacteriaceae resistant to tetracycline and sulfonamide antibiotics, and the taxonomic composition of the microbiota by sequencing the 16S rRNA genes of one kit per nest. Changing the surrounding microbes of the kits can hinder the transmission of antibiotic resistance genes from one generation to the next, but the three communities widely differed in their ability to orient gut microbes and in their impact on antibiotic resistance genes. The most efficient delivery of the microbial community reduced the proportion of resistant Enterobacteria from 93 to 9%, decreased the relative abundance of eight antibiotic resistance genes, and changed the gut microbes of the kits at weaning. The least efficient did not reduce any ARG or modify the bacterial community. In addition, adding fecal pellets was more efficient than the oral inoculation of the anaerobic suspension derived from these fecal pellets. However, we were unable to predict the outcome of the exclusion from the data of the donor does (species composition and abundance of antibiotic resistance genes). In conclusion, we revealed major differences between microbial communities regarding their ability to exclude antibiotic resistance genes, but more work is needed to understand the components leading to the successful exclusion of antibiotic resistance genes from the gut. As a consequence, studies about the impact of competitive exclusion should use several microbial communities in order to draw general conclusions.
... Coprophagy is the habit of eating or feeding on one's own (autocoprophagy) or other individual's (or species) excrement (allocoprophagy) (Galef 1979). This phenomenon was first reported in 1882 in rabbits (Morat 1882) which form excreta (that are later ingested later) in the cecum, and the term cecotrophy refers to coprophagy practiced by rabbits and sometimes rodents (Soave and Brand 1991). ...
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The Central American squirrel monkey, Saimiri oerstedii citrinellus is endemic to Costa Rica and listed by IUCN (2002) as Critically Endangered. The last optimistic estimate of the population of S. o. citrinellus was of 1,500 individuals. According to The second Squirrel Monkey Population and Habitat Viability Assessment Workshop (PHVA) took place in Costa Rica in June 1995 and Boinski and Sirot (1997), the principal recommendation was to verify in situ the localities where S. oerstedii has been recorded, to obtain counts of the number of troops and individuals, along with data on forest size, its characteristics and status. Following these recommendations, we carried out an intensive survey to assess the presence of the subspecies, number of monkeys, troop size and composition in every forest fragment in the central area of the squirrel monkey’s total distribution range. The study area was in the Costa Rican Central and South Pacific lowlands, from 0 to 350 m above sea level, between the western margins of Ríos Parrita and Naranjo. Within our study area, we identified every forest fragment below 350 m above sea level detectable on 1:35.000 and 1:60.000 aerial photographs. During April 1995 our team of 14 biologists divided into four to five subgroups to carry out surveys and interviews which totaled 1220 hoursperson effort, and a 400 hours-team effort. Forest fragments, African oil palm, fruit and silviculture plantations were surveyed. Each forest fragment identified was traversed along a line as close to its center as possible. Whenever we found squirrel monkeys we registered troop size, sex and age composition. We interviewed local farmers and ranch owners near every fragment, totaling 124 interviews. The foothill forests were not considered as a fragment because of their extent, covering 30 km² rising from 400 m and reaching 1000 m above sea level. We surveyed these foothills and conducted interviews below 700 m above sea level. We surveyed 45 fragments that ranged from 10 to 200 ha, with a mean of 60 ha. The total number of squirrel monkeys sighted was 445. Troop sizes ranged from 15 to 80 individuals, with a mean of 32. We recorded 48 infants with an average of three infants per troop, ranging from 9% to 25% of infants per troop. We saw squirrel monkeys in 13 fragments (at six locations the presence of squirrel monkeys had never been reported before) and another 17 fragments (12 unreported locations) were considered to hold troops after interviews. This gives a total of 18 new locations for S. o. citrinellus. Two of these locations were in the foothills where we saw squirrel monkeys. We found troops with 34, 55 and 58 monkeys in 14, 20 and 33 ha forest fragments, connected with other fragments by fruit plantations or creeks. Fifty six percent of the fragments located between the Ríos Parrita and Naranjo were connected by riparian forests, fruit, silvicultural, and African oil palm plantations. During our field work we saw troops traveling along hedgerows, plantations, and electric wires which were rarely insulated, and we also obtained reports of squirrel monkeys crossing highways and pastures between forest strips. We observed troops feeding in natural forests, fruit plantations of guava (Inga sp.), banana (Musa acuminata), and pink apple (Eugenia jambos), and on the outskirts of villages. Surprisingly one of the palm plantations where we saw them (Finca Cerros) had no forest in the immediate vicinity. The squirrel monkey was known by 98% of the interviewees who informed that it is common in the region. Interviews confirm that squirrel monkeys move through African oil palm, fruit and wood plantations. Those carried out in the foothills also confirmed the monkey’s presence in the area. There were no reports of squirrel monkeys above 400 m above sea level. The study area has three zones containing squirrel monkeys: the foothills, the forest fragments and Manual Antonio National Park (MANP). In the foothill forests, we estimated around 750 individuals (based on the lowest density estimate of 25 individuals/km²). In the forest fragments we saw 445 individuals. There are two population estimates for the MANP based on different methodologies: 1) 105 individuals after a brief survey by Boinski et al. (1998) and 2) 581 individuals after a nine-month census (Wong 1990). With this information and not including the 12 new localities where the monkey’s presence was confirmed through interviews, we conservatively estimate that there are at least 1300-1780 squirrel monkeys living in the study area. These numbers surpass those reported for the subspecies within its entire distribution (Boinski et al. 1998). Taking into account that some areas such as Tulín (Arauz 1993), Londres and Ventana de Osa (Arauz 1993, Boinski et al. 1998) where the monkey occurs have not been included in our study and not included in our estimate, we indicate that the total population size reported for S. o. citrinellus is significantly larger than has been previously estimated
... Coprophagia can be classified into three categories: cecotrophy, attributed to lagomorphs and rodents, which ingest specific types of feces; autocoprophagia, when there is ingestion of self-produced feces; and alocoprophagia, when ingestion of feces from other animals is observed (Galef, 1979). There are periods in the life of dogs in which coprophagia is considered normal, for example, by females during lactation to keep the nest clean (Boze, 2010;Houpt, 1982). ...
... In addition, it has been proven that in certain species (e.g. rats), pups consume maternal faeces at the first bouts of feeding on solid food (Galef, 1979). Also the domestic chinchilla-breed rabbit kits prefer those foods which the mother ate during pregnancy and weaning (Altbäcker et al., 1995). ...
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Transmission of information on food preferences of other group members helps animals learn about the properties of food sources, which often results in decreased novelty of the food and reduces food neophobia. This is true mainly for omnivores, which run a higher risk of ingesting toxic foods. In a social setting, animals start gathering information about food already in the first days of life. Initially, this process involves learning the mother’s food preferences; subsequently an animal learns about food preferences of other group members. Information is transferred between group members by different means (olfactory cues, vocalization, observation, etc.). Other important factors include social facilitation, conformity and behaviors related to cultural phenomena. Although social learning enables an animal to learn which foods other group members prefer, behaviors of other individuals may cause some group members to avoid certain foods. While social influences are important in shaping an animal’s diet, individual experiences are equally significant in food selection.
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Cães de canis experimentais ficam alojados individualmente no período de experimentação, podendo causar assim, alguns problemas comportamentais, os quais prejudicam seu bem-estar. Com isso, uma ferramenta que pode ser utilizada para minimizar esses efeitos e melhorar o bem-estar dos animais é o enriquecimento ambiental. Assim, o objetivo desse trabalho foi avaliar o comportamento de cães de canil experimental e a digestibilidade da dieta, com e sem enriquecimento ambiental. Foram utilizados oito cães adultos, os quais permaneceram 10 dias sem enriquecimento ambiental, seguidos por 10 dias com, totalizando 20 dias de experimento. O enriquecimento utilizado foi uma esfera oca, contendo furos, na qual o alimento era liberado conforme manipulação pelos cães. A dieta foi fornecida duas vezes ao dia. Foram realizados dois ensaios de digestibilidade, com a mesma dieta, sendo um no período sem enriquecimento e outro com. Cada ensaio de digestibilidade teve cinco dias de adaptação à dieta, seguido por cinco dias de coleta total de fezes. Foram observados os comportamentos dos cães durante o início e final de cada período. Houve aumento no tempo comendo (0,3% para 1,2%) e no comportamento exploratório (0,3% para 1,7%) dos cães no período que foi utilizado enriquecimento ambiental (P>0,05). Houve diminuição da coprofagia (1 vez para 0) no final do período que os animais estavam com enriquecimento (P<0,05). Os demais comportamentos não diferiram (P>0,05). Não houve diferença na digestibilidade da dieta mensurada sem e com enriquecimento (P>0,05). Com isso, o enriquecimento ambiental melhora alguns comportamentos, auxiliando no bem-estar de cães de canil experimental, sem interferir na mensuração da digestibilidade da dieta.
By attaching to their mothers’ nipples and sucking, mammalian neonates obtain all their necessary fluids and nutrients. This behaviour, a defining characteristic of Mammalia known as “suckling”, shows a remarkably similar form across species (Peiper 1963), from rodent pups to young human infants (Fig. 3.1). Though specific features may differ, suckling serves the ingestive requirements of the preweaning period.
The exposure of immature rodents to distinctive foods or odors can cause these animals to subsequently recognize and orient towards the previously experienced stimulus. Cheal (1975) and Leon (1975) have provided excellent reviews of this literature. One method of undertaking such treatment is by feeding maternal rats some specially scented or uniquely flavored substance. Pups reared by such dams show a preference or tolerance for the distinctive cue which had been added to the food or water supply of their maternal caretaker (Bronstein and Crockett, 1976a, b; Capretta and Rawls, 1974; Galef, 1979; Galef and Henderson, 1972; Leon, 1977). The mechanisms responsible for these effects have received little attention, although vague allusions to an imprinting-like process have appeared (Burghardt and Hess, 1966; Porter and Etscom, 1974). The present investigations are attempts to determine the processes employed by rat pups in establishing a preference for their mother’s rations.
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Conducted 3 experiments with 33 female hooded rats and their offspring. Results of previous experiments by B. Galef and M. Clark (see PA, Vol.46:Issue 4) had indicated that adult members of a wild rat colony play a major role in determining the diet on which rat pups born to colony members 1st feed. The present experiments examined the nature of the interactions between adult and young rats which affect the initial food choices of the young. Results indicate that the interaction is not due to imitation of the adults by the young, but rather to a tendency on the part of the young to approach areas in which the adults are located and begin feeding there. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
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Weanling domestic rat pups feed and explore in areas containing residual olfactory cues deposited by conspecific adults in preference to clean areas. Both nulliparous and lactating Long-Evans female rats deposit residual cues in an area that induce pups to explore and feed in it. Residual cues continue to affect the feeding and exploratory behavior of pups to maturity. Discrepancies between results obtained in the olfactory discrimination apparatus used by Leon and Moltz and those of the present experiments are resolved, and evidence is presented for the existence of residual cues not contained in anal excreta, which are attractive to pups. It is suggested that residual cues deposited by adult rats can play a role in directing weanlings to their first meals of solid food in the natural environment.
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Reported that 24 nursling rat pups poisoned following ingestion of 1/2-cc of milk from a female rat eating a diet different from that of their own mother showed an aversion to that female's diet during weaning. A 2nd experiment showed that pups fed 31/2-cc meals of milk from a female rat and which were not poisoned showed a slightly increased preference for that female's diet at weaning. Results are interpreted as offering additional evidence that (a) a mother's milk contains gustatory cues reflecting the flavor of her diet and (b) these cues are sufficient to influence dietary preference at weaning.
The development of behavior in Sprague-Dawley descendants was observed in 13 litters, and detailed qualitative and quantitative descriptions are reported. Results include information on postural development, (lying, sitting, standing), reflex figures (twitching, head waving, stretching and yawning, body flexion, righting reaction, freezing, sniffing, auditory orientation reactions, visual orientating reactions), functional activities (sleeping, consummatory behavior, locomotor activity, climbing, grooming, exploration, manipulation, digging, defecation) and social behavior. (19 ref.) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Weanling rats, when first exposed to solid food, showed relatively elevated intake if offered the same diet as eaten by their foster dams. Maternal caretakers pass some specific food-related information to their offspring.
The importance of suckling experience for later feeding in the rat was tested by means of an isolate rearing technique that eliminated oral feeding. Pups reared in the nearly complete absence of suckling and feeding ate and drank at weaning and then grew normally. Furthermore, the characteristics of apparently normal ingestion and growth make the artificially reared rat a useful preparation for other developmental investigations.
The intake of a 131BaSO4 labelled solid laboratory diet by young rats kept in nests of 3, 8 or 15 was studied by measuring the radioactivity of the whole nests in vivo. In every case, solid food intake was found to start at the same time (on the 15th day of life). This means that initiation of the physiological weaning period for young rats does not depend, under the given conditions, on the rate of their body growth and maturation. On the basis of the measured values and using earlier results on the transfer of 85Sr in the maternal milk, the weight curves of the young in the period from the 6th to the 23rd day of life were expressed by equations characterizing maternal milk and solid food intake and energy output.