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The paradox of canine conspecific coprophagy
Benjamin L. Hart* , Lynette A. Hart
†
, Abigail P. Thigpen
†
, Alisha Tran* and
Melissa J. Bain
‡
*Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California-Davis, Davis, California 95616,
USA
†
Department of Population Health and Reproduction, School of Veterinary Medicine, University of California-Davis, Davis, California 95616, USA
and
‡
Department of Medicine and Epidemiology School of Veterinary Medicine, University of California-Davis, Davis, California 95616, USA
Abstract
Canine conspecific coprophagy, the tendency or predisposition of some dogs to eat their own faeces or those of
other dogs, seems paradoxical because dogs typically show an aversion to conspecific faeces. In an attempt to
resolve this paradox, we set out to determine the factors associated with the occurrence of this behaviour and
to evaluate the efficacy of 11 products marketed for treating coprophagy as well as behaviour modification pro-
cedures. Because a large sample of dogs was needed to address these issues, two web-based surveys were uti-
lized. One, intended to compare coprophagic dogs and non-coprophagic dogs, yielded 1552 returns. The other,
yielding 1475 usable returns, specifically recruited owners of coprophagic dogs to gather information about the
characteristics of coprophagy and treatment success. The findings revealed that 16% of dogs sampled engaged
in frequent conspecific coprophagy, defined as having been seen eating stools at least six times. No evidence
was found relating the coprophagy to diet or the dog’s age. Coprophagic dogs were as easily house trained as
non-coprophagic dogs, suggesting a normal aversion to faeces. Coprophagic dogs were more likely to be
reported as greedy eaters than non-coprophagic dogs. The reported success rate of the commercial products
and behaviour modification approaches was close to zero, indicating that the behaviour is not readily changed.
The coprophagy was overwhelmingly directed at fresh stools, defined as being no more than 2 days old. A
hypothesis is offered that coprophagy reflects a tendency inherited from the ancestral wolf to keep the den area
free of faecal-borne intestinal parasites that might be deposited in the den resting area and would typically
have parasite ova that are not initially infective, but could develop infective larvae after 2 days. An evolved
parasite defence strategy to consume fresh faeces in the rest area would be adaptive.
Keywords: canine, coprophagy, dogs, faeces eating, stool eating.
Correspondence: Benjamin L. Hart, School of Veterinary Medicine, University of California-Davis, Department of Anatomy,
Physiology and Cell Biology, 1 Shields Avenue, CA 95616, USA. E-mail: blhart@ucdavis.edu
Introduction
A puzzling, but common, behaviour in some domes-
tic dogs is a persistent tendency to consume their
own faeces or those of other adult dogs. While there
seems to be no clinically established abnormality
associated with the behaviour, such as a gastrointesti-
nal upset, nutritional deficiency or compulsive disor-
der, dog owners are often very disturbed by the
behaviour. In fact, as of this writing, there were 11
commercial products specifically marketed for deal-
ing with the problem: 21st Century Deterrence
â
;
Coproban
â
; Deter
â
; Dis-Taste
â
; For-Bid
â
; Nasty
Habit
â
; NaturVet Deterrent
â
; Potty Mouth
â
;
S.E.P
â
; Stop Stool Eating
â
; Stop Tablets
â
.
A rather interesting paradox, presented by the
occurrence of conspecific coprophagy, is that dogs
seem to find conspecific faeces aversive and typically
keep their ‘den’ areas clean by eliminating outside
the house (Hart et al. 2006). This aversion to faeces
is viewed as an innate behavioural adaptation inher-
ited from wild wolf ancestors for avoiding exposure
to faecal-borne intestinal parasites and pathogens
(Hart 1990, 2012). In nature, wolf and other canid
faeces typically carry intestinal parasites as identified
in scats (Bynum et al. 1977; Custer & Pencet 1981;
©2018 The Authors. Veterinary Medicine and Science Published by John Wiley & Sons Ltd.
Veterinary Medicine and Science (2018), , pp. –
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and
reproduction in any medium, provided the original work is properly cited.
Original Article
DOI: 10.1002/vms3.92
1
Stancampo & Francisci 1993; Marquard-Peterson
1997; Kloch & Bajer 2005).
There are no data-based published studies dealing
with the overall prevalence of conspecific copro-
phagy in domestic dogs or demographic factors, such
as association with breed, gender, age, number of
dogs in the household, diet or eating style. And,
there are no data on the evaluation of efficacy of
commercial products marketed specifically for the
syndrome or the use of behaviour modification
approaches to eliminate the problem long term.
One study reported that 28% of the dogs surveyed
engaged in eating either herbivore or canine stools,
but did not distinguish between the two behaviours
(Boze 2008). A study of 14 coprophagic Labrador
Retrievers found that punishing of attempts at eating
stools with a citronella spray reduced the behaviour
by about two-thirds during the 3-week trial, but the
long-term success was not reported (Wells 2003).
We addressed the topic of canine coprophagy with
four objectives. One was to collect demographic data
on the prevalence of conspecific stool eating by dogs
in the general population and examine demographic
factors such as gender, spaying or neutering, age, num-
ber of dogs in the household, type of food eaten, eat-
ing behaviour style and breed of the dog. The second
objective was to look at the association of coprophagy
with aversion, or absence of aversion, to conspecific
faeces as indicated by ease or difficulty in house train-
ing. A third objective was to establish the characteris-
tics of stool eating especially with regard to age of dog
stools eaten. A fourth objective was to evaluate the
therapeutic success of various behaviour modification
approaches and the use of commercial products specif-
ically marketed for treating stool eating. It was envi-
sioned that learning about conspecific coprophagy in
dogs might reveal some useful information in under-
standing and dealing with this problem behaviour.
Two contrasting testable hypotheses were consid-
ered. One is that coprophagic dogs exhibit an abnor-
mal behaviour stemming from one or more
contributing causes such as weak aversion to faeces,
a dietary deficiency and association with a recog-
nized compulsive behaviour. Depending on the pos-
sible cause, the predictions of this hypothesis were
that: coprophagic dogs would be more difficult to
housetrain than non-coprophagic dogs, reflecting
poor faeces aversion; coprophagic dogs would be
fed a diet markedly different than that of non-
coprophagic dogs; and/or coprophagic dogs would be
more likely than non-coprophagic dogs to show one
or more compulsive behaviours, such as tail chasing.
Based on a presumed motivation for commercial
production of food additives or pills for treating
coprophagy, this hypothesis would also predict that
one or more of the commercial products would be
beneficial in some instances.
The second hypothesis was that coprophagic dogs
may be exhibiting a variant of an innate behavioural
predisposition, possibly stemming from wolf ancestors,
that we hypothesize would have a tendency to keep
the den resting area free of accumulating faeces left in
the rest area by an injured or sick wolf. The behaviour
would reduce the risk of parasitic infection from fae-
cesjustleftalone.Thishypothesisiscoveredmore
fully in the Discussion section where it is pointed out
that infective forms of intestinal parasites become
much more predominant after the faeces are over
2 days old. The predictions of this second hypothesis
are: coprophagic dogs are as easily housetrained as
non-coprophagic dogs (reflecting normal aversion to
faeces); and coprophagic dogs would tend to consume
fresh faeces (no more than 2 days old) more than
older faeces that in nature would contain infective par-
asite larvae. In contrast to the first hypothesis, another
prediction is that this presumably innate predisposi-
tion would be very difficult to change by behaviour
modification approaches or treatment with products
specifically marketed for this syndrome.
Methods
Data collection
The types of information sought in this study
required a large database, far beyond what one could
obtain by interviewing dog owners. From past studies
at this centre, and knowing that statistical analyses
for the information sought would require responses
from at least 1000 dog owners, two web-based sur-
veys were designed, carefully planned and pilot-
tested. Similar web-based surveys have been used in
©2018 The Authors. Veterinary Medicine and Science Published by John Wiley & Sons Ltd.
Veterinary Medicine and Science (2018), , pp. –
B.L. Hart et al.2
a variety of data-based behavioural and medical pub-
lications (McCobb et al. 2001; Gobar & Kass 2002;
Janson & Wist 2004; Tynes et al. 2007; Sueda et al.
2008), and have been shown to provide data of a
quality and validity comparable to traditional paper
and pencil survey methods (Reips 2002; Rhodes
et al. 2003; Gosling et al. 2004). The self-
administered surveys were intended to take
10–15 min of the respondents’ time.
Launched in 2010–11, the surveys were completed
anonymously and voluntarily, with no personal iden-
tifiers, by interested dog owners recruited on dog
listservs. As with other published and anonymous
web-based surveys from this centre, there was no fol-
low-up contact with those responding to the survey,
and only the anonymous data responses to the survey
were viewed. Therefore, no human subject commit-
tee approval was needed for such data use.
The two surveys were launched 6 months apart
(SurveyMonkey
â
). One was intended to estimate the
prevalence of coprophagy and compare coprophagic
dogs and non-coprophagic dogs, and was labelled,
‘Dog Behavior: The Rest of the Story’. The title and
introductory information did not mention stool eat-
ing, and the specific stool-eating questions were
imbedded in a series of questions about the dog’s
diet, eating behaviour and behaviours not relevant to
coprophagy (Appendix S1). The criterion for being
coprophagic in this survey was that the dog had been
seen eating stools at least six times. Table 1 provides
a summary of question categories in this survey.
The second survey was labelled ‘Why Dogs Eat
Their Stools’, and owners of coprophagic dogs were
intentionally recruited so as to obtain detailed infor-
mation on dogs that were well-known by their own-
ers to be frequently coprophagic (Appendix S2).
Questions sought information on the age of stools
that dogs consumed, the frequency of the behaviour
and success in resolving the behaviour using products
marketed for the problem and success with beha-
viour modification approaches. There was some
overlap in questions between the two surveys, pro-
viding a cross-check in reliability. Table 2 provides a
summary of question categories in this survey. The
criterion for keeping responses in the database was
that the dog was seen eating stools more than 10
times and at least once a month to increase the likeli-
hood that the responses regarding the details of stool
eating were accurate.
Statistical analyses
Chi-square tests and Fisher’s Exact tests for non-
parametric comparisons were used for pairwise
Table 1. Survey 1; Dog behavior, the rest of the story
Categories of Questions
Demographic data, such as number of dogs in household,
sex, age, breed of dog
Yard space available to dogs
Ease of housetraining
Type of food given
Type of eater: finicky; greedy; normal
Dog’s level of affection
Problem behaviors the dog has from list of 10
Howling at sirens
Eating non-nutritional material other than grass or stools of dogs
Frequency of grass or plant eating
For stool eaters: frequency of eating stools: daily; weekly;
monthly; yearly
For stool eaters: dog mostly eats only own stools; only stools of
other dogs; both
For stool eaters: age of stools mostly eaten: 1–2 days;
2–4 days; >4 days
Table 2. Survey 2; why dogs eat stools
Categories of Questions
Demographic data, such as number of dogs in household, sex, age,
breed of dog
Ease of housetraining
Type of food given
Type of eater: finicky; greedy; normal
Dog’s level of affection
Problem behaviors the dog has from list of 10
Frequency of grass or plant eating
Age that stool eating first noticed
Total times observed eating stools
Whether dog mostly eats only own stools; only stools of other
dogs; both
Age of stools mostly eaten: 1–2 days; 2–4 days; >4 days
Frequency of eating stools: daily; weekly; monthly; yearly
Ways that you know a stool was eaten
Behavior modification treatments tried from a list of 7 and success
of treatment
Commercial treatments tried from a list of 11 and success of
treatment
©2018 The Authors. Veterinary Medicine and Science Published by John Wiley & Sons Ltd.
Veterinary Medicine and Science (2018), , pp. –
Canine conspecific coprophagy 3
comparisons between dogs specified as coprophagic,
having been seen eating stools at least six times, and
non-coprophagic dogs, designated as never having
been seen eating stools. The level of significance was
set at P<0.05, two-tailed, and the Chi-square value is
given. In all cases, the Chi-squared and Fisher tests
produced qualitatively identical results; so, just the
Chi-square values are given. The logistic regression
analysis was a stepwise logistic regression including
only the variables that had a significance of P≤0.01.
This value was chosen to reduce the likelihood of a
false positive of a variable. All analyses were run using
SAS, version 9.4 (SAS Institute, Cary, North Caro-
lina).
Results
Prevalence of conspecific coprophagia in dogs
and demographics
The data for this section were from the survey, ‘Dog
Behavior: The Rest of the Story’, where a total of
1552 useable responses were returned before the
survey was closed and the data were gathered for
analyses. The returns from the surveys came over-
whelmingly from the United States (89.8%) and
Canada (5.1%). For multi-dog households, the
respondents were told to choose the dog they knew
best, or had known the longest, for answering ques-
tions; this was referred to as the specified dog. The
specified dog could not be a mother with puppies,
where some stool eating might be expected. Of the
1441 respondents answering the questions about con-
specific stool eating, 76.9% (1108) reported never
having seen their dog eating stools (referred to as
non-stool eaters or non-coprophagic), while 16.0%
(230) reported having seen their dogs eating stools
≥6 times (referred to as frequent stool eaters or
coprophagic). Those reporting having seen their dogs
eating stools 1–5 times (classified as neither copro-
phagic nor non-coprophagic) were 7.1% (103).
Accordingly, about 23% of the dogs sampled report-
edly were seen eating stools at least one time.
Depending upon how one categorizes a stool eater,
that is, seen ≥6 times, or ≥1 time, the prevalence of
stool eating among dogs represented by this survey
ranged from 16 to 23%. Of the respondents with fre-
quent stool eaters, 79.6% reported seeing their dogs
eating stools greater than 10 times.
To make the contrast between coprophagic and
non-coprophagic dogs clear in the results presented
below, unless otherwise noted, only dogs that were
never seen eating stools were compared with dogs
seen eating stools at least six times. An extensive
table showing responses to each of the questions with
all responses, and where dogs referred to as copro-
phagic are compared with non-coprophagic dogs, is
available in Appendix S3. In this survey, 82% of
coprophagic dogs were described as consuming
stools that were no more than 2 days old.
The occurrence of coprophagy was distributed
among all four gender-neuter groups and this mea-
sure did not distinguish between frequent stool
eaters and non-stool eaters. The distribution for neu-
tered males, spayed females, intact males and intact
females was 45.2%, 41.7%, 6.1%, and 7.0%, respec-
tively, for stool eaters and 41.3%, 40.7%, 10.2%, and
7.8% for non-stool eaters. Coprophagy does not
seem to be a reflection of juvenile behaviour. Of
coprophagic dogs 1.7% were less than 1 year of age
and 75.1% were over 4 years of age, compared with
non-coprophagic dogs of which 3.2% were <1 year
of age and 69.7% were over 4 years of age. Copro-
phagy does not seem to be related to age of separa-
tion from the dam. Of coprophagic dogs 59.1% were
reported as being left with the dam for at least
7 weeks compared with 49.7% of non-coprophagic
dogs. Diet appears not to be related to coprophagy
in that for 82.3% of frequent stool eaters, and 78.3%
of non-eaters, kibble was the main food.
An indication that coprophagy does not reflect a
weak aversion to faeces is that 78% of dogs that were
frequent stool eaters had been easily housetrained
and remained well house trained, and a similar 82%
of non-stool eaters fell into this category of house
training.
Coprophagy does not seem to be associated with
the occurrence of compulsive-like behaviours. Com-
pulsive-like behaviours were noted in 3.5% of fre-
quent stool eaters and 2.9% of non-eaters. The list of
problem behaviours that could be noted, in addition
to compulsive-like behaviours by the responders,
©2018 The Authors. Veterinary Medicine and Science Published by John Wiley & Sons Ltd.
Veterinary Medicine and Science (2018), , pp. –
B.L. Hart et al.4
included separation anxiety, various types of aggres-
sive behaviour, destructive behaviour and excessive
barking, none of which were related to coprophagy.
Several variables were statistically associated with
coprophagy, and Table 3 presents a stepwise logistic
regression analysis of factors significantly related to
coprophagy. The variable most highly associated
with coprophagy was the reported eating style, with
51.1% of coprophagic dogs referred to as greedy
eaters compared with just 28.2% of non-coprophagic
dogs.
Breed identification was considered in two
respects. One was with regard to breed group accord-
ing to the American Kennel Club designation. In
Table 3 of the logistic regression analysis, it can be
seen that terriers and hounds are most likely to be
coprophagic. With regard to specific breeds, the
database, even with 1552 responses, could only pro-
vide limited information on individual breeds occur-
ring frequently enough for comparisons. The specific
breeds examined in this regard were those for which
there were at least 15 dogs that met the criterion of
being either coprophagic or non-coprophagic. Shet-
land Sheepdogs (N=27), with 41% being copropha-
gic, were overrepresented in comparison to 17% of
other breeds (P=0.003). On the other hand, with
pooling of the three varieties of Poodles (Standard,
Miniature, and Toy) (N=29), none of the dogs was
coprophagic (P=0.006). Given that about 90% of
the responses came from the United States, and the
presumed differences in dog breeds between the
United States and other countries, the information
about breed groups or specific breeds is offered as
relevant mostly to the United States.
The number of dogs in the household was impor-
tant with dogs living in households with two or more
dogs most likely to be coprophagic. While eating
non-nutritional substances was asked about in the
survey, there was no question about the opportunity
of the dog to eat the various non-nutritional sub-
stances, such as horse or cattle stools. However,
because dirt and cat stools would be frequently
around, these were left in the logistic regression anal-
ysis. Having been reported as eating dirt and eating
cat stools were positively associated with
coprophagy.
Specific characteristics of coprophagia
The data for this section were from the survey enti-
tled, ‘Why Dogs Eat Their Stools’. There were 2561
returns before the survey was closed. Inclusion crite-
rion were then applied, one being that the dog had to
have been seen eating stools greater than 10 times.
This criterion was posed in a question giving several
options: 1–5 times, 6–10 times and greater than 10
times. A second criterion applied was that stool eat-
ing had to have been observed at least on a weekly
basis. This criterion was posed in a question giving
several options: daily, weekly, monthly, yearly and
less than once a year. These rather demanding crite-
ria were considered necessary to focus on dogs that
were reliably coprophagic and where the behaviour
was observed frequently. The survey with these crite-
ria yielded 1475 returns, of which 62% ate stools
daily and 38% weekly.
Coprophagic dogs from this survey were 30% neu-
tered males, 42% spayed females, 9% intact males
and 19% intact females. In this survey, 74% of the
dogs had been housetrained easily, similar to the
78% of frequent stool eaters being easily house-
trained in the first survey. With regard to eating
style, in this survey, 52% were referred to as greedy
eaters, compared with an almost identical 51% of
frequent stool eaters in Survey 1 being referred to as
greedy eaters.
The coprophagic dogs in this survey primarily con-
sumed stools that were no more than 2 days old –
referred to as fresh stools –with 85% identified as
eating fresh stools. This corresponds to Survey 1 with
Table 3. Stepwise logistic regression analyses of factors related to
coprophagy
Factor Parameter Chi sq P-value
Greedy eating 0.86 27.90 <0.0001
Breed group NA 20.79 0.0077
Multiple dogs in household 0.62 11.07 0.0005
Eating dirt 1.70 14.72 0.0001
Eating cat stools 0.51 10.84 0.001
See text for more details. The parameter measure for breed group
evaluated nine different breed groups, each with a different value,
so this is indicated as NA.
©2018 The Authors. Veterinary Medicine and Science Published by John Wiley & Sons Ltd.
Veterinary Medicine and Science (2018), , pp. –
Canine conspecific coprophagy 5
82% of frequent stool eaters having been seen eating
stools no older than 2 days. The two surveys, taken
together, confirm that coprophagic dogs overwhelm-
ingly consume fresh stools.
An important finding in this survey is that the
coprophagy appears not to have been altered by
either behaviour modification and/or management
techniques attempted by caregivers. In descending
order of frequency of use, the various procedures
were: chase away from stools (n=1048); reward the
successful command of ‘leave it alone’ (n=424);
lace stools with pepper (n=295); and punish by
electronic or sound-emitting collar (n=56). The
reported success rate was 1–2% except for ‘leave it
alone’ which was slightly higher at 4%.
The responses regarding the success of the 11 food
additives or tablets specifically advertised for treat-
ment of coprophagy are given in Table 4. While we
have no information about the degree to which
respondents followed instructions given with the
products, coprophagy appeared not to be meaning-
fully altered by any of the products. The number of
responders using these products ranged per product
from 6 to 352. The reported rate of success ranged
from 0 to 2%.
Discussion
As indicated by the Internet attention given to this
behaviour, canine conspecific coprophagy is, undeni-
ably, an important concern for owners of companion
dogs. One purpose of this study was to estimate the
prevalence of conspecific coprophagy in the general
population of dogs, as well as determine what envi-
ronmental, biological, and management factors
might differentiate coprophagic dogs from those that
are not coprophagic. Another purpose was to
explore the frequency of stool eating for those that
are coprophagic, the age of stools eaten and the suc-
cess of dog owners in using various behaviour modifi-
cation techniques to eliminate this behaviour as well
as their success with any of the 11 products marketed
specifically for treating canine coprophagy. Finally,
there was a goal to offer a hypothesis for the occur-
rence of canine conspecific coprophagy in a broad
population of dogs.
One finding from the first web-based survey with
1552 usable responses was that 16% of dogs in gen-
eral are coprophagic, defined as having been
observed eating stools at least six times. The occur-
rence of dogs seen eating dog stools at least once was
23%. Thus, depending on how one defines canine
coprophagy, the occurrence is between 16 and 23%.
In this paper, a coprophagic dog is defined as one
having been seen eating dog stools at least six times,
and a non-coprophagic dog as one never having been
seen eating dog stools.
In contrasting coprophagic with non-coprophagic
dogs, it was found that there was no difference with
regard to distribution among sex or neuter cate-
gories, age, diet, ease of house training or association
with a compulsive behaviour. Coprophagy could not
be ascribed to a lack of normal mothering, because
where information was available, coprophagic dogs
were as likely to have been left with the dam for over
7 weeks as non-coprophagic dogs.
Several factors did, however, distinguish between
coprophagic and non-coprophagic dogs in a signifi-
cant manner with a significance value of P≤0.01
(chosen to reduce the likelihood of false positives).
Coprophagic dogs were much more likely to be
described as greedy eaters, and were more likely to
be found in multi-dog households, where presumably
Table 4. Food additives and pills marketed for coprophagia.
Name of product Responses
for product
Per cent
reporting success
For-Bid
â
352 1
Deter
â
238 1
Dis-Taste
â
154 1
Coproban
â
58 2
S.E.P
â
58 0
Stop Stool Eat
â
27 0
Stop Tablets
â
26 0
Potty Mouth
â
24 0
NaturVet Deter
â
20 0
Nasty Habit
â
13 0
21st Century
â
60
Responders were given a list of products and asked to say if the
stool eating in their specified dog was resolved. Shown are the 11
products found, as of the writing of the paper. Some of these are
dispensed through a veterinarian and some sold over the counter.
The survey did not explore the degree to which the respondent
closely followed directions on the label.
©2018 The Authors. Veterinary Medicine and Science Published by John Wiley & Sons Ltd.
Veterinary Medicine and Science (2018), , pp. –
B.L. Hart et al.6
there would be a greater concentration of stools.
Eating dirt and cat stools were positively associated
with coprophagy, as was breed group, with terriers
and hounds being most coprophagic. Of individual
breeds for which sufficient numbers were reported,
Shetland Sheepdogs were overrepresented and Poo-
dles (all varieties) underrepresented.
With regard to specific information on coprophagy
from the second survey with 1475 responses meeting
the criteria where the dogs were seen eating stools
over 10 times and at least once a week, 85% were
reported to eat stools no more than 2 days old (fresh
stools). Similar results were found in the first survey,
confirming that coprophagic dogs overwhelmingly
consume fresh stools.
The success in eliminating the coprophagia with
the various behavioural procedures ranged from only
1 to 4% . The survey did not request information on
whether the behavioural techniques were directed
from a canine behaviour specialist or were just tried
on the respondents’ own initiative. The reported suc-
cess rate for food additives or tablets marketed for
coprophagy ranged from 0 to 2%. The survey did not
get into the extent to which the respondent did or
did not follow instructions that may have come with
the product.
Two contrasting hypotheses were formulated for
explaining coprophagy. One is that coprophagic dogs
are exhibiting an abnormal behaviour stemming
from one or more contributing causes. The second is
that coprophagy is an expression of an adaptive
behaviour inherited from ancestral wolves. None of
the findings reviewed above supported the first
hypothesis. Coprophagic dogs seemed to be as easily
house trained as non-coprophagic dogs, which we
assume is an indication of aversion to faeces. There-
fore, we do not ascribe coprophagy to an abnormal
lack of aversion to faeces.
The perspective of the second hypothesis refers to
an adaptive behavioural defence against parasites of
wolves living in nature where faeces of injured or sick
pack members might be deposited in the rest areas
near the den. If wolves were to remove the faeces
from rest areas where infective larvae from intestinal
parasites would become more numerous over time,
consumption is the only method available. For the
most frequently reported intestinal parasites in wolf
faeces, larvae from ova expelled in faeces that can
directly transmit parasites do not develop into infec-
tive forms for at least 2 days. A list of the reported
intestinal parasites found in scats of wolves, with
development times in faeces (Bowman 2014), is shown
in Table 5. For the parasites in the faeces, the ova
passed in the shed faeces develop into infective larvae
after a few days, depending upon parasite species and
ambient temperatures. Leaving the faeces alone
would allow the ova to hatch into infective larvae that
could be picked up on the hair of wolves and groomed
off, thus transmitting the parasites. If the faeces are
consumed while fresh, however, within about 2 days,
the larvae will not yet have developed into infective
forms and the risk is presumably much less.
Table 5. Intestinal Parasites found in scats of wild wolves and other
canids.
Helminths (parasitic worms)
Cestodes (tapeworms)
Taenia spp., Echinococcus spp. Require ingestion by an
intermediate host before infecting definitive host
Trematodes (flatworms or flukes)
Alaria spp. Require two intermediate hosts in water. Common
in wolves, not dogs
Nematodes (roundworms)
Ancylostomidae and Uncinaria spp. Hook worms. Larvae
develop into infective forms in the ova 2–9 days after being
shed in the faeces. Infective larvae then develop in the
environment (soil) and can then penetrate the skin of hosts.
Trichuris spp. Whipworms. Infective larvae develop in ova of
shed faeces after 10–25 days
Toxocara spp. Ascarids. Infective larvae develop in ova in shed
faeces in 2–4 weeks
Strongyloides spp. Pinworms or threadworms. Infective larvae
hatch from ova in faeces in 2–3 days, and typically infect
through the skin. Infections are usually mild.
Coccidea (single cell parasites)
Isospora spp. Oocysts develop into infective sporulated oocysts
in faeces in 3-5 days
Listed above is a classification of different genera of intestinal par-
asites found in dogs and in scats of wild wolves (Bynum et al.
1977; Custer & Pencet 1981; Stancampo & Francisci 1993; Mar-
quard-Peterson 1997; Kloch & Bajer 2005). In wild canids, several
species are generally mentioned. The various parasite species of
each type have the same basic life cycle. Note that the various par-
asite types require either an intermediate host before being infec-
tive, or require at least 2 days of development in the faeces,
before being infective to the canid that is the definitive host. Life
cycle information summarized from various resources (Bowman
2014).
©2018 The Authors. Veterinary Medicine and Science Published by John Wiley & Sons Ltd.
Veterinary Medicine and Science (2018), , pp. –
Canine conspecific coprophagy 7
There are other, less frequently occurring parasites
found in canid faeces, as well as pathogenic bacteria
from sick individuals, that can be immediately infec-
tive, so the consumption of fresh faeces can be con-
sidered ‘the lesser of two evils’ –leaving them alone
or immediately consuming them.
This hypothesis that some domestic dogs could be
displaying a wolf-like coprophagy behaviour is a paral-
lel to other wolf-like behavioural predispositions seen
in dogs. In fact the finding that being a ‘greedy eater’
is the strongest differentiating variable associated
being a coprophagic dog would seem to support this
wolf origin of coprophagy because one would expect
greedy eating to be a common wolf characteristic.
We are aware of no study on wolves (or othercanids)
in nature that involves detailed observations of stool
eating in the rest areas. Indeed, according to the per-
spective presented here, one would expect this beha-
viour not only to be infrequent, but to be carried out
swiftly so that an observer could easily miss seeing it.
However, a comment by noted wolf authority L. David
Mech that ‘wolves do commonly practice coprophagy,
at least in captivity’ (Harrington & Asa 2003), offers
support for this perspective, which was further rein-
forced by a personal communication with Mech.
In the current environment, intestinal parasites of
domestic dogs are commonly prevented and/or trea-
ted by an anthelmintic, which could result in relaxed
natural selection for behaviours that would be
related to avoidance of intestinal parasites. Conse-
quently, one would expect some dogs to be vigilant
in consuming stools, others to have completely lost
this behaviour and others to be stool eaters on a spo-
radic basis. Additional variability in coprophagy
would have come about in the selective breeding of
dogs over centuries where one could expect differ-
ences in selection against this behaviour. Consistent
with this perspective, we found an apparent under-
representation of coprophagy in Poodles and over-
representation in Shetland Sheepdogs. We are not
aware of any publicized comments in breed develop-
ment literature that may have played a role in the
selection against coprophagy, but given the repulsive
nature of the behaviour to humans, one would expect
some breeders to avoid breeding dogs that are
frequently coprophagic.
While the coprophagic syndrome seems to be
medically harmless, it is very disturbing for many
dog owners. One publication discussing this syn-
drome notes that some people find it so disgusting
that the bond with their dog is irreparably damaged
to the point where euthanasia is considered
(McKeown et al. 1988).
There are several caveats that need to be men-
tioned in this study. One is with regard to the finding
of no successful results in treating coprophagy with
any of the commercial products. To the best of our
knowledge, there have been no clinical trials with
designated procedures for recruiting subjects to be
treated and assuring that treatment guidelines were
followed. Thus, there could be treatments that would
be effective if instructions were followed. Secondly,
the rule-out of a compulsive disorder could be stud-
ied by careful observations on a sample of frequently
coprophagic dogs and treatment with a psychotropic
medication considered effective for some compulsive
disorders. Thirdly, the explanation referring to a
hypothetical parasite defence of wolf ancestors has
no substantiating field observations and should be
considered tentative.
Acknowledgements
The authors thank Dr. Neil Willits of the Depart-
ment of Statistics, University of California-Davis for
the statistical analyses and Dr. Walter Boyce of the
Department of Pathology, Microbiology and
Immunology, School of Veterinary Medicine,
University of California-Davis, for consultation on
parasitology.
Source of funding
Supported by the Center for Companion
Animal Health University of California, Davis
(# 2009-54-F/M).
Conflicts of interest
The research was conducted in the absence of any
commercial or financial relationships that could be
construed as a potential conflict of interest.
©2018 The Authors. Veterinary Medicine and Science Published by John Wiley & Sons Ltd.
Veterinary Medicine and Science (2018), , pp. –
B.L. Hart et al.8
Ethics statement
The authors confirm that the ethical policies of the
journal, as noted on the journal’s author guidelines
page, have been adhered to. No ethical approval was
required as no animals were used in this research
and responses were provided anonymously.
Contributions
BLH and LAH conceived and designed the study;
BLH, APT, AT and MJB performed data collection
and data analyses; BLH and LAH wrote the paper;
LAH, MJB, APT and AT edited the paper.
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Supporting information
Additional Supporting Information may be found
online in the supporting information tab for this
article:
Appendix S1. Dog behavior: The rest of the story.
Appendix S2. Why dog eat their stools.
Appendix S3. Responses to survey, dog behaviour.
Appendix S4. Responses to why dogs eat their stools.
©2018 The Authors. Veterinary Medicine and Science Published by John Wiley & Sons Ltd.
Veterinary Medicine and Science (2018), , pp. –
Canine conspecific coprophagy 9
