Dogs as predators and trophic regulators

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DOI: 10.1093/acprof:osobl/9780199663217.003.0002 ·
In book: Free-ranging dogs and wildlife conservation, Chapter: 2, Publisher: Oxford University Press, Editors: Matthew Gompper, pp.55-68
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This chapter identifies the roles of dogs in the ecosystem and how they vary within and between types of dogs and different environmental setting. It evaluates the predation pressure exerted by dogs and its influence in trophic patterns of communities. It also identifies several factors contributing to the extent of dog predation on wildlife.
Free-Ranging Dogs and Wildlife Conservation. Edited by Matthew E. Gompper
© Oxford University Press 2014. Published 2014 by Oxford University Press.
parts of the world dogs, and in particular free-rang-
ing dogs, have declined substantially due to direct
human persecution and active management pro-
grams, whereas in other parts they have increased
considerably, bene ting from human food and shel-
ter subsidies ( Gompper and Vanak, 2008 ; Ritchie
et al., 2012 ; Vanak and Gompper, 2009b ).
To better understand the consequences of changes
in the distribution and abundance of dogs we require
information on the roles dogs have in ecosystems,
and how these vary both within and between types
of dogs and different environmental contexts. Such
information is also critical for scenarios where efforts
are necessary to effectively manage or conserve free-
ranging dogs. With this in mind, we review what is
known about the predation pressure that is exerted
by dogs and how this may in uence trophic patterns
of communities. We have deliberately chosen not to
focus extensively on the theory regarding predators
(including dogs) and their effects, as this is covered
in detail by other recent reviews ( Letnic et al., 2012 ;
Prugh et al., 2009 ; Ritchie and Johnson, 2009 ; Ritchie
et al., 2012 ; Vanak and Gompper, 2009a ); instead we
present an overview of recent work concerning the
ecological roles of dogs as predators.
We based this review mainly on the primary liter-
ature that examines patterns of predation by dogs.
We also used anecdotal reports from the popular
press and other media to determine the range of
species that are preyed upon by dogs and the extent
of predation pressure. We identi ed several factors
that contribute to the extent of predation pressure
by dogs on wildlife. These range from population
2.1 Introduction
There is increasing interest in the ecology of dogs,
the world’s most abundant carnivore (estimated 700
million–1 billion worldwide) ( Hughes and Macdon-
ald, 2013 ; Silva-Rodríguez and Sieving, 2012 ; Vanak
and Gompper, 2009a ; Gompper, Chapter 1 ). Like
other large-bodied predators, dogs have important
functional roles in structuring and maintaining
ecological communities ( Letnic et al., 2012 ; Ritchie
and Johnson, 2009 ; Vanak and Gompper, 2009a ),
but they are also a regular source of con ict with
humans due to their negative effects on people and
their enterprises, for instance through their roles in
disease transmission and the killing of livestock and
wildlife ( Baker et al., 2008 ; Hughes and Macdonald,
2 0 1 3 ; K i n g e t a l . , 2 0 1 2 ; Ritchie et al., 2012 ; V a n B o m -
mel and Johnson, 2012 ; Young et al., 2011 ). Indeed,
some of the negative effects of maintaining dogs in
the landscape have led to considerable recent debate
about their management, most notably for dingoes,
whose structuring role in Australian ecosystems
may be comparable to that of wolves ( Canis lupus ) in
North American settings ( Allen et al., 2011a ; Houston
et al., 2010 b, 2013 ; Fleming et al., 2012 ; Letnic et al.,
2 0 1 1 a ; M e c h , 2 0 1 2 ; J o h n s o n a n d R i t c h i e , 2 0 1 3 ) .
Despite their controversial effects, global ubiquity,
and signi cant ecological roles, dogs and their eco-
logical impacts remain surprisingly poorly under-
stood. In particular, we know little about how dogs
in uence other species across environmental gradi-
ents (from wild to urban) and how their in uence
varies between different ‘types’ of dogs (see Box 2.1).
This lack of information is concerning, as in some
Dogs as predators and trophic
Euan G. Ritchie , Christopher R. Dickman , Mike Letnic , and Abi Tamim Vanak
03-Gompper-Chap02.indd 5503-Gompper-Chap02.indd 55 14/09/13 9:20 AM14/09/13 9:20 AM
Before we can defi ne and understand the ecological roles
of dogs, we must be clear about what we actually mean by
a dog. This may seem obvious, as most people would have
no problem identifying a dog from either a direct observa-
tion or from a picture, but in fact the issue of defi nition is
far more complex. Importantly, the way dogs are defi ned
directly infl uences the way they are managed ( Claridge and
Hunt, 2008 ; Glen, 2010 ). Uncertainty as to what defi nes
a dog exists in two contexts: (1) taxonomic and (2) at the
level of association and dependence on humans. Such dif-
culties in defi nitions are evident by examining the dingo,
a naturalized canid of mainland Australia. Dingoes are re-
ferred to as invasive by some and native by others, having
arrived in Australia less than 5,000 years ago ( Savolainen
et al., 2004 ; but see Oskarsson et al., 2012 ). Like large
canids elsewhere ( Gottelli et al., 1994 ), dingoes have un-
dergone hybridization to varying degrees with dogs intro-
duced to Australia over the past several centuries ( Radford
et al., 2012 ; Savolainen et al., 2004 ). ‘Pure’ dingoes are
therefore regarded as rare in many parts of the continent
and dingoes, feral dogs, and their hybrids are all frequently
referred to collectively as wild dogs ( Letnic et al., 2012 ),
and managed similarly as pests, with the ultimate goal
being extermination. In the absence of combined genetic
and ecological information about ‘dingoes,’ it is diffi cult
to ascertain whether previous studies (e.g., Johnson and
Vanderwal, 2009 ; Johnson et al., 2007 ; Letnic et al., 2009b ;
Wallach et al., 2009 , 2010 ) actually provide information on
dingoes only, or dingoes, feral dogs, and their hybrids. If it is
the latter, then it is diffi cult to ascertain the extent to which
the ecology of these dog types differs according to their
genetics ( Claridge and Hunt, 2008 ).
Coupled with this problem of taxonomic and genetic
identity is the variation in association and dependency of
dingoes with humans. A review by Vanak and Gompper
( 2009a ) places dogs under one of six categories: owned
dogs, urban free-ranging dogs, rural free-ranging dogs, vil-
lage dogs, feral dogs and wild dogs (e.g., dingoes, feral dogs,
and their hybrids).
1. Owned dogs: Dogs that are owned and restricted in
movement to a prescribed outdoor or indoor area.
Although the potential for these dogs to interact with
wildlife is limited, they can nonetheless have an effect
on wildlife when they accompany humans into natural
areas or if their unvaccinated status enhances the
disease reservoir competency of the broader dog popu-
lation ( Banks and Bryant, 2007 ; Fiorello et al., 2006 ;
Koster, 2008 ; Lenth et al., 2008 ).
2. Urban free-ranging dogs: Dogs that are not owned by
humans, but are commensals, subsisting on garbage
and other human-derived material (HDM) as their
primary food source ( Beck, 1975 ). They usually do not
come into contact with wildlife, except in urban parks
( Banks and Bryant, 2007 ; Lenth et al., 2008 ).
3. Rural free-ranging dogs: Dogs that are owned or
peripherally associated with human habitations, but are
not confi ned to a prescribed outdoor area. These include
(but are not limited to) ‘stray’ dogs and owned farm and
grazing companion dogs whose daily activity pattern
may involve ranging that can bring them into contact
with wildlife, especially when human habitations border
wildlife reserves or other natural areas ( Butler et al.,
2004 ; Vanak, 2008 ).
4. Village dogs: Unconfi ned dogs that are associated with
human habitations in rural environments, but rarely
leave the immediate vicinity of the village ( Macdonald
and Carr, 1995 ; Vanak, 2008 ).
5. Feral dogs: Dogs that are completely wild and independ-
ent of human-derived food sources ( Green and Gipson,
1994 ; Nesbitt, 1975 ).
6. Wild dogs: Dingoes and their hybrids in South-east Asia
and Australasia that have a long history of independ-
ence from humans and are no longer considered
domesticated ( Corbett, 1995 ; Sillero-Zubiri et al., 2004 ).
Yet with the exception of urban free-ranging dogs, din-
goes and their hybrids could actually fi t all of these cat-
egories, as they are sometimes owned by people in urban
and rural environments, they occur on the fringes of rural
properties and aboriginal communities, and they also occur
as completely wild populations that are entirely independ-
ent of humans ( Hamilton, 1972 ; Letnic et al., 2012 ; Smith
and Litchfi eld, 2009 ). These observations illustrate the dif-
culty in categorizing dogs, and raise questions about their
ecological roles and to what degree we can generalize
about dogs. With such classifi cation complexity in mind, we
assert that regardless of the name ascribed to a dog type
and the categorization of where and how it lives, it is most
important to focus on the ecological function of dogs within
the spatial and temporal context of where they have been
Box 2.1 A problem of defi nitions: ecological functions versus the identities of predators
03-Gompper-Chap02.indd 5603-Gompper-Chap02.indd 56 14/09/13 9:20 AM14/09/13 9:20 AM
sh, and insects being less common prey items. As
a comparison, the diet of dingoes contains a very
high percentage of mammals and birds. Diet may
be specialized further within a particular food class.
As an example, in a comprehensive review of the
diet of dingoes across Australia ( Corbett, 1995 ),
which included 12,802 diet samples collected be-
tween 1966 and 1986, 72% of prey identi ed were
mammal. This mammal prey category was further
subdivided, and comprised 20.3% large mammals,
29.7% small mammals, and 50% medium-sized
mammals. This shows that dingoes have high con-
sumption rates of medium-sized mammals.
The impact of dogs on wildlife is not only depend-
ent on the size of their potential prey, but also, and
perhaps more importantly, on the mean encounter
rate between dogs and wildlife. It is clear that some
categories of dogs (such as feral, wild dog, and rural
free-ranging) can potentially have greater impacts
on wildlife than others (such as urban or village
dogs). The relationship between ranging behav-
ior, location, and diet was explored by Vanak and
Gompper ( 2009a ). They found that all examples of
urban dogs had a limited range and diets that were
entirely human-dependent ( Figure2.1 ). However,
as ranging behavior increased and the location of
density and ranging behavior to the diversity and
size of prey species available, and the presence and
abundance of other sympatric and potentially com-
peting predators.
2.2 Dog diet: infl uence of location
and ranging behavior
Dogs are generalist and opportunistic predators,
and their exibility in this regard is illustrated in
Figure 2.1 . Between global regions, dog diet is high-
ly variable and changes according to the resources
that are locally available. In some cases the diets of
dogs at a local scale may be dominated by one or two
food types (e.g., human-derived materials (HDM)
and vegetation in India or mammals in Zimbabwe;
Figure 2.1 ). However, this does not imply that dogs
are specialized with respect to their diets, but sim-
ply that they are able to capitalize on different food
sources where and when these foods are abundant.
This dietary plasticity is a major contributing factor
to the success of dogs and their ability to survive
in a diverse range of environments. In general, the
diets of free-ranging dogs tend to contain a high
proportion of vegetation (including fruits), HDM,
and mammals, with birds, reptiles, amphibians,
Reptile, amphibian & sh
Human-derived food
Vegetation (including fruit)
Non-food and Other
(a) (b) (c)
(d) (e)
Figure 2.1 A comparison of rural dog diets derived from fi ve studies on four continents. (a) Free-ranging dogs in India ( Vanak and Gompper,
2009b ); (b) Free-ranging dogs in Brazil ( Campos et al., 2007 ); (c) Free-ranging dogs in Chile ( Silva-Rodríguez et al., 2010 ); (d) Free-ranging dogs
in Zimbabwe ( Butler et al., 2004 ); (e) Dingoes in Australia ( Corbett, 1995 ).
03-Gompper-Chap02.indd 5703-Gompper-Chap02.indd 57 14/09/13 9:20 AM14/09/13 9:20 AM
effects of dogs in the context of their position in the
carnivore guild, their population size, and their de-
pendence on humans. We also draw a distinction
between individual and population-level effects of
dogs on prey. For example, a change in the behavior
or the death of a prey animal has obvious effects
on that individual, but if the animal would not
have survived or its death allowed increased sur-
vival or reproduction of surviving members of its
population, it is possible that no population-level
effects would occur. That is, while changes in prey
demography due to predation by dogs may alter
population growth rates (e.g., because prey of dif-
ferent age or sex classes may differ in reproductive
output), more generally a simpli ed framework
for considering the risk that dogs represent to prey
populations is that for predation to in uence prey
population size, mortality must be additive to exist-
ing causes of mortality rather than compensatory to
those sources.
Examples of the impact of dogs on wildlife, ac-
cording to their categorization and local context, are
further explored in Table 2.1 below. What emerges
from these studies is that dogs have the capacity to
impact a range of wildlife species (often mammals
and birds), via direct predation of individuals as
well as through harassment and disturbance that
results in lowered breeding success. It is also appar-
ent that dogs, whether owned, un-owned, or wild,
and whether restrained or free-ranging, may signif-
icantly impact other species across landscape gradi-
ents from urban settings to rural and wild habitats.
2.3.1 Direct killing
D o g s a r e c a p a b l e o f k i l l i n g s i g n i cant numbers of
individuals of species, across a range of taxa and
body sizes (see Vanak et al., Chapter 3 ; Young et al.,
2 0 1 1 ) . F o r example, approximately 10,000 saiga ante-
lope ( Saiga tatarica ) were reportedly killed annually
by dogs in Kazakhstan ( Sludskii, 1962 ). However,
the extent of predation pressure exerted by dogs
on prey populations varies considerably across
studies. In some cases, no or low evidence of pre-
dation is found (e.g., Lowry and McArthur, 1978 ;
Scott and Causey, 1973 ) or it is not possible to ver-
ify if dogs were the primary predators or scaven-
gers (e.g., Bergeron and Pierre, 1981 ). Nonetheless,
dogs became more rural, their diets become more
opportunistic and less human-dependent. For ex-
ample, ve of eight (~63%) feral dog populations
were almost entirely dependent on wild-caught
food. Vanak and Gompper ( 2009a ) concluded that
the diet of dogs was closely linked to their location
and ranging behavior, such that as dogs ranged
farther into natural areas, they were more likely to
have an impact as predators on wildlife.
2.3 Predation by dogs and its effects
In environments where predator guilds are large-
ly intact and relatively diverse (e.g., parts of Asia,
Africa, and North America), dogs often assume
the roles of smaller-bodied and subordinate mes-
opredators, due to the presence of larger (apex)
predators such as wolves and large cats ( Puma
concolor a n d Panthera spp.) ( Butler et al., 2004 ; Da-
lerum et al., 2009 ; Ritchie and Johnson, 2009 ). How-
ever, when the predator guild is severely depleted
or absent altogether, dogs can function as the top-
predator. For example, in Australia, the ~15–20 kg
dingo is similar in body size to the New World
coyotes ( C. latrans ), and not considerably larger
than Old World golden jackals (including the sub-
species now considered a wolf species; Rueness
et al., 2011 ) and side-striped jackals ( C. aureus a n d
C. adustus , respectively). Dingoes are considered
the apex terrestrial predator due to the early extinc-
tion of much larger-bodied native carnivores, such
as the marsupial lion ( Thylacoleo carnifex ) ( Johnson,
2006 ; Wroe et al., 2005 ). Indeed, the situation in
Australia re ects an overall trend whereby, due to
the dramatic reduction or extinction of many larg-
er predators around the globe ( Estes et al., 2011 ),
dogs now ful ll the role of apex predators in many
environments. In addition to these in uences, sup-
plementation of the diet of dogs by humans may
serve to exacerbate (through hyper-predation and
diet switching) or potentially reduce the impact
on wildlife by dogs ( Silva-Rodríguez and Sieving,
2011 , 2012 ; Vanak and Gompper, 2009a ).
Dogs may suppress prey by killing them (lethal)
or through instilling fear (non-lethal), which may
cause changes in prey behavior, physiology, and
habitat use ( Clinchy et al., 2013 ; Ritchie and Johnson,
2009 ). Here, we explore these lethal and non-lethal
03-Gompper-Chap02.indd 5803-Gompper-Chap02.indd 58 14/09/13 9:20 AM14/09/13 9:20 AM
cats, Felis catus ( Iverson, 1978 ), while in New Zealand
a single dog was estimated to have killed at least 500
North Island brown kiwi ( Apteryx mantelli ) i n a p o p u -
lation of just 900 ( Taborsky, 1988 ). Populations of rare
species are likely to be particularly susceptible and
less able to cope with dog predation, as small and iso-
lated populations may not be able to recover due to
insuf cient reproduction and immigration that could
compensate for dog-induced mortality.
Elevated levels of predation occur in another sit-
uation that can potentially exacerbate the negative
impact of dogs on prey populations still further. In
some situations the rate of killing by dogs greatly
exceeds that necessary to meet the needs of the
predator for food, and so prey carcasses frequently
are not consumed after being killed. This has been
termed ‘surplus killing’ ( Kruuk, 1972 ). Two key rea-
sons for surplus killing of prey by dogs include: (1)
ineffective predator responses on the behalf of prey,
particularly for species that have not coevolved
with dogs and hence interactions with dogs are
novel encounters for which prey are unlikely to
exhibit effective anti-predator responses; and, (2)
dogs have the ability to defend multiple kills due
to their tendency to hunt and live in groups, which
allows hunting to continue despite suf cient food
often being available from an initial kill ( Short et al.,
2002 ). Short et al. ( 2002 ) noted in their study that
they found no instances of surplus killing by cats,
whereas it was a common feature of hunting by
both red foxes ( Vulpes vulpes ) and dingoes. Howev-
er, it remains conjectural whether this difference in
several studies have shown that dogs can have sig-
ni cant localized impacts that lead to decreases in
some prey populations ( Barnett and Rudd, 1983 ;
Genovesi and Dupre, 2000 ; Iverson, 1978 ; Kruuk,
1972 ; Taborsky, 1988 ; Azhar et al., 2013).
Dogs may also limit species not only by killing
adults, but also by affecting reproductive success.
A study of the nesting success of freshwater croco-
diles ( Crocodylus johnstoni ) in northern Australia
( Somaweera et al., 2011 ) demonstrated that 72%
of nests were opened by predators, and dingoes
were responsible for 98% of these disturbances in
one part of the study region and 54% in the other.
Dogs are one of the main contributors to a declin-
ing kid/female ratio in mountain gazelles Gazella
gazella in Israel ( Manor and Saltz, 2004 ), and in a
study of chiru ( Pantholops hodgsonii ), dogs killed 19
mostly young individuals that were malnourished
and impeded by deep snow near a highway in
Qinghai, China ( Schaller, 1998 ). Similarly, dogs also
have been reported to chase young argali Ovis am-
mon ( Fedosonko and Blank, 2005 ) which, through
increased energy expenditure and elevated stress
levels, has the capacity to negatively impact argali
condition, growth, and survival. However, the oc-
currence and severity of such effects remains to be
determined for most species.
Elevated levels of predation such as those above
may have severe consequences for some prey popu-
lations. In the Caicos Islands, an initial estimated pop-
ulation of 5,500 rock iguanas ( Cyclura carinata ) was
nearly extirpated due to predation by both dogs and
Table 2.1 Examples of the impacts of dogs on prey according to dog categorization and habitat.
Type of dog Location of study Habitat Major prey Effects on prey Reference
Owned Australia Suburban forest
None: human-provided Reduced bird abundance and
( Banks and Bryant,
2007 )
Urban free-ranging New Zealand Coastal None: human-provided Reduced shorebird breeding
( Lord et al., 2001 )
Rural free-ranging Malaysia Plantations Wildlife Reduced abundance ( Azhar et al., 2013 )
Rural free-ranging
or village
Australia Forest and heath Medium-large macropods Harassment and killing;
reduced abundance
( Meek, 1999 )
Feral New Zealand Forest Kiwi Reduced population ( Taborsky, 1988 )
Wild Australia Forest Medium-large macropods Elevated (compensatory)
reproduction and reduced
population size
( Robertshaw and
Harden, 1986 )
03-Gompper-Chap02.indd 5903-Gompper-Chap02.indd 59 14/09/13 9:20 AM14/09/13 9:20 AM
to have invoked fear of dogs in pudu and explain
why pudu distribution models are best explained
by the probability of dog presence. In another
study, Banks and Bryant ( 2007 ) investigated the re-
sponses of birds in suburban woodland sites to the
presence of dogs. They found that the simple act
of a person walking with a dog on a leash caused
a 41% reduction in numbers of individual birds
and a 35% reduction in species richness compared
with control sites where no walking occurred;
people walking alone induced less than half the
disturbance compared with when they were walk-
ing a dog. This study showed further that dog-
induced disturbance to birds was similar in areas
where dog-walking occurred regularly compared
to areas where it was not allowed, thus suggesting
that birds did not become habituated to dog pres-
ence and could be at risk of long-term population
Limited work has investigated the indirect ef-
fects of generalized disturbance by dogs (Weston
and Stankowich, Chapter 4 ). It is clear from stud-
ies such as that by Lord et al. ( 2001 ), which found
that off-leash dog walking disturbs shorebirds on
their breeding nests, that the potential for indirect
impacts on reproductive success is high if the prey
species perceives dogs as a predation risk. Such ef-
fects have the capacity to alter the trophic structure
of communities by causing lower-order predators
(e.g., shorebirds) to avoid areas of habitat through
fear ( Laundre et al., 2001 ), which in turn may ben-
e t smaller prey and/or the competitors of those
species affected.
2.4 Human facilitation of dog predation
of wildlife
The role of humans in mediating dog predation
of other species is a critical consideration when
attempting to manage dog populations and for
conserving biodiversity. In some cases, ready sup-
plies of food for dogs may serve to reduce impacts.
Silva-Rodríguez and Sieving ( 2011 ) found that dogs
preyed on most endemic and threatened mammals
in their study region in Chile, but that the probabil-
ity of dogs eating these prey was higher for poorly
fed than adequately fed dogs. While these results
suggest that feeding dogs may be an easy way to
hunting behavior between cats, foxes, and dingoes
is widespread and consistent. Indeed, it is impor-
tant to note that dogs do not always exhibit surplus
killing, even for easily accessible prey ( Kruuk and
Snell, 1981 ).
Where surplus killing does occur the impacts
of dogs on wildlife can be strong. In the example
of dog predation on kiwis noted above, Taborsky
( 1988 ) commented that the presumed killing of 500
birds over a period of just 6 weeks would have met
the energetic requirements of the single dog many
times over. He also reported nding carcasses of
kiwi that had been bitten but not eaten. In another
example, Shepherd ( 1981 ) reported the killing of 83
red kangaroos ( Macropus rufus ) near a water hole
over a 7-week period by a group of just 5 dingoes.
Dingoes are known to target smaller individuals
(juveniles and females) of sexually size-dimorphic
prey, such as macropods ( Grigg et al., 1989 ), as has
also been found for wolves and their prey ( Stahler
et al., 2006 ). In Shepherd’s (1981) study, 96% of the
kangaroos killed were juveniles but, regardless of
their size, their combined mass would have been
more than enough to support the food require-
ments of the dingoes; indeed, many animals had
been killed and not consumed at all, while others
had been consumed only in part. Given that dogs
often target juveniles and females, it is possible
that relatively few individuals may be able to im-
pact and suppress populations ( Ritchie and John-
son, 2009 ). Wild and feral dogs in many parts of the
world are notorious for their disproportionately in-
tense attacks on livestock (e.g., Mech and Boitani,
2003 ; Short et al., 2002 ). In these situations prey are
often aggregated, unable to run far owing to their
con nement in a paddock, and may show inap-
propriate responses to the presence of dogs. These
factors may combine to elicit continued killing be-
havior that ceases only when no further prey are
conspicuous ( Short et al., 2002 ).
2.3.2 Non-lethal effects
In a camera trapping study in Chile, Silva-
Rodríguez and Sieving ( 2012 ) found that the prob-
ability of dog attacks (>85%) on a forest ungulate,
pudu ( Pudu puda ), and the lethality of these at-
tacks (50%), was high. These attacks are presumed
03-Gompper-Chap02.indd 6003-Gompper-Chap02.indd 60 14/09/13 9:20 AM14/09/13 9:20 AM
their direct predatory effects on individual species,
and may extend to whole communities and ecosys-
tems. At this broader ecosystem scale, the ecologi-
cal effects of dogs become more complex and may
include both negative and positive effects on the
abundances and phenotypes of other species. Posi-
tive effects for some species can arise because dogs
suppress the abundances and shape the activity
patterns of smaller carnivores and herbivores. This
suppression of smaller carnivores and herbivores
by dogs can result in increases in the abundance
and biomass of vegetation and small prey. Thus
dogs can induce ecosystem-wide trophic cascades
and indirectly facilitate increases in the abundances
of species at lower trophic levels within the same
food chain.
For example, in Australia, recent research has
shown that dingoes, through their suppression of
reduce their impacts on wildlife, there may be an
unexpected and long-term negative consequence
of such actions. By feeding dogs, which inevitably
leads to sustaining dog populations at levels be-
yond their natural carrying capacity, humans may
assist in maintaining constant and high predation
rates on prey, which may become compounded
during times when dogs have reduced access to
human food and switch their diets to hunt native
animals ( Butler et al., 2004 ; Daniels and Bekoff,
1989 ).
In addition to human food subsidies for dogs,
but far less understood, are the effects that habitat
modi cation may play in mediating dog access to,
and capture of, prey. Silva-Rodríguez et al. ( 2010 )
observed that the impact of dogs on pudu appeared
to be exacerbated by roads that allowed dogs to
increase their access to protected areas of forest.
Habitat change (e.g., more roads, fragmentation,
increased edge habitats) may serve to increase dog
predation and threaten biodiversity by providing
dogs with easier and more open access to hunt in
otherwise complex habitats ( Paschoal et al., 2012 ;
Torres and Prado, 2010 ).
2.5 Ecosystem-wide effects of dogs
The non-consumptive effects of dogs on prey spe-
cies are not restricted to their primary prey and
competitors. For example, in the Strzelecki Desert
of Australia, dingoes suppress the abundances of
smaller invasive red foxes and in turn provide the
dusky hopping mouse ( Notomys fuscus ) with refuge
from predation by foxes ( Letnic et al., 2009a ). In are-
as where dingoes are present, hopping mice are less
likely to occur in predator scats, are more abundant
and forage less apprehensively ( Figure 2.2 ; Letnic
and Dworjanyn, 2011 ). These ndings provide evi-
dence that dingoes, through their suppression of
fox populations, create a safer environment for hop-
ping mice where the frequency of fatal encounters
with foxes is reduced and the non-consumptive ef-
fects of foxes are lower.
The direct killing by dogs, or the fear dogs in-
duce, may have strong negative effects on species
depending on the environmental context and the
identities of species comprising the faunal assem-
blage. The effects of dogs, however, go beyond just
Dingoes No dingoes
Giving up density
Dingoes No dingoes
Foxes sighted per kilometer
(a) Fox abundance
(b) Notomys fuscus
giving up density
Figure 2.2 The presence of dingoes may alter the occurrence of
smaller carnivore species as well as those taxa fed on by these smaller
predators. (a) The abundance of red foxes,
Vulpes vulpes
, in areas
where dingoes were present and where dingoes were rare. (b) The
giving up density of dusky hopping mice,
Notomys fuscus
, determined
using foraging trays where dingoes were present and rare. Lower
giving up densities in the presence of dingoes indicate that
N. fuscus
foraged less apprehensively. Redrawn from Letnic and Dworjanyn
( 2011 ) . Reproduced with permission from John Wiley & Sons.
03-Gompper-Chap02.indd 6103-Gompper-Chap02.indd 61 14/09/13 9:20 AM14/09/13 9:20 AM
( Letnic et al., 2009b ; Pople et al., 2000 ; Wallach
et al., 2010 ). Together, the limiting effects of din-
goes on cat, fox, and herbivore populations have
been shown to protect smaller native prey, with
native mammals in particular achieving higher
diversity and abundance where dingoes are com-
mon ( Letnic et al., 2012 ; Ritchie and Johnson, 2009 ;
Ritchie et al., 2012 ; Wallach and O’Neill, 2009 ;
Wallach et al., 2009 , 2010 ).
Despite the bene ts for biodiversity of dogs
such as the dingo, in most other cases dogs appear
to have signi cant detrimental effects. In Europe,
for example, the common practice of dog walking
may impact the European Nightjar Caprimulgus
europaeus ( Langston et al., 2007 ) and, as mentioned
above, Banks and Bryant ( 2007 ) showed that bird
diversity was reduced by more than one third and
abundance by ~40% in woodland areas where dogs
are walked. Where dogs are human- subsidized
it would appear they frequently have negative
Many studies, including a large number of those
mentioned above, report the impact of dogs on prey
species as measured and inferred primarily through
smaller predators and herbivores ( Figure 2.3 ), in-
duce ecosystem-wide trophic cascades with a net
positive effect for biodiversity conservation ( Letnic
et al., 2012 ) ( Figure 2.4 ). Within the last 200 years,
two novel invasive predators have been intro-
duced to the continent: the red fox and the domes-
tic cat ( Johnson, 2006 ). These species have been
implicated in a large number (>20 species) of na-
tive mammal extinctions ( Johnson, 2006 ). Com-
parisons of ecosystem attributes in areas where
dingoes are actively controlled or not controlled
( Figure 2.5 ) indicate that the impacts of these
mesopredators are moderated by the presence or
absence of dingoes ( Johnson et al., 2007 ; Letnic
et al., 2009b ). Where studied, dingoes appear to
suppress both cats and foxes, through the direct
killing of individuals, but also by dingoes caus-
ing these subordinate predators to avoid them
both spatially and temporally ( Brook et al., 2012 ;
Johnson and VanDerWal, 2009 ; Kennedy et al.,
2012 ; Letnic and Dworjanyn, 2011 ). In addition,
dingoes have been shown to be very effective at
suppressing herbivore populations, contributing
to more available food and shelter for native prey
0 0.2 0.4 0.6 0.8
Fox tracks per plot night
Dingo tracks per plot night
0 0.2 0.4 0.6 0.8
Kangaroo dung groups
per transect
Dingo tracks per plot night
(a) Red foxes
(b) Kangaroos
Figure 2.3 D o g s o f t e n h a v e s t r o n g , n o n l i n e a r
effects on the abundances of their competitors and
prey. For example, plots of abundance indices of
dingoes versus those of (a) red foxes,
Vulp es vulpes
and (b) kangaroos,
s p p . , i n d e s e r t r e g i o n s
of Australia display threshold relationships which
suggest that even low density populations of dingoes
have strong suppressive effects on the abundances
of mesopredators and herbivores. Redrawn from (a)
L e t n i c e t a l . ( 2 0 1 1 b ) a n d ( b ) L e t n i c a n d C r o w t h e r 2 0 1 3 .
Reproduced with permission from John Wiley & Sons.
03-Gompper-Chap02.indd 6203-Gompper-Chap02.indd 62 14/09/13 9:20 AM14/09/13 9:20 AM
in essence, a formulation of Caughley’s contrast
of small population versus declining popula-
tion paradigms ( Caughley, 1994 ).
There is no question dogs can pose a severe risk to
species that are already threatened due to their low
population sizes, but to assess the true impacts of
dogs on other species, and hence to ensure appro-
priate biodiversity conservation and management,
there is an urgent need for studies that address
these two points.
2.6 Future research
From our review it is clear that dogs, spanning both
wild and urban environments, interact with and
affect biodiversity through a variety of important
pathways. Most importantly, this occurs by dogs
acting as predators or competitors within commu-
nities. In doing so, in some cases, they may contrib-
ute to the decline of already rare and threatened
dog–wildlife habitat associations and dog diet
( Hughes and Macdonald, 2013 ; Vanak and Gomp-
per, 2009a ; Young et al., 2011 ). With few exceptions
what remains largely unknown and should be of
concern is:
1. Whether dog predation on wildlife is addi-
tive (total annual mortality rate that is greater
than what would occur without the predation)
or compensatory (a population’s total mortal-
ity remains unchanged because the other, pre-
sumably natural, causes of mortality, such as
intraspeci c competition for food, decrease
to compensate for reduced density caused by
dogs’ predation; see Ritchie and Johnson, 2009 ).
2. Whether dogs are the principal drivers of de-
cline for particular species, or whether they are
contributing to the nal decline or extinction of
populations and species only because they have
already been heavily impacted by other causal
agents, such as habitat loss and disease. This is,
Strzelecki North
Strzelecki Central
Strzelecki South
Strzelecki North
Strzelecki Central
Strzelecki South
Percent cover (%)
(a) Kangaroos (b) Foxes
(c) Grasses
Fox tracks per plot night
Mammal species/grid
(d) Native small mammals
Figure 2.4 Evidence that dingoes induce a community-wide trophic cascade is provided by a comparison of the abundances of kangaroos, red
foxes, and grasses and the species richness of small mammals at eight paired study sites situated on either side of the dingo fence in arid Australia
( Letnic et al., 2009b ). Within each pair of sites, dingoes were common in one (black bars) and rare in the other (white bars). Kangaroos and foxes
were more abundant in the absence of dingoes. Grasses, the preferred forage of kangaroos, were more abundant in the presence of dingoes. Small
mammals are subject to high rates of predation by foxes. Small mammal communities were more species rich in the presence of dingoes.
03-Gompper-Chap02.indd 6303-Gompper-Chap02.indd 63 14/09/13 9:20 AM14/09/13 9:20 AM
ies of their ecology. Indeed, the impacts of cats are
far better known ( Fitzgerald and Turner, 2000 ; Loss
et al., 2013 ; Medina et al., 2011 ; Woinarski et al.,
2011 ), with this species being listed in the 100 worst
invasive species globally ( Lowe et al., 2004 ). Given
the dif culty of working on cats, due to their large-
ly solitary and cryptic nature and their generally
lower abundance than dogs globally, it is surpris-
ing we know so little about dogs, including basic
information such as their diets, hunting behavior,
and whether they impact native species to the same
or greater degrees as do other non-native species.
There are many key questions that remain to be an-
swered in regards to dogs, and below we suggest
what we consider to be urgent research priorities.
First, determine more broadly the importance
of differences in dog categories ( Box 2.1 ). How do
such differences in uence the functional roles of
dogs within similar environments? Further, how do
the behaviors of these different categories of dogs
differ? The dingo provides an excellent model sys-
tem in which to examine these questions, given the
large area and range of environments in which it
occurs, and its complex Holocene and recent his-
tory. Determining the answer to these questions has
strong implications for how we should manage the
dingo and other dog populations worldwide.
Second, more work needs to be done comparing
dog populations from across the world, in both sim-
ilar and different environments. Do dogs in South
America, North America, Asia, Europe, Australia,
and Africa behave in similar ways? Much could be
learned from such comparisons and the ensuing
knowledge would aid a global synthesis about dogs
and their roles as trophic regulators. At present we
have too few studies to do this.
Third, more experimental work on dogs (dog
removals or dog additions) is needed to establish
their effects, as the majority of work to date has
been largely observational and correlative.
Finally, a greater focus on dog behavior is re-
quired, rather than just focusing on the effects of
dogs in relation to their abundance. Dogs may af-
fect other species in sublethal ways as these species
respond to perceived predation risk. These indirect
and subtle effects are only just beginning to be ap-
preciated. Given the densities of dogs in many parts
of the world, their perception as a predatory risk by
species, or indeed of common species. But in other
instances, conversely, through their suppression of
other predators (including invasive species) and
herbivores, dogs may help to protect and promote
biodiversity, maintaining the resilience of ecosys-
tems. It is therefore dif cult to generalize about the
trophic roles and ecological functions of dogs, as
they are environmentally and temporally context
Humans have important roles in either facilitat-
ing or reducing the effects of dogs on other wild-
life. Through anthropogenic changes to habitat and
the supply of food provided to dogs, humans may
make areas more or less suitable for dogs, with con-
comitant effects on wildlife. However, despite dogs
being the most widespread and abundant carni-
vores worldwide, there are surprisingly few stud-
Figure 2.5 A dingo left to hang on Australia’s dingo barrier fence.
This sight is common across much of arid Australia, with confl ict
occurring between cattle and sheep production and dingoes. Dingoes
are known to prey on livestock, sometimes causing signifi cant
economic damage (photo courtesy of Mike Letnic).
03-Gompper-Chap02.indd 6403-Gompper-Chap02.indd 64 14/09/13 9:20 AM14/09/13 9:20 AM
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  • ... Today, although the majority of humans no longer interact with dogs during hunting or foraging, the global dog population has increased along with the h u m a n p o p u l a t i o n t o a n e s t i m a t e d o n e b i l l i o n animals (Gompper 2014a). While the level of association between humans and dogs varies widely, most dogs depend on human-derived food sources (Ritchie et al. 2014). Therefore, the majority of dog populations can be considered subsidized predators, that is, populations of predators whose densities are above what one might normally expect if human-derived resources were unavailable (Gompper 2014b). ...
    ... The way dogs interact with wildlife depends on dog population density, the extent to which these dogs are constrained and cared for by humans (fed, sheltered, or vaccinated, for instance), and how other species perceive dogs. Vertebrate wildlife species likely perceive dogs as potential predators (Gompper 2014b), which triggers strong and diverse responses, particularly among prey species (Ritchie et al. 2014). For mammalian carnivores, the presence of dogs can also elicit responses, as dogs may be seen as potential predators, competitors, or even as prey ). ...
    ... The ownership status of dogs that are accessing protected areas in São Paulo and Rio de Janeiro is uncertain. Nevertheless, like most free-ranging dog populations Gompper 2009a, 2009b;Ritchie et al. 2014), they probably depend greatly on localized human resources such as food directly or indirectly provided by households to meet nutritional requirements. These food sources are likely more available during the day. ...
    Free-ranging dogs (Canis familiaris) negatively impact wildlife worldwide. Yet despite being members of the order Carnivora, we have relatively little information on the role that dogs play in carnivore communities. To evaluate if activity patterns of wild carnivores are influenced by the activity of dogs and if the latter is influenced by the activity of pumas (Puma concolor), we placed camera traps in eight protected areas in São Paulo State and in six in Rio de Janeiro State, Brazil, from 2011 to 2017. We obtained 551 photo-captures of dogs in 20,524 trap nights in 11 of the 14 protected areas. Dogs were active primarily during the day and therefore overlapped mainly with diurnal carnivores, such as tayras (Eira barbara) and coatis (Nasua nasua). Mesocarnivore temporal activity did not appear affected by the activity of dogs, since the activity patterns of tayras, coatis, maned wolves (Chrysocyon brachyurus), and ocelots (Leopardus pardalis) were similar (from 67 to 82% of overlap) in areas with and without dogs. Further, the activity of dogs was not influenced by puma activity; dog activity patterns in areas with pumas and without pumas overlapped by 84%, with minimal differences. While mesocarnivores might alter their spatial behavior to avoid overlap with dogs, it appears that dog use of protected areas does not result in shifts in the temporal activity of mesocarnivores. Further, we hypothesize that dogs that use protected areas are mostly provisioned by humans (owners), and therefore, their activity patterns may be more related to that of their owners than to the presence of native carnivore species.
  • ... For example, Fia consumed by far the most vegetation and anthropogenic food and was the only dog that did not have any livestock remains in her scats, while Rex consumed mostly wild ungulates and some livestock, despite both dogs being accompanied by an Ecoranger. Thus, caution is needed when generalizing the ecological impact of LGDs (as was the case in Allen et al. 2019) as they have been shown to be environmentally and temporally context-dependent (Ritchie et al. 2014). Corrective training of unwanted behaviours in LGDs by shepherds has proven successful in many cases (Green et al. 1984, Hansen et al. 2002, Marker et al. 2005a. ...
    The use of livestock guarding dogs (LGDs) has been widely advocated as a responsible tool for reducing livestock predation and conserving wildlife. However, their hidden ecological costs have rarely been investigated. We analysed scats (n = 183) from six LGDs and visited Global Positioning System (GPS) location clusters (n = 352) from nine GPS-collared LGDs to reconstruct their diet and assess impacts on wildlife and livestock in Namaqualand, South Africa. Wild mammals, including 10 native species, and small-livestock were the main secondary foods (i.e. besides dog food pellets). A total of 90% of scats and one third of GPS clusters investigated had associated animal remains. When accompanied by a human attendant, fewer LGD scats contained animal matter (39.9%; of which 32.3% wild mammals and 4.6% livestock), in contrast to scats of LGDs on their own (93.2%; 14.4% wild mammals, 75.4% livestock). Similarly, few clusters of accompanied LGDs included animal remains (5.7%; of which 43.8% wild mammals and 31.3% livestock), whereas unaccompanied dogs clustered frequently at carcasses (92.4%; 16% wild mammals, 74% livestock). While sample sizes were relatively small and some dogs might have scavenged, we emphasize the importance of rigorous training and intensive monitoring of LGDs to correct unwanted predation behaviour and to maximize their ecological and protective benefits.
  • ... Il y a dans le monde entre 700 millions et 1 milliard de chiens dits sauvages ou de villages (Bradshaw, 2011 ;Ritchie et al., 2014). Parmi les particularités des villes latino-américaines, l'une, rarement mentionnée, est l'omniprésence du chien. ...
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  • ... Their economic well-being may result in a greater intensity of harvest on huemul, the Western Hemisphere's rarest large mammal. Ensuing terrestrial impacts stem from interactions among disease, livestock, and dogs (Ritchie et al., 2013;Doherty et al., 2017;Flueck and Smith-Flueck, 2017), all of which conflate because of humans and may indirectly and directly impact huemul. ...
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    The human population grows inexorably. When Charles Darwin explored the southern cone of South America in 1830, fewer than 1.2 billion people inhabited Earth. When Ehrlich’s Population Bomb appeared in 1968, there were ∼3.5 billion people. We approach eight billion today, and biospheric impacts do not abate. We have affected most life forms through climate modification, harvest, erasure and fragmentation of habitat, disease, and the casting of alien species. Given the lack of abatement in human population growth, herein we focus on the modalities of ecological disruption–direct and indirect–that mitigate the changing role of ungulates in landscapes. Much of what was once generally predictable in terms of pattern and process is no longer. Offshore climatic events have strong onshore consequences, as exemplified by toxic algal blooms in the Patagonian Pacific. These have diminished the harvest of fish and likely resulted in fishermen using dogs to hunt huemul (Hippocamelus bisulcus), the most endangered large terrestrial mammal of the Western Hemisphere. Similarly, human economies foment change in the Himalayan realm and Gobi Desert by increasing the number of cashmere-producing goats, and where dogs that once followed tourists or guarded livestock now hunt a half-dozen threatened, endangered, and rare ungulates, including kiang (Equus kiang), chiru (Pantholops hodgsonii), saiga (Saiga tatarica), and takin (Budorcas taxicolor), spread disease, and displace snow leopards (Panthera uncia). In North America’s Great Basin Desert, 100 years of intense livestock grazing created a phase shift by which changed plant communities enabled mule deer (Odocoileus hemionus) colonization. An altered predator–prey system ensued with the arrival of pumas (Puma concolor). Patterns of resilience postulated by Holling (1973) become more difficult to witness in the absence of humans as our domination of Earth destabilizes systems beyond return points. These include ungulates both in and out of protected areas. Consequently, only messy projections of future community reorganization seem reasonable, whether related to food webs or assembly rules that once governed ungulate communities of the very recent past.
  • ... There are between 700 million and 1 billion so-called feral or village dogs in the world today [1,2]. Among the many peculiarities of Latin American cities, but one that is rarely mentioned, is the omnipresence of dogs. ...
    Full-text available
    Stray dogs are a common sight in cities all over the world, especially in Latin America, but research on their behavior is scarce. Studying their very considerable presence in Concepción (Chile) provided a unique opportunity to learn more about the extent of the sociality and territoriality patterns of the dog species. Interestingly, a wide range of socialities with humans (and with other dogs) were shown to be dependent on human activities and urban zoning signaled by passages, physical boundaries and landmarks. New forms of sociality were also evidenced, with dogs exhibiting intermediate degrees of sociality between the pet and stray dog categories. We postulate that this unique diversity of sociospatial positioning and level of adjustment (e.g., dogs using crosswalks either alone or with people) is made possible by the city’s specific human culture and range of urban areas. The dog species thus exhibits a considerable potential for social and spatial adjustment. The fact that it depends on the spatial layout and human culture of their environment explains the presence of dogs wherever humans are. Furthermore, it has implications for coping with the presence of dogs in numerous and varied human societies.
  • ... Free-roaming dogs can compromise the conservation of wild animals through a combination of pathogen pollution (i.e., the spread of pathogens to naive hosts) [8,33,34], predation [35], competition [36], and hybridisation [9,37,38]. It is estimated that dogs have played a role in the extinction of 11 vertebrate species and threaten the survival of at least 188 more species [10]. ...
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    The worldwide population of domestic dogs is estimated at approximately 700 million, with around 75% classified as “free-roaming”. Where free-roaming dogs exist in high densities, there are significant implications for public health, animal welfare, and wildlife. Approaches to manage dog populations include culling, fertility control, and sheltering. Understanding the effectiveness of each of these interventions is important in guiding future dog population management. We present the results of a systematic review of published studies investigating dog population management, to assess: (1) where and when studies were carried out; (2) what population management methods were used; and (3) what was the effect of the method. We evaluated the reporting quality of the published studies for strength of evidence assessment. The systematic review resulted in a corpus of 39 papers from 15 countries, reporting a wide disparity of approaches and measures of effect. We synthesised the management methods and reported effects. Fertility control was most investigated and had the greatest reported effect on dog population size. Reporting quality was low for power calculations (11%), sample size calculations (11%), and the use of control populations (17%). We provide recommendations for future studies to use common metrics and improve reporting quality, study design, and modelling approaches in order to allow better assessment of the true impact of dog population management.
  • ... This aligns more with the hypothesis of Allen et al. (2019a) and, if taken at face value, would support an edited version of their suggestion that [a small proportion of] LGDs are acting as anthropogenically introduced predators in these landscapes with associated ethical implications. However, care should be taken to avoid generalising the ecological impact and trophic role of dogs since they are temporally and environmentally context-dependent (Ritchie et al., 2014). Programmes managing these dogs such as those here and in Namibia (Marker et al., 2005;Potgieter et al., 2016) utilise regular monitoring points to detect instances of undesirable behaviours, subsequently implementing corrective measures, or removing the dogs from the farm. ...
    Livestock depredation by carnivores is a key cause of detrimental human-wildlife interactions around the world. Recently, the use of livestock-guarding dogs (LGDs) to reduce livestock depredation has been challenged in terms of their impact on wild animal welfare and survival, but the prevalence of LGD-wildlife interactions is poorly understood. Using data for 225 LGDs on South African farms, we determined the prevalence of farmer-reported LGD-wildlife interactions to contextualise the potential concerns. Wildlife interactions were reported for a total of 71 dogs (32%); McNemar’s tests revealed non-lethal herbivore interactions (8%) were significantly lower than non-lethal predator interactions (17%; p < 0.01), but no significant difference was detectable in the proportion of lethal interactions according to type of wildlife (9% for herbivores and 10% for predators). All reported predator interactions were defensive, compared to only 25% of reported herbivore interactions (p = 0.016). Of the dogs for which data on corrective measures were available, 44% were successfully corrected following intervention. Of those deemed uncorrected, 42% had ceased exhibiting this behaviour independently or were acting defensively, 21% were removed from the programme, 26% had unclear intervention outcomes and 11% had died. Reported interactions with predators were rare, entirely defensive, and predominantly non-lethal. However, interactions with non-target species (herbivores) were more prevalent, necessitating remedial interventions. Overall, the conservation benefit of LGDs does not appear to be outweighed by ethical implications of their use; LGDs were shown to be highly targeted and discriminatory towards predators attempting to predate on livestock.
  • ... Wild carnivores may have contact with domestic dogs when they move to human areas or even when dogs venture into natural areas. This fact is a consequence of an anthropogenic effect on natural populations in protected areas (Woodroffe, 2004;Ritchie et al., 2014). Thus, the presence of exotic animals in the interior of protected areas is a concern because it increases the frequency of contact between these animals and the local wildlife. ...
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    Highlights • Helminths were identified in wild ring-tailed coatis in PARNA Iguaçu. • Some helminths identified in ring-tailed coatis also affect domestic dogs. • Some helminth species found have zoonotic importance.
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