Status and Ecological Effects of the World's Largest Carnivores

Abstract

Large carnivores face serious threats and are experiencing massive declines in their populations and geographic ranges around
the world. We highlight how these threats have affected the conservation status and ecological functioning of the 31 largest
mammalian carnivores on Earth. Consistent with theory, empirical studies increasingly show that large carnivores have substantial
effects on the structure and function of diverse ecosystems. Significant cascading trophic interactions, mediated by their
prey or sympatric mesopredators, arise when some of these carnivores are extirpated from or repatriated to ecosystems. Unexpected
effects of trophic cascades on various taxa and processes include changes to bird, mammal, invertebrate, and herpetofauna
abundance or richness; subsidies to scavengers; altered disease dynamics; carbon sequestration; modified stream morphology;
and crop damage. Promoting tolerance and coexistence with large carnivores is a crucial societal challenge that will ultimately
determine the fate of Earth’s largest carnivores and all that depends upon them, including humans.

Full text

Status and Ecological Effects
of the World’s Largest Carnivores
William J. Ripple,* James A. Estes, Robert L. Beschta, Christopher C. Wilmers, Euan G. Ritchie,
Mark Hebblewhite, Joel Berger, Bodil Elmhagen, Mike Letnic, Michael P. Nelson,
Oswald J. Schmitz, Douglas W. Smith, Arian D. Wallach, Aaron J. Wirsing
Background: The largest terrestrial species in the order Carnivora are wide-ranging and rare
because of their positions at the top of food webs. They are some of the world’s most admired mam-
mals and, ironically, some of the most imperiled. Most have experienced substantial population
declines and range contractions throughout the world during the past two centuries. Because of the
high metabolic demands that come with endothermy and large body size, these carnivores often
require large prey and expansive habitats. These food requirements and wide-ranging behavior
often bring them into confl ict with humans and livestock. This, in addition to human intolerance,
renders them vulnerable to extinction. Large carnivores face enormous threats that have caused
massive declines in their populations and geographic ranges, including habitat loss and degrada-
tion, persecution, utilization, and depletion of prey. We highlight how these threats can affect the
conservation status and ecological roles of this planet’s 31 largest carnivores.
Advances: Based on empirical studies, trophic cascades have been documented for 7 of the 31 larg-
est mammalian carnivores (not including pinnipeds). For each of these species (see fi gure), human
actions have both caused declines and contributed to recovery, providing “natural experiments” for
quantifying their effects on food-web and community structure. Large carnivores deliver economic
and ecosystem services via direct and indirect pathways that help maintain mammal, avian, inverte-
brate, and herpetofauna abundance or richness. Further, they affect other ecosystem processes and
conditions, such as scavenger subsidies, disease dynamics, carbon storage, stream morphology, and
crop production. The maintenance or recovery of ecologically effective densities of large carnivores
is an important tool for maintaining the structure and function of diverse ecosystems.
Outlook: Current ecological knowledge indicates that large carnivores are necessary for the main-
tenance of biodiversity and ecosystem function. Human actions cannot fully replace the role of large
carnivores. Additionally, the future of increasing human resource demands and changing climate will
affect biodiversity and ecosystem resiliency. These facts, combined with the importance of resilient
ecosystems, indicate that large carnivores and their habitats should be maintained and restored wher-
ever possible. Preventing the extinction of these species and the loss of their irreplaceable ecological
function and importance will require novel, bold, and deliberate actions. We propose a Global Large
Carnivore Initiative to coordinate local, national, and international research, conservation, and policy.
ARTICLE OUTLINE
Ecological Effects of Large Carnivores
Ecosystem and Economic Services
Anthropogenic Impacts
Climate Change
Outlook
A Final Word
SUPPLEMENTARY MATERIALS
Figs. S1 to S4
Tables S1 to S3
ADDITIONAL RESOURCES
“Lords of nature: Living in a land of
great predators”; www.youtube.com/
watch?v=PagO3gmwmA0
George Monbiot, TED “For more won-
der, rewild the world”; www.youtube.com/
watch?v=8rZzHkpyPkc
Trophic Cascades Program, www.cof.orst.edu/
cascades/
Large Carnivore Initiative for Europe, www.lcie.
org/Home.aspx
RELATED ITEMS IN SCIENCE
J. A. Estes et al., “Trophic downgrading of planet
Earth.” Science 333, 301–306 (2011).
Sea otter
(Enhydra lutris)
Lion
(Panthera leo)
Dingo
(Canis dingo)
Puma
(Puma concolor)Leopard
(Panthera pardus)
Eurasian lynx
(Lynx lynx)
Gray wolf
(Canis lupus)
A B C
Ecologically important carnivores. Seven species of
large carnivores with documented ecological effects
involving (A) “tri-trophic cascades” from large carni-
vores to prey to plants, (B) “mesopredator cascades”
from large carnivores to mesopredators to prey of
mesopredators, and (C) both tri-trophic and meso-
predator cascades. [Photo credits: sea otter (N. Smith),
puma (W. Ripple), lion (K. Abley), leopard (A. Dey), Eur-
asian lynx (B. Elmhagen), dingo (A. McNab), gray wolf
(D. Mclaughlin)]
READ THE FULL ARTICLE ONLINE
http://dx.doi.org/10.1126/science.1241484
Cite this article as W. J. Ripple et al.,
Science 343, 1241484 (2014).
DOI: 10.1126/science.1241484
The list of author affi liations is available in the full article online.
*Corresponding author. E-mail: bill.ripple@oregonstate.edu
www.sciencemag.org SCIENCE VOL 343 10 JANUARY 2014 151
REVIEW SUMMARY
Published by AAAS

Status and Ecological Effects of the
World’s Largest Carnivores
William J. Ripple,
1
*James A. Estes,
2
Robert L. Beschta,
1
Christopher C. Wilmers,
3
Euan G. Ritchie,
4
Mark Hebblewhite,
5
Joel Berger,
6
Bodil Elmhagen,
7
Mike Letnic,
8
Michael P. Nelson,
1
Oswald J. Schmitz,
9
Douglas W. Smith,
10
Arian D. Wallach,
11
Aaron J. Wirsing
12
Large carnivores face serious threats and are experiencing massive declines in their populations
and geographic ranges around the world. We highlight how these threats have affected the
conservation status and ecological functioning of the 31 largest mammalian carnivores on
Earth. Consistent with theory, empirical studies increasingly show that large carnivores have
substantial effects on the structure and function of diverse ecosystems. Significant cascading
trophic interactions, mediated by their prey or sympatric mesopredators, arise when some of
these carnivores are extirpated from or repatriated to ecosystems. Unexpected effects of trophic
cascades on various taxa and processes include changes to bird, mammal, invertebrate, and
herpetofauna abundance or richness; subsidies to scavengers; altered disease dynamics; carbon
sequestration; modified stream morphology; and crop damage. Promoting tolerance and
coexistence with large carnivores is a crucial societal challenge that will ultimately determine
the fate of Earth’s largest carnivores and all that depends upon them, including humans.
The order Carnivora consists of 245 ter-
restrial species inhabiting nearly every
major habitat on Earth (1). These mam-
malian species, which we call carnivores, are
generally unified by a shared heritage of sub-
sisting largely on other animals and are nat-
urally rare because of their position at the top
of the food web. These are also some of the
world’s most revered and iconic species. Ironi-
cally, they are also some of the most threatened.
During the previous two centuries, many car-
nivores have experienced substantial population
declines, geographic range contractions, and frag-
mentation of their habitat (2,3).
Carnivores of various sizes play an important
role in regulating ecosystems (4–7). These roles,
moreover, may not be redundant among carni-
vore species, because the strength and nature of
their impacts are influenced by factors such as the
carnivore’s size, metabolic demands, density, so-
ciality, and hunting tactics. The larger carnivores
especially tend to have large energetic constraints,
slow life histories, and low population densities
and roam widely in search of larger prey (8–10).
This conflation of low population densities and
reproductive rates with high food requirements
and wide-ranging behavior, bringing them into
conflict with humans and livestock, is what makes
them vulnerable and poorly able to respond to
persecution.
Large carnivores can exert ecological effects
despite existing at low densities (11), but perse-
cution can affect their social structure and in-
fluence their ecological role (12). Classically,
the effects of large carnivores are thought to ex-
tend down the food web to herbivores and to
plants, but we are learning that their cascading
influences propagate broadly to other species
as mediated by their controlling effects on meso-
carnivores (4,13,14). Large carnivores have the
dual role of potentially limiting both large her-
bivores through predation and mesocarnivores
through intraguild competition, thus structuring
ecosystems along multiple food-web pathways.
Together, these controls influence the nature and
strength of ecosystem functioning. What makes
the conservation of large carnivores exceptionally
important, therefore, is both their vulnerability
to extinction and their ability to structure ecosys-
tems. With this in mind, our focus here is on the
largest carnivores.
We review the conservation status and eco-
logical effects of the 31 largest (average adult
body masses ≥15 kg) species of Carnivora (not
including pinnipeds). Although most of these
species are obligate meat eaters, some are omni-
vorous and one is herbivorous (Table 1). The
remaining 214 carnivore species with body masses
<15 kg are not considered here, but we acknowl-
edge they also can play important and varied roles
in communities (4,13). The 31 largest carni-
vores belong to five families: Canidae, Felidae,
Mustelidae, Ursidae, and Hyaenidae. They gen-
erally have small population sizes (Fig. 1 and
table S1), often due to high levels of range loss
(Table 1). Many of these species (61%) are listed
by the International Union for the Conservation
of Nature (IUCN) as threatened (vulnerable, en-
dangered, or critically endangered) and are at risk
of local or total extinction. Most (77%) are under-
going continuing population declines (Table 1).
Estimates of range contractions for 17 of the 31
species revealed that they currently occupy on
average only 47% (minimum <1%, maximum
73%) of their historical ranges (Table 1). These
range losses can result in local population extinc-
tions, which have implications for the mainte-
nance of ecosystem and socioeconomic services.
Thus, many of these species are gradually disap-
pearing just as we are beginning to understand
and appreciate their roles in ecosystems and the
many societal benefits that accrue from their pre-
servation (5,15).
We report our current understanding of the
substantial ecological roles large-carnivore spe-
cies play in ecosystems and how their population
declines, extirpations, and recoveries stand to in-
fluence ecological communities and ecosystems
across the globe. We further consider how those
roles may change as environmental conditions
become altered when humans cause habitat loss
and climate change. We end by addressing the
outlook for the future and the looming uncertain-
ties motivating an urgent need for more research
on carnivore interactions in food webs and the
conservation of these species.
Ecological Effects of Large Carnivores
Seven of the 31 species of large carnivores are
associated with documented trophic cascades.
Therefore, we focus on these seven species with
analysis and discussion. Each of the seven species
is well studied in comparison to other large car-
nivores (fig. S2). In all cases, these seven species
of large carnivores clearly have cascading influ-
ences on ecological communities and ecosystems.
We assessed the general strength of these effects
using available data to calculate the log
10
(X
a
/X
p
)
effect magnitudes, where X
a
and X
p
are the values
for the response variables with the large-carnivore
species absent and present, respectively [for methods,
see (6)]. The effect magnitude of large-carnivore
removal on the abundance of prey, plants, and
mesopredators ranged from –2.3 to 2.3 (Fig. 2).
These are considered large effects. For example,
an effect size of 2 or –2 represents a difference of
two orders of magnitude (100 times) in the effect
REVIEW
1
Trophic Cascades Program, Department of Forest Ecosystems
and Society, Oregon State University, Corvallis, OR 97331,
USA.
2
Department of Ecology and Evolutionary Biology,
University of California, Santa Cruz, CA 95060, USA.
3
Center
for Integrated Spatial Research, Department of Environmental
Studies, University of California, Santa Cruz, CA 95064, USA.
4
Centre for Integrative Ecology and School of Life and Envi-
ronmental Sciences, Deakin University, Burwood, Victoria 3125,
Australia.
5
Wildlife Biology Program, Department of Ecosystem
and Conservation Sciences, College of Forestry and Conserva-
tion, University of Montana, Missoula MT, 59812, USA, and
Department of Biodiversity and Molecular Ecology, Research
and Innovation Centre, Fondazione Edmund Mach, Via Mach 1,
38010 San Michele all'Adige (TN), Italy.
6
Department of Or-
ganismic Biology and Ecology, University of Montana, Missoula,
MT 59812, and Wildlife Conservation Society, Bronx, NY 10460,
USA.
7
Department of Zoology, Stockholm University, SE-106 91
Stockholm, Sweden.
8
School of Biological, Earth and Environ-
mental Sciences, University of New South Wales, Sydney, New
South Wales 2052, Australia.
9
School of Forestry and Environ-
mental Studies, Yale University, New Haven, CT 06511, USA.
10
Yellowstone Center for Resources, Yellowstone National Park,
Post Office Box 168, Mammoth, WY 82190, USA.
11
School of
Marine and Tropical Biology, James Cook University, Townsville,
Queensland 4811, Australia.
12
School of Environmental and
Forest Sciences, University of Washington, Seattle, WA 98195,
USA.
*Corresponding author. E-mail: bill.ripple@oregonstate.edu
www.sciencemag.org SCIENCE VOL 343 10 JANUARY 2014 1241484-1

between when carnivores are absent as compared
to present. These values also rank relatively high
when compared to a meta-analysis of 114 case
studies of predators from both aquatic and ter-
restrial systems, where effects, expressed in log
10
ratios, ranged from –0.3 to 1.0 (16). With the
exception of the sea otter, all of the aquatic and
terrestrial predators included in that study were
≤2 kg in body mass, suggesting a potential link
between carnivore size and ecological influence.
Below we provide a brief synthesis for each of
the seven large-carnivore species. Following these
species accounts is a general discussion of other
large-carnivore species, for which less is known
about their ecological effects.
Lions and Leopards
The African lion (Panthera leo) occupies 17% of
its historical range and is listed as vulnerable by
the IUCN. Its abundance has declined dramati-
cally in recent decades because of habitat loss
and indiscriminate killing in defense of humans
and livestock (17). The leopard (Panthera pardus)
is near threatened and occupies 65% of its his-
torical range. When sympatric, lions and leopards
exert control on mesopredators. In West Africa,
olive baboons (Papio anubis) increased in abun-
dance at rates most closely correlated with de-
clines in these apex predators relative to seven
other environmental variables that might explain
baboon abundance and range occupancy (18).
Increases in baboons correlated with accelerated
declines in small ungulates and primates. Among
large mammals, baboons pose the greatest threat
to livestock and crops and they use many of the
same sources of animal protein and plant foods as
humans in sub-Saharan Africa. In some areas,
baboon raids in agricultural fields require fami-
lies to keep children out of school so they can
help guard planted crops (18).
Dingoes
The dingo (Canis dingo), thought to have arrived
in Australia around 5000 years ago (19), became
the sole remaining mammalian apex predator on
the continent after the extinction of the Tasma-
nian tiger (Thylacinus cynocephalus). With Euro-
pean settlement, dingo populations have been
affected across the continent, notably by the erec-
tion of a 5500-km dingo-proof fence designed to
keep dingoes out of Australia’s major sheep-grazing
region. The presence and absence of dingoes on
either side of the fence, along with variation in
dingo management practices among properties,
has produced a continental-scale experiment. The
most significant and well-understood effects of
dingoes are in the control of populations of native
Table 1. Large-carnivore species list, body mass (in kilograms),
diet, endangerment status, population trend, and percent of his-
torical range occupied. Body masses are from Gittleman (15), Mammalian
Species Accounts, and the Animal Diversity Web. Diet categories are from
Hunter (1) as follows: M, meat eater; V, vegetation and/or fruit eater; O,
omnivore. Species status and trend are from the IUCN Red List (16): LC, least
concern; NT, near threatened; VU, vulnerable; EN, endangered; CR, critically
endangered.
Family/species*Common name Mass, diet IUCN status (trend) % of historical range Reference for % of historical range
Canidae
Canis lupus Gray wolf 33, M LC (stable) 67 (1)
Canis rufus Red wolf 25, M CR (increasing) <1 (91)
Chrysocyon brachyurus Maned wolf 23, O NT (unknown) 68 (2)
Lycaon pictus African wild dog 22, M EN (decreasing) 10 (17)
Cuon alpinus Dhole 16, M EN (decreasing) ––
Canis dingo†Dingo 15, M VU (decreasing) 84 (20)
Canis simensis Ethiopian wolf 15, M EN (decreasing) 2 (17)
Felidae
Panthera tigris Tiger 161, M EN (decreasing) 18 (3)
Panthera leo Lion 156, M VU (decreasing) 17 (17)
Panthera onca Jaguar 87, M NT (decreasing) 57 (3)
Acinonyx jubatus Cheetah 59, M VU (decreasing) 17 (17)
Panthera pardus Leopard 53, M NT (decreasing) 65 (3)
Puma concolor Puma 52, M LC (decreasing) 73 (3)
Panthera uncia Snow leopard 33, M EN (decreasing) ––
Neofelis nebulosa Clouded leopard 20, M VU (decreasing) ––
Neofelis diardi Sunda clouded leopard 20, M VU (decreasing) ––
Lynx lynx Eurasian lynx 18, M LC (stable) ––
Mustelidae
Enhydra lutris Sea otter 28, M EN (decreasing) ––
Pteronura brasilliensis Giant otter 24, M EN (decreasing) ––
Aonyx capensis Cape clawless otter 19, M LC (stable) ––
Ursidae
Ursus maritimus Polar bear 365, M VU (decreasing) ––
Ursus arctus Brown bear 299, O LC (stable) 68 (3)
Ailuropoda melanoleuca Giant panda 134, V EN (decreasing) ––
Ursus americanus American black bear 111, O LC (increasing) 59 (35)
Tremarctos ornatus Andean black bear 105, O VU (decreasing) ––
Ursus thibetanus Asiatic black bear 104, O VU (decreasing) ––
Melursus ursinus Sloth bear 102, O VU (decreasing) ––
Helarctos malayanus Sun bear 46, O VU (decreasing) ––
Hyaenidae
Crocuta crocuta Spotted hyena 52, M LC (decreasing) 73 (17)
Hyaena brunnea Brown hyena 43, O NT (decreasing) 62 (17)
Hyaena hyaena Striped hyena 27, O NT (decreasing) 62 (17)
*Changes to taxonomic status have influenced the number of species included in this group, and some less-known and taxonomically ambiguous carnivores may be missing from this analysis
because they have yet to be listed by the IUCN. †Currently incorporates the New Guinea singing dog, C. hallstromi, whose taxonomic and conservation status is yet to be elucidated.
10 JANUARY 2014 VOL 343 SCIENCE www.sciencemag.org1241484-2
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herbivores, introduced herbivores, and the exotic
mesopredator the red fox (Vulpes vulpes). The
suppression of these species by dingoes reduces
total herbivory and predation pressure, in turn
benefiting plant communities and smaller native
prey (12,14,20,21). The dingo’s social stability
and associated behavior are thought to be key to
its ecological effectiveness (12). Overall, the sup-
pression of dingoes has probably contributed to
the endangerment and extinction of small marsu-
pials and rodents over much of the continent (21,22).
Eurasian Lynx
The Eurasian lynx (Lynx lynx) maintains an ex-
tensive distribution in eastern and northern Eu-
rasia, but it has been extirpated from large parts
of Western Europe (23). At the continental scale,
the effects of lynx predation increase with harsh
winter conditions (23,24). Lynx may limit both
prey (roe deer Capreolus capreolus)andmeso-
carnivore (red fox) abundance, so changes in lynx
status may trigger cascading effects along two
pathways, of which the mesocarnivore-mediated
cascade is the more explored (25). The recent
recovery and enhanced conservation protection
of Eurasian lynx in Finland were accompanied
by a decline in red fox abundance and a com-
mensurate recovery in the abundance of forest
grouse (Tetrao tetrix and T. urogallus) and moun-
tain hare (Lepus timidus)(7,25). Moreover, where
lynx density had recovered to “ecologically effec-
tive”levels, the controlling effects of lynx on red
foxes and prey increased with ecosystem pro-
ductivity, indicating that the strength of predator
control may vary as a function of the net primary
productivity of the ecosystem (26,27).
Sea Otters
Sea otters (Enhydra lutris) were hunted to near-
extinction during the Pacificmaritimefurtradein
the 18th and 19th centuries (28). Sea otter pop-
ulations are presently stable or increasing from
about Kodiak Island eastward, deeply depleted
[presumably because of killer whale predation
(29)] from about Kodiak Island westward through
the Aleutian archipelago, and largely recovered
in Russia. The earlier recovery of these popula-
tions and the more recent decline of recovered
populations in southwest Alaska (29)offernat-
ural experiments to study the sea otter’sinflu-
ences on coastal ecosystems. The best-documented
cascade of effects involves sea otters limiting
herbivorous sea urchins and, in turn, enhancing
the abundance and distribution of kelp and other
fleshy macroalgae in coastal inshore ecosystems
(Fig. 3A) (30). As sea otter populations recover
and decline, shifts between the kelp-dominated
and urchin-dominated conditions can be abrupt
(31). Once reached, these different ecological states
tend to persist (32) unless the system is pushed
strongly to the other state by substantial increases
or reductions in otter abundance. The follow-on
effects of these shifts influence numerous other
species and ecological processes in coastal eco-
systems through three basic mechanisms: the cre-
ation of biogenic habitat (i.e., created by living
organisims), the enhancement of primary pro-
duction, and the influence of kelp forests in
dampening coastal waves and currents [reviewed
in (31)].
Gray Wolves
The gray wolf (Canis lupus) is one of the world’s
most widely distributed mammals and the most
studied large carnivore (fig. S2). It has been ex-
tirpated from much of Western Europe, the United
States, and Mexico, and its overall range has been
reduced by approximately one-third because of
persecution by humans and habitat fragmentation
(1). In recent decades, wolf population declines
have been arrested because of enhanced legal
protection, reintroduction programs, and natural
recolonization, resulting in population recoveries
in portions of the Rocky Mountains, Great Lakes,
and southwestern regions of North America, as
well as in various parts of Europe. Other than
humans, gray wolves, by virtue of their wide-
spread geographic distribution, group hunting,
and year-round activity, are the most important
predator of cervids in the Northern Hemisphere
(33). Predation by wolves with sympatric bears
(Ursus spp.) generally limits cervid densities (33).
In North America and Eurasia, cervid densities
were, on average, nearly six times higher in areas
without wolves than in areas with wolves (34). As
early as the 1940s, cervid irruptions, after wolf and
other predator declines, were first documented in
various ecosystems of western North America
(35). The shifts in plant communities consequent
to the cascading effects of wolf extirpations and
of recoveries have been found across a variety of
areas of North America, representing a wide range
of productivity (6). In Yellowstone National Park,
wolves were reintroduced in 1995–1996, making
this park one of the most predator-rich areas in
North America. This reintroduction triggered var-
ious direct and indirect effects, as mediated by both
mesopredators and cervid prey (Figs. 3B and 4).
Pumas
The range of the puma (Puma concolor)inthe
Western Hemisphere remains larger than that of
any other terrestrial mammal, even though they
have been extirpated from most of the eastern
United States (36). In the absence of pumas and
sometimes other large carnivores, hyperabundant
cervids [such as the white-tailed deer (Odocoileus
virginianus)] in the eastern United States and
Canada now affect many aspects of ecosystem
function, including plant recruitment and surviv-
al, endangered species status, forest stand struc-
ture, nutrient dynamics, and socioeconomics through
vehicle collisions (37). Where pumas are present,
they can be important drivers of cervid popula-
tions and associated trophic relations, as in can-
yon settings in western North America, where they
locally limit mule deer (O. hemionus) densities, re-
leasing woody plants from browsing suppression
(38,39). Pumas also appear to influence processes
affecting terrestrial and aquatic species, includ-
ing hydrophytic plants, wildflowers, amphibians,
Fig. 1. Worldwide population
estimates of large-carnivore
species. Error bars represent the
low and high range of the esti-
mates when available. Population
estimates were not available for
all species. Species ranges vary
widely, and range sizes can have
a strong influence on species pop-
ulation levels (table S1). Sources:
Gray wolf (90), all other species
IUCN (91).
American
black bear
Brown bear
Spotted hyena
Lion
African wild dog
Brown hyena
Asiatic
black bear
Eurasian lynx
Tiger
Snow leopard
Giant otter
Estimated population size (worldwide)
Dhole
Giant panda
Ethiopian wolf
Red wolf
0
Polar bear
Maned wolf
Gray wolf
Sea otter
Andean bear
Sloth bear
Striped hyena
Cheetah
850,000 - 950,000
50,000 100,000 150,000 200,000
www.sciencemag.org SCIENCE VOL 343 10 JANUARY 2014 1241484-3
REVIEW

lizards, and butterflies. Their presence may also
help to stabilize stream banks and channels (38).
Pumas may induce their prey to engage in “human
shielding”as an antipredator strategy. Deer at risk
from pumas, for example, associated themselves
with human development at high densities, in turn
causing plant damage (38,39).
Other Large Carnivores
Little is known about the ecological effects of the
other large-carnivore species listed in Table 1,
and questions remain about their potential roles
in controlling food webs and ecosystem func-
tioning, especially in the tropics and subtropics
(Fig. 5). However, some valuable lessons come
from the flooding of a forest region in Venezuela
to generate hydroelectric power. This once-intact,
productive tropical system was composed of a
species-rich food web with multiple linkages
among species. Flooding fragmented the region
to produce mountaintop islands—the Lago Guri
islands—resulting in the loss of an entire predator
guild of jaguars (Panthera onca), pumas, lesser
mammalian predators, large raptors, and snakes
(40). This loss of predators had cascading effects
on species of pollinators, seed dispersers, seed
predators, folivores, and mesopredators, as well
as on woody plant recruitment, bird abundance,
and soil carbon/nitrogen ratios (41).
Predator species often co-occur, requiring con-
sideration of their joint effects. Multiple predator
effects on prey species and on ecosystems can be
synergistic (15). Thus, in some cases, the strength
of a trophic cascade may be due to synergisms
owing to complementarity among species in the
top carnivore guild of communities. This implies
that the combined effects of predator species may
need to be conserved to fully ensure control over
communities and ecosystem functioning. For ex-
ample, bears of northern latitudes (Ursus spp.)
may control the recruitment of juveniles into
populations of their prey species (42). Because
bears are opportunistic omnivores and eat a varie-
ty of foods, their effects may complement those of
gray wolves (34). In North America, both black
(U. americanus) and brown (U. arctos) bears com-
monly prey on neonatal cervids, taking a large
percentage of the annual offspring that are less
than 1 month old, and these effects could be ad-
ditive. In Yellowstone National Park, bears killed
more elk (Cervus elaphus) calves than did gray
wolves, coyotes (Canis latrans), and pumas com-
bined (43). In Europe, roe deer densities were
significantly lower in areas with sympatric wolves
andlynxthaninareaswithwolvesaloneorareas
where both predators were absent (24,34). The
effect of multiple predators on prey, however,
need not always be synergistic. Adult female elk
mortality was similar in areas of western North
America with pumas alone as compared to areas
with sympatric pumas and wolves (44).
Questions persist about how large-carnivore
effects interact with habitat productivity. Theory
Effects after large carnivore decline
Log10 ratio effect size
Declining speciesLarge carnivore
Sea otter
7 years
Dingo
50+ years
Gray wolf
60+ years
Puma
60+ years
Lion &
leopard
17 years
Increasing species
Urchin
Fox
Kangaroo
Deer
Olive baboon
Kelp
Dusky hopping mouse
Grasses
Hardwood
tree
Hardwood tree
Herpetofauna
Butterflies
Small primate & ungulate
00.5-0.5 1-1 1.5-1.5 2-2 2.5-2.5 3
Fig. 2. Examples of effect sizes, shown as log
10
ratios, after the re-
moval of large-carnivore species. Sea otters (29,92), dingoes-foxes and
dingoes-kangaroo (21,93), dingoes-mice (Notonmys fuscus)(93), dingoes-
grasses (20), gray wolves–hardwood trees (94,95), pumas–hardwood trees
(38,39), pumas-deer-herpetofauna-butterflies (38),andlionsandleopards
(18). The number of years refers to the time since large-carnivore extirpation.
The log
10
ratios were calculated by dividing the values of each response
variable without predator by those with predator and then taking the log
10
of
that ratio. Positive log ratios
10
indicate a positive effect, and negative log
10
ratios indicate a negative effect of removing large carnivores. For studies using
time-series data, we used the final sampling date in our analysis. The orange
bars indicate direct effects and the blue bars indicate indirect effects. Error
bars represent standard errors and were only available in some cases. [Photo
credits: sea otter (N. Smith), dingo (A. McNab), gray wolf (Yellowstone National
Park), puma (Washington Department of Fish and Wildlife), lion (K. Abley),
leopard (A. Dey)]
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predicts that the strength of cascading effects may
vary with the productivity of ecosystems and
should show a “humped relationship”with eco-
system productivity (26,27). That is, we might
not expect to see strong trophic cascades in eco-
systems such as extreme deserts, high elevations,
or high latitudes, where low primary productivity
limits herbivore populations and where there is
insufficient energy available to support popula-
tions of large carnivores (27). The trophic effects
of single carnivore species might also be dimin-
ished in extremely productive environments,
because prey species diversity may also be high
in such systems and, consequently, the strength
of interspecific interactions is diffused across a
greater number of interaction pathways (20,41,45).
For example, in a productive tropical forest, Sunda
clouded leopards (Neofelis diardi) had no mea-
surable effect on the abundance of the main large
ungulate prey species (46). Conversely, there is
also empirical evidence indicating that some canids
consistently limit prey densities regardless of eco-
system productivity (34,47). Accordingly, more
analyses of how productivity interacts with trophic
interactions are needed. To this end, regions har-
boring large-carnivore populations with different
conservation statuses, including places without
them, can be used as broad bioclimatic contexts
for natural experiments.
Ecosystem and Economic Services
Large carnivores deliver economic and ecosys-
tem services in a variety of direct and indirect
ways. Because of their iconic and charismatic
nature, large carnivores provide direct economic
benefits associated with tourism. In both Minnesota
and Yellowstone (48,49) and the African photo-
safari industry (50), the opportunity to simply
observe large carnivores can drive tourism re-
venue. In Yellowstone alone, wolf-related tour-
ism expenditures range from $22 million to
$48 million (in U.S. dollars) per year (49).
Large carnivores also have strong potential to
indirectly deliver ecosystem services, such as car-
bon storage to buffer climate change, biodiversity
enhancement, reestablishment of native plant diver-
sity, riparian restoration, and even regulation of
diseases. In some ecosystems, large carnivores may
enhance carbon storage by limiting the numbers
of their herbivore prey, thus allowing plants (all
of which absorb and store CO
2
) to flourish. Car-
nivore conservation and restoration might reverse
declines in forests stands and production, thereby
aiding carbon storage, especially in the highly
productive tropics, where declines in plant bio-
mass occur after predator extirpation (40,41).
Maintaining gray wolf populations and their in-
teractions with moose is estimated to help store
significant amounts of carbon in boreal ecosys-
tems (51). The restoration of sea otter populations
can reduce sea urchin herbivores, thereby allow-
ing kelp ecosystems to flourish at levels that
can, in the North American range, lead to a 4.4- to
8.7-teragram increase in stored carbon valued at
$205 million to $408 million (in U.S. dollars) on the
European Carbon Exchange (52). Predators may
enhance scavenger diversity (53) and thereby con-
tribute to nutrient cycling, in addition to myriad
other documented cascading and ramifying path-
ways (15). In riparian systems, large carnivores
may reduce stream bank erosion through the
growth of woody plants and enhance water qual-
ity and flood control through the restoration of
beaver that benefit from the restored plants (54–57).
Large carnivores help reduce disease prevalence
in ungulate prey populations, thereby mitigating
agricultural costs because of spillover effects on
domestic livestock (58). Perhaps counterintuitive-
ly, large carnivores may also provide crucial ser-
vices for the very industry they are perceived to
be at most in conflict with: pastoralism. By limit-
ing the density of wild herbivores and promoting
productivity, large carnivores may enable pasto-
ral activities that are sustainable (12,59). This is
not to deny that large carnivores also have direct
costs, often associated with livestock losses (60),
and balancing these costs against potential ben-
efits for human-dominated ecosystems as a whole
is a pressing challenge (61). Regardless, the po-
tentially widespread beneficial ecosystem and eco-
nomic services associated with large carnivores
are underappreciated by society.
Anthropogenic Impacts
Large-carnivore population declines are typically
precipitated by multiple, and sometimes concur-
rent, human threats, including habitat loss and
degradation, persecution, utilization (such as for
traditional medicine, trophy hunting, or furs), and
depletion of prey. Globally, the strength of these
threats varies substantially by region (Fig. 6 and
table S2). These threats are sometimes localized
to only parts of a carnivore’s range and, in some
cases, may extend beyond its range, thus acting
to limit reoccupation of former habitats.
Fig. 3. Examples of plant re-
sponse after sea otter reduction
and after gray wolf recovery. (A)
An area of seafloor near Kirilof
Point, Amchitka Island, Alaska, in
1971 (upper left, photo by P. Dayton),
at which time sea otters were abun-
dant, and in 2001 (lower left, photo
by M. Kenner) at which time sea
otter numbers had been reduced
by more than 90% by killer whale
predation. (B)PhotosoftheYellow-
stone Northern Range taken in
October 1994 (top right, photo by
National Park Service) and Novem-
ber 2012 (bottom right, photo by
D. Mclaughlin), showing increased
recruitment of aspen since wolf re-
introduction in 1995–1996 at the
site of the Crystal Creek gray wolf
holding pen, which was removed in
1998. Young aspen in the 1994
photo were mostly less than 1 m
tall and those in the 2012 photo
were typically 3 to 4 m tall.
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Human actions may dampen or even elimi-
nate cascading effects. For example, Mexican gray
wolves in southwestern North America have not
yet been restored to an ecologically effective den-
sity in relation to that of their main prey, elk, be-
cause of ongoing conflicts with livestock grazing
and repeated management translocations (62).
Likewise, recent wide-scale hunting of recover-
ing gray wolf populations in parts of the Great
Lakes region and the western United States may
reduce wolf populations below sizes at which
they are able to exert their effects on communities
and ecosystems (63–65). Furthermore, wolves
and other carnivores may have little influence on
other species in areas where human hunters have
disproportionate effects on prey densities (66).
Few large carnivores can persist in parts of Latin
America, Asia, and Africa because of the loss of
wild ungulate prey species caused by activities
such as hunting for bushmeat. The extraction of
bushmeat, in turn, has created “empty forests”
(1). Conversely, hyperabundant exotic ungulates
(domestic livestock) are present in much of the
world. These livestock are a potential prey base
and thus a continuing source of conflict between
humans and large carnivores (17).
Hunting by humans, whether legal as in North
America and Europe or illegal as in the pantrop-
ical bushmeat trade, may itself cause trophic
cascades, because humans are also predators with
the potential for ecological impacts. Indeed, hu-
man hunting pressure on moose (Alces alces)has
led to the release of control on willow (Salix spp.)
shrub production and hence encouraged increases
in neotropical migrant bird abundances (42). Al-
though it is often claimed that human hunting
substitutes for predators, it remains doubtful
whether such substitution actually leads to the
same functional consequences for communities
and ecosystems. Effects may be different because
of differences in the intensity and timing of pre-
dation by humans versus predators, as well as hunt-
ing effects on the behavior, age, and sex of prey
(67). Many carnivores hunt year-round, day or night,
and away from human access points. The behavioral
responses of prey to predation risk caused by
carnivores may create an “ecology of fear”with
myriad cascading effects on ecosystems (68). In
the end, it is not surprising that various human
activities in Australia (12), North America (13,34),
and Eurasia (24) have been unsuccessful in sub-
stituting for large carnivores to control populations
of native and nonnative herbivores and mesopred-
ators. The huge importance of carnivores is exem-
plified by the fact that humans typically cannot
replicate the effects of carnivores on ecosystems.
Habitat fragmentation, and more generally the
intensity of human uses of landscapes, continue to
be persistent threats to larger-bodied carnivores,
with the potential for cascading impacts on spe-
cies diversity (5,38). There exists, therefore, an
increasing need to understand the interacting ef-
fects of anthropogenic land-use changes and al-
tered large-carnivore guilds on community structure
and function. Because of differences in their
ecology and human tolerance, pumas are able to
persist in areas with much higher levels of human
land use than are gray wolves, even though these
two carnivores are of similar size. Such differen-
tial predator species loss in the face of landscape
changes may be especially critical if synergism
among multiple large carnivores within predator
guilds is required to maintain control over prey
populations (34,43). These and other carnivore
species make kills in different habitats, or scav-
enge to supplement their diets, which can de-
termine the nature and rates of prey kills and
consumption (53,69). In addition to altering
predator communities, increased human land use
can alter nutrient and water availability, thereby
mitigating natural controls over ecological com-
munities and ecosystem functioning (70).
Perhaps one of the most insidious threats to
carnivores is global human population size and
its associated resource consumption, which are
expected to continue rising significantly through
at least 2050 (Fig. 7). Increased human popula-
tion size can lead to increased demand for meat.
Interestingly, human carnivory competes with
Fig. 4. Conceptual diagram showing direct (solid lines) and indirect (dashed lines) effects of
gray wolf reintroduction into the Greater Yellowstone ecosystem. Wolf direct effects have been
documented for elk (96)andcoyotes(97), whereas indirect effects have been shown for pronghorn (98),
small mammals (99), woody plants (100), stream morphology (54), beaver (55), birds (101), berry
production (63), scavengers (53), and bears (56,63). This is a simplified diagram, and not all species and
trophic interactions are shown. For example, the diagram does not address any potential top-down effects
of pumas, bears, and golden eagles ( Aquila chrysaetos),whichareallpartoftheYellowstonepredator
guild where juvenile or adult elk are prey.
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large carnivores. For example, the need for hu-
mans to either produce meat through livestock
production or to exploit wild sources necessarily
puts extra pressure on large carnivores on mul-
tiple fronts, including ongoing habitat loss from
land conversion, depletion of prey, and direct per-
secution due to conflicts with livestock. In light
of their slow life histories and requirement for
large continuous habitat, such trends exacerbate
the vulnerability of large carnivores to extinction
(9). Increases in both human population and meat
consumption can also affect biodiversity, green-
house gas emissions, food security, deforestation,
desertification, and water quality and quantity
(71,72). Therefore, policy for carnivore conser-
vation needs to be joined up with policy address-
ing these other converging issues having implications
at the global scale (71,72). Ideally, discussions
regarding potential decreases in both human fer-
tility rates and per-capita meat consumption would
be part of a long-term strategy for overcoming
these concurrent challenges.
Climate Change
Looking forward, the status of large carnivores
will influence the extent to which individual spe-
cies, biotic communities, and ecosystems respond
to climate change. For example, mesopredators
that have been released from control by the loss
of their carnivore predators may increase further
in abundance wherever climate change relaxes
limitations on their own prey (23). Large car-
nivores may instrumentally determine resilience
against invading species, because both native and
introduced species are less likely to become in-
vasive in ecosystems in which food-web inter-
dependencies remain intact (7). These potential
buffering capacities remain both poorly appre-
ciated and poorly understood. Widespread mod-
eling approaches forecasting climate change effects
on species still simplistically assume that such
interactions and interdependencies do not require
consideration, let alone quantification (73). Further-
more, climate change is already causing species
geographic range shifts that stand to disrupt ex-
isting species interactions (74,75). As species
move at different rates and in different directions,
novel communities are likely to be created as
new combinations of predator and prey species
assemble on landscapes. The recently documented
change in hunting locations and food habits
among polar bears (Ursus maritimus) is a case in
point. With receding sea ice, polar bears have
more difficulty hunting seals, their traditional prey,
and are now feeding onshore on the eggs of
migratory waterfowl (76).
As climate change progresses, large carnivores
might serve as important buffers or amplifiers of
effects on ecosystems (77). In Yellowstone Na-
tional Park, reintroduced gray wolves control the
timing and abundance of ungulate carrion re-
sources, on which a suite of scavenger species,
ranging in size from grizzly bears to magpies
(Pica hudsonia), depend for winter survival and
reproduction. The return of wolves has buffered
the influence of climate change on late-winter
carrion availability (77) by shifting the dynamics
of carrion availability from a boom–and-bust cy-
cle, linked to climate variability, to a more depend-
able resource based on shifting patterns of wolf
pack size (53). Large carnivores might also help
augment ecosystem carbon storage by suppressing
herbivores, thereby allowing plants to flourish
(34). For instance, the decline of large carnivores
in western North America was followed by a de-
cline in hardwood tree recruitment in riparian
areas of over two orders of magnitude (6). In north-
ern North America, gray wolves limiting moose
populations may be responsible for increased net
ecosystem uptake of carbon due to decreased
browsing and increased net primary productivity
(51). Likewise, the presence of sea otters in near-
shore environments suppresses sea urchins, al-
lowing macroalgael kelp to thrive and thereby
Number of large
carnivore species
0
1
2
3
4
5
6
7
8
gray wolf
puma
brown bear
American black bear
maned wolf
jaguar
puma
giant otter
African wild dog
lion
cheetah
leopard
spotted hyena
brown hyena
Cape clawless otter
African wild dog
lion
cheetah
leopard
spotted hyena
striped hyena
Cape clawless otter
dingo gray wolf
dhole
snow leopard
clouded leopard
leopard
Eurasian lynx
brown bear
Asiatic black bear
gray wolf
dhole
tiger
leopard
Eurasian lynx
brown bear
Asiatic black bear
gray wolf
Eurasian lynx
brown bear
A
ABC DEFGH
B
C
D
E
FG
H
Fig. 5. Contemporary overlap of large carnivore ranges throughout the
world. Compared to historical times, large-carnivore range contractions have
been most extensive in Europe, southeastern North America, and western and
central Africa. The areas with the highest number of species and with intact large-
carnivore guilds are some of the best regions for research and conservation (e.g.,
southeastern Asia, eastern and southern Africa, and northwestern North America).
Northern Eurasia is the region with the most expansive range for a three-species
guild (gray wolves, Eurasian lynx, and brown bear). The percent of the total
terrestrial land area in each of the eight classes in the map includes 0, 13.3%; 1,
29.1%; 2, 23.5%; 3, 20.5%; 4, 9.1%; 5, 2.8%; 6, 1.1%; 7, 0.4%; 8, 0.1%. Only
~5% of Earth’s land surface currently contains more than four overlapping large-
carnivore species. See fig. S4 for individual range maps. Source: IUCN (91).
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increasing ecosystem carbon production and stor-
age by one to two orders of magnitude (52). Glob-
ally, several billion head of ruminating livestock
affect global climate change by contributing sig-
nificant amounts of methane, nitrous oxide, and
carbon dioxide (~5.7 gigatons of CO
2
equivalent
per year) to the atmosphere, making domestic ru-
minants a significant contributor to climate change
(11.6% of all anthropogenic emissions of green-
house gases) (72). Decreasing global livestock
numbers to reduce greenhouse gas emissions
would both mitigate climate change and benefit
large-carnivore conservation by reducing ongoing
worldwide conflict between large carnivores and
livestock.
Outlook
The loss of large carnivores across global eco-
systems is predicted to lead to two general out-
comes. First, as apex predators are lost, we should
expect continued change in cascading controls
over communities and ecosystem function. Al-
though these effects will differ with the variation
in precipitation, temperature, productivity, diver-
sity, and overall landscape features, the continued
loss of carnivores nonetheless will be accom-
panied by changes in plant species diversity, bio-
mass, and productivity. In forest and arid ecosystems,
the loss of palatable perennial plant species may
interact with global warming to increase the rate
of desertification. Because plants are the trophic
foundation of all ecosystems, these vegetation
changes can be expected to have wide-ranging
influences on virtually all other species. The grow-
ing list of case studies, some of which we presented
above, may well represent the tip of the proverbial
iceberg. Changes in species abundance resulting
from the loss of large carnivores can be expected
to influence numerous other ecological processes,
including disease dynamics (78,79), wildfire (80),
and carbon sequestration (51). Furthermore, the
effects of large carnivores are now known to have
wide ramifications through highly interconnected
food-web networks within their associated eco-
systems (81). Second, we should expect surprises,
because we have only just begun to understand
the influences of these animals in the fabric of
nature (82).
The classic conception of large-carnivore in-
fluences on ecosystems held that predators were
responsible for depleting resources such as fish,
wildlife, and domestic livestock. This assumption
is still used to justify wildlife management prac-
tices aiming to limit or eradicate predators in
some regions (83,84). This conception of car-
nivore ecology is now outdated and in need of
fundamental change. Indeed, evidence shows that
their roles are far more complex and varied, and
their myriad social and economic effects on hu-
mans include many benefits. Conservation deci-
sions must begin to account for these integral roles
and the attendant economic costs of carnivore
species losses.
Currently, the IUCN Species Survival Com-
mission (SSC) action plan series represents per-
haps the most comprehensive attempt to establish
priorities for individual species or taxa (84,85).
These action plans not only provide assessments
of threats but recommend conservation monitor-
ing and actions for each large-carnivore species
(table S3). Action plans are compiled by the tax-
onomically organized SSC’s Specialist Groups
(for example, the Canid Specialist Group com-
piles action plans for all canid species). Large
carnivores, however, also share common conser-
vation challenges that cross taxonomic bounda-
ries: slow life histories, requirement for extensive
and continuous habitat, low densities, complex
A
C
B
D
Habitat loss & fragmentation Persecution (conflict with humans)
Utilization (e.g. traditional medicine, fur) Depletion of prey
0
1
2
3
4
5
6
7
8
0
1
2
3
4
5
6
0
1
2
3
4
5
6
7
0
1
2
3
4
Fig. 6. Maps showing the the spatial overlap for the ranges of large-
carnivore species by threat category for habitat loss and fragmenta-
tion, persecution, utilization, and depletion of prey. The number of
large-carnivore species affected by specific threats is shown in the map legend.
Threat catgories include: (A) Habitat loss and fragmentation. Forest logging
and/or the development of urban, agricultural, and road infrastructure reduces
land available to large carnivores and creates barriers between and within
populations. (B) Persecution. Culling (poison baiting, trapping, and shooting)
for the purpose of removal or reduction, in some cases reinforced with a
government-subsidized bounty system, in response to real or perceived threat
to pastoral and agricultural activities and human lives. (C) Utilization. Large
carnivores are killed for sport, body parts for traditional medicine, fur, and
meat for human consumption, and live animals are captured and sold. (D)
Depletion of prey. The decline of prey populations due to human hunting,
competition with livestock, habitat loss, and other factors reduces the prey
base for large carnivores. See table S2 for raw data. Source: IUCN (91).
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social structures, importance to ecological func-
tion, and conflict with humans. These common
traits and challenges have given rise to the crea-
tion of the Large Carnivore Initiative for Europe,
aSpecialistGroupwhosevisionis“to maintain
and restore, in coexistence with people, viable
populations of large carnivores as an integral part
of ecosystems and landscapes across Europe”
(86). We propose the expansion of this initia-
tive, to establish a Global Large Carnivore Initia-
tive (GLCI).
There is now a substantial body of research
demonstrating that, alongside climate change,
eliminating large carnivores is one of the most
significant anthropogenic impacts on nature (5).
Unlike climate change, however, large-carnivore
conservation has yet to become a focus of wide-
spread public recognition, possibly because they
are rare, remote, and in some cases perceived to
be dangerous and a threat to economic prosperity.
The formation of a GLCI would be an important
step for the advancement of international public
recognition of the ecological role and inherent
value of large carnivores, and for developing and
coordinating strategies for conservation actions
that promote human/large-carnivore coexistence.
Such an organization could be modeled, in part,
after the Global Tiger Initiative, which is coor-
dinating local, national, and international tiger
conservation policy across their distribution and
was endorsed in 2010 by the leaders of all 13
tiger-range countries, with funding from the World
Bank (87). These 13 countries and partners have
moved well beyond words to accomplishments on
the ground, including securing funding, establish-
ing new tiger reserves, passing laws on tiger con-
servation, creating high-level commissions to
improve wildlife law enforcement, addressing
habitat loss and fragmentation, promoting con-
nectivity, and more (87). The success of any fu-
ture GLCI would probably include these types
of authoritative actions, orchestrated by politi-
cally bold commitments from nations around
the world.
A Final Word
One of the main ecological arguments for the
conservation of large carnivores is that they are
often capable of exerting strong regulatory effects
on ecosystems (5,15). Although we present evi-
dence that seven of the top carnivore species we
reviewed here have such trophic effects, we know
much less about the trophic impacts of the 24
other species of large carnivores. More research
directed at these species is needed. Also, we need
a better understanding of minimum required den-
sities for large carnivores to maintain trophic
cascades in different ecosystems, and when and
where the strength of those effects is likely to be
large versus small. It is also important to under-
stand which human activities are most in conflict
with the conservation of specific large carnivores.
A crucial societal challenge is finding creative
solutions to maintain viable populations of large
carnivores in the face of alternative land uses
(7,59). This is most urgent because global live-
stock production continues to encroach on land
needed by large carnivores, particularly in the de-
veloping world, where livestock production tri-
pled between 1980 and 2002 (88). If the world
continues to transition into one that replaces top
carnivores with livestock and mesopredators, it is
incumbent on us to understand more about the
ecological effects of such a downward ratcheting
on ecosystems. More large and livestock-free
protected areas are needed, especially in regions
such as southeastern Asia, where large-carnivore
richness (Fig. 5) remains the highest in the world.
Yet even in these regions, carnivore populations
are decreasing (Table 1) and few large reserves
exist (fig. S3). More protected areas alone will
not be sufficient, so strategies are also needed to
facilitate human coexistence with these animals
across working landscapes (59).
Large-carnivore conservation might best be
served by a two-pronged approach. First, there is
a need for increased recognition of and focus on
conserving the full range of the potential effects
provided by large carnivores, because this may
lead to broader biodiversity, as well as social and
economic benefits (5,15,89). In areas where large
carnivores have been displaced or locally extir-
pated, their reintroduction may represent a par-
ticularly effective approach for passively restoring
those ecosystems. However, harnessing the pos-
itive effects of large carnivores while (i) mini-
mizing their impacts on humans and (ii) getting
humans to adapt to large-carnivore presence, rep-
resents a major sociopolitical challenge. Biodi-
versity conservation programs intended to retain
or reintroduce large carnivores must ultimately
address both of these challenges if they are to
succeed. Second, large-carnivore conservation
might also be seen as a moral obligation—the
recognition of the intrinsic value of all species. A
40-year history of the field of environmental
ethics has both rigorous and systematic ratio-
nales for valuing species and nature itself. Large-
carnivore conservation, therefore, might benefit
greatly from a more formal relationship with prac-
titioners of environmental ethics. It will probably
take a change in both human attitudes and actions
to avoid imminent large-carnivore extinctions. A
future for these carnivore species and their con-
tinued effects on planet Earth’s ecosystems may
depend upon it.
References and Notes
1. L. Hunter, Carnivores of the World (Princeton Univ. Press,
Princeton, NJ, 2011).
2. G. Ceballos, P. R. Ehrlich, Mammal population losses and
the extinction crisis. Science 296, 904–907 (2002).
doi: 10.1126/science.1069349; pmid: 11988573
3. J. C. Morrison, W. Sechrest, E. Dinerstein, D. S. Wilcove,
J. F. Lamoreux, Persistence of large mammal faunas as
indicators of global human impacts. J. Mammal. 88,
1363–1380 (2007). doi: 10.1644/06-MAMM-A-124R2.1
4. L. R. Prugh et al., The rise of the mesopredator.
Bioscience 59, 779–791 (2009). doi: 10.1525/
bio.2009.59.9.9
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Acknowledgments: We thank S. Arbogast, J. Batchelor,
A. Cloud, R. Comforto, A. Comstock, T. Newsome, L. Painter,
L. Petracca, and C. Wolf for assisting in this project.
Supplementary Materials
www.sciencemag.org/content/343/6167/1241484/suppl/DC1
Figs. S1 to S4
Tables S1 to S3
10.1126/science.1241484
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