The Status of the World's Land and Marine Mammals: Diversity, Threat, and Knowledge

Abstract

Knowledge of mammalian diversity is still surprisingly disparate, both regionally and taxonomically. Here, we present a comprehensive
assessment of the conservation status and distribution of the world's mammals. Data, compiled by 1700+ experts, cover all 5487 species, including marine mammals. Global macroecological patterns are very different for land and marine species but suggest common mechanisms driving diversity and endemism across systems. Compared with land species, threat levels are higher among marine mammals, driven by different processes (accidental mortality and pollution, rather than habitat loss), and are spatially distinct (peaking in northern oceans, rather than in Southeast Asia). Marine mammals are also disproportionately poorly known. These data are made freely available to support further scientific developments and conservation action.

Full text

DOI: 10.1126/science.1165115
, 225 (2008); 322Science
et al.Jan Schipper,
Mammals: Diversity, Threat, and Knowledge
The Status of the World's Land and Marine
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The Status of the World’s Land
and Marine Mammals: Diversity,
Threat, and Knowledge
Jan Schipper,
1,2
* Janice S. Chanson,
1,2
Federica Chiozza,
3
Neil A. Cox,
1,2
Michael Hoffmann,
1,2
Vineet Katariya,
1
John Lamoreux,
1,4
AnaS.L.Rodrigues,
5,6
Simon N. Stuart,
1,2
Helen J. Temple,
7
Jonathan Baillie,
8
Luigi Boitani,
3
Thomas E. Lacher Jr.,
2,4
Russell A. Mittermeier,
2
Andrew T. Smith,
9
Daniel Absolon,
10
John M. Aguiar,
2,4
Giovanni Amori,
11
Noura Bakkour,
2,12
Ricardo Baldi,
13,14
Richard J. Berridge,
15
Jon Bielby,
8,16
Patricia Ann Black,
17
J. Julian Blanc,
18
Thomas M. Brooks,
2,19,20
James A. Burton,
21,22
Thomas M. Butynski,
23,24
Gianluca Catullo,
25
Roselle Chapman,
26
Zoe Cokeliss,
8
Ben Collen,
8
Jim Conroy,
27
Justin G. Cooke,
28
Gustavo A. B. da Fonseca,
29,30
Andrew E. Derocher,
31
Holly T. Dublin,
32
J. W. Duckworth,
33
Louise Emmons,
34
Richard H. Emslie,
35
Marco Festa-Bianchet,
36
Matt Foster,
2
Sabrina Foster,
37
David L. Garshelis,
38
Cormack Gates,
39
Mariano Gimenez-Dixon,
40
Susana Gonzalez,
41
Jose Fernando Gonzalez-Maya,
42
Tatjana C. Good,
43
Geoffrey Hammerson,
44
Philip S. Hammond,
45
David Happold,
46
Meredith Happold,
46
John Hare,
47
Richard B. Harris,
48
Clare E. Hawkins,
49,50
Mandy Haywood,
51
Lawrence R. Heaney,
52
Simon Hedges,
33
Kristofer M. Helgen,
34
Craig Hilton-Taylor,
7
Syed Ainul Hussain,
53
Nobuo Ishii,
54
Thomas A. Jefferson,
55
Richard K. B. Jenkins,
56,57
Charlotte H. Johnston,
9
Mark Keith,
58
Jonathan Kingdon,
59
David H. Knox,
60
Kit M. Kovacs,
61,62
Penny Langhammer,
9
Kristin Leus,
63
Rebecca Lewison,
64
Gabriela Lichtenstein,
65
Lloyd F. Lowry,
66
Zoe Macavoy,
16
Georgina M. Mace,
16
David P. Mallon,
67
Monica Masi,
25
Meghan W. McKnight,
68
Rodrigo A. Medellín,
69
Patricia Medici,
70,71
Gus Mills,
72
Patricia D. Moehlman,
73
Sanjay Molur,
74,75
Arturo Mora,
76
Kristin Nowell,
77
John F. Oates,
78
Wanda Olech,
79
William R. L. Oliver,
80
Monik Oprea,
34
Bruce D. Patterson,
52
William F. Perrin,
55
Beth A. Polidoro,
1
Caroline Pollock,
7
Abigail Powel,
81
Yelizaveta Protas,
82
Paul Racey,
56
Jim Ragle,
1
Pavithra Ramani,
37
Galen Rathbun,
83
Randall R. Reeves,
84
Stephen B. Reilly,
55
John E. Reynolds III,
85
Carlo Rondinini,
3
Ruth Grace Rosell-Ambal,
86
Monica Rulli,
25
Anthony B. Rylands,
2
Simona Savini,
25
Cody J. Schank,
37
Wes Sechrest,
37
Caryn Self-Sullivan,
87
Alan Shoemaker,
88
Claudio Sillero-Zubiri,
89
Naamal De Silva,
2
David E. Smith,
37
Chelmala Srinivasulu,
90
Peter J. Stephenson,
91
Nico van Strien,
92
Bibhab Kumar Talukdar,
93
Barbara L. Taylor,
55
Rob Timmins,
94
Diego G. Tirira,
95
Marcelo F. Tognelli,
96,97
Katerina Tsytsulina,
98
Liza M. Veiga,
99
Jean-Christophe Vié,
1
Elizabeth A. Williamson,
100
Sarah A. Wyatt,
2
Yan Xie,
101
Bruce E. Young
44
Knowledge of mammalian diversity is still surprisingly disparate, both regionally and
taxonomically. Here, we present a comprehensive assessment of the conservation status and
distribution of the world’s mammals. Data, compiled by 1700+ experts, cover all 5487 species,
including marine mammals. Global macroecological patterns are very different for land and marine
species but suggest common mechanisms driving diversity and endemism across systems.
Compared with land species, threat levels are higher among marine mammals, driven by different
processes (accidental mortality and pollution, rather than habitat loss), and are spatially distinct
(peaking in northern oceans, rather than in Southeast Asia). Marine mammals are also
disproportionately poorly known. These data are made freely available to support further scientific
developments and conservation action.
M
ammals play key roles in ecosystems
(e.g., grazing, predation, and seed dis-
persal) and provide important benefits
to humans (e.g., food, recreation, and income),
yet our understanding of them is still surpris-
ingly patchy (1). An assessment of the conser-
vation status of all known mammals was last
undertaken by the International Union for Con-
servation of Nature (IUCN) in 1996 (2). These
IUCN Red List classifications of extinction risk
(fig. S1) for mammals have been used in nu-
merous studies, including the identification of
traits associated with high extinction risk (3, 4),
and prioritization of species for conservation
action (5). However , the 1996 assessment was
based on categories and criteria that have now
been superseded, and the assessments are of-
ficially outdated for about 3300 mammals never
assessed since. Previously compiled global dis-
tribution maps for terrestrial mammals (6, 7)
have been used in a variety of analyses, including
recommending global conservation priorities
(7–9), and analyzing the coverage of protected
areas (10). However, nearly 700 currently recog-
nized species, including marine mammals, were
not covered in previously published analyses.
Here, we present the results of the most com-
prehensive assessment to date of the conservation
status and distribution of the world’s mammals,
covering all 5487 wild species recognized as
extant since 1500. This 5-year, IUCN-led col-
laborative effort of more than 1700 experts in
130 countries compiled detailed information on
species’ taxono my, distribu tion, habitats, and pop-
ulation trends, as well as the threats to, human
use of, ecology of, and conservation measures for
these species. All data are freely available for
consultation and downloading (11).
Diversity. Mammals occupy most of the
Earth’s habitats. As in previous studies (8, 12),
we found that land species (i.e., terrestrial,
including volant, and freshwater) have particularly
high levels of species richness in the Andes and
in Afromontane regions in Africa, such as the
Albertine Rift. We also found high species
richness in Asia, most noticeably in the
Hengduan mountains of southwestern China,
peninsular Malaysia, and Borneo (Fig. 1A). The
ranges of many large mammals have recently
contracted substantially in tropical Asia (13), so
local diversity was once undoubtedly even
higher . Overall, the species richness pattern for
land mammals is similar to that found for birds
and amphibians (12), which s uggests that
diversity is similarly driven by energy avail-
ability and topographic complexity (14, 15).
Marine mammals concentrate in tropical and
temperate coastal platforms, as well as in off-
shore areas in the Tasman and Caribbean seas,
east of Japan and New Zealand and west of Cen-
tral America, and in the southern Indian Ocean.
As with land species, marine richness seems to
be associated with primary productivity: Where-
as land species’ richness peaks toward the
equator, marine richness peaks at around 40° N
and S (16) (fig. S4), corresponding to belts of
high oceanic productivity (17). An interesting
exception is the low species richness in the high-
ly productive North Atlantic Ocean (17). Only
one species’ extinction [Sea Mink, Neovison
macrodon (18) ] and one extirpation [Gray Whale,
Eschrichtius robustus (19)] are recorded from
this region, yet evidence for many local extinc-
tions comes from historical records of species
exploitation where they no longer occur ([e.g.,
Harp Seal, Phoca groenlandica, in the Baltic
Sea (20); Bowhead Whale, Balaena mysticetus,
off Labrador (21); Walrus, Odobenus rosmar us,
in Nova Scotia (22)]. Past human exploitation
may therefore have depleted natural species
richness in the North Atlantic—as it probably
did with land mammals in Australia (23) and
the Caribbean (24).
Phylogenetic diversity is a measure that takes
account of phylogenetic relationships (and hence,
evolutionary history) between taxa (16, 25)(fig.
S3). It is arguably a more relevant currency of
diversity and less affected by variations in taxo-
RESEARCH ARTICLES
www.sciencemag.org SCIENCE VOL 322 10 OCTOBER 2008 225
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nomic classification than species richness. Spe-
cies richness (Fig. 1A) and phylogenetic diversity
(Fig. 1B) are very closely related for land spe-
cies (r
2
= 0.98) (fig. S5), but less so in the ma-
rine environment (r
2
= 0.73). Disproportionately
high phylogenetic diversity in the southern oceans
suggests that either species here are less related
than elsewhere, or that current species may in
fact be poorly known complexes of multiple spe-
cies, with new species awaiting discovery (con-
sistent with the poor species knowledge in this
area, see below).
The size of land species’ ranges varies from
a few hundred square meters (Bramble Cay
Melomys, Melomys rubicola; Australia), to 64.7
million km
2
(Red Fox, Vulpes vulpes;Eurasia
and North America). For marine species, ranges
vary from 16,500 km
2
(Vaquita, Phocoena sinus;
Gulf of California), to 350 million km
2
(Killer
Whale, Orcinus orca; all oceans). Despite these
extremes, most species have small ranges (fig.
S6): Most land taxa occupy areas smaller than
the UK, and the range of most marine mam-
mals is smaller than one-fifth of the Indian Ocean
(fig. S6).
Among land mammals, restricted-range spe-
cies (those 25% of species with the smallest
ranges) are concentrated on highly diverse is-
lands (e.g. , Madagascar , Sri Lanka, and Sulawesi)
and tropical mountain systems (e.g., Andes,
Cameroonian, and Ethiopian Highlands) (Fig.
1C). Marine restricted-range species are al-
most entirely found around continental plat-
forms, particularly in the highly productive
waters off the Southern Cone of South Amer-
ica (Fig. 1C) (17). Both land and marine patterns
of endemism are thus apparently associated
with highly productive areas subject to strong
environmental gradients (altitudinal in land;
depth in marine).
A different perspective on patterns of spe-
cies’ endemism is obtained by mapping global
variation in median range size (Fig. 1D). For land
species, there is a strong association between
landmass width and median range size: The
1
International Union for Conservation of Nature (IUCN)
Species Programme, IUCN, 28 Rue Mauverney, 1196 Gland,
Switzerland.
2
Center for Applied Biodiversity Science, Con-
servation International, 2011 Crystal Drive, Arlington, VA
22202, USA.
3
Department of Animal and Human Biology,
Sapienza Università di Roma, Viale dell'Università 32, 00185
Roma, Italy.
4
Department of Wildlife and Fisheries Sciences,
Texas A&M University, College Station, TX 77843, USA.
5
Department of Zoology, University of Cambridge, Cambridge,
CB2 3EJ, UK.
6
Environment and Energy Section, Mechanical
Engineering Department, Instituto Superior Técnico, Portugal.
7
IUCN Species Programme, 219c Huntingdon Road, Cambridge,
CB3 0DL, UK.
8
Institute of Zoology, Zoologi cal Society of London,
Regent's Park, London, NW1 4RY, UK.
9
School of Life
Sciences, Arizona State University, Post Office Box 874501,
Tempe, AZ 85287, USA.
10
62 Bradford Road, Combe Down,
Bath, BA2 5BY, UK.
11
CNR–Institut e for Ecosystem Studies,
Consiglio Nazionale Delle Ricerche, Via A. Borelli, 50, 00161
Rome, Italy.
12
Department of Environmental Science and
Policy, School of International and Public Affairs, Columbia
University, 420 West 118th Street, New York, NY 10027,
USA.
13
Centro Nacional Patagónico, Consejo Nacional de
Investigaciones Científicas y Técnicas (CONICET), 9120 Puerto
Madryn, Argentina.
14
Patagonian and Andean Steppe Program,
Wildlife Conservation Society, Boulevard Brown 2825, 9120
Puerto Madryn, Argentina.
15
Mantella-Con servation.o rg, 75
Plover Way, London, SE16 7TS, UK.
16
Centre for Population
Biology, Imperial College London, Silwood Park, Ascot,
Berkshire, SL5 7PY, UK.
17
Facultad de Ciencias Naturales e
Instituto Miguel Lillo, Miguel Lillo 205, 4000 Tucumán, Ar-
gentina.
18
The Convention on International Trade in En-
dangered Species of Wild Fauna and Flora (CITES), MIKE–
Monitoring the Illegal Killing of Elephants, Post Office Box
47074, Nairobi, 00100, Kenya.
19
World Agroforestry Center
(ICRAF), University of the Philippines, Los Baños, Laguna 4031,
Philippines.
20
University of Tasmania, Hobart, Tasmania 7001,
Australia.
21
Earthwatch Institute (Europe), 256 Banbury Road,
Oxford, OX2 7DE, UK.
22
Veterinary Biomedical Sciences, The
Royal (Dick) School of Veterinary Studies, The University
of Edinburgh, Edinburgh, EH25 9RG, Scotland.
23
Eastern
Africa Primate Diversity and Conservation Program, Post
Office Box 149, 10400 Nanyuki, Kenya.
24
Department of
Bioscience and Biotechnology, Drexel University, Philadel-
phia, PA 19104, USA.
25
Istituto di Ecologia Applicata, via
Arezzo 29, 00162 Rome, Italy.
26
23 High Street, Watlington,
Oxfordshire, OX49 5PZ, UK.
27
Celtic Environment Ltd, 10 Old
Mart Road, Torphins, Banchory, Kincardineshire, AB31 4JG,
UK.
28
Centre for Ecosystem Management Studies, Mooshof
1a, 79297 Winden, Germany.
29
Global Environment Facility,
1818 H Street NW, G 6-602, Washington, DC 20433, USA.
30
Department of Zoology, Federal University of Minas Gerais,
31270-901 Belo Horizonte, MG, Brazil.
31
Department of
Biological Sciences, University of Alberta, Edmonton, Alberta
T6G 2E9, Canada.
32
IUCN Species Survival Commission, c/o
South African National Biodiversity Institute, Centre for
Biodiversity Conservation, Private Bag X7, Claremont 7735,
Cape Town, South Africa.
33
Wildlife Conservation Society–Asia
Programs, Wildlife Conservation Society, Bronx, NY 10460,
USA.
34
Department of Vertebrate Zoology, Division of Mam-
mals, National Museum of Natural History, Smithsonian In-
stitution, Washington, DC, 20013, USA.
35
IUCN SSC (Species
Survival Commission), African Rhino Specialist Group, Box
1212, Hilton 3245, South Africa.
36
Département de biologie,
Université de Sherbrooke, Sherbrooke, Québec J1K 2R1,
Canada.
37
Department of Environmental Sciences, University
of Virginia, Charlottesville, VA 22904, USA.
38
Minnesota De-
partment of Natural Resources, 1201 East Highway 2, Grand
Rapids, MN 55744, USA.
39
Environmental Science Depart-
ment, University of Calgary, Calgary, AB T2N 1N4, Canada
40
Chemin de la Perroude 2 B, CH-1196 Gland, Switzerland.
41
Genética de la Conservación–IIBCE-Facultad de Ciencias,
Avenida Italia 3318, Montevideo, 11600, Uruguay.
42
ProCAT
International, Las Alturas, Coto Brus, Costa Rica.
43
Australian
Research Council, Centre of Excellence for Coral Reef Studies,
James Cook University, Townsville, Queensland 4811, Aus-
tralia.
44
NatureServe, 1101 Wilson Boulevard, 15th Floor,
Arlington, VA 22209, USA.
45
Sea Mammal Research Unit,
Gatty Marine Laboratory, University of St. Andrews, St.
Andrews, Fife, KY16 8LB, UK.
46
Australian National Uni-
versity, Canberra, Australian Capital Territory 0200, Australia.
47
Wild Camel Protection Foundation, School Farm, Benenden,
Kent, TN17 4EU, UK.
48
Department of Ecosystem and Conser-
vation Sciences, University of Montana, Missoula, MT 59812,
USA.
49
Threatened Species Section, Department of Primary
Industries & Water, General Post Office Box 44, Hobart,
Tasmania 7001, Australia.
50
School of Zoology, University of
Tasmania,PrivateBag5,Hobart,Tasmania7001,Australia.
51
The Centre for Science Communication, Natural History
Filmmaking, 303 Great King Street, University of Otago,
Dunedin, 9054, New Zealand.
52
Department of Zoology, Field
Museum of Natural History, 1400 South Lake Shore Drive,
Chicago, IL 60605, USA.
53
Wildlife Institute of India, Post Box
18, Dehra Dun, 248 001, India.
54
Tokyo Woman's Christian
University, 2-6-1 Zempukuji, Suginami-ku, Tokyo, 167-8585,
Japan.
55
Southwest Fisheries Science Center, National Oceanic
and Atmospheric Administration Fisheries, 8604 La Jolla Shores
Drive, La Jolla, CA 92037, USA.
56
School of Biological Sciences,
University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24
2TZ, UK.
57
Madagasikara Voakajy, Boite Postale 5181,
Antananarivo (101), Madagascar.
58
Animal, Plant and Environ-
mental Sciences, University of the Witwatersrand, Johannesburg
2050, South Africa.
59
Department of Zoology, University of
Oxford, The Tinbergen Building, South Parks Road, Oxford, OX1
3PS, UK.
60
Conservation International, Private Bag X7, 7735,
Claremont, South Africa.
61
Norwegian Polar Institute, 9296
Tromsø, Norway.
62
TheUniversityCentreinSvalbard,9171
Longyearbyen, Norway.
63
Copenhagen Zoo and Conservation
Breeding Specialist Group–European Regional Office, p/a An-
nuntiatenstraat 6, 2170 Merksem, Belgium.
64
Biology De-
partment, San Diego State University, 5500 Campanile
Road, San Diego, CA 92182, USA.
65
Instituto Nacional de
Antropologia y Pensamiento Latinoamericano, 3 de Febrero
1378 (1426), Buenos Aires, Argentina.
66
School of Fisheries and
Ocean Sciences, University of Alaska, Fairbanks, AK 99701, USA.
67
Department of Biological Sciences, Manchester Metropolitan
University, Manchester, M1 5GD, UK.
68
Nicolás Ruiz No. 100,
Barrio de Guadalupe, San Cristóbal de las Casas, CP 29230,
Chiapas, México.
69
Instituto de Ecología, Universidad Nacional
Autónoma de México, Apartado Postal 70-275, 04510 Ciudad
Universitaria, D.F., México.
70
Lowland Tapir Conservation Ini-
tiative, IPE
^
–Instituto de Pesquisas Ecoló gicas (Institute for
Ecological Research), Caixa Postal 47, Nazaré Paulista, CEP
12960-000, São Paulo, Brazil.
71
Durrell Institute of Conserva-
tion and Ecology (DICE), University of Kent, Kent, UK.
72
The
Tony and Lisette Lewis Foundation, 305 Hyde Park Corner,
Hyde Park, Sandton 2196, South Africa.
73
Wildlife Trust
Alliance, 460 West 34th Street, New York, NY 10001, USA.
74
Zoo Outreach Organisation, Box 1683, 9A, Gopal Nagar, Lal
Bahadur Colony Peelamedu, Coimbatore – 641 004 Tamil
Nadu, India.
75
Wildlife Information & Liaison Development
Society, 9A Lal Bahadur Colony, Peelamedu, Coimbatore,
Tamil Nadu 641004, India.
76
Species Unit, IUCN South America
Regional Office, Calle Quiteño Libre E 15–12 y la Cumbre,
Quito, Pichincha, Ecuador.
77
Cat Action Treasury, Post Office
Box 332, Cape Neddick, ME 03902, USA.
78
Department of
Anthropology, Hunter College of the City University of New
York, New York, NY 10065, USA.
79
Warsaw University of Life
Sciences, 02-787 Warsaw, Poland.
80
Philippine Biodiversity
Conservation Programme, Fauna & Flora International, 3A
Star Pavilion Apartments, 519 Alonso Street, Malate, Manila
1004, Philippines.
81
Victoria University of Wellington, Well-
ington 6140, New Zealand.
82
Department of Ecology, Evo-
lution, and Environmental Biology, Columbia University, 10th
Floor Schermerhorn Extension, MC 5557, 1200 Amsterdam
Avenue, New York, NY 10027, USA.
83
Department of Orni-
thology and Mammalogy, California Academy of Sciences (San
Francisco), Post Office Box 202, Cambria, CA 93428, USA.
84
Okapi Wildlife Associates, 27 Chandler Lane, Hudson,
Quebec, J0P 1H0, Canada.
85
Mote Marine Laboratory, 1600
Ken Thompson Parkway, Sarasota, FL 34236, USA.
86
Conserva-
tion International (CI)-Philippines, 6 Maalalahanin Street,
Teacher’s Village, Diliman, Quezon City 1101, Philippines.
87
Sirenian International, 200 Stonewall Drive, Fredericksburg,
VA 22401, USA.
88
IUCN Tapir Specialist Group, 330 Shareditch
Road, Columbia, SC 29210, USA.
89
Wildlife Conservation Re-
search Unit, Zoology Department, University of Oxford, Tubney
House, Tubney OX13 5QL, UK.
90
Department of Zoology,
University College of Science, Osmania University, Hyderabad,
Andhra Pradesh – 500 007, India.
91
WWF International, Ave-
nue du Mont Blanc, CH-1196 Gland, Switzerland.
92
Interna-
tional Rhino Foundation, c/o White Oak Conservation Center
581705 White Oak Road, Yulee, FL 32097, USA.
93
Aaranyak,
50 Samanwoy Path (Survey), Post Office Beltola, Guwhati – 781
028, Assam, India.
94
2313 Willard Avenue, Madison, WI
53704, USA.
95
Fundación Mamíferos y Conservación, Post Of-
fice Box 17-23-055, Quito, Ecuador.
96
IADIZA (The Argentinean
Arid Research Institute) – CONICET, Center for Science &
Technology Mendoza, CC 507, 5500 – Mendoza, Argentina.
97
Department of Environmental Sciences & Policy, University
of California, Davis, Davis, CA 95616, USA.
98
Russian Bat Re-
search Group, Novocherksassky Prospect, 51-84, St. Petersburg
195196, Russia.
99
Zoology Department, Emílio Goeldi Mu-
seum, Avenida Perimetral, 1901, Terra Firme, Belém, Pará,
Brazil.
100
Department of Psychology, University of Stirling,
Stirling FK9 4LA, Scotland, UK.
101
Institute of Zoology, Chi-
nese Academy of Science, Datunlu, Chaoyang District,
Beijing, 100101, China.
*To whom correspondence should be addressed. E-mail:
jan.schipper@iucn.org
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largest ranges tend to be found across the wid est
part of each continent, particularly in northern
Eurasia, whereas islands (e.g., in Southeast Asia
and the Caribbean) and narrow continental areas
(e.g., southern North and South America) tend
to have narrowly distributed species. Superim-
posed on this general pattern, ranges also tend to
be small in topographically complex areas (e.g.,
the Rockies, Andes, and Himalayas). These re-
sults agree with those for birds, which suggest
that range sizes are constrained by the availability
of lan d are a wit hi n the climatic zones to which
species are adapted (14, 26). Among marine spe-
cies, small median range sizes are found around
the continental platforms, which also suggests that
steep environmental gradients (here, associated
with depth) determine species’ distributions.
However , the global marine pattern is dominated
by a latitudinal effect, with ranges generally de-
clining toward both poles (fig. S7), which may
reflect the latitudinal gradient in the overall
ocean area. As with previous studies (14, 26),
we found no support for the Rapoport rule (27)
that the sizes of species’ ranges increase with
latitude.
Threat. T wenty-five percent (n = 113 9) of
all mammals for which adequate data are
available (data sufficient) are threatened with
extinction (Table 1). The exact threat level is
unknown, as the status of 836 speci e s havin g
insufficient information for evaluation (Data-
Deficient species) is undetermined, but is some-
where between 21% (assuming no Data-Deficient
species threatened) and 36% (assuming all Data-
Deficient species threatened). The conservation
status of marine species is of particular concern,
with an estimated 36% (range, 23 to 61%) of
species threatened.
Critically Endangered species (n = 188)
(Table 1) face a very high probability of extinc-
tion. For 29 of them, it may already be too late:
Species like the Baiji (Lipotes vexillifer), flagged
as “Possibly Extinct,” have only a very small
chance of still persisting (28). For the 76 species
classified as Extinct (since 1500), no reasonable
evidence suggests that they still exist. Two Extinct
in the W ild species, Scimitar-horned Oryx (Oryx
dammah) and Père David’s Deer (Elaphurus
davidianus), persist only in captivity .
Species not classified as threatened are not
necessarily safe, and indeed, 323 mammals are
classified as “Near Threatened” (Table 1). Many
species have experienced large range and pop-
ulation declines in the past (e.g., Grey Wolf, Canis
lupus, and Brown Bear, Ursus arctos), which are
not accounted for in their current Red List status
(13). Moreover, 52% of all species for which
population trends are known are declining, includ-
ing 22% of those classifie d as of Least Concern.
These trends indicate that the overall conservation
status of mammals will likely deteriorate further
in the near future, unless appropriate conserva-
tion actions are put in place. On a positive note,
at least 5% of currently threatened species have
stable or increasing populations (e.g., European
Fig. 1. Global patterns of mammalian diversity, for land (terrestrial and freshwater, brown) and marine
(blue) living species, on a hexagonal grid (fig. S2). (A) Species richness. (B) Phylogenetic diversity (total
branch length of the phylogenetic tree representing those species in each cell in millions of years). (C)
Number of restricted-range species (those 25% species with the smallest ranges). (D)Medianrangesize
of species in each cell (in million km
2
).
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Bison, Bison bonasus, and Black-footed Ferret,
Mustela nigripes), which indicates that they are
recovering from past threats.
Among land mammals, threatened species
are concentrated in South and Southeast Asia
(Fig. 2A). Among primates, for example, a stag-
gering 79% (range, 76 to 80%) of species in this
region are threatened with extinction. Other peaks
of threat include the tropical Andes, Cameroonian
Highlands, Albertine Rift, and Western Ghats in
India, all regions combining high species rich-
ness (Fig. 1A), high endemism (Fig. 1, B and C),
andhighhumanpressure(29). Threatened ma-
rine species are concentrated in the North Atlantic,
the North Pacific, and Southeast Asia, areas of
high endemis m (Fig. 1C) and high human impact
(30). Low threat levels in the southern hemi-
sphere may reflect history—as these oceans be-
came heavily exploited much more recently—
and/or knowledge gaps (see below).
Worldwide, habitat loss and degradation (af-
fecting 40% of species assessed) and harvesting
(hunting or gathering for food, medicine, fuel,
and materials, which affect 17%) are by far the
main threats to mammals (table S2). Yet, the rela-
tive importance of different threats varies geo-
graphically and taxonomically (Fig. 2, B and C).
Among land species, habitat loss is prevalent
across the tropics, which coincides with areas of
high deforestation in the Americas, Africa, and
Asia (Fig. 2B) (31). Harvesting is having devas-
tating effects in Asia, but African and South
American species are also affected (Fig. 2C).
Harvesting affects large mammals (Cetartiodactyla,
Primates, Perissodactyla, Proboscidea, and Car-
nivora) disproportionately: 90% in Asia, 80% in
Africa, and 64% in the Neotropics (compared with
28, 15, and 11% of small mammals, respectively).
Among marine mammals, the dominant threat
is accidental mortality (which affects 78% of
species), particularly through fisheries by-catch
and vessel strike (table S2). Although coastal
areas are the most affected (Fig. 2D), accidental
mortality also threatens species in off-shore wa-
ters (e.g., from purse seines in the eastern trop-
ical Pacific). Pollution (60% of species) is the
second most prevalent threat (Fig. 2E), but this
designation includes a diversity of mechanisms,
such as chemical contaminants, marine debris,
noise, and climate change. Sound pollution (mil-
itary sonar) has been implicated in mass strand-
ings of cetaceans (32), and climate change is
already impacting sea ice–dependent species
(e.g., Polar Bear , Ursus maritimus,andHarp
Seal, Pagophilus groenlandicus). Despite pro-
gress through international agreements, harvest-
ing remains a major threat for marine mammals
(52% of species).
Disease affects relatively few mammals
(2%), but it has led to catastrophic declines in
some, most dramatically the Tasmanian Devil
(Sarcophilus harrisii) on account of facial tu-
mor disease (33).
Threat levels are not uniform across mam-
malian groups (Fig. 3 and table S1). Those with
disproportionately high incidence of threatene d
or extinct species include tapirs (T apiridae), hip-
pos (Hippopotamidae), tarsiers (Tarsiidae),
bears (Ursidae) , pot oroids (Potoroidae), pigs
and hogs (Suidae), and golden moles (Chryso-
chloridae). Families less threatened than expected
include moles (T alpidae), dipodids (Dipodidae),
oposs ums (Didelphidae), and free-tailed bats
(Molossidae).
A positive association has been reported
between body size and threat among mam-
mals (3, 4), and indeed, we found that the most
threatened families are dominated by large spe-
cies, such as primates and ungulates, whereas
the least threatened include small mammals,
such as rodents and bats. Larger species tend
to have lower population densities, slower life
histories, and larger home ranges and are more
likely to be hunted—factors that put them at
greater risk (4). For smaller mammals, mostly
threatened by habitat loss (34), conservation
status is mainly determined by range size and
location (4). However, some families of small
mammals (e.g., golden moles) are also highly
threatened (Fig. 3). Furthermore, although large
mammals have a significantly higher fraction of
threatened or extinct species (c
2
≈ 0; P <
0.0001), large and small mammals have suffered
similar levels of extinction (c
2
= 0.74; not sig-
nificant) (34).
Knowledge. Although mammals are among
the best-known organisms, they are still being
discovered at surprisingly high rates (1). The
number of recognized species has increased by
19% since 1992 (fig. S8) and includes 349 newly
described species and 512 taxa that were elevated
to species level. The spatial pattern of new
species description (Fig. 4A) reflects the interac-
tion between the local state of knowledge and
taxonomic effort. Peaks in Madagascar and the
Amazon result from relatively high, recent taxo-
nomic activity in these poorly known areas, where-
as the lack of new species in Africa (particularly
in the poorly surveyed Congo Basin) may reflect
more limited efforts there.
Newly described mammals are generally poo r-
ly known (44% are Data Deficient; 13% for pre-
1992 species) and disproportionately threatened
[51% (29 to 73%); pre-1992 species: 23% (20
to 33%)]. These factors reinforce the concern
that species may be vanishing even before they
are known to science.
Newly described species have been named in
areas where knowledge has increased in the re-
cent past (Fig. 4A), whereas Data-Deficient spe-
cies are concentrated in regions in need of future
research (Fig. 4B). Most Data-Deficient species
on land are in tropical forests (Fig. 4B), which
reflects species’ richness patterns (Fig. 1A); in
regions where these forests are vanishing very
rapidly (e.g., Atlantic Forest, W est Africa, Borneo)
(31), many Data-Deficient species may be dan-
gerously close to extinction.
Marine species are less well studied than land
mammals, with 38% Data Deficient (T able 1).
Species that breed on land tend to be better un-
derstood, but whales, dolphins, porpoises, and
sirenians are so difficult to survey that declines
that should result in a V ulnerable listing would
go undetected at least 70% of the time (35). Ma-
rine Data-Deficient species are particularly con-
centrated along the Antarctic Convergence (Fig.
4B), largely driven by the beaked whales, 19 of
which are Data Deficient. A relative absence of
Data-Deficient species in the northern Atlantic
and Pacific Oceans may reflect higher research
effort and expertise—as well as a longer history
of exploitation.
Conclusion. Our results paint a bleak picture
of the global status of mammals worldwide. W e
estimate that one in four species is threatened
with extinction and that the population of one in
Table 1. Number of species in each IUCN Red List category and threat level for all mammals, and for land
and marine species. Categories: EX, Extinct; EW, Extinct in the Wild; CR, Critically Endangered; EN,
Endangered; VU, Vulnerable; NR, Near Threatened; LC, Least Concern; DD, Data Deficient. Threat level =
[(VU+EN+CR)/(Total – DD)] × 100. The range is between [(VU+EN+CR)/Total] × 100 and [(VU+EN+CR+DD)/
Total] × 100. NA, not applicable because they are not mapped.
Total and Red List category
Mammal species by habitat
All Land Marine
Number of species (% of total)
Total 5487 5282 120
EX 76 (1.4) NA NA
EW 2 (0.04) NA NA
CR 188 (3.4) 185 (3.5) 3 (2.5)
EN 448 (8.2) 436 (8.3) 12 (10.0)
VU 505 (9.2) 497 (9.4) 12 (10.0)
NT 323 (5.9) 316 (6.0) 7 (5.8)
LC 3109 (56.7) 3071 (58.1) 40 (33.3)
DD 836 (15.2) 777 (14.7) 46 (38.3)
Threat level (%)
Threat level
(range)
25
(21 to 36)
25
(21 to 36)
36
(23 to 61)
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two is declining. The situation is particularly se-
rious for land mammals in Asia, through the com-
bined effects of overharvesting and habitat loss,
and for marine species, victims of our increas-
ingly intensive use of the oceans. Yet, more than
simply reporting on the depressing status of the
world’s mammals, these Red List data can and
should be used to inform strategies for ad-
dressing this crisis (36), for example to identify
priority species (5) and areas (8, 10) for con-
servation. Further , these data can be used to
indicate trends in conservation status over time
(37). Despite a general deterioration in the status
of mammals, our data also show that species
recoveries are possible through targeted conser-
vation efforts.
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Materials and Methods
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26 August 2008; accepted 16 September 2008
10.1126/science.1165115
Fig. 3. Threat status of each mam-
malian family in relation to overall
threat levels across all mammals (dashed
line, 26%). Each family represented
by a dot, indicating the percentage of
threatened or extinct species, in rela-
tion to the total number of data suffi-
cient species in the family. Colored
bands indicate significance levels (one-
tailed binomial test). Families 1 to 25
have threat levels significantly (P <
0.01) different from expected (between
brackets, number of threatened or ex-
tinct species/number of data sufficient
species).
Fig. 4. Global patterns of knowledge, for land (terrestrial and freshwater, brown) and marine (blue)
species. (A) Number of species newly described since 1992. (B) Dat a-Defici ent species.
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