Nature © Macmillan Publishers Ltd 1997
letters to nature
3 JULY 1997 61
12. Kutzbach, J. E. & Guetter, P. J. The inﬂuence of changing orbital patterns and surface boundary
conditions on climate simulations for the past 18,000 years. J. Atmos. Sci. 43, 1726–1759 (1986).
13. Hall, N. M. J., Valdes, P. J. & Dong, B. The maintenance of the last great ice sheets: a UGAMP GCM
study. J. Clim. 9, 1004–1009 (1996).
14. Barnosky, C. W. A record of late-Quaternary vegetation from the southwestern Columbia Basin,
Washington. Quat. Res. 23, 109–122 (1985).
15. Sarna-Wojcicki, A. J. in Late Quaternary Environments of the United States Vol. 2 (ed. Wright, H. E. Jr)
52–77 (Univ. Minnesota, Minneapolis, 1983).
16. Berger, G. W. & Busacca, A. J. Thermoluminescence dating of Late Pleistocene loess and tephra from
eastern Washington and southern Oregon and implications for the eruptive history of Mount St.
Helens. J. Geophys. Res. 100, 22361–22374 (1995).
17. Grimm, E. C. in Vegetation History (eds Huntley, B. & Webb, T.) 53–76 (Kluwer, Dordrecht, 1988).
18. Martinson, D. G. et al. Age dating and the orbital theory of the ice ages: development of a high
resolution 0 to 300,000-year chronostratigraphy. Quat. Res. 27, 1–29 (1987).
19. Mack, R. N. & Bryant, V. M. Jr Modern pollen spectra from the Columbia Basin, Washington.
Northwest Sci. 48, 183–194 (1974).
20. Franklin, J. F. & Dyrness, C. T. Natural Vegetation of Oregon and Washington (Oregon State Univ.,
21. Bond, G. et al. Correlations between climate records from North Atlantic sediments and Greenland
ice. Nature 365, 143–147 (1993).
22. Imbrie, J. et al.inMilankovitch and Climate (eds Berger, A., Imbrie, J., Hays, J., Kukla, G. & Saltzman,
B.) 269–305 (Reidel, Dordrecht, 1984).
23. Berger, A. & Loutre, M. F. Insolation values for the last 10 million years. Quat. Sci. Rev. 10, 297–317
24. Greenland Ice-core Project (GRIP) Members. Climate instability during the last interglacial period
recorded in the GRIP ice core. Nature 364, 203–207 (1993).
25. Thouveny, N. et al. Climate variations in Europe over the past 140 kyr deduced from rock magnetism.
Nature 371, 503–506 (1994).
26. Morley, J. J., Pisias, N. G. & Leinen, M. Late Pleistocene time series of atmospheric and oceanic
variables recorded in sediments from the subarctic Paciﬁc. Paleoceanography 2, 49–62 (1987).
27. Stuiver, M. & Reimer, P. J. Extended
C data base and revised CALIB 3.0
C age calibration program.
Radiocarbon 35, 215–230 (1993).
28. Bard, E., Hamelin, B., Fairbanks, R. G. & Zindler, A. Calibration of the
C timescale over the past
30,000 years using mass spectrometric U-Th ages from Barbados corals. Nature 345, 405–410 (1990).
29. Mazaud, A., Laj, C., Bard, E., Arnold, M. & Tric, A. E. Geomagnetic ﬁeld control of
over the last 80kyr: implications for the radiocarbon time-scale. Geophys. Res. Lett. 18, 1885–1888 (1991).
30. Cleveland, W. S. Visualizing Data (Hobard, Summit, 1993).
Acknowledgements. We thank A. Sarna-Wojcicki for tephra identiﬁcations, R. J. Nickmann for help with
the pollen analysis, and J. Guiot and R. E. Gresswell for reviews. The work was supported by the NSF and
the Westinghouse-Hanford Paleoclimate Program.
Correspondence and requests for materials should be addressed to C.W. (e-mail: whitlock@oregon.
Endemic African mammals
shake the phylogenetic tree
Mark S. Springer*, Gregory C. Cleven*, Ole Madsen
Wilfried W. de Jong
, Victor G. Waddell§,
Heather M. Amrine* & Michael J. Stanhope§
* Department of Biology, University of California, Riverside, California 92521,
Department of Biochemistry, University of Nijmegen, PO Box 9101,
6500 HB Nijmegen, The Netherlands
Institute for Systematics and Population Biology, University of Amsterdam, PO
Box 94766, 1090GT Amsterdam, The Netherlands
§ Biology and Biochemistry, Queen’s University, 97 Lisburn Road,
Belfast BT9 07BL, UK
The order Insectivora, including living taxa (lipotyphlans) and
archaic fossil forms, is central to the question of higher-level
relationships among placental mammals
. Beginning with
, it has been argued that insectivores retain many primi-
tive features and are closer to the ancestral stock of mammals than
are other living groups
. Nevertheless, cladistic analysis suggests
that living insectivores, at least, are united by derived anatomical
. Here we analyse DNA sequences from three mito-
chondrial genes and two nuclear genes to examine relationships
of insectivores to other mammals. The representative insectivores
are not monophyletic in any of our analyses. Rather, golden moles
are included in a clade that contains hyraxes, manatees, elephants,
elephant shrews and aardvarks. Members of this group are of
presumed African origin
. This implies that there was an exten-
sive African radiation from a single common ancestor that gave
rise to ecologically divergent adaptive types. 12S ribosomal RNA
transversions suggest that the base of this radiation occurred
during Africa’s window of isolation in the Cretaceous period
before land connections were developed with Europe in the
early Cenozoic era.
Relationships among orders of placental mammals have proved
difﬁcult to resolve
. To extend the available mitochondrial (mt)
sequences, a 2.6-kilobase (kb) segment containing the 12S rRNA,
valine transfer RNA, and 16S rRNA genes was sequenced for nine
taxa to generate a data set that is representative of 12 of the 18
placental orders and all three insectivore suborders
analyses provide strong support for well-established mammalian
clades such as carnivores, hominoids, and Cetacea plus Artiodactyla
(Fig. 1a). In agreement with other molecular studies
included an assortment of taxa, most interordinal associations are
not resolved at bootstrap values .75%. However, the mtDNA data
do provide strong support for the association of the two paen-
ungulates (hyrax, manatee) together, and of these with elephant
shrews, aardvarks and golden moles (Fig. 1a and Table 1). The
association of hyraxes with proboscideans and sirenians was sug-
gested by Cope
. A competing hypothesis is an association of
hyraxes with perissodactyls
. Our results agree with earlier
and DNA studies
supporting Cope’s paenungulate
hypothesis. In addition to bootstrap support, T-PTP
tests also support paenungulate monophyly (Table 2).
Anatomical data provide some evidence that aardvarks and/or
elephant shrews may be related to paenungulates
other hypotheses as well: for example, six osteological features are
putative synapomorphies uniting elephant shrews with lagomorphs
. All the available sequence data, including amino-acid
, DNA sequences for three nuclear genes
, and the
present mitochondrial genes, support an association of aardvarks
and elephant shrews with paenungulates. What is most unexpected
is that golden moles, a family of insectivores, are also part of this
clade. 12S rRNA sequences earlier suggested an association of
golden moles with paenungulates, but did not provide convincing
bootstrap support for this hypothesis
. Our expanded data set
demonstrates that insectivores are not monophyletic (Table 2)
Table 1 Bootstrap support for select clades based on different methods
Paenungulata Paenungulata þ aardvark
þ elephant shrew
Parsimony 99 95
Transversion parsimony 64 90
Tamura–Nei I 100 92
Tamura–Nei II 100 78
Logdet 99 90
Maximum likelihood 100 100
All positions 49 99
1st and 2nd positions 24 65
3rd positions 51 93
Transversion parsimony 30 95
Tamura–Nei I 37 99
Tamura–Nei II 30 99
Logdet 43 97
Maximum likelihood 78 100
All sites 71 88
1st and 2nd positions 49 81
3rd positions 31 67
Transversion parsimony 71 54
Tamura–Nei I 83 84
Tamura–Nei II 28 25
Logdet 79 78
Maximum likelihood 81 89
Only two of the three paenungulate orders were represented among the mitochondrial and
A2AB sequences. Tamura–Nei
I and II distances were calculated by using an equal-rates
assumption and a gamma-distribution of rates, respectively.
Nature © Macmillan Publishers Ltd 1997
letters to nature
3 JULY 1997
Figure 1 Majority-rule parsimony bootstrap trees based on mitochondrial (a),
vWF (b), and A2AB (c) sequences. Bootstrap values and decay indices,
respectively, are above and below branches. The minimum-length tree (3,836
steps; consistency index, 0.430) for the mitochondrial data is 4, 7, 43 and 66 steps
shorter than trees that constrain shrew þ hedgehog, rodent monophyly, insecti-
vore monophyly, and hyrax þ horse, respectively. Insectivore monophyly and a
hyrax-perissodactyl association require 29 and 64 additional steps, respectively,
in comparison to ﬁve minimum-length vWF trees (2,401 steps; consistency index,
0.511). Insectivore monophyly requires 26 additional steps in comparison to the
shortest A2AB tree (1,469 steps; consistency index, 0.730).
Nature © Macmillan Publishers Ltd 1997
letters to nature
3 JULY 1997 63
and that golden moles, elephant shrews, aardvarks and paenungu-
lates are part of the same clade.
To corroborate these ﬁndings, we obtained sequences from exon
28 of the von Willebrand factor (vWF) gene for golden mole,
hedgehog and pangolin. Adding these to the existing vWF data
, we found high bootstrap support for the inclusion of golden
moles with paenungulates, elephant shrews and aardvarks (Fig. 1b
and Table 1). Sequences from the a-2B adrenergic receptor gene
(A2AB) also support the association of golden moles with paenun-
gulates, elephant shrews and aardvarks (Fig. 1c and Table 1).
Parsimony and maximum-likelihood trees supporting the paenun-
gulate–golden mole–aardvark–elephant shrew clade are signiﬁ-
cantly better than the best trees that constrain insectivore
monophyly (Table 2).
This expanded clade, which includes ﬁve placental orders plus
golden moles, has not been previously hypothesized on the basis of
morphological or molecular data. Elephants, sirenians, hyraxes,
golden moles, aardvarks and elephant shrews show a variety of
ecological and morphological specializations and it is not surprising
that morphology has not elucidated their common ancestry, now
evident from DNA sequences. It is notable that all six of these groups
are of probably African origin or, in the case of the aquatic sirenians,
from along the margins of the former Tethys Sea
. In two cases
(golden moles and elephant shrews), geographic distribution has
been restricted to Africa for the complete temporal range of these
. Thus geographic evidence adds to the molecular data in
support of this ‘African origin’ clade. The radiation of the African
clade parallels endemic radiations of other vertebrate taxa on
Southern Hemisphere continents during the breakup of Gondwana-
land; for example, marsupials and passerine birds in Australia
marsupials, edentates and notoungulates in South America
Paenungulate orders diverged from each other 51 to 59 million
years (Myr) ago, as deduced from 12S rRNA transversions (Table 3).
Deeper in the African clade, average divergence times between
paenungulates and other lineages range from 67 to 80 Myr. The
mean divergence time between taxa in the African clade and the
other 13 orders of placental mammals is ,91 Myr. These divergence
times support the hypothesis that many eutherian orders arose
before the extinction of dinosaurs at the end of the Cretaceous
imply that conventional views on the origins of the African mammal
are incorrect. Africa’s window of isolation extended from the
Late Cretaceous, when Africa became separated from South Amer-
ica, to the early Cenozoic, when tenuous connections developed
between northern Africa and Europe. The window of isolation
extended from at least 80 Myr (ref. 20), if not earlier, until the early
Cenozoic. The traditional view is that condylarths, prosimian
primates and creodont carnivores reached Africa from the north
after the docking of Africa with Europe
. From the condylarth stock,
groups such as proboscideans and sirenians ostensibly originated in
Africa. Other elements of the African mammal fauna, including
perissodactyls, artiodactyls, insectivores and living carnivore
families, presumably arrived in the Neogene with the establishment
of the Arabian Peninsula. Evidence for an extensive African clade,
including taxa with divergence times as old as 80 Myr, is inconsistent
with this view. The ancestor of the African clade probably resided in
Africa before the window of isolation and did not arrive from the
north in the early Cenozoic. The role of geographic isolation and
continental break-up in the early diversiﬁcation of placental mam-
mals is potentially more important than previously recognized.
. . . . . .. .. .. .. . . . . . . . . .. .. . . . . . . . . . . .. .. . . . . . . . . .. .. . . . . . . . . . . .. .. .. .. . . . . . . .. .. .. . . . . . . .. . . .. .. . . . . . . . . . . .. .. . . . . . . . . .. ..
Ampliﬁcation and sequencing. 12S rRNA and tRNA genes were ampliﬁed
and sequenced as described
. 16S rRNA genes were ampliﬁed using primers for
valine-tRNA (for example, 59-tacaccyaraagatttca-39) and leucine-tRNA (for
example, 59-agaggrtttgaacctctg-39) and sequenced. Accession numbers for the
new mitochondrial sequences (Echymipera kalubu (bandicoot); Dromiciops
gliroides (monito del monte); Sorex palustris (shrew); Manis sp. (pangolin);
Amblysomus hottentotus (golden mole); Procavia capensis (hyrax); Trichechus
manatus (manatee); Orcyteropus afer (aardvark); Elephantulus rufescens
(elephant shrew)) are U97335–U97343. 12S rRNA sequences for several of
these taxa have been deposited in GenBank (M95108 (golden mole), U61073
(monito del monte), U61079 (pangolin), U61083 (manatee), U61084 (hyrax)).
Accession numbers for additional mitochondrial sequences are as follows: cow
(J01394); blue whale (X72204); ﬁn whale (X61145); horse (X79547); cat
(U20753) harbour seal (X63726); grey seal (X72004); human (J01415); gorilla
(D38114); orang-utan (D38115); guinea-pig (L35585); hedgehog (X88898); rat
(X14848); mouse (J01420); opossum (Z29573); platypus (U33498; X83427).
Exon 28 of the vWF gene was ampliﬁed and sequenced as described
numbers for Manis sp., Erinaceus europaeus (hedgehog), and Amblysomus
hottentotus vWF sequences are U97534–U97536. Additional vWF sequences
are from ref. 9. Part of the single-copy, intronless A2AB gene was ampliﬁed
using the primers A2ABFOR (59-asccctactcngtgcaggcnacng-39) and A2ABREV
(59-ctgttgcagtagccdatccaraaraaraaytg-39). PCR products were cloned into a T/
A cloning vector (Promega) and both strands were sequenced for at least two
clones using the Thermo Sequenase ﬂuorescent-labelled primer cycle sequen-
cing kit (Amersham). Accession numbers for the new A2AB sequences (Elephas
maximus (elephant); Orycteropus afer (aardvark); Macroscelides proboscideus
(elephant shrew); Amblysomus hottentotus (golden mole); Procavia capensis
(hyrax); Erinaceus europaeus (hedgehog); Talpa europaea (mole)) are Y12520–
Y12526. Additional a-2 adrenergic sequences are M34041 (human); M32061
(rat); (L00974) (mouse), and U25722–U25724 (guinea-pig).
Sequence alignment and phylogenetic analysis. Sequences were aligned
using CLUSTAL W (ref. 23). rRNA alignments were modiﬁed in view of
. Ambiguous regions were omitted from subsequent
; this resulted in 2,152, 1,261 and 1,132 nucleotide positions,
respectively, for the mt, vWF and A2AB genes. The mt, vWF and A2AB data
sets contain 810, 497 and 393 informative sites, respectively. Phylogenetic
analyses (parsimony, minimum evolution with Tamura–Nei
distances, maximum likelihood under the HKY85 (ref. 29) model) were
conducted with PAUP 4.0d52-54, written by D. L. Swofford. The mitochondrial
tree was rooted using platypus and marsupial sequences. The vWF tree was
rooted with the sloth
; alternatively, rooting with either hedgehog or rodents
supports the ‘African’ clade and contradicts insectivore monophyly. For the
A2AB tree, sequences with the sufﬁx B are from the A2AB subfamily.
GuineaPigA and GuineaPigC sequences are from other subfamilies in the a-2
adrenergic receptor family and were used as outgroups. Bootstrap analyses used
full heuristic searches with 500 replications for parsimony and minimum
Table 2 Signiﬁcance levels of T-PTP and Kishino–Hasegawa tests
Constraint Mitochondrial DNA vWF A2AB
T-PTP KH-P KH-L T-PTP KH-P KH-L T-PTP KH-P KH-L
Perissodactyls þ hyracoids 0.01 0.0011–0.0022 ,0.0001 0.00 ,0.0001 ,0.0001 MT MT MT
Insectivore monophyly 0.05 ,0.0001 0.0001 0.01 0.0311 0.0477 0.00 0.0002–0.0067 0.0001
In each case, trees with constraints were compared against either minimum length (T-PTP, KH-P) or highest likelihood (KH-L) trees. T-PTP tests were based on 100 permutations. KH-P,
Kishino–Hasegawa test with parsimony; KH-L, Kishino–Hasegawa test with maximum likelihood; MT, missing taxa.
Table 3 Divergence times (Myr) based on 12S rRNA transversions
Divergence event N Mean Standard
Among Paenungulates 3 54.8 4.2 2.4
Paenungulates to golden mole 3 67.1 8.7 5.0
Paenungulates to aardvark 3 74.0 12.0 6.9
Paenungulates to elephant shrew 3 79.9 9.9 5.7
African clade to other 13 orders 78 91.1 15.5 1.6
Nature © Macmillan Publishers Ltd 1997
letters to nature
3 JULY 1997
evolution and 100 replications for maximum likelihood. Shape parameters for
the gamma distribution were estimated from minimum length trees
0.32 (mtDNA), 0.59 (vWF) and 0.52 (A2AB).
Divergence times. 12S rRNA transversions accumulated linearly as far back as
the eutherian–metatherian split
. Nine independent cladogenic events were
selected based on 12S rRNA sequence availability and paleostratigraphic
(for example, Rattus to Mus (14 Myr); Sus to Tayassu (45 Myr);
ruminants to Cetacea (60 Myr); Erinaceus to Metatheria (130 Myr)). Relative
rates were calculated in reference to xenarthrans. Tamura–Nei transversion
distances (transversions only) were adjusted for relative rate differences
against the xenarthran standard. Rate-adjusted estimates of sequence diver-
gence were regressed against paleostratigraphic divergence estimates for each of
the nine calibration points (origin forced through zero; r
P ¼ 0:0000002). The resulting equation ðdivergence time ðin MyrÞ ¼ sequence
divergence=0:00063Þ was used to estimate interordinal divergence times after
making similar adjustments for relative rates. Additional details will be
presented elsewhere (M.S., manuscript in preparation).
Received 23 December 1996; accepted 18 April 1997.
1. Novacek, M. J. Mammalian phylogeny: shaking the tree. Nature 356, 121–125 (1992).
2. Huxley, T. H. On the application of the laws of evolution to the arrangement of the Vertebrata, and
more particularly to the Mammalia. Proc. R. Soc. Lond. 43, 649–662 (1880).
3. Matthew, W. D. The Carnivora and Insectivora of the Bridger Basin, Middle Eocene. Mem. Am. Mus.
Nat. Hist. 9, 291–567 (1909).
4. MacPhee, R. D. E. & Novacek, M. J. in Mammal Phylogeny Vol. 2, Placentals (eds Szalay, F. S., Novacek,
M. J. & McKenna, M. C.) 13–31 (Springer, New York, 1993),
5. Carroll, R. L. Vertebrate Paleontology and Evolution (Freeman, New York, 1988).
6. Gheerbrant, E., Sudre, J. & Cappetta, H. A Palaeocene proboscidean from Morocco. Nature 383, 68–
7. Lavergne, A., Douzery, E., Stichler, T., Catzeﬂis, F. M. & Springer, M. S. Interordinal mammalian
relationships: evidence for paenungulate monophyly is provided by complete mitochondrial 12S
rRNA sequences. Mol. Phyl. Evol. 6, 245–258 (1996).
8. Madsen, O., Deen, P. M. T., Pesole, G., Saccone, C. & de Jong, W. W. Molecular evolution of
mammalian aquaporin-2: further evidence that elephant shrew and aardvark join the paenungulate
clade. Mol. Biol. Evol. 14, 363–371 (1997).
9. Porter, C. A., Goodman, M. & Stanhope, M. J. Evidence on mammalian phylogeny from sequences of
exon 28 of the von Willebrand factor gene. Mol. Phys. Evol. 5, 89–101 (1996).
10. Stanhope, M. J. et al. Mammalian evolution and the interphotoreceptor retinoid binding protein
(IRBP) gene: convincing evidence for several superordinal clades. J. Mol. Evol. 43, 83–92 (1996).
11. Cope, E. D. The condylarthra. Am. Nat. 18, 790–805, 892–906 (1884).
12. Fischer, M. S. & Tassy, P. in Mammal Phylogeny Vol. 2, Placentals (eds Szalay, F. S., Novacek, M. J. &
McKenna, M. C.) 217–234 (Springer, New York, 1993).
13. de Jong, W. W., Zweers, A. & Goodman, M. Relationship of aardvark to elephants, hyraxes and sea
cows from a-crystallin sequences. Nature 292, 538–540 (1981).
14. de Jong, W. W., Leunissen, J. A. M. & Wistow, G. J. in Mammal Phylogeny Vol. 2, Placentals (eds Szalay,
F. S., Novacek, M. J. & McKenna, M. C.) 5–12 (Springer, New York, 1993).
15. Faith, D. P. Cladistic permutation tests for monophyly and nonmonophyly. Syst. Zool. 40, 366–375
16. Kishino, H. & Hasegawa, M. Evaluation of the maximum likelihood estimate of the evolutionary tree
topologies from DNA sequence data, and the branching order in Hominoidea. J. Mol. Evol. 29, 170–
17. Glover, T. D. Aspects of sperm production in some east African mammals. J. Reprod. Fertil. 35, 45–53
18. Hartenberger, J. L. Hypothese paleontologique sur l’origine des Macroscelidea (Mammalia). C.R.
Acad. Sci. 302, 247–249 (1986).
19. Novacek, M. in Macromolecular Sequences in Systematic and Evolutionary Biology (ed. Goodman, M.)
3–41 (Plenum, New York, 1982).
20. Sibley, C. G. & Ahlquist, J. E. Reconstructing bird phylogeny by comparing DNAs. Sci. Am. 254, 82–92
21. Hedges, S. B., Parker, P. H., Sibley, C. G. & Kumar, S. Continental breakup and the ordinal
diversiﬁcation of birds and mammals. Nature 381, 226–229 (1996).
22. Springer, M. S., Hollar, L. J. & Burk, A. Compensatory substitutions and the evolution of the
mitochondrial 12S rRNA gene in mammals. Mol. Biol. Evol. 12, 1138–1150 (1995).
23. Thompson, J. D., Higgins, G. D. & Gibson, T. J. CLUSTAL W: improving the sensitivity of progressive
multiple sequence alignment through sequence weighting, position-speciﬁc gap penalties and weight
matrix choice. Nucleic Acids Res. 22, 4673–4680 (1994).
24. Springer, M. S. & Douzery, D. Secondary structure and patterns of evolution among mammalian
mitochondrial 12S rRNA molecules. J. Mol. Evol. 43, 357–373 (1996).
25. De Rijk, P., Van de Peer, Y., Chapelle, S. & De Wachter, R. Nucleic Acids Res. 22, 3495–3501 (1994).
26. Swofford, D. L., Olsen, G. J., Waddell, P. J. & Hillis, D. M. in Molecular Systematics (eds Hillis, D. M.,
Moritz, C. & Mable, B. K.) 407–514 (Sinauer, Sunderland, MA, 1996).
27. Tamura, K. & Nei, M. Estimation of the number of nucleotide substitutions in the control region of
mitochondrial DNA in humans and chimpanzees. Mol. Biol. Evol. 10, 512–526 (1993).
28. Lockhart, P. J., Steel, M. A., Hendy, M. D. & Penny, D. Recovering evolutionary trees under a more
realistic model of sequence evolution. Mol. Biol. Evol. 11, 605–612 (1994).
29. Hasegawa, M., Kishino, H. & Yano, T. Dating of the human–ape splitting by a molecular clock of
mitochondrial DNA. J. Mol. Evol. 21, 160–174 (1985).
30. Arnason, U., Gullberg, A., Janke, A. & Xu, X. Pattern and timing of evolutionary divergences among
hominoids based on analyses of complete mtDNAs. J. Mol. Evol. 43, 650–661 (1996).
Acknowledgements. This work was supported by the Alfred P. Sloan Foundation, the European
Commission, the NSF, the Nufﬁeld Foundation and the Royal Society. We thank D. Willemsen for
technical assistance, D. Swofford for permission to use PAUP 4.0d52-54, and F. Catzeﬂis, E. Harley, J.
Kirsch, G. Olbricht, J. Wensing and the Noorder Zoo for tissue samples.
Correspondence and requests for materials should be addressed to M.S.S. (e-mail: mark.springer@ucr.
Hypothermia in foraging
Y. Handrich*, R. M. Bevan
, J.-B. Charrassin*,
P. J. Butler
, K. Pu
, A. J. Woakes
J. Lage* & Y. Le Maho*
* Centre d’Ecologie et Physiologie Energe
tiques, Centre National de la Recherche
Scientiﬁque, 23 rue Becquerel, 67087 Strasbourg cedex 2, France
School of Biological Sciences, University of Birmingham, Edgbaston,
Birmingham B15 2TT, UK
Abteilung Meereszoologie, Institut fu
r Meereskunde, Du
sternbrooker Weg 20,
D-24105 Kiel, Germany
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The ability to dive for long periods increases with body size
relative to the best human divers, marine birds and mammals of
similar or even smaller size are outstanding performers. Most
trained human divers can reach a little over 100 m in a single-
breath dive lasting for 4 min (ref. 2), but king and emperor
penguins (weighing about 12 and 30 kg, respectively) can dive to
depths of 304 and 534 m for as long as 7.5 and 15.8 min, respec-
. On the basis of their assumed metabolic rates, up to half
of the dive durations were believed to exceed the aerobic dive
limit, which is the time of submergence before all the oxygen
stored in the body has been used up
. But in penguins and many
, the short surface intervals between dives are
not consistent with the recovery times associated with a switch to
. We show here that the abdominal tem-
perature of king penguins may fall to as low as 11 8C during
sustained deep diving. As these temperatures may be 10 to 20 8C
below stomach temperature, cold ingested food cannot be the only
cause of abdominal cooling. Thus, the slower metabolism of
cooler tissues resulting from physiological adjustments associated
with diving per se, could at least partly explain why penguins and
possibly marine mammals can dive for such long durations.
King penguins are pelagic predators. To obtain food for their
chicks, the parents forage at sea up to the subantarctic or polar
frontal zones, 300–1,000 km away from their breeding colony
They essentially rely on myctophid ﬁsh, of which most are captured
in daytime at 150–300 m depths
. As sea temperatures there are
4 8C or lower, their stomachs are cooled by ingested prey
freely foraging king penguins, which normally have a body tem-
perature of 38 8C on land, stomach temperatures as low as 19 8C
have been reported
. There is a 2–4 8C fall in body temperature
during free diving activity in seals
and it has been
suggested that a slight reduction in body temperature during diving
might enhance aerobic diving time
. The cold food that
antarctic animals eat could contribute to this hypothermia
or the aerobic dive limit (ADL) of penguins might be prolonged by a
process of temperature-induced metabolic suppression that is
independent of stomach cooling.
To investigate these possibilities, the separate inﬂuences of feed-
ing and diving on the abdominal temperatures of foraging animals
have to be determined. It is important to obtain simultaneous
measurements of the temperatures inside and outside the stomach
while the animals are freely diving, so that the extent of the
temperature changes in relation to diving and feeding activity
during the course of a foraging trip can be found. We therefore
implanted three data loggers into each of 12 free-ranging king
penguins (see Methods). The data loggers (Fig. 1) measured the
temperature of each bird at the top (T
) and bottom (T
the abdomen, as well as inside the stomach (T
pressure was also recorded to monitor the diving behaviour. Both
the upper-abdominal and stomach loggers measured the full range
of temperatures; the lower-abdominal device recorded temperatures