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Paleoecological Implications Inferred from Stable Isotopic Signatures (δ13C, δ15N) in Bone Collagen of Ursus spelaeus ROS.-HEIN

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Abstract

Stable isotopic signatures measured in bone collagen provide with data related to the species diet type. In this paper we compare δ13C and δ15N outcomes in Ursus spelaeus ROS.-HEIN. bone remains from Liñares site and Cova Eirós site (Galicia, NW of the Iberian Peninsula). Some data on fossil Ursus arctos L. and Pleistocene Cervus elaphus L. from Galician caves are also presented, as a first approach to distinguish paleodiets of different species inferred from their isotopic signatures. Once all data have been analyzed with proper statistical tools and since this work was planned in order to reduce variation in stable isotopic signals caused by metabolic causes, we may assume that the observed differences between both studied groups are exclusively due to environmental factors and show a migration of the cave bear population in the Serra do Courel mountains from higher to lower altitudes because of the transition from warm climatic conditions to colder ones.
Cadernos Lab. Xeolóxico de Laxe
Coruña. 1999. Vol. 24, pp. 73-87
PPaalleeooeeccoollooggiiccaall iimmpplliiccaattiioonnss iinnffeerrrreedd
ffrroomm ssttaabbllee iissoottooppiicc ssiiggnnaattuurreess
((δδ1133CC,δδ1155NN)) iinn bboonnee ccoollllaaggeenn ooff
UUrrssuuss ssppeellaaeeuuss RROOSS..--HHEEIINN..
Implicaciones paleoecológicas inferidas de la
caracterización isotópica (δ13C,δ15N) del
colágeno óseo de Ursus spelaeus ROS.-HEIN.
VILA TABOADA, M.; FERNÁNDEZ MOSQUERA, D.; LÓPEZ GONZÁLEZ, F.;
GRANDAL d’ANGLADE, A. & VIDAL ROMANÍ, J.R.
AABBSSTTRRAACCTT
Stable isotopic signatures measured in bone collagen provide with data related to the species
diet type. In this paper we compare δ13C and δ15N outcomes in Ursus spelaeus ROS.-HEIN. bone
remains from Liñares site and Cova Eirós site (Galicia, NW of the Iberian Peninsula). Some
data on fossil Ursus arctos L. and Pleistocene Cervus elaphus L. from Galician caves are also pre-
sented, as a first approach to distinguish paleodiets of different species inferred from their iso-
topic signatures. Once all data have been analyzed with proper statistical tools and since this
work was planned in order to reduce variation in stable isotopic signals caused by metabolic
causes, we may assume that the observed differences between both studied groups are exclusi-
vely due to environmental factors and show a migration of the cave bear population in the Serra
do Courel mountains from higher to lower altitudes because of the transition from warm clima-
tic conditions to colder ones.
KKeeyy wwoorrddss: δ13C, δ15N, collagen, paleodiets, Ursus spelaeus, Ursus arctos, Cervus elaphus, paleocli-
matology, Late Pleistocene, Galicia, NW Spain.
Instituto Universitario de Xeoloxía “Isidro Parga Pondal”. Universidade da Coruña. Facultade de Ciencias.
Campus da Zapateira s/n. 15071. A Coruña. Galicia. Spain. http://www.udc.es/dep/geda
IINNTTRROODDUUCCTTIIOONN
This work goes on with isotopic bio-
chemistry research on Quaternary fossils
from Galician sites, started
(FERNÁNDEZ, 1998) with Ursus spelaeus
ROS.-HEIN. from Cova Eirós. In this
paper we show first outcomes on U. spela-
eus from Liñares site and even some data
from Cervus elaphus L. and Ursus arctos L.
We are going to tackle the reconstruction
of paleoenvironmental changes inferred
from isotopic data got from fossil bone
remains. This kind of studies -recently
started (FERNÁNDEZ, 1998) on
Galician sites- have proved to be a proper
tool in helping the reconstruction of
ancient environments when those are cou-
pled with the most common geological
data, as sediments or geomorphology
(GRANDAL et al., 1997). In the last
years, the knowledge about Quaternary
Period in Galicia (VIDAL ROMANÍ,
1996) has undergone a strong impulse due
to a multidisciplinary approach and the
use of highly specialized techniques,
which contribute to solve the problem of
understanding a period of time so scarce
in fossil data as happens in Galicia.
The objetive of this work is to deter-
mine what kind of paleoenvironmental
conditions surrounded the occupation of
sites such as Liñares and Eirós (GRAN-
DAL & LÓPEZ, 1998; LÓPEZ & GRAN-
DAL, 1998) with an important record of
Pleistocene macrofauna. Both are conside-
red as different steps in the migration pro-
cess of populations happened during gla-
cial terms.
Isotopic signals are thought as impor-
tant tools in order to supporte the hypote-
sis of paleoclimatic changes in late
Pleistocene in Galicia. Such a theory has
been proposed from geological data rela-
ted to glaciar phenomena (VIDAL
ROMANÍ, 1996), faunistic assemblages
found in different sites (GRANDAL et al.,
1997) and some modern techniques for
dating rock surfaces (FERNÁNDEZ,
1999).
The meaning of stable isotopic signa-
tures preserved in fossil animal tissues can
vary depending on metabolic or environ-
mental causes. Our attention will be focu-
sed in the cave bear, extinct aproximately
15,000 years ago and with a well known
trend towards herviborism (KURTÉN,
1976). Then, the aim of this paper will be
to analyse isotopic signals of Ursus spelaeus
bone collagen in order to distinguish
whether a qualitative climatic change
existed or not between the ages when
those sites were occupied; taking into
account the influence of climate in the iso-
topic fractionation along the trophic
chains.
As stable isotopic outcomes from car-
bon and nitrogen signals in fossil bones
have been used as paleoenvironmental
markers, it should be possible to compare
outcomes with close and distant contem-
poraneous individuals data.
Often, teeth and bones are the only
remains that survive in the fossil record,
but as they are not closed systems, they
can suffer weathering, infiltration and
quite enough damage because of several
process after death; so, a critic step in any
study will be to evaluate collagen preser-
vation. Thus, a suitable C/N atomic value
(between 2,9 and 3,6 after DE
NIRO,1985) will be required. During
74 Vila Taboada, et al. CAD. LAB. XEOL. LAXE 24 (1999)
CAD. LAB. XEOL. LAXE 24 (1999) Paleoecological implications 75
diagenesis, C/N values can raise due to
deamination of aminoacids or invasion by
soil humic acids, and even fall because of
inorganic material contamination (TUR-
BAN-JUST & SCHRAMM, 1998). By
proving that isotopic signals are original,
and taking into account that collagen
damage is not dependant on time, but fos-
sil preservation conditions (TUROSS &
STATHOPLOS, 1993), isotopic data will
be able to be used as markers of paleoenvi-
ronmental conditions.
Stable isotopic compositions of food
and drinks of animals have a strong
influence on the isotopic compositions of
the tissues they synthesize. Conversely, the
isotopic composition of animals tissues
can serve as a natural tracer of different
dietary inputs with distinct isotopic sig-
natures (DE NIRO, 1985). However, the
exact relationship between the isotopic
compositions of ingested materials and
those associated to any particular tissue or
molecular component is quite complex,
responding not only to changes in nutri-
tional status, but turnover rate of the tis-
sue and biosynthethic pathway. Then, sta-
ble isotope analysis provides more than
just a tracer of the materials that go into
an animal, but it offers a view of the bio-
logical processes within an organism
(KOCH et al., 1994) and thus, some clues
to reconstruct the environment where it
lived.
As many authors have noted, the ato-
mic ratio between heavy isotopes and
lighter ones (Rx= mX/nX, being m>n) is
compared with a reference control. Delta
symbol (δ) means the difference between
sample R and the control one (LAJTHA &
MICHENER, 1994). So:
δ(‰) = [(Rsample – R reference)/ R reference].1000
Carbon and nitrogen stable isotope
signatures may differ depending on some
factors. The former element is influenced
not only by isotopic composition of
atmospheric CO2influences, but also by
photosynthesis type (C3or C4) in the base-
ment of trophic chain too. Thus, plants
with Calvin cycle (C3) absorb less 13C from
CO2than Hatch-Slack (C4) ones. Then,
alimentary chains based in a vegetal step
with C3as dominants will be depleted in
the heavy isotope, which -according to
logical fractionations at the same time we
get higher levels- make animal tissues to
have minor δ13C values. We should remark
that C3plants are associated with tempe-
rate or boreal climates, excluding tropical
conditions which are supposed for C4ele-
ments. Moreover, other factors as species,
physiology -example of lipidic catabolism
in ursids during hibernation (ANDER-
SON, 1992)- and kind of tissue might
affect these values (AMBROSE & DE
NIRO, 1989; BOCHERENS et al.,
1991a; KOCH et al., 1994; LAJTHA &
MARSHALL, 1994).
Dealing with nitrogen signal, inputs of
heavy isotope are determined by atmosphe-
ric N2fixation by micoorganisms in sym-
biosis with some particular plant species.
Thus, fixator plants display a lower δ15N
than non-fixators. Several factors affect frac-
tionation process and enrichment when
considering higher trophic steps in the ali-
mentary chain: soil conditionants as humi-
dity, acidity and age, animal physiology,
specific metabolism pathways for nitrogen,
kind of tissue, suckling in mammals and,
only in high vegetal density forest, the
canopy effect (AMBROSE, 1991; BOCHE-
RENS et al, 1991a; BOCHERENS et al.,
1991b; NELSON et al., 1975; CORMIE &
SCHWARCZ, 1994).
SSaammppllee aanndd TTeecchhnniiqquueess
A sample of 38 bone remains from
several Galician sites was assembled. It has
been used 23 cave bear (Ursus spelaeus)
ribs, and the vertebra - Lus24- and meta-
pod -Lus25- used on ancient DNA studies
(VILA, 1998); all of them came rom
Liñares site (Galicia, NW of Iberian
Peninsula) Furthermore, a metatarsian -
Lce1- and 6 ribs from deer (Cervus elaphus)
of Liñares site were also added, as well as 8
ribs of Holocene brown bear (Ursus arctos)
from Tarelo and Purruñal sites (Galicia,
NW Iberian Peninsula). All selected
bones belonged to adult individuals.
Liñares site (LÓPEZ, 1996; LÓPEZ et
al., 1997; GRANDAL & LÓPEZ, 1998)
is a small karst cave, located in the Serra do
Courel mountains, at 1,115 m above sea
level (Fig. 1).
76 Vila Taboada, et al. CAD. LAB. XEOL. LAXE 24 (1999)
FFiigguurree 11..-- GGeeooggrraapphhiiccaall llooccaattiioonn ooff LLiiññaarreess ssiittee..
CAD. LAB. XEOL. LAXE 24 (1999) Paleoecological implications 77
Figure 1 plots the location of Liñares
(LÓPEZ & GRANDAL, 1998; GRANDAL
& LÓPEZ, 1998) and Tarelo site, where an
Ursus arctos skeleton comes from. The age of
the mentioned sites has been inferred from
absolute datings carried out on bone fossil
remains preserved on their sediments. Thus,
Tarelo site occupation is assumed during
Holocene term due to geomorphological
data and a brown bear bone dated -by 14C
method- in 7,460 ± 95 yBP (GRANDAL et
al., 1997). Liñares site is supposed to be acti-
ve around 35-40,000 yBP, this is inferred
from a Cervus elaphus bone dated around
37,000 yBP (LÓPEZ, 1996; GRANDAL et
al., 1997) and age outcomes for
Ursus spelaeus bone remains from
Liñares were 35,000 ± 1,440 yBP
and >38,000 yBP (GRANDAL et
al., 1997; VILA, 1998).
As %N is a first indicator about
collagen preservation, bone powder
(got after sewing and crashing the
bone) was analyzed in a Carlo-Erba
1108 Elemental Analyzer with
analytical reproducibility better
than 0.1%. Once it was rejected
those bones not suitable enough for
isotopic determination due to their
minimum bone %N (IACUMIN et
al., 1997), we followed a common
extraction method for collagen
(BOCHERENS et al, 1997b) based
on some digestions with HCl and
NaOH and filtrations, in order to
remove carbonates, humic contami-
nants and make soluble the extrac-
tion product. Afterwards, this mate-
rial was freezed-dried and analyzed
by SIRMS (Stable Isotopic Ratios
Mass Spectrometry). Collagen isotopic sig-
nals for carbon and nitrogen were measured
in a Finnigan Mat Delta Plus joint to a
Elemental Analyzer Carlo-Erba 1108 with
analytic reproducibility better than 0.1‰
for carbon and 0.2‰ for nitrogen.
Outcomes are referred to international stan-
dars PDB and atmospheric N2.
Taking into account that well preserved
collagen, from isotopic point of view, would
yield an atomic C/N ratio between 2.9 and 3.6
(DE NIRO, 1985) we must reduce the initial
number of 38 bone samples to 30. Proportions
for each site are shown in figure 2, whereas
final outcomes are shown in table 1.
FFiigguurree 22..-- SSaammppllee ssiizzee ooff tthhee ssttuuddiieedd bboonneess ddeeppeennddiinngg oonn ssiittee
((aa)) aanndd ssppeecciieess ((bb)).. FFiinnaall ssaammppllee ssiizze
e iiss rreedduucceedd dduuee
ttoo tthhee 22..99--33..66 ccrriitteerriioonn ffoorr ccoollllaaggeenn pprreesseerrvvaattiioonn ((DDEE
NNIIRROO,, 11998855))..
78 Vila Taboada, et al. CAD. LAB. XEOL. LAXE 24 (1999)
RReessuullttss
SSaammpplleeBBoonneeYYiieelldd%%NN ccooll%%CC ccoollAAttoommiiccδδ1155NN ccoollδδ1133CC ccooll
%% NNmmgg//ggCC//NN ccooll
Lus1 0.79 70.40 5.70 15.60 3.17 3.04 -21.24
Lus2 2.61 70.63 9.12 24.69 3.14 3.49 -21.23
Lus3 2.44 219.14 8.85 23.99 3.14 3.24 -21.14
Lus4 2.26 111.94 9.07 24.42 3.12 3.35 -20.65
Lus6 3.04 78.48 11.80 32.16 3.16 3.35 -20.86
Lus7 2.35 85.12 7.41 20.71 3.24 3.56 -21.50
Lus8 3.09 98.86 10.34 28.40 3.19 3.12 -20.87
Lus9 2.52 88.57 12.10 32.73 3.14 2.93 -20.97
Lus10 2.09 30.87 13.19 35.51 3.12 3.20 -20.90
Lus11 2.67 50.54 11.64 30.74 3.06 2.96 -21.28
Lus12 2.64 112.82 13.45 36.20 3.12 2.81 -20.63
Lus13 0.55 35.45 8.53 17.69 3.07 3.11 -21.41
Lus14 0.59 36.30 7.86 20.45 3.02 2.15 -21.13
Lus16 3.06 92.88 8.80 23.92 3.16 3.18 -20.97
Lus17 2.33 55.08 10.25 27.89 3.16 3.39 -21.72
Lus18 3.02 86.31 9.98 25.77 3.00 2.17 -20.92
Lus19 2.48 73.16 10.83 30.21 3.24 3.61 -20.92
Lus20 3.01 67.43 11.93 31.95 3.11 3.05 -20.77
Lus24 2.68 127.68 7.55 20.49 3.15 2.92 -21.23
Lus25 3.07 229.08 9.07 24.41 3.12 2.11 -20.94
Lce2 2.76 59.06 6.40 17.20 3.12 5.88 -19.65
Lce3 2.69 83.14 12.33 33.15 3.12 7.42 -19.92
Lce4 2.85 56.81 6.64 18.17 3.18 5.71 -20.10
Lce5 1.94 49.09 10.31 27.37 3.08 6.19 -19.72
Lce6 2.98 67.92 10.86 29.17 3.12 6.18 -20.00
Lce7 3.00 59.14 10.53 28.27 3.11 6.65 -19.77
Pua1 3.05 139.39 12.01 32.64 3.15 5.21 -20.00
Pua2 2.62 143.26 13.94 36.95 3.08 5.40 -19.54
Pua3 2.43 111.05 12.79 32.52 2.95 4.94 -19.41
TTaabbllee 11..-- OOuuttccoommeess ffrroomm 3300 bboonnee ssaammpplleess.. LL ((ffiirrsstt lleetttteerr ffrroomm ssiittee aass ffiigguurree 22,, ii..ee..:: LLiiññaarreess)),, uuss ((iinniittiiaall ooff
ssppeecciieess,, ii..ee..:: UUrrssuuss ssppeellaaeeuuss))..
According to previous works (BOCHERENS, 1997; CORMIE & SCHWARCZ,
1994), isotopic signals allow to distinguish different species. Following those references
we can ensure that isotopic signals for the Cervus elaphus and Ursus arctos remains inclu-
ded in this paper are feasible. (Fig. 3).
FFiigguurree 33:: IIssoottooppiicc ssiiggnnaattuurreess oouuttccoommeess ffoorr UUrrssuuss
ssppeellaaeeuuss (( )),, CCeerrvvuuss eellaapphhuuss ((³³)) aanndd UUrrssuuss
aarrccttooss
((++))..
We have chosen a Kruskal-Wallis test,
which works with sample median instead
of the mean, in order to resolve whether
differences in δ13C are significant. Results
are shown in figure 4.
FFiigguurree 44..-- SSiiggnniiffiiccaanntt ddiiffffeerreenncceess iinn δδ1133CC ddeeppeennddiinngg
oonn ssppeecciieess.. CCaavvee bbeeaarr vvaalluueess aarree rreeaallllyy ddiiffffee--
rreenntt ffrroomm ddeeeerr aanndd bbrroowwnn bbeeaarr oonneess:: pp--
vvaal
luuee 00..0000001144.. KKrruusskkaall--WWaalllliiss tteesstt rreessuullttss
aaggrreeee wwiitthh AANNOOVVAA--II.. SSeeggmmeennttss sshhooww tthhee
iinntteerrvvaall ((9955%% ccoonnffiiddeen
nccee)) ggoott ffoorr ssaammppllee
mmeeaann ((++)).. NNoottcchh sseettss mmeeddiiaann ppoossiittiioonn..
Another Kruskal-Wallis test proved
that differences for δ15N were significant
depending on species: p-value < 0.05. So,
our 30 data agree with trophic levels for
these species (IACUMIN et al., 1997;
BOCHERENS, 1997).
Focusing in Ursus spelaeus isotopic sig-
natures, we should remark the difference
in δ15N depending on age stage
(FERNÁNDEZ, 1998). Data from Eirós
non-suckling individuals will be plotted
in figure 5 together with Liñares cave bear
in order to distinguish differences in
nitrogen signatures
FFiigguurree 55..-- CCaarrbboonn aanndd nniittrrooggeenn ssttaabbllee iissoottooppiicc ssiigg--
nnaallss ooff UUrrssuuss ssppeellaaeeuuss bboonnee ccoollllaaggeenn.. δδ1155NN
iinnddiiccaatteess ttwwoo sseeppaarraattee ggrroouuppss ddeeppeennddiinngg oonn
tthhee ssiittee..
We can appreciate that Liñares data are
close grouped. δ13C variation among indi-
viduals is not higher than ± 0.5 ‰ nor
δ15N one is higher than ± 0.6 ‰ (WANG
& CERLING, 1994). Thus, inside each
population, variation is caused by metabo-
lic parameters, whilst variation among
different populations would be due to
environmental ones.
A t-Student test for δ13C depending on
site, Eirós and Liñares, shows no signifi-
cant differences (p-value < 0.05). A U-
Mann-Whitney for δ15N let us reject (p-
value < 0.0001) the null hypothesis of
similar medians between Eirós and Liñares
data (see figure 5).
CAD. LAB. XEOL. LAXE 24 (1999) Paleoecological implications 79
As the extraction product is true colla-
gen, with a C:N ratio close to 3, it can be
seen in figure 6 that the regression line got
from Liñares bones (cave bear and deer)
shows a slope close to the proposed value.
Brown bear remains from Purruñal site fit
properly to this linear trend.
Determination coefficient, R2, also agree
with the hypothesis of collagen as extra-
tion product: 96.07 % of sample variabi-
lity can be explained by a linear regression.
Whereas, the Eirós equation for the
same parameters was:
YY == 22..5522 XX ++ 11..440022; Pearson r= 0.991
(FERNÁNDEZ, 1998).
By testing -with a paired t-test- the
null hypothesis of non difference between
collagen %C mean from Eirós to Liñares,
we got a p-value = 0.57, and we cannot
reject such a null hypothesis. Same fact
was obtained for collagen %N. It can be
concluded that a time difference of 13,000
years between Eirós (25,000 yBP aprox)
and Liñares (38,000 yBP aprox) remains
has not affected to collagen preservation.
80 Vila Taboada, et al. CAD. LAB. XEOL. LAXE 24 (1999)
FFiigguurree 66:: CCaarrbboonn aanndd nniittrrooggeenn ppeerrcceenntt iinn eexxttrraaccttiioonn pprroodduucctt.. LLiinneeaarr rreeggrreessssiioonn ttrreenndd lliinnee ffoorr LLiiññaarreess
((UUrrssuuss ssppeellaaeeuuss aanndd CCeerrvvuuss eellaapphhuuss bboonneess)) eexxppllaaiinnss 9966%% ooff tthhee ssaammppllee vvaarriiaabbiilliittyy,, ssllooppee cclloossee
ttoo 33.
.
DDIISSCCUUSSSSIIOONN
This paper integrates very different
information: isotopic biochemistry, metric
palaeontology, absolute dating, and geo-
morphology with the final result of attai-
ning paleoclimatic reconstructions.
Focused in Ursus spelaeus from Galician
sites, we use the non-suckling group from
Eirós Cave (FERNÁNDEZ, 1998) as iso-
topic reference. As we have reduced the
metabolic causes of variation by using the
same species, same kind of tissue and non
suckling individuals, we could blame
environmental parameters as origin of iso-
topic differences.
In figures 4 and 5, cave bear shows the
lowest δ15N and δ13C values among herbi-
vores (BOCHERENS, 1997; BOCHE-
RENS et al., 1997a). Its low isotopic signal
in bone collagen relates with diet, climate
and physiology,(AMBROSE, 1991). δ13C
from Liñares -as Eirós (FERNÁNDEZ,
1998)- is consistent with an alimentary
chain based in C3plants, under
humid/temperate conditions (BOCHE-
RENS et al., 1991b; BOCHERENS et al.,
1997b).
Nutritional and hydric stress are
important conditionings for δ13C and δ15N
isotopic signals. In order to avoid the
influence of metabolic parameters, it is
really crucial to keep in mind different
requirements as: choosing the same spe-
cies, tissue and age stage. Nevertheless,
some previous works (see table 2) have
used time intervals too large and thus,
influence of metabolic parameters cannot
be discriminated.
In this work, Liñares data (occupation
around 38-40,000 y BP and 1,115 m
above sea level), and Eirós ones (around
25,000 y BP and 715 m a.s.l.) have been
compared. It must be granted that, once
eliminated the metabolic influence in
δ15N, differences in this signal (between
Liñares and Eirós) correspond exclusively
to environmental factors.
CAD. LAB. XEOL. LAXE 24 (1999) Paleoecological implications 81
SSIITTEEδδ1133CCδδ1155NNAAggeenn
1. Eirós (suckling) [-22.79 to -21.06] [5.16 to 9.96] * 25
2. Eirós (non suckling) [-22.22 to -20.44] [3.85 to 6.94] 24,090 ± 440 yBP ζ23
3. Liñares [-21.72 to -20.63] [2.11 to 3.61] > 38,000 yBP ζ20
35,000 ± 1,440 yBP) ζ
TTaabbllee 22:: IInntteerrvvaallss ffoorr GGaalliicciiaann ccaavvee bbeeaarr δδ1133CC aanndd δδ1155NN vvaalluueess.. ((11,, 22)) FFEERRNNÁÁNNDDEEZZ,, 11999988.. [[nn]] SSaammppllee ssiizzee..
[[ζζ]] DDaattiinnggss bbyy 1144CC AAMMSS bboonneess.. [[**]] SSaammee ssttrraattiiggrraapphhiicc lleevveell tthhaatt nnoonn ssuucckklliinngg,, ssoo iitt iiss aassssuummeedd tthhee
ssaammee aaggee tthhaatt tthhee E
Eiirróóss nnoonn--ssuucckklliinngg ggrroouupp..
According to previous literature, there
is a good correlation between low δ15N
values and forestry habitats (BOCHE-
RENS et al., 1994). Lower values for δ15N
(as Liñares) are related to cool and wet con-
ditions. As the assumption of a dense
forest, with cold and humid soils, is made
from a present point of view, it would be
naïve to suppose that Liñares individuals
lived in a colder phase than Eirós inhabi-
tants. Initially, Liñares and Eirós sites are
so close that would not seem very real to
establish strong climatic differences bet-
ween these two sites. Then, δ15N differen-
ces between Eirós and Liñares (see figure 5)
point out minor thermic optima in the last
glacial phase (see figure 7). This means
good conditions for N2-fixer-organisms
activity, allowing shrubs and maybe trees
to grow in the higher settlement (Liñares).
82 Vila Taboada, et al. CAD. LAB. XEOL. LAXE 24 (1999)
+5 0-5 -10 Isotopic
Stage
Macropaleontological
data
Glacial data
Temperature (ºC)
0
50
100
Age (thousand years)
1
2
3
4
5
a
b
c
d
5
6
Ursus spelaeus (24.090 ± 440 BP)
e
Inner drumlin
15,465 ± 6,991 BP
(Q4) Queixa
Outer drumlin
21,646 ± 16,963 BP
(Q3) Queixa
13,000
28,000
60,000
75,000
115,000
130,000
Frontal moraine complex
126,184 ± 13,260 BP (Q2) Queixa
Difluent valley
130,732 ± 16,838 BP (AX1) Xurés
Speleothem (28,233 ± 5.027 BP) Eirós
Ursus spelaeus (35,230 ± 1.430 BP) A Ceza
Ursus spelaeus (35,000 ± 1.440 BP) Liñares
Ursus spelaeus (>38,000 BP) Liñares
Cervus elaphus (>38,000 BP) Liñares
Homo sapiens sapiens (210 ± 70 BP) Arcoia
Ursus arctos (7,460 ± 95 BP) Tarelo
85,000
92,000
(1,795 ± 75 BP) Doniños
(1)
(3,970 ±50 & 4,350 ±90 BP) Seselle
(2)
(4,135 ± 80 BP) Puerta Real
(2)
(12,275 ± 95 BP) Ares
(2)
(8,990 ± 400 BP) Lucenza
(3)
(13,400±400 BP)
Laguna Grande
(3)
(23,300±400 BP) Villaseca
(3)
(25,000 BP) La Mata
(3)
150
Coastal
sedimentary data
Sedimentary
Frontal moraine complex:
Chaguazoso (Queixa)
Lagoa de Marinho (Gerês)
Prada-II (Queixa)
Moraine complex from:
Fafião (Gerês)
Fecha (Gerês, Xurés)
Vilamés (Gerês, Xurés)
Castiñeiras y Prada-I (Queixa)
Slope series:
(37,505 ± 1.925 BP) Sorrizo
(38,000 BP) Leira
(>38,000 BP) Rañal
Speleothem (117,252 ± 75,438 BP) Eirós
Speleothem (97,051 ± 15,426 BP) Eirós
Cervus elaphus (17,720 ± 185 BP) Liñares
Geomorphological
Eirós
More or less 38-40,000 y BP, climate
would be in a warm/soft short phase (inside
a general cooling corresponding to the last
glacial phase, see figure 7). At this
moment, around Liñares cave could exist a
kind of C3 vegetation which is now reflec-
ted, as basement of trophic chain, in Ursus
spelaeus signals. As signal δ15N is lower
than Eirós one, we understand that
atmospheric-nitrogen fixation should be
very active due to better conditions for
this process. Soil acidity and soil age, with
influence in soil δ15N are equivalent in
both sites. Non-suckling δ15N data agree
with colder conditions: limitation in N2-
fixers activity when parameters as tempe-
rature and available liquid water decrease.
Liñares site is demonstrated as Ursus
spelaeus refuge around 35,000 yBP
(GRANDAL & LÓPEZ, 1998). Its occu-
pation does not correspond with Eirós one
(approximately 25,000 yBP). The former
felt more influence of glacial conditions
(even when both were out of glacial-ice-
limits) because of its altitude and location
(GRANDAL et al., 1997). It is consistent
to suppose that when weather conditions
were so hard to prevent a normal activity
of cave bears -we guess around 25,000
yBP- they would descend from sites as
Liñares to easier stuffs as Eirós.
As figure shows 7, Liñares occupation
(40,000 yBP aprox.) would be located insi-
de Isotopic Stage 3. That age coincides
with a wet climate, warm enough to allow
the growing of significant taxa in moun-
tains. On the other side, Eirós term would
belong to Isotopic Stage 2, when all refe-
rences show a hardening in conditions at
the highest locations of the Courel Sierra.
The soft phase in Isotopic Stage 3 agree
with some polinic records at lower altitude
(FERNÁNDEZ et al., 1991 and RAMIL,
1992 In PÉREZ & RAMIL, 1996).
CCOONNCCLLUUSSIIOONNSS
Isotopic biochemistry data support the
theory of herbivore diet for Ursus spelaeus
due to low δ15N and δ13C values.
This isotopic study does not consider
other factors than environmental ones due
to sample selection (see Sample and
Techniques). The studied sample corres-
ponds to different sites, Liñares and Eirós,
with a non contemporaneous animal occu-
pation (GRANDAL & VIDAL, 1997;
LÓPEZ & GRANDAL, 1998). We
understand the significant differences in
δ15N as caused by environmental changes.
As N2fixation raises during a warm
event included in a glacial period, it can
be identified a a warm phase around
40,000 yBP (Isotopic Stage 3) included in
the last glacial event for NW Iberian
Peninsula. Then, caves as Liñares (1,115
m.a.s.l.) were occupied by Ursus spelaeus.
Around 25,000 y BP (Isotopic Stage 2)
the climate changed towards colder condi-
CAD. LAB. XEOL. LAXE 24 (1999) Paleoecological implications 83
FFiigguurree 77..-- PPaalleeoocclliimmaattiicc rreeccoonnssttrruuccttiioonn ffoorr LLaattee
PPlleeiissttoocceennee iinn NNWW IIbbeerriiaann PPeenniinnssuullaa.. OOnn
tthhee lleefftt,, ggl
loobbaall tthheerrmmiicc rreeffeerreennccee ccuurrvvee
ffrroomm VVoossttookk iiccee ccoorree ((mmooddiiffiieedd ffrroomm JJOOUU--
ZZEELL eett aall..,, 11998877 IInn AANNDDEERRSSEENN &
&
BBOORRNNSS,, 11999944)).. DDaattaa ffrroomm ddiiffffeerreenntt ssuubb--
jjeeccttss aaggrreeee wwhheenn ddeeffiinniinngg cchhaannggeess iinn ppaallee--
ooeennvviirroonnmmeennttaall cco
onnddiittiioonnss
((FFEERRNNÁÁNNDDEEZZ,, 11999999;; VVIILLAA,, 11999999))..[[11]]
LLaaggoooonn,, [[22]] RRiiaa bboottttoomm sseerriieess,, [[33]] GGllaacciiaall
llaakkee..
84 Vila Taboada, et al. CAD. LAB. XEOL. LAXE 24 (1999)
tions and individuals moved to lower sites
as Eirós (780 m.a.s.l.).
Global references as the Vostok ice core
prove that the alternation -cold and warm
phases- pattern included in the last glacial
event and inferred by the paleontological iso-
topic record of Eirós and Liñares is feasible.
AAkknnoowwlleeddggeemmeennttss
This paper is a contribution to the
Research Project XUGA10308A97.
Laboratorio Xeolóxico de Laxe has provided
with a high valuable sample in order to
carry this work out. Juan Ouro was really
patient with our computer doubts.
CAD. LAB. XEOL. LAXE 24 (1999) Paleoecological implications 85
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... The bear species of the Mammoth Steppe identified as meat-eaters based on their relatively high δ 15 N values were the extinct short-faced bear (Arctodus simus) in eastern Beringia, with a specialized diet on reindeer (Fox-Dobbs et al. 2008, Yeakel et al. 2013, and the brown bear (Ursus arctos) in Europe . In contrast, the cave bear (Ursus spelaeus), exclusive to Europe, systematically had relatively low δ 13 C and δ 15 N values as the result of a vegetarian diet (e.g., Bocherens et al. 1997Bocherens et al. , 2006Bocherens et al. , 2011aBocherens et al. , 2011bBocherens et al. , 2014aNelson et al. 1998;Vila Taboada et al. 1999;Terlato et al. 2019). Over all tested locations in Europe, only a few specimens in Romania with high δ 15 N values appeared to be an exception to this herbivorous diet (Richards et al. 2008, Robu et al. 2013, Krajcarz et al. 2016. ...
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... Understanding feeding habits of cave bear is essential as it might give insight into those factors contributing to their extinction: whether they were strictly herbivores or more flexible omnivores could have resulted in different scenarios, whereby the relative influence of climate change, human pressure could have played different roles (Pacher & Stuart, 2009;Bocherens et al., 2014a). In this context, herbivorous feeding habits inferred from tooth, skull and jaw morphology (Kurté, 1976;van Heteren et al., 2016) as well as the stable isotopic composition of cave bear collagen from a large majority of European sites, ranging from Spain to Romania, indicate an essentially vegetarian diet (Bocherens et al., 1997;2006;Vila Taboada et al., 1999;Grandal-d'Anglade et al., 2011;Münzel et al., 2011;Horacek et al., 2012;Pacher et al., 2012;Krajcarz et al., 2016;Naito et al., 2016). In contrast, δ 13 C and δ 15 N analyses on cave bears from two Romanian sites (Richards et al., 2008;Robu et al., 2013) suggested that some cave bears included a substantial amount of meat in their diet. ...
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... Further isotopic analyses of cave bears from other areas in Western and Central Europe such as France, Spain, Germany, Belgium, Austria, as well as in the northern Caucasus, confirmed this view (e.g. Bocherens et al. 1997Bocherens et al. , 2001Bocherens et al. , 2006Bocherens et al. , 2011bBocherens et al. , 2014aFernandez Mosquera 1998;Vila Taboada et al. 1999;Münzel et al. 2011; Bocherens 2015) ( Figure 1). In parallel, it was also recognised that some physio- logical aspects, such as milk suckling, growth and hibernation, also had an impact on the isotopic values measured on fossil bears and could interfere with the paleodietary interpretations (e.g. ...
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... Zarówno szczegóły budowy czaszki i zębów, jak i wyniki analiz izotopowych są intepretowane jako dowody świadczące za jego roślino- żernością (np. Kurtén 1976, Mattson 1998, Bocherens et al. 1994, Vila et al. 1999, Fernández-Mosquera et al. 2001) lub wszystkożernością (np. Hilderbrand et al. 1996, Pinto Llona & Andrews 2004, Richards et al. 2008, Figueirido et al. 2009, Peigné et al. 2009, Dotsika et al. 2011, Robu et al, 2013). ...
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Chapter
IntroductionCarbon IsotopesNitrogen IsotopesHydrogen and Oxygen IsotopesConclusions References
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Stable carbon and nitrogen isotope ratios have been determined for tooth collagen of 27 prehistoric herbivores from a rock shelter in the central Rift Valley of Kenya. Collagen samples whose isotope ratios were not altered by diagenesis were identified using several analytical methods. During the later Holocene, when the climate was as dry or drier than at present, the isotopic compositions of individual animals are similar to those of modern individuals of the same species. During the earlier Holocene, when the climate was wetter than at present, the δ15N and δ13C values are lower than those for their modern counterparts. When diagenetic factors can be discounted and adequate modern comparative data are available, stable isotope analysis of herbivore teeth and bones can be used to evaluate prehistoric climate and habitat conditions.
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