A detailed study of isotopic relationships in

European Pleistocene ursid teeth have been presented

by Bocherens et al. (1994). We agree with

the resu1ts and broad conclusions derived from the

stable carbon isotope relationships. These are findings

that confirm the previous hypothesis relating

to the diets of Ursus deningeri and Ursus spelaeu

Torres Pérez-Hidalgo, Trinidad José

English

A detailed study of isotopic relationships in European Pleistocene ursid teeth have been presented by Bocherens et al. (1994). We agree with the resu1ts and broad conclusions derived from the stable carbon isotope relationships. These are findings that confirm the previous hypothesis relating to the diets of Ursus deningeri and Ursus spelaeu

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Comments on : diet, physiology and ecology of fossil mammals as inferred from stable carbon and nitrogen isotope biogeochemistry: implications for Pleistocene bears

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Comments on: Diet, physiology and ecology of fossil mammals as
inferred from stable carbon and nitrogen isotope biogeochemistry:
Implications for Pleistocene bears by H. Bocherens et al.
Trinidad de Torres a, Nuria García b
a Escuela Técnica Superior de Ingenieros de Minas, Ríos Rosas 21,28003, Madrid, Spain
b Department de Paleontología, Facultad de Ciencias Geológicas, U. C.M., 28040, Madrid, Spain
A detailed study of isotopic relationships in
European Pleistocene ursid teeth have been pre-
sented by Bocherens et al. (1994). We agree with
the resu1ts and broad conclusions derived from the
stable carbon isotope relationships. These are find-
ings that confirm the previous hypothesis relating
to the diets of Ursus deningeri and Ursus spelaeus.
We do, however, wish to take issue with a few
points, notably the first paragraph in the sub-
section on p. 220 "teeth stop their growth at an
early ontogenic state" and the statement on p. 222
" ...most of the formation of the teeth occurs when
the cubs are suckling and the mother is still in the
den, consuming her fat".
Torres et al. (1991) demonstrate a clear size dis-
tribution in Ursus spelaeus sites (Fig. 1): (1) the
remains of animals that died in the perinatal period
or before leaving the cave for the first time (before
weaning), (2) bearcubs that died during their first
winter, and (3) mature bears that had become inde-
pendent hibernants.
The mandibular remains of the group 1 animals
consist only of deciduous teeth and sorne buds of
definitive dentition composed of dentine. In this
stage the animal is clearly suckler.
The mandibular remains of the group 2 (first
year cubs) reveal ename1 formation in premolars
and molars and a very thin dentine layer in the
roots, while the canine (without roots) has a 2 mm
thick dentine in the apical portion of the crown.
These animals with jaws that are replete with
cusped teeth cannot be sucklers.
The mandibular remains of group 3 (mature ani-
mals), reveal that the roots from the youngest spec-
imens are hollow.
Fig. 2 shows thin sections through Ursus dening-
eri canines from the Middle Pleistocene site of Sima
de los Huesos in Atapuerca, Burgos (Torres, 1988).
Fig. 2: A, A' show a transversal section from a two
years old bear, based on techniques for age deter-
mination of mammals from annual layers in teeth
from Klevezal and Kleinenberg (1967) and
Lieberman (1994). The apical portion of the root
is open and the root is totally hOllOW. Fig. 2: B, B'
show a transversal section from the canine six-
seven year old bear. Here the pulp cavity diameter
is much greater than in very old animals, where it
is almost sealed with dentine.
In our opinion, the idea that during ontogeny
the total volume of any tooth portion, crown or
root, maybe configured is not admissible. A given
tooth reaches its definitive volume after several
years into the lifetime of a given specimen.
Therefore, any "anomalous" isotopic relationships
410 20
o
Fig. 1. XY plot of transversal (abscisae) and anteroposterior (ordinates) diaphysis of long bones. A. Humerus. B. Radius. C. Femur.
D. Tibia. Group l newborn and unweaned bears, group 2 cubs, group 3 subadults and adults. Sex dimorphism can be observed in
groups 2 and 3. AH the measurements are in mm. From Torres et al. (1991)
must be interpreted in the context of the metabo-
lism and the physiology in hibernating bears, which
may be surnmarized as follows.
During hibernation, bears undergo a "lipid diet"
derived from consuming body fat as a source of
energy. The animal has evolved protective hepatic
mechanisms to cape with this in order to reduce the
toxicity of the highest quantities of ursodeoxicholic
acid in the blood (Couturier, 1954; Camarra, 1989;
Hagy et al., 1993).
Also during hibernation, bears do not excrete
and reabsorb urea via the bladder. Therefore,
during this period the proportion of amino acids in
the blood does not decrease, despite the general
weight loss. Indeed, an increase in sorne amino
acids has been demonstrated (Nelson et al., 1975).
The hibernation does not produce a protein
reduction.
According to Nelson et al. (1975), if the bear is
to maintain itself under summer starvation condi-
tions, fat and protein will be used as a source of
energy continuously and the nitrogenous waste
products of the amino acids are excreted in the
usual way via urine and faeces (Lyman et al.,
1982).
Because of this, conc1usions about hibernation
may be interpreted in terms of an energy balance.
It is c1ear that during the months of activity bears
Fig. 2. Canine thin sections (general view and detail). A, A' cub
canine genn, B, B' adult, 6-7 years old, canine.
eat and this leads to 15N-depleted collagen relative
to their winter condition. During lactation (new-
Bocherens, H., Fizet, M. and Mariotti, A., 1994. Diet, physiol-
ogy abd ecology of fossil marnmals as inferred from stable
carbon and nitrogen isotope biogeochemistry: implications
for Pleistocene bears. Palaeogeogr. Palaeoclimatol.
Palaeoecol., 107: 213-225.
Camarra, J.I., 1989. L'Ours Brun. Hatier, 213 pp.
Couturier, M., 1954. Gite, taniere sornmeil hivernal. L'Ours
Brun, Grenoble, pp. 519-537.
Hagy, L.R., Crombie, D.L., Espinosa, E., Carei, M.C., Igimi,
H. and Hofman, A.F., 1993. Ursodeoxycholic acid in the
Ursidae: Biliary bile acids of bears, Pandas and related
carnivores. J. Lipid Res., 34: 1911-1917.
K1evezal, G.A. and Kleinenberg, S.E., 1967. Age detennination
of marnmals from annuallayers in teeth and bones. 128 pp.
Liebennan, D.E., 1994. The biological basis for seasonal
increments in dental cementum and their application to
Archaeological research. J. Archaeol. Sci., 21: 525-539.
Lyman, c.P., Willis, J.S., Malan, A. and Wang, L.C.H., 1982.
Intennediary Metabolism in Hibernation. Hibernation and
Torpor in Marnmals and Birds. Academic Press,
pp. 124-171.
Nelson, R.A., Jones, J.D., Wahner, H.W., McGill, D.B. and
Code, C.F., 1975. Nitrogen metabolism in bears: Urea
metabolism in surnmer starvation and in winter sleep and
role of urinary bladder in water and nitrogen conservation.
Mayo Clinic Proc., 50: 141-146.
Torres, T., Cobo, R. and Salazar, A., 1991. La población de
oso de las cavernas (Ursus spelaeus parvilatipedis n. ssp.) de
Troskaetáko Kobea (Ataun-Gipuzcoa). Munibe (Antropol.-
Arkeol.), 43: 3-85.
Torres, T., 1988. Osos (Mammalia, Carnivora, Ursidae) del
Pleistoceno de la Peninsula Ibérica. Publ. Esp. Bol. Geol.
Min., 316 pp.
References
boms) and hibemation (cubs and mature bears),
howewer, urea resorption enables 15N enrichment.


Comments on : diet, physiology and ecology of fossil mammals as inferred from stable carbon and nitrogen isotope biogeochemistry: implications for Pleistocene bears

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