Size and density of East Greenland polar bear (Ursus maritimus) skulls: valuable bio-indicators of environmental changes?

TY - JOUR

T1 - Size and density of East Greenland polar bear (Ursus maritimus) skulls

T2 - valuable bio-indicators of environmental changes?

AU - Sonne, Christian

AU - Bechshoft, Thea Ø.

AU - Rigét, Frank F.

AU - Baagøe, Hans J.

AU - Hedayat, Abdi

AU - Andersen, Mogens

AU - Bech-Jensen, Jens-Erik

AU - Hyldstrup, Lars

AU - Letcher, Robert. J.

AU - Dietz, Rune

PY - 2013/11/1

Y1 - 2013/11/1

N2 - There is an increasing interest in assessing the relationship between climatic oscillations, environmental contaminants and the modelling of animal physiological and morphological responses. We therefore undertook a study of skull condylobasal length (CBL; reflecting body size) and bone mineral density (BMD) in 87 East Greenland male polar bears (Ursus maritimus) sampled in the time period of 1892-2010. The purpose of the study was to investigate if these measures are potential candidates as indicators for stress associated with climate change and long-range transported toxic industrial chemicals. The analyses showed that both BMD and CBL in polar bears sampled in period 4 (1999-2010, n = 57) were significantly lower when compared with period 2 (1920-1936, n = 19) (both p < 0.02). Groups of persistent organohalogen contaminants (PCBs [polychlorinated biphenyls], DDT [dichlordiphenyltrichlorethane], HCH [hexachlorocyclohexane], HCB [hexachlorobenzene], chlordanes, dieldrin, PBDEs [polybrominated diphenyl ethers]) were measured in period 4 and multiple regression analyses controlling for age showed that dieldrin had a significant negative effect on BMD (p = 0.03, n = 52) while significant positive correlations with CBL were found for DDT, dieldrin and PBDE (all p < 0.05, n = 52). When testing the correlation with the North Atlantic Oscillation climate index no significant relationship was found for BMD (p = 0.97, r = -0.01, n = 27) nor CBL (p = 0.31, r = -0.2, n = 27). We therefore suggest that BMD and body size have decreased in East Greenland polar bear males over the past 120 years and that exposure to organohalogen contaminants may explain the BMD reductions. It is, however, not entirely clear if and how climatic oscillations affected the reductions in body size and BMD mainly because of the limited sample size in period 2 and lower mean age in period 4. Therefore, precautions should be taken towards a final conclusion on BMD and CBL as bioindicators for climate oscillations and exposure to toxic environmental chemicals. It is recommended that the sampling and archiving of East Greenland polar bear skulls continue in order to further explore how CBL and BMD reflect individual and population response upon exposure to environmental stress.

AB - There is an increasing interest in assessing the relationship between climatic oscillations, environmental contaminants and the modelling of animal physiological and morphological responses. We therefore undertook a study of skull condylobasal length (CBL; reflecting body size) and bone mineral density (BMD) in 87 East Greenland male polar bears (Ursus maritimus) sampled in the time period of 1892-2010. The purpose of the study was to investigate if these measures are potential candidates as indicators for stress associated with climate change and long-range transported toxic industrial chemicals. The analyses showed that both BMD and CBL in polar bears sampled in period 4 (1999-2010, n = 57) were significantly lower when compared with period 2 (1920-1936, n = 19) (both p < 0.02). Groups of persistent organohalogen contaminants (PCBs [polychlorinated biphenyls], DDT [dichlordiphenyltrichlorethane], HCH [hexachlorocyclohexane], HCB [hexachlorobenzene], chlordanes, dieldrin, PBDEs [polybrominated diphenyl ethers]) were measured in period 4 and multiple regression analyses controlling for age showed that dieldrin had a significant negative effect on BMD (p = 0.03, n = 52) while significant positive correlations with CBL were found for DDT, dieldrin and PBDE (all p < 0.05, n = 52). When testing the correlation with the North Atlantic Oscillation climate index no significant relationship was found for BMD (p = 0.97, r = -0.01, n = 27) nor CBL (p = 0.31, r = -0.2, n = 27). We therefore suggest that BMD and body size have decreased in East Greenland polar bear males over the past 120 years and that exposure to organohalogen contaminants may explain the BMD reductions. It is, however, not entirely clear if and how climatic oscillations affected the reductions in body size and BMD mainly because of the limited sample size in period 2 and lower mean age in period 4. Therefore, precautions should be taken towards a final conclusion on BMD and CBL as bioindicators for climate oscillations and exposure to toxic environmental chemicals. It is recommended that the sampling and archiving of East Greenland polar bear skulls continue in order to further explore how CBL and BMD reflect individual and population response upon exposure to environmental stress.

KW - Body size

KW - Bone mineral density

KW - Climate oscillations

KW - Condylobasal length

KW - East Greenland

KW - Persistent pollutants

KW - Polar bear

U2 - 10.1016/j.ecolind.2013.04.015

DO - 10.1016/j.ecolind.2013.04.015

M3 - Journal article

SN - 1470-160X

VL - 34

SP - 290

EP - 295

JO - Ecological Indicators

JF - Ecological Indicators

ER -