Fluctuating asymmetry in skulls of Svalbard and East Greenland polar bears (Ursus maritimus) in relation to time, geography and organohalogen pollution

Fluctuating asymmetry (FA) as a measure of environmental stress was studied in polar bear (Ursus maritimus) skulls from East Greenland (n = 300, collected during the period 1892-2004) and Svalbard (n = 391, collected during the period 1950-2004). Nine bilateral metric traits in skull and lower jaw were measured twice. The measured levels of FA for each trait were compared between sex/age groups (subadult, adult females, adult males), time periods (¡Ü1960 and >1960), and localities (East Greenland and Svalbard). The time period before 1960 was chosen to represent a period prior to the appearance of organohalogens (PCBs, HCB, HCHs, DDTs, dieldrin, CHLs, PBDEs, mirex) in the Arctic, while the time period after 1960 represents the period when the polar bears have been subjected to such organohalogens. One of the traits had a significantly higher degree of FA (for all sex/age groups) during the first period, while in two other traits, the subadults had a significantly higher FA during the second period. The Svalbard polar bears had a significantly higher FA in one trait than did the bears from East Greenland. This latter trend was reflected in the investigation of a pooling of four of the traits. Levels of fluctuating asymmetry of each trait were furthermore assessed over time on bears born during the period 1950-2004. The polar bears were divided into sex/age groups, but not according to locality. All significant results from these analyses had a negative slope, with FA decreasing over the period of time. Correlation analyses of FA for each trait versus the levels of contaminants in adipose tissue samples was performed for a subsample of the East Greenland polar bears, collected recently (1999-2002). The majority of the significant results of these correlation analyses showed a negative trend in the data, with higher levels of FA corresponding to lower levels of contaminants. Overall, the present study showed no substantial evidence of a relation between levels of FA and organochlorines. Instead, the indications were of subpopulations with generally declining levels of FA over time, suggesting the existence of positive population level effects powerful enough to overrule the negative influence of stress caused by factors such as global warming, pollution, and overharvesting. Or, alternatively, a) that the individuals with the highest levels of stress and thus ditto values of FA are aborted or die as neonates, and thus are not included in the collections of polar bears examined in the present study, b) that FA of metric skulls traits is not a suitable predictor of stress in polar bears, c) that the organohalogen toxic loads are not at high enough levels to elicit a measurable positive response in the FA of the examined polar bears

(Table 1) Retinol (vitamin A) and alpha-tocopherol (vitamin E) concentration in polar bear (Ursus maritimus) kidney

Vitamins A and E content of inner organs, among these the kidneys, are increasingly being used as an indicator of adverse effects caused to the organism by e.g. environmental contaminants. In general, only a renal sub sample is used for analyses, and it is thus essential to know which part of the organ to sample in order to get a representative value for this important biomarker. The aim here was to assess the distribution of vitamins A (retinol) and E (alpha-tocopherol) within the polar bear multireniculate kidney (i.e. polar vs. medial position) and also within the cortex vs. medulla of each separate renculi. The results showed no significant difference between the medial and polar renculi with regards to either retinol (p = 0.44) or alpha-tocopherol (p = 0.75). There were, however, significant differences between cortex and medulla for both vitamins (retinol, p = 0.0003; alpha-tocopherol, p<0.0001). The kidney cortex contained higher values of both vitamins than the medulla; on average 29% more retinol and 57% more alpha-tocopherol. Mean concentrations in the medulla was 2.7 mg/kg for retinol and 116 mg/kg for alpha-tocopherol, and in the cortex 3.5 mg/kg for retinol and 182 mg/kg for alpha-tocopherol. These results clearly indicate that one should take precautions when analyzing retinol and alpha-tocopherol in polar bear kidneys. Prior to analysis, the renculi should be separated into medulla and cortex. The results indicated no significant differences between renculi from different parts of the kidney

Length of skull traits and time of attainment of full size of traits in East Greenland and Svalbard polar bears

Size, growth and sexual dimorphism of nine skull traits was studied in 300 East Greenland and 391 Svalbard polar bears (Ursus maritimus). Two traits were significantly larger in bears from East Greenland compared to Svalbard bears, and trait size was smaller after 1960 in five traits. For both localities and both age groups (sub adult, adult), mean trait size values were higher in males than females (all: P < 0.05). Gompertz growth models showed trait size increasing with age in seven traits. Depending on the trait, males reached 95% asymptotic trait size at age 3-10, females at age 2-6. The females of both localities matured at approximately the same age, whereas the Svalbard males generally matured years later than their East Greenland peers. The differences found in the present study between the two polar bear subpopulations support the notion that East Greenland and Svalbard polar bears probably should be managed as separate units

(Table 1) Cortisol concentration in hair of East Greenland polar bears (Ursus maritimus)

To demonstrate the ability to assess long-term hypothalamic-pituitary-adrenocortical (HPA) axis activity in polar bears (Ursus maritimus), a pilot study was conducted in which cortisol concentration was analyzed in hair from 7 female (3-19 years) and 10 male (6-19 years) East Greenland polar bears sampled in 1994-2006. The hair was chosen as matrix as it is non-invasive, seasonally harmonized, and has been validated as an index of long-term changes in cortisol levels. The samples were categorized according to contamination: eight were clean (2 females, 6 males), 5 had been contaminated with bear blood (2 F, 3 M), and 4 with bear fat (3 F, 1 M). There was no significant difference in cortisol concentration between the three categories after external contamination was removed. However, contaminated hair samples should be cleaned before cortisol determination. Average hair cortisol concentration was 8.90 pg/mg (range: 5.5 to 16.4 pg/mg). There was no significant correlation between cortisol concentration and age (p = 0.81) or sampling year (p = 0.11). However, females had higher mean cortisol concentration than males (females mean: 11.0 pg/mg, males: 7.3 pg/mg; p = 0.01). The study showed that polar bear hair contains measurable amounts of cortisol and that cortisol in hair may be used in studies of long-term stress in polar bears