So named because whalers thought them the "right" whales to hunt, the whales were easy to approach and lived close to shore, and their high blubber content kept them afloat once killed.
Right whales were a preferred target for whalers because of their docile nature, their slow surface-skimming feeding behaviors, their tendencies to stay close to the coast, and their high blubber content (which makes them float when they are killed, and which produced high yields of whale oil).
The microscope of whole-genome studies and comparisons also gives glimpses into the adaptation of polar bears to the Arctic environment, including genes for high fat content in milk and for blubber accumulation.
The condition of the carcass might be responsible for these differences in blubber lipid content among individuals but no significant difference was reported in the lipid content of the blubber between fresh, moderately decomposed and advanced decomposed carcasses.
However, carcass condition had no significant effect on either blubber lipid content or PCB/tDDT concentrations in blubber lipids (see Results section).
The effects of carcass condition (fresh, moderately decomposed, advanced decomposed) on blubber lipid content as well as on the PCB or tDDT levels in blubber lipids were first examined using a one-way fixed-model analysis of variance (ANOVA) since decomposition of the carcass and a resulting change in blubber lipid content can affect PCB or DDT concentration.
This relationship was observed in a previous study on California sea lions [ 22], which reported that the highest concentrations of both tDDT and PCBs were found in individuals with the lowest blubber lipid content.
Conversely, there was a negative relationship between blubber lipid content and tDDT and PCB concentrations (F = 6.780; df = 1,22; p = 0.016 for tDDT; F = 11.060; df = 1,22; p = 0.003 for PCBs).
Despite the marked decline in tDDT in California sea lions over the last 3 decades, levels remain higher in this animal than in most other marine mammals, even when only samples with blubber lipid content >20% were taken into account.
The effect of blubber lipid content of the blubber (lipid), sex and age category (sex-age category), and the location where the sample was collected (location) on tDDT or PCB concentrations in blubber lipids were examined using a three-way fixed-model analysis of covariance (ANCOVA), with lipid as a continuous variable and sex-age category and location as categorical variables.
To better assess the decline in tDDT levels over the last 30 years and to avoid the potential confounding factor of sex, we compared males in this study with blubber lipid contents higher than 20% with a similar sample of males reported in previous studies [ 19, 21] (Fig. 3).
