Abstract

A high prevalence of a distinctive alopecia (hair loss) syndrome occurs in juvenile female Australian fur seals at what historically has been the largest breeding colony for this species. We compared juvenile female serum concentrations of thyroid hormones in cases (n = 41) and controls (n = 38) and found no difference in free and total triiodothyronine (T3) or thyroxine (T4). Comparison of case seals based on severity of alopecia showed that more severe cases had higher concentrations of free T4 (p = 0.016) than control seals, perhaps indicating increased thermoregulatory demands. Seals with alopecia were in poorer body condition (p < 0.001) than unaffected animals and a recent population census showed a large decline in pup numbers at this site compared to other colonies. To investigate possible endocrine disruption in the juvenile female cohort, we controlled for case status, season and body condition and performed multiple regression models on blubber and serum samples from 24 individuals. These revealed significant positive associations between total blubber polychlorinated biphenyls (ΣPCBs) and the thyroid hormones free T3 (p = 0.0005), total T3 (p = 0.0005) and total T4 (p = 0.029). In addition, ΣDDT metabolites were positively associated with free T3 and total T3. These results suggest endocrine disruption is occurring in this cohort associated with pollutants, but it is unlikely that thyroid hormone perturbation is the proximate cause of alopecia.

* Presenting author