Age- and sex-dependent distribution of persistent organochlorine pollutants in urban foxes.

Abstract

The colonization of urban and suburban habitats by red foxes (Vulpes vulpes) provides a novel sentinel species to monitor the spread of anthropogenic pollutants in densely populated human settlements. Here, red foxes were collected in the municipal territory of Zürich, Switzerland, and their perirenal adipose tissue was examined for persistent organochlorine residues. This pilot study revealed an unexpected pattern of contamination by polychlorinated biphenyls (PCBs), with significantly higher levels of the predominant congeners PCB-138, PCB-153, and PCB-180 in juvenile foxes relative to adult animals. Further data analysis demonstrated that the observed difference was attributable to an age-dependent reduction of PCB concentrations in females, whereas male foxes retained approximately the same PCB burden throughout their life span. A similar sex-related bias between population members has been observed, primarily in marine mammals. Interestingly, the reduction of organochlorine contents with progressive age is reminiscent of human studies, where an extensive maternal transfer of xenobiotics to the offspring has been shown to result in increased exposure levels of infants relative to adults. To our knowledge, this is the first example of an urban wildlife species that faithfully reflects the dynamic distribution of toxic contaminants in the corresponding human population. Suburban and urban foxes occupy habitats in close proximity to humans, depend on anthropogenic food supplies, are relatively long-lived and readily available for sampling, can be easily aged and sexed, have a limited home range, and, therefore, meet several important requirements to serve as a surrogate species for the assessment of toxic health hazards.

Sex-dependent accumulation and maternal transfer of Dechlorane Plus flame retardant in fish from an electronic waste recycling site in South China

“…The lower levels of DP in female fish could be attributed to the transfer of DP from mothers to their eggs. Clear sexual differences in PCBs and other organochlorine pesticides have been previously observed in frogs (Rana ornativentris and Rana japonica) and red foxes (Vulpes vulpes), resulting from the maternal transfer of these chemicals in females (Kadokami et al, 2004;Dip et al, 2003).…”

Garbage in the diet of carnivores in an agricultural area

“…Peirce and Van Daele (2006) have shown that eating garbage may provide earlier maturation, higher growth rates, and gain some calorific benefit. However, foraging close to human settlements may be risky, because many of the carnivorous species are regarded as pests, and are persecuted because of the possibility of being poisoned (Birks 1998;Dip et al 2003). There is also a possible risk of damage to or blockage of the digestive track (Sadove & Morreale 1990).…”

Animal behavior in urban ecosystems: Modifications due to human-induced stress

“…They postulated that these high lead concentrations could have adverse effects on predators such as small falconiformes due to bioaccumulation. Dip et al (2003) found high concentrations of organochlorine pollutants in urban red foxes (Vulpes vulpes). However, they documented that this resulted in high levels of mortality among adult males but not females.…”