ABSTRACT

Barren-ground caribou (Rangifer tarandus) faecal pellets were collected from several sites in the NWT and analysed for evidence of exposure to major dust and soil sources using two methods. The collection sites included two areas of tailings at the Colomac mine (abandoned), with on-site and off-site control areas and seasonal ranges, and sites at or near the Ekati and Diavik diamond mines. Insoluble ash content of the faecal material averaged 9.3% of the dry matter (D.M.) and varied significantly between sites. A group of samples from the tailings areas at Colomac had elevated ash contents and exceeded 30% of dry matter in five samples. Based on several assumptions, the dietary soil intake necessary to achieve the high ash contents in the faecal samples from Colomac would exceed 50% of the diet in one sample. The average ash content of all the samples collected from the tailings area at Colomac was significantly (p<0.05) higher than the off-site control samples. Ash from the faecal pellets was chemically similar to tailings collected at Colomac. Consistent differences were also observed between the Ekati samples and those from natural range areas, although the variance explained by the associations was relatively low. The results of the study are generally consistent with published reports on high rates of soil ingestion at lick sites by ungulates. This ingestion can result in very high levels of soil in the diet, similar to the maximum levels noted here. The ecological risk assessment for Colomac included an explicit soil ingestion model for caribou which assumed an ingestion rate of 20% of the diet. The data in the present study support the use of this average value but indicate that maximum values may range as high as 50% in some caribou. The study was not designed to describe the amount of the elements absorbed by caribou which have ingested the tailings.

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