Reproduction and mortality of invasive raccoon dogs (Nyctereutes procyonoides) in the Białowieża Primeval Forest (eastern Poland)

We investigated reproduction and mortality of raccoon dogs (Nyctereutes procyonoides) in the Białowieża Primeval Forest (eastern Poland). The species invaded the forest in 1955 and is more common than native species of medium-sized carnivores. The mean litter size of raccoon dogs, based on placental scars and foetuses was 8.4 (SD = 2.0). Mortality of pups was 61% during the first three months following parturition. Of 82 cases of raccoon dog deaths recorded from 1996 to 2006, 55% were caused by natural factors (predation and diseases), 40% were human-related (vehicle collisions, harvest, poaching), and 5% were indeterminable. Rabies was the most important disease. The main predators of raccoon dogs were wolves (Canis lupus) and domestic dogs (Canis familiaris). Almost all raccoon dogs killed by cars were dispersing juveniles. We did not find differences in causes of mortality between collared and uncollared individuals. The annual survival rate of radio-tracked raccoon dogs (n = 18, 1997–2000) was 0.38 (SD = 0.05), and did not differ between males and females. Survival of raccoon dogs varied seasonally. It was highest in winter (0.82) when raccoon dogs settle in burrows, which may protect them against predation. The life table constructed based on the age at death indicates that mortality was highest in the first year of the raccoon dog life (0.82), and lower in the following years (0.58–0.68). Most raccoon dogs (98%) died during the first three years of their life and the maximum life span was 7 years. Life expectancy at birth was 0.8 years.