The presence and implications of viable seed in the faeces of invasive free-ranging European Rabbits and Red Foxes

Abstract

Invasion by weeds and other undesirable plants threatens global biodiversity. However, the role of mammals in maintaining and spreading weeds is often overlooked. Here we confirm that two widely distributed and abundant Australian mammalian pests, the European Rabbit (Oryctolagus cuniculus) and the Red Fox (Vulpes vulpes), can spread viable seed. Our assessment mainly involved determining the number and viability of seeds recovered from faeces of free-ranging individuals inhabiting several areas within the Mediterranean region of south-western Australia, an internationally recognized biodiversity hotspot. In summer, viable seeds were recovered from 3?4% of the rabbit faecal pellets (n = 190) compared to 21?40% of pellets in autumn (n = 235). Ten (77%) of the 13 species of seed identified were weeds. Of the 1,136 seeds recovered, 16% germinated. In all, 13-30% of rabbits passed viable seeds in summer, increasing to 44?73% of rabbits in autumn. In captive wild rabbits, mean passage time of marked seed through the intestinal tract ranged from 4?7 h. This, together with the small home ranges of Australian European rabbits, suggests that they may generally disperse seeds over 1?2 km. Nine to 27% of foxes passed viable seed. Although 48% of scats (n = 62) contained whole seed, only 12.9% of all scats contained viable seed (range 9.1%?19.0%). Viable seeds (4/8) were also recovered from the hides of some shot foxes. In all, 63% (12/19) of seed species identified in the scats and pelts of foxes were weeds. Rabbits (primary dispersal) and foxes (primary, and secondary dispersal via seeds ingested with prey) may be important dispersers of viable seed, and may be essential for less common, but important, long-distance plant dispersal, particularly by some invasive species. Thus, suppression of weeds can be added to the benefits of reducing the abundance of rabbits and foxes to protect the unique biota and agricultural production in southwestern Australia.