Small mammals as potential seed dispersers in New Zealand

Weed invasion success is strongly influenced by availability of seed disper sal vectors, which may include animals. We examined the potential of severa l small introduced mammals (mice, kiore, ship rats and possums) to disperse germinable seeds in New Zealand. Captive animals were fed fleshy fruit of weeds (Berberis glaucocarpa, Cotoneaster spp., Crataegus monogyna, Ilex aqu ifolium, Leycesteria formosa, Ligustrum sinense, Lonicera japonica, Passifl ora mollissima, Pyracantha angustifolia, Sorbus hupehensis) and native spec ies (Coprosma spp., Prumnopitys ferruginea and Solanum aviculare). We recor ded the percentage of fruit consumed, seed ingested and gut passage time. F aeces were collected and the seeds extracted and tested for germination pot ential in an unheated glasshouse (two weed species) or under controlled con ditions (11 species). The smallest rodents (mice and kiore) generally destr oyed all seeds eaten. Large numbers of viable seeds of the small-seeded (< 1 mg) species, L. formosa and S. aviculare, passed through ship rats. Possu ms consumed the seeds of all adventive and native fruits except P. ferrugin ea. The proportion of seeds recovered intact from possum faeces varied with plant species and ranged from 6 to 83%. The time required for 50% of all s eeds to be passed by possums ranged from 2.5 to 5.5 days with an average of 3.7 days, and was generally unrelated to simple fruit parameters such as p ercentage pulp and moisture content. For seeds where germination also occur red in the uneaten controls, the germination of seed from possums ranged fr om 3 to 78%. Germination was mostly lower in seeds from possums than in the controls, where differences were significant. Possums have major potential to disperse a wide range of fleshy fruit-producing native and introduced p lant species. Ship rats have the potential to disperse those with very smal l seeds.