How many possums make a cow?
- Landcare Research, Private Bag 11052, Palmerston North, New Zealand
The importance of possums as competitors with livestock for pasture is sometimes used as justification for possum control. Unfortunately a confusion of wet and dry weight values of pasture and daily consumption by possums appears to have resulted in a significant overestimate of the economic costs of possums as pasture pests. A correctly estimated daily dry matter intake of pasture by possums is 0.0144 kg pasture dry matter per possum per day. For a possum density of 1 ha-1, this amounts to a reduction of about 1% of a stock unit ha-1 year-1. At higher possum densities, which often occur on farms adjacent to forest or scrub, losses would be correspondingly higher. A more direct way to measure possum impact on pasture production would be to use exclosures.