Cleared and uncleared pellet plots as indices of brown hare density
- Ecology Group, Institute of Natural Resources, Massey University, Private Bag 11222, Palmerston North 4474, New Zealand
Faecal pellet counts are commonly used as indices of lagomorph abundance but uncertainty over variation in decay rates among sites has led to most researchers recommending the use of pellet accumulation rates in previously cleared plots rather than the simpler and quicker method of counting uncleared plots. We use data from cleared and uncleared 0.1-m2 brown hare pellet plots at six sites in the central North Island of New Zealand to test the reliability of the two methods. The sites varied considerably in hare pellet density and also varied in altitude and rainfall, but the initial cleared count was extremely tightly correlated with the subsequent pellet accumulation rate (r = 0.987) suggesting there is minimal bias from differential decay rates in uncleared plot counts. Our results show that the simpler and less time-consuming uncleared-plot method is an adequate index of hare density across a range of hare densities and climates and is not unduly biased by differential decay rates. This should simplify the work of land managers interested in assessing relative abundance. At one site (the area round Manson Hut on the Kaweka Range) where the plots were followed for a year in a variety of habitat types, there were strong seasonal changes in hare abundance (peaking in summer and declining through winter), and strong habitat preferences for exotic grasslands and grassland–herbfield mixes, while pure herbfield, and particularly rocky scree and southern beech forest were not favoured. We estimated that based on published defecation rates of hares, population densities at our six sites varied from 0.03 to 3.93 hares per hectare and that they consumed between 1.4 and 188 kg ha–1 of biomass annually.