animal density

To assess the effect of possum browse on plant growth, an index of the amount of foliage on about 50 trees of Fuchsia excorticata and the number of trees that died or were completely defoliated was measured at five sites in South Westland over 5 years. This index was compared to possum density indices taken at each site each year. At one site, possums were reduced from a high density about 6 months before the final measurement. The degree of defoliation of fuchsia was significantly related to the density of possums at each site.

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.