This study was begun in 2005 and is still ongoing. Adult females
were identified from 2005 onwards and adult males from 2008 onwards
(see below). In this paper we consider sightings primarily
from 2007 to 2008, except in estimating density, where we include
data from 2009. Sampling effort is quantified in terms of the number
of field days per month (Table 1). We infer inter-calving intervals
from informal observations over the past 5 years. We
performed observations by vehicle during park hours from
0600 h to 1830 h, typically remaining inside for the full day. Driving
routes were alternated such that all parts of the road network
were covered at least once per week. Thus the entire motorable
area of the park was covered each week, which constituted approximately
1/3 of the total 308 km2 area of the national park