The population trend of southern elephant seals (Mirounga leonina L.) at Macquarie Island (1952-2004)

Total numbers of adult female southern elephant seals (cows) breeding at Macquarie Island were determined for 19 of the 52 year period between 1952 and 2004. Totals for 1952-1987 (exc. 1959 and 1985) were estimated from the relationship between censuses of the isthmus study area and concurrent censuses for the whole island. Totals for 1987-2004 were obtained by direct census of the entire island in mid-October. Cow numbers decreased from a maximum of about 40,000 in the 1950s to a minimum of 18,300 in 2000, but then increased slightly to 19,200 in 2004. Nonlinear and post-hoc linear analysis of the count data identified 1999 as the year when the exponential rate of change (r) slowed from -1.4% per annum to near zero. The rate of change was not uniform for each census sub-area counted (1987-2004), suggesting that certain terrestrially based density-dependent mechanisms were influencing the annual distribution of cows.