Macquarie Island Elephant Seal Populations 1985 Onwards

Brief description

This dataset contains the results from studies of the Elephant Seal (Mirounga leonina) at Macquarie Island. Results from branding surveys and photographs from 1985 onwards are reported. Numbers, life stage, sex, moult stage and migration patterns have been reported. Currently some 2000 pups a year are branded and the dataset includes birth dates, weights at birth and weaning and at 6, 12 and 18 months.

This work was completed as part of ASAC (AAS) project 2265 (ASAC_2265).

Objectives:

1. To prepare research papers, from the extensive southern elephant seal dataset, that deal with key demographic parameters of the population such as size, age specific survivorship, fecundity, recruitment into the breeding population, age specific growth rates, and intrinsic rate of change of the population. In addition, later papers will investigate interannual variability in these parameters, how these relate to changing environmental conditions, and the effects of this on long term population fluctuations.

2. To analyse and compare stable isotope ratios in the facial vibrissae of the seals and the hard parts of their prey to determine the geographical positions of the major foraging grounds of the seals. The isotope values will also allow the food webs, that support the seals, to be better defined.

3. To measure the growth rates of elephant seal vibrissae so that changing isotope values, related to the prey and foraging areas, can be referred to particular foraging periods. Elephant seals characteristically have two separate periods of foraging: one in summer and one in winter. The positions of these episodes on a vibrissa can be identified once the growth rates of vibrissae are known.

Taken from the progress report for the 2009-2010 season:

Progress against objectives:
1. One paper published from the elephant seal dataset. Two papers also published during 2009/10 using data collected opportunistically during the life of this project.

2. PhD student Andrea Walters continues to analyse the results of the whisker analyses. She has presented some of her results at the AMSA 2009 marine connectivity conference in Adelaide.

An honours student has been engaged (start date March 2010) to analyse the squid component of the seals' diet.

3. John van den Hoff spent the early summer at Macquarie Island finalising the collection of the demographic data. 2154 tag/brand resights were recorded. Collection of the data has continued on the island by Chris Oosthuizen, Ben Arthur and Iain Field since John returned to Australia. When those field workers return data collection will cease.

Lineage

Progress Code: completed