State of Environment

Indicator 31 - Annual population estimates of Southern Elephant Seals at Macquarie Island

Index: Description | Data | Custodian evaluation | Related resources | Parameters
Responsible
Organisation
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Australian Antarctic Division Details
Custodians
ROSEMARY GALES
rgales@dpiwe.tas.gov.au
INVESTIGATOR
TECHNICAL CONTACT
Parks and Wildlife Service
DEPARTMENT OF PRIMARY INDUSTRY,
WATER AND ENVIRONMENT
GPO BOX 44A



Ph +61 3 6233 3865
Theme Area Biodiversity
Indicator Type Condition   
Criteria the
Indicator Satisfies
The following 14 out of 15 criteria
1. Serve as a robust indicator of environmental change
2. Reflect a fundamental or highly-valued aspect of the environment or an important environmental issue
3. Be either national in scope or applicable to regional environmental issues of national significance
4. Provide an early warning of potential problems
5. Be capable of being monitored to provide statistically verifiable and reproducible data that shows trends over time and, preferably, apply to a broad range of environmental regions
6. Be scientifically credible
7. Be easy to understand
8. Be monitored with relative ease
9. Be cost-effective
10. Have relevance to policy and management needs
11. Contribute to monitoring of progress towards implementing commitments in nationally important environmental policies
12. Where possible and appropriate, facilitate community involvement
13. Contribute to the fulfillment of reporting obligations under international agreements
15. Where possible and appropriate, be consistent and comparable with other countries’ and state and territory indicators
For details of indicators, see the State of Environment Bibliography entries 16336 and 16337
Date Input Yearly measurements
Monitoring Location Macquarie Island Details  

Geographic Coverage is

    Latitude (-54.7 to -54.6)
    Longitude (158.8 to 158.9)

Data
Temporal range of the available data, as described by the metadata record, is from 15-Oct-1985.

Timespan: 1988 to 2012.
Number of data points: 42.

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Macquarie Island: Number of breeding females - Full census

Macquarie Island: Number of breeding females - Partial census

Data Quality, Interpretation and
Analysis of Indicator Data
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Two different methodologies have been employed to collect these data. From 1988 to 2004 a full census of all colonies on the island were conducted each year between the 13th and 17th of October - details of which are presented below. From 2005 onwards, owing to diminishing resources, a decision was made to only census a representative sample of the southern elephant seal colonies on the island. 5 colonies were selected as being representative of the whole island. Further information about this ''partial'' census can be found in a word document available for download from the URL given below.

In the data graphs displayed below, the ''Full Census'' graph present data collected between 1988 and 2004 using the full census method. The ''Partial Census'' graph present data from 1988 onwards using the partial census method - for the period 1988-2004, the figures for the 5 colonies used in the partial census have been obtained from the full census data.

Full Census Method:

Female Elephant seals haul-out to pup on island beaches according to a very regular pattern (Gaussian or Normal distribution) and timetable (peak haul-out between 13 and 17 October). They group together in ''harems'' with a few associated dominant males and are readily counted due to their obvious locations on open beaches and their lack of movement once ashore and having pupped. Thus counts of females can be made accurately to within +/- 5\\%.

The counts of the adult females (cows), fully weaned pups and dead pups are summed daily, and separately, through October for the west and east isthmus beaches. These totals represent the time distribution of numbers of cows ashore for each of these beaches. Corrections to the census totals are made in two stages:

Firstly, Gaussian curves are fitted to these distributions by least-squares calculations. From the equation to the curve for the west isthmus, the day of maximum numbers is determined as the calculated mean day. If the day of maximum numbers is not October 15, then the total for October 15 is increased by the proportional difference between it and the peak total of the fitted curve.

Secondly, the totals of the numbers for each of the five island zones counted on October 15 are increased to numbers predicted for the actual day of maximum cows ashore. This is done by transforming the fitted curve for the west isthmus into daily values of the proportion of cows present, from 1 (which is the number of cows at the peak of the curve) to fractions for each day on either side of the peak. Then the zone totals are divided by the fraction appropriate for their number of days delayed. This is done because the island beaches are grouped into five zones (see figure in instructions) which have characteristic day delays in their elephant seal cow numbers reaching a maximum with respect to the west isthmus area.

These delays are given in days:
ZONE- DAYS (delay from calc. peak day, west Isthmus)
North Head to Aurora Point - 0
Aurora Point to Caroline Cove - 3
Garden Cove to Sandy Bay - 2
Sandy Bay to Waterfall Bay - 3
Waterfall Bay to Hurd Point - 5

The total for the census is the sum of all these five adjusted zone totals.
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Data Usage Constraints '
This data set conforms to the PICCCBY Attribution License
(http://creativecommons.org/licenses/by/3.0/).

Please follow instructions listed in the citation reference provided at http://data.aad.gov.au/aadc/metadata/citation.cfm?entry_id=SOE_elephant_seals when using these data.
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Data Access Constraints '
These data are publicly available for download from the URL given below.

A copy of the word document describing the census methodology adopted in 2005 is also available for download from the URL given below.
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Custodian Evaluation
Date entered Evaluation
15-Apr-2002 The data to date show that the number of breeding cows on Macquarie Island have been declining at ~1.2% per year for the last decade. This indicates that the large ocean environment that the seals forage in (the whole Southern Ocean between M.I. and Antarctica and west to Heard Is and east to the Ross Sea) is becoming less and less suitable for foraging by Southern Elephant Seals. It seems likely that present changes in ocean circulation in this huge area have resulted in reductions of plankton stocks to squid and myctophid fish (the major prey groups of Southern Elephant Seals) in accessible foraging areas for the seals compared to previous decades. There has been no appreciable and current competition between Southern Elephant Seals and fisheries in the Southern Ocean to date. Thus the seal decrease is attributable to "natural causes" as above.

11-Nov-2002
Condition scale - 4 - fair condition

1 - the environment degraded to the point where rehabilitation is impossible
0 1 2 3 4 5 6 7
7 - the environment is pristine, in perfect condition, no anthropogenic influences

State of Knowledge scale - 6

1 - Poor
0 1 2 3 4 5 6 7
7 - Excellent

For definitions of the Scale categories, consult the Explanation of the Status Categories

Related resources

Metadata SOE_elephant_seals - Annual population estimates of Southern Elephant Seals at Macquarie Island from censuses made annually on October 15th.
Project 2265 - Factors controlling the population status of the southern elephant seal Mirounga leonina at Macquarie Island
Scientific Bibliography 17287 - Hindell, M.A., Burton, H.R. (1987) Past and Present Status of the Southern Elephant Seal (Mirounga leonina) at Macquarie Island. Journal of Zoology 213. pp 365-380.
SOE Indicator 27 - Regional populations of Adelie penguins in the vicinity of Casey, Davis and Mawson.
SOE Indicator 28 - Standard demographic parameters for Adelie penguins at Mawson
SOE Indicator 29 - Breeding population of the Southern Giant Petrel at Heard Island, the McDonald Islands and within the AAT
SOE Indicator 31 - Annual population estimates of Southern Elephant Seals at Macquarie Island
SOE Indicator 32 - Fecundity and pup growth in fur seal colonies on Macquarie Island
SOE Indicator 33 - Annual catch in tonnes of marine species harvested in Australian Antarctic and sub-Antarctic waters
SOE Indicator 36 - Numbers of species protected at various levels of conservation status
SOE Indicator 37 - Species and numbers of species killed, taken or interfered with or disturbed in the Antarctic and the sub-Antarctic for the purpose of scientific research
SOE Indicator 45 - Monthly collections of marine debris from Sandell Bay beach on Macquarie Island (categories and mass)
Taxonomy 26 - Mirounga leonina Southern Elephant Seal
Parameters
The properties link can be used to view details of the parameters measured for this indicator.

Parameter NameUnit of measure Properties
Number of breeding females - Full census Properties
Number of breeding females - Partial census Properties
The following parameters and/or sensor notes are from the metadata record.

Parameters -
EARTH SCIENCE > BIOLOGICAL CLASSIFICATION > ANIMALS/VERTEBRATES > MAMMALS
EARTH SCIENCE > BIOSPHERE > ECOLOGICAL DYNAMICS > SPECIES/POPULATION INTERACTIONS


Related URL's
http://data.aad.gov.au/aadc/metadata/citation.cfm?entry_id=SOE_elephant_seals
Citation reference for this metadata record and dataset

http://data.aad.gov.au/aadc/portal/download_file.cfm?file_id=1272
Download page for Australian Antarctic Data Centre - SIMR Access 2000 Database

http://data.aad.gov.au/aadc/portal/download_file.cfm?file_id=2308
Download point for the word document detailing the methodology adopted in 2005

http://data.aad.gov.au/aadc/portal/download_file.cfm?file_id=2412
Download point for the complete census spreadsheets