Table 1 Information about moult surveys during 2013–2016, including quartiles for pupping dates and mean ± standard deviation moult initiation dates for each year and reproductive category.

	2013	2014	2015	2016
Sighting Metadata
# Sightings	1810	1470	2212	3423
# Seals	1038	866	937	1411
# Survey Days	19	10	11	26
First Moult Survey Date	Jan 13	Jan 17	Jan 18	Jan 18
Last Moult Survey Date	Feb 13	Feb 14	Feb 15	Mar 8
Pupping Quartiles
Minimum	*	Oct 11	Oct 13	Oct 14
25^th percentile	*	Oct 22	Oct 22	Oct 24
Median	Oct 29	Oct 26	Oct 27	Oct 28
75^th percentile	Nov 02	Oct 30	Oct 30	Nov 02
Maximum	Nov 15	Nov 26	Nov 13	Nov 19
Moult Initiation Dates
Attendant Non-Parturient	Dec 28 ± 11.9ⁱ	Jan 05 ± 10.7ⁱⁱ	Jan 07 ± 9.9ⁱⁱ	Jan 12 ± 9.8ⁱⁱⁱ
Non-Attendant Juvenile Females	Jan 06 ± 11.6ⁱ	Jan 07 ± 13.7ⁱ	Jan 11 ± 9.7ⁱ	Jan 17 ± 12.1ⁱⁱ
Attendant Juvenile Females	Jan 04 ± 11.3ⁱ	Jan 11 ± 6.7ⁱⁱ	Jan 15 ± 8.3ⁱⁱ	Jan 15 ± 14.6ⁱⁱ
Non-Attendant Adult Females	Jan 07 ± 14.5ⁱ	Jan 11 ± 11.8ⁱ	Jan 17 ± 11.7ⁱ	Jan 19 ± 9.6ⁱ
Attendant Parturient	Jan 19 ± 8.4ⁱ	Jan 15 ± 11.1ⁱⁱ	Jan 18 ± 9.2ⁱ	Jan 29 ± 13.2ⁱⁱⁱ
Males	Jan 09 ± 13.1ⁱ	Jan 13 ± 10.6ⁱⁱ	Jan 16 ± 8.1ⁱⁱ	Jan 24 ± 12.9ⁱⁱⁱ
Ice break-out date**	Jan 14	Jan 14	Jan 02	Feb 04
Colony attendance***
Attendant Non-Parturient	22%	22%	18%	25%
Non-Attendant Parous	10%	6%	22%	20%
Attendant Parturient	68%	72%	60%	55%

Significant differences in moult initiation dates among years (by row, within a reproductive category) are denoted with Roman numerals (α level = 0.05).
*In 2013, the United States government shut down delayed the Weddell seal research program by several weeks, and pup tagging began only after 50% of the pups were born; as a result, the dates of the earlier quartiles are not known (see methods).
**Date when 7-day running mean of ice concentration falls below 50%. See Beltran⁴² for details.
***Colony attendance proportions for the following year.

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