Fig 1.
The location of the Prince Edward Islands in relation to fronts and currents in the Southern Ocean region between Africa and Antarctic.
The location of the study area, Cave Bay, marked in the insert.
Table 1.
Statistics (mean, standard deviation, minimum and maximum) summarising attributes of completed foraging trips (duration, distance travelled from study site and round trip distance) by individual study animals, per season at Prince Edward Island (2011–2012).
Where trips extended between seasons they were allocated to the season within which the longest period of the trip occurred. An X in the ID field indicates a female which behaved aberrantly, relocating to Marion Island shortly after deployment. This female is omitted from the “All combined” statistics at the end of the table.
Fig 2.
Distance rose plots summarising the distances, within different direction classes, of all positions of the adult Subantarctic fur seal females tagged at Prince Edward Island (n = 12), from the study colony during the study period (March 2011-Feb 2012).
Fig 3.
Switching state space model predicted tracks of adult Subantarctic fur seal females tagged at Prince Edward Island in March 2011, overlaid on seasonal averages of sea surface height anomaly for (A) Autumn (March-May; n = 12 seals), (B) Winter (June-August; n = 8 seals), (C) Spring (September-November; n = 6 seals), (D) Summer (December-February; n = 4 seals). The segments of predicted tracks that were associated with area restricted search (ARS) behaviour are distinguished from those associated with travelling. The dashed lines show the average surface locations of the Subtropical Convergence (STC), Subantarctic Front (SAF), and Antarctic Polar Front (APF), identified by the 14°C, 8°C, and 4°C sea surface temperature isotherms, respectively.
Fig 4.
Switching state space model predicted tracks of the adult Subantarctic fur seal females (n = 12) tagged at Prince Edward Island in March 2011 and tracked between then and February 2012, overlaid on bathymetry (m).
The individual seals identified by their PTT numbers are in the legend; the black circle is the study site.
Fig 5.
The mean relative abundances (± standard deviations) of fish prey items per scat collected from Prince Edward Island in March 2011 (n = 16).
The percentage frequency of occurrence of each prey item is given in parentheses.
Fig 6.
Random forest model response curves for the different predictors of behavioural activity of the twelve adult Subantarctic fur seal females tagged at Prince Edward Island in March 2011 and tracked between then and February 2012.
Distance represents distance from the study colony, Distance8 is the distance from the Subantarctic Front and Distance14 is the distance from the Subtropical Convergence Zone. The final panel shows the relative importance of all the predictors in terms of their influence on the predictive accuracy of the model.
Fig 7.
Foraging habitat suitability (preferred areas for ARS) in the study domain for Subantarctic fur seals Arctocephalus tropicalis in each of the four seasons as predicted by a random forest model with behavioural state (travelling or area restricted search) as a function of geographical and environmental variables.
The dashed lines show the average surface locations of the Subtropical Convergence (STC), Subantarctic Front (SAF), and Antarctic Polar Front (APF), identified by the 14°C, 8°C, and 4°C sea surface temperature isotherms, respectively.
Table 2.
Results of chi-square tests with Bonferroni corrections to test whether or not the frequency of ARS depends on the size of the area inside vs outside the MPA, in each season.
In the test, the frequencies were weighted by the size differences between the MPA and non-MPA areas (0.34: 0.66).