Frequency distribution of group sizes recorded for familiar and unfamiliar humpback whales groups off west South Africa.

<p>Familiar groups contained at least one resighted whale, and unfamiliar groups contained no resightings.</p

Average daily ‘operational sex ratio’ (OSR) by season in humpback whales identified off west South Africa.

<p>Whales were identified from tail fluke and dorsal fin pictures and microsatellites collected during boat encounters. Data shown for both those whales only seen once (n = 93) and those resighted (51 individuals in 151 sightings); calves of the year were excluded.</p

Occurrence¹ and Occupancy² of humpback whales off west South Africa resighted on different days during selected season cycles (1993–2007).

1<p> =  number of different days on which an individual was seen in a seasonal cycle; minimum Occurrence is always one.</p>2<p> =  number of days between the first and last sightings in the same seasonal cycle of individuals seen on more than one day.</p

Social network diagram based on half-weight association index (HWI) values calculated between pairs of 60 individually identified humpback whales off west South Africa.

<p>Numbers are individual whale identifiers (#); for associations of ≥0.3 the thickness and shading of lines are scaled according to HWI values (rounded to the nearest 0.1); non-resighted calves A, B, C and F (dashed lines) included for information but not used in social structure analysis (also see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0081238#pone-0081238-t002" target="_blank">Table 2</a>). Symbols and colours used: triangles  =  males, black circles  =  females, squares  =  sex not determined, white circles  =  cows, grey fill  =  known calves.</p

Sighting history, number of associations, sex, and maximum half-weight association index (HWI)¹ of individual humpback off west South Africa.

1<p> =  of whales with mean HWI at or above 0.03.</p>†<p> =  known mortality.</p

Regions of relevance to West African humpback whales (a) and detail of primary study area and distribution of research effort (b).

<p>Key to (a): the Gulf of Guinea where known coastal breeding areas are located; west South Africa migratory corridor/mid-latitude feeding area (rectangle); and Southern Ocean and Antarctica with position of permanent ice shelf (solid white) and ice edges (white lines) in late spring and summer feeding season (Nov – Feb in white font) based on median of measurements, 1979–2000 (data from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0081238#pone.0081238-Fetterer1" target="_blank">[100]</a>). White arrows indicate relative difference in possible migration distance from breeding areas to ‘traditional’ Antarctic and west South African feeding grounds. Key to (b): West South Africa and localities of all photo identification and biopsy collections, or mentioned in text (white fill circle  =  boat encounter, black fill circle  =  encounters where #006/<i>Ampersand</i> was sighted).</p

Details of humpback whale encounters involving mother-calf pairs off west South Africa of which all the mothers and some calves (in post-natal years) were resighted.

<p>Identification of calves based on calf size relative to mother, and observation of close association.</p>1<p> =  Calves of the year not seen again after natal year are identified by capital letters A-H.</p>2<p> =  Maternity confirmed by PO relationship shown in ML-Relate, where samples were available.</p

Results from STRUCTURE showing ancestry estimates for: a) <i>K</i> = 3 (with ‘locprior’ option; and b) <i>K</i> = 2 (without ‘locprior’ option).

<p>Each individual in the data set is represented by a single vertical line, which is partitioned into <i>K</i> colored segments that represent the estimated membership fraction of that individual in each of the <i>K</i> inferred clusters.</p

Bayesian skyline plot obtained with the mitochondrial DNA dataset, showing changes in effective population size through time (Ma).

<p>Bayesian skyline plot obtained with the mitochondrial DNA dataset, showing changes in effective population size through time (Ma).</p

Bayesian phylogenetic tree constructed from 170 haplotypes from Stocks X, C, D, E, F and North Pacific.

<p>Stock X haplotypes are indicated by arrows.</p