Fig 1.
Important prey areas and observations of seal-feeding killer whale groups.
The left panel (A) shows seasonal herring grounds since 1990 while the middle panel (B) shows areas of abundance of coastal seals since 1990 [32]. The right panel (C) shows locations of K and KI whales sightings since 1988. (The map was made in ESRI ArcGIS software [33] using public domain map data @ naturalearthdata.com).
Fig 2.
Photographs of seal-feeding killer whales KI-03, KI-05 and KI-06.
Individuals in upper photographs, observed off central coast of Norway in 1988, match individuals visible on the lower row of photographs, taken off Andenes in June 2015.
Fig 3.
Photograph of KI-03 preying upon a harbor seal pup in June 2015.
The photograph (A) illustrates the predation observation and the inset (B) confirms effective prey consumption.
Table 1.
Summary of recorded predation events on seals where involved individual killer whales could be identified.
Fig 4.
Observations of seal-feeding killer whales in relation to effort from 2010 through 2016.
The plot (A) shows the cumulative sighting distribution of KI (dark bars) and K (light bars) whales while the plot (B) reports on the cumulative number of effort days spent in the field for each month, from 2010 through 2016 in northern Norway.
Table 2.
Sighting histories of KI and K whales.
Fig 5.
Sociogram of seal-feeding killer whales observed in at least four sampling periods.
Occurrence and thickness of links show association patterns between pairs of individuals, revealing the two assemblages KI and K.
Fig 6.
Plots of lagged association rates.
The blue plot represents our real data set while the red plot shows the expected lagged association rates if individuals associated at random.