The two matrilines, I17 and I18, have been encountered only 48 times over the 25-year-long study. They where together on about one-third of these encounters.
It is a burgeoning group, however, increasing from 5 whales in 1975 to an 20 in 2007.
Acousticaly,I18 pod is very closely related to I1 and I2 pods
Source: Killer whales Second edition
