Diving patterns in relation to diet of Gentoo and Macaroni penguins at South Georgia
The depthsa ttainedo n 1,444d ivesb y 14 GentooP enguins(P ygosceliPs apua)
and 6,352d ivesb y eightM acaroniP enguins(E udyptesc hrysolophusw)e re recordedt,o gether
with the timing and durationo f the foragingt rip and the amounta nd type of prey caught.
MacaroniP enguinsa te only Antarctick rill Euphausias uperba.W hen feedingo nly at night
they maden o divesd eepert han 20 m; on all-day trips 36% of divesw ereb etween2 0 to 80
m. GentooP enguinsfe dd uringt he day.W hen theyc aughkt rill, 77%o f divesw eres hallower
than 54 m; when fish were taken, 59% of dives were 54 to 136 m, which is consistent
with the benthic-demersahla bit of thej uvenile Nototheniaa nd Champsocephalufsis ht hey
eat. The patterno f predationo n krill by both penguins peciesis consistenwt ith its vertical
migrationt o the surfacea t night and dispersatlh rought he water column during the day.
The food requirements of chick-rearing Macaroni Penguins would be met by catching at
least six adult krill per dive (or 150 juvenile krill or amphipods). For similar Gentoo
Penguins, a minimum of 15 adult krill per dive (one every 8 set), or one fish every third
dive, is needed. Recorded interannual variations in krill size can treble these rates, which
would also be doubled if half the dives were for travelling, not feeding.