The initial journey of juvenile emperor penguins

Abstract

1. The first major journey of emperor penguins, among several in their lifetime, is the juveniles' dispersal from their natal colony on a trip that takes them beyond Antarctic waters. The route taken by fledglings from Cape Washington (74.5° S; 165.4° E) was studied by applying satellite transmitters to ten individuals during December 1994–1996. In January 2001 transmitters with longer transmission capacity were also applied to six hand-fed fledglings, which had been held captive for one month while attaining a body mass exceeding that of wild birds. These post-captive birds were released at the ice edge of McMurdo Sound (77.5° S; 165.0° E), which is in the vicinity of other emperor penguin colonies, and 320 km south of their natal colony of Cape Washington. 2. Independent of their parents, the wild birds travelled north-east for the next two months, reaching locations as low as 57° S. The post-captive birds travelled north also, but their trek reached only to about 63° S before they turned south, or remained near their most northerly position from March through May. 3. It was concluded that among colonies in the southern Ross Sea: (a) most healthy fledglings survive at least the first two months at sea, feeding themselves as they go; (b) the Cape Washington fledglings travelled as far north as 57° S, and much of this journey was in ice free waters; (c) by April, the post-captive birds reached at least as far as the large-scale pack ice edge and possibly beyond the edge at 63° S; (d) by early March the trend north ends, and by about late March the birds travel to, or remain near the northern ice edge. 4. The reason the birds travel so far north remains a mystery. Copyright © 2008 John Wiley & Sons, Ltd.