Albatrosses dine with killer whales
7 October 2009, by Tamera Jones
Scientists have used a tiny camera mounted on the back of an albatross to record the first images of the birds scavenging next to a killer whale in the Southern Ocean. The images show other albatrosses trailing the surfacing whale.
Black-browed albatrosses (Thalassarche melanophrys).
Although scientists know albatrosses feed on squid, fish and krill, until now they knew very little about how they find their prey.
'The only way to find out is to either watch albatrosses from ships, which may be intrusive and not reflect their true behaviour, or to attach tiny instruments to the birds to get more detailed information,' says Dr Richard Phillips, an albatross expert from the British Antarctic Survey (BAS).
Researchers including Dr Philip Trathan from BAS attached a miniature digital camera onto the backs of four black-browed albatrosses (Thalassarche melanophrys) breeding in colonies on Bird Island, South Georgia in the Southern Ocean.
The camera is the size of a packet of polo mints and at 82 grams weighs less than 2.7 per cent of the total body weight of the birds.
'One surprising finding was that some of the pictures show one of the albatrosses flying fairly close to a killer whale.'
Dr Richard Phillips, British Antarctic Survey
'The idea was to get pictures of the birds' prey, but what we've got is the first indication of how they find their food,' adds Phillips.
The researchers report today in the journal PLoS ONE how they attached the cameras to the albatrosses during January 2009, a time of year when chicks have recently hatched and the adult birds are away just for a couple of days at a time searching for food.
'The adults are easy to catch, because both parents take it in turns to go out to sea to look for food,' explains Phillips.
Albatrosses interacting with a killer whale.
'Later on in the season, the birds go out to sea for much longer periods of time and only return to the nest for around ten minutes at a time, so are much more difficult to work with,' he adds.
Trathan and colleagues from the National Institute of Polar Research, Tokyo, and Hokkaido University, Japan, managed to retrieve three of the four cameras and downloaded a total of 28,725 images.
They painstakingly sifted through the images to find the most telling ones. Nearly half of the images showed featureless open ocean or, sometimes, icebergs. Many of the images were either blocked by the birds' feathers or must have been taken during the night because they were too dark to make anything out.
'One surprising finding was that some of the pictures show one of the albatrosses flying fairly close to a killer whale. Three other albatrosses were also following the killer whale in some of the images. The birds are almost certainly picking up scraps from the killer whale kill,' says Phillips.
Albatrosses can't dive deeper than four or five metres, which means they're generalist scavengers, feeding on whatever food they can find in the vastness of the Southern Ocean.
'We know they sometimes feed on large squid and fish which live in deep water. We think they must be scavenging from killer whales or other marine mammals, including sperm whales, or getting discards from fishing vessels,' says Phillips.
The small number of images of albatrosses feeding around killer whales suggests that this behaviour isn't common. 'Killer whales are a fairly rare sight around South Georgia,' says Phillips.
The researchers say the next step is to develop even smaller cameras that can be mounted on albatrosses' heads. 'Maybe we won't get so many pictures of fluttering feathers if we can do that,' says lead researcher, Dr Akinori Takahashi from the National Institute of Polar Research, Tokyo.
From the eye of the albatrosses: a bird-borne camera shows an association between albatrosses and a killer whale in the Southern Ocean by Kentaro Q. Sakamoto, Akinori Takahashi, Takashi Iwata and Phil N. Trathan is published this week in the journal PLoS ONE Public Library of Science.
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