The deaths of more than 120 penguins near Australia’s Mawson station late last year appear to have been caused by natural events, probably severe spring storms, scientists have determined.

The unusual number of deaths, discovered by Australian Antarctic Division ornithologist Ms Lyn Irvine during routine studies at Adélie penguin colonies late last year, was feared to be the result of a disease outbreak.

Post-mortem examination of penguin carcases by the CSIRO’s Australian Animal Health Laboratories in Geelong have found no evidence of infectious disease, but did discover some internal injuries suggesting that the birds suffered violent deaths.

Severe storms are the likeliest cause of the deaths. Winds of 100km/h were experienced at Mawson in mid-November 2001 and two further blizzards occurred within the following three weeks.

Dr Knowles Kerry, the Australian Antarctic Division scientist in charge of the Adélie penguin studies, said today that a swell under the sea ice is likely to have caused violent movement of ice floating close to the shore which crushed or severely injured penguins arriving at or leaving their colony.

Dr Kerry said that the reason that the dead penguins were predominantly female could be explained by the fact that at this time of year, during egg-laying, the females become thirsty and need to leave the nest to be guarded by their partner. They go to nearby snow-banks or on to the sea ice to drink, which is where their injuries appear to have occurred.