Tuesday, 27 January 2015

An Early Death

Yesterday I received the sad news that Jarrkanpa was unfortunately found dead. Recent tracking data downloaded on 20th January showed a lack of movement on the afternoon of 15th and for the whole of 16th January, but at the time of that download, no further data was available. As previous tracking data on a juvenile eagle (Kuyurnpa) had shown birds can remain stationary or show limited movement for more than a day, I made the decision to wait and see. But when the next set of data came in 3 days later, still no movement had been recorded. The Lorna Glen managers were away and out of contact but yesterday the caretaker managed to visit the location shown by Jarrkanpa's tracking data and confirm the outcome.

So what happened? A postmortem was unable to reveal the exact cause of death but it did conclude that the harness was still attached as normal and there were no injuries caused by the Teflon straps. What is most likely is Jarrkanpa died of heat exhaustion. Temperatures at Lorna Glen during the past fortnight have been exceptionally hot, with one daily maximum of 50.3˚C recorded at Lorna Glen during the week of 12th January. The table below shows the temperatures recorded at Lake Carnegie (~60 km east of Lorna Glen) for the week in which Jarrkanpa died.

Date in January
Min. Temp (˚C)
Max. Temp (˚C)
Young birds not used to such conditions may not yet have learned the behavioural or physiological adaptations which help older, more experienced birds survive. For example, it is thought that one of the reasons adult eagles soar so high (as shown by altitude readings recorded in this study) is to keep cool and conserve energy. Considering he was on the wing for less that 2 months, Jarrkanpa may not have known that if he gets too hot, he can simply 'go up' to cool off. Also, premature death in juvenile eagles during extended periods of hot weather has been recorded previously at Lorna Glen. Two eaglets aged 7-8 weeks both died on their nests in October 2012 when the recorded temperatures at Wiluna and Lake Carnegie exceeded 40˚C for more than 10 days in a row. 

Although it is never nice to have a study bird die unexpectedly, it is an accepted part of research on wild animals that this sort of thing will happen, especially for a species for which, like many other large eagles, the juveniles have a high natural mortality rate (as shown by extensive research by the CSIRO in the 1970's). This event only reiterates how precious life is, and how difficult it is for animals to survive in one of the harshest ecosystems in the world. It also makes me think how amazing it is that Kuyurnpa not only survived her post-fledging period, but that she is still being tracked after dispersing from Lorna Glen over 12 months ago.

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