It is now almost four weeks since Leri's transmitter sent its last signal. Despite spending much of this time trying to figure out exactly what has happened to her, we cannot come up with a definitive conclusion.
These are the last data points we have for Leri from October 24th to 29th.
Each satellite transmitter sends out an activity reading every time the transmitter moves. This is a randomly generated number that changes for every new position, the problem is, from October 24th onwards this number stayed exactly the same, never changing, indicating that the transmitter was not moving. (See previous Leri diary for more information on this). Worryingly, no GPS points came in at all for October 25th and 26th. For the next three days however, October 27th, 28th and 29th, we received a full set of data.
This is the big dilemma: Despite this activity reading not changing, and notwithstanding the fact that many of these GPS readings were coming from one central location, we have several other readings that showed the tracker in other positions - see the map above. These other positions are several hundreds of metres apart form each other but Leri/the tracker, kept coming back to the same central position, time after time. The data is conflicting and confusing. If the activity reading was indicating no movement, why all these other GPS points? It's a bit like stopping your car at a red light and then looking at the speedometer showing your doing 60mph - something isn't right.
What are the options? Initially we thought Leri had been predated and was being dragged around which would explain the other GPS points; but which animal would keep taking its prey back to the same position every few hours? Maybe she was floating on the water, but surely she wouldn't find herself coming back to the same position repeatedly?. Maybe the GPS positions outside this central location were slightly inaccurate and that she wasn't infact moving at all? Well, many of these other locations were of 'Class 3' quality - the most accurate you can get. These should be more or less spot on. As a test we looked back at Leri's positions for those weeks before she started her migration where we knew where she was in the Dyfi - on the nest, a feeding tree, the camera tree and so on.. her tracker was incredibly accurate, down to just a metre or two. Several satellites pass over the tracker to send these Class 3 readings, up to six or seven sometimes, these GPS positions should be spot on.
The only logical explanation we can come up with is that Leri had found a favourite perching tree (i.e. at this central GPS location on the map) and was periodically flying off to nearby areas to fish, preen, perch etc, and then coming back to her central perch.
Finally we have the research sent in to us from Frederic. He found a dead acacia tree at this central spot, ideal for an osprey to perch on. He also found white droppings nearby (osprey droppings are white). He found many catfish in shallow water - very easy for an osprey to catch which would negate any need to fly far and wide in search of food. But most importantly perhaps, he did not find Leri's body nor her tracker.
Frederic with Cheikh Aïdara looking for Leri in Senegal - image Rozenn Le Roux
So we have a situation where we simply don't know what has happened to Leri. If suddenly we get another signal from her transmitter, we will of course let you know but after four weeks now of nothing, it looks unlikely. Maybe the answer will come in May or June of 2013 - wouldn't that be something!
Please let us know if you have any theories of your own or any comments below. We would again like to thank Frederic and his friends for trying to find Leri for us - here is the email he sent after searching for Leri at that central position on the Marigot a couple of weeks ago.
We went to the 'marigot de Khant', last 11th of november, with my friends Rozenn Le Roux and Cheikh Aïdara.
Aïdara and me walked in the marsh and looked for Leri and some indications.
Above the marigot: more eurasian marsh harriers than the 3th of november, one Montagu's harrier, one african fish eagle; and 6+ ospreys !
We did'nt find any body, line hooks or traps, anor any human presence as well crossing way of cows inside. Water level is everywhere from 15 to 30 cm, with many aquatic grass (level ~1m and more): in the middle of the lake, some water ponds without grass where caspian terns and ospreys can dive and fish (a lot of fishes but not big, usually catfishes). We found on the ponds, blocked by the grass, many little feathers and downs (ospreys diving !), and some grey herons feathers. Near Leri's lat signals in the swamp we watched for some tamarix senegalensis bushes in the water where Leri probably perched - especially a dead acacia young tree with many white droppings. When we walked (12-13h in the middle day) in the swamp, grey and purple herons, one black crowned crane and some spur-winged gooses (many joungs) flyed off. Where Leri was, 10 black storks glided at this time just above us !
A few meters from Leri's last data, a strange discovery: two places where grass had been made into a bed, with drops on: probably the bed of a Seba's python. There are numerous in the Bango's area. But we think it would be incredible that the big snake could catch the osprey ! By night ?
Our photographer took pictures of many of the ospreys we watched. I am going to send them in the next mail.
You can take others pics on my blog when the post will be finished.
We didn' see anybody (just cows drinking) and warthogs are very quiet... The hunter's season not began.
We think that Leri's aerial has a problem, and your nice female osprey alive, somewhere, between the others ospreys of the marigot de Khant, maybe elsewhere, now ?!