Sunday, 15 August 2010

Beware of rivers!

Dear all,

July has come and gone in a flash as the dry season continues. The Boteti River has risen significantly and having recently passed Rakops is now closing on Mopipi and Lake Xau. The river was deeper than I expected and unfortunately caught me out as I got stuck trying to cross. Thanks to Leroo La Tau I was recovered from the river but with everything a little wetter. Upon later examination it turned out that there was an electrical immobiliser in the car which I was unaware of and which had been disabled previously but upon getting wet it became active once more and caused all of the electrics to cut out leaving me stranded. Needless to say the immobiliser has since been removed but I don’t intend to try and cross the Boteti again except by boat!

In the eastern Makgadikgadi the remaining surface waterholes are drying up but there is still enough water in some of the deeper waterholes to provide sufficient water for a few thousand zebra and wildebeest. The remainder of the zebra population has already migrated back to the Boteti and are making full use of the fresh Boteti river water.

The movement data provided by the GPS collars is very interesting and is raising many more questions. In the Boteti zebra are regularly choosing to graze 18km away from the nearest source of water while one zebra has been recorded 23.5km from the nearest source of water. The zebra are actively choosing to walk past areas which appear to have good quality grass in order to reach their current grazing areas. What is it about these areas which the zebra will walk such large distances for? How do the zebra know how to find these areas and return to them so regularly? Why have some zebra migrated back to the Boteti while others have remained in the Eastern Makgadikgadi? What triggers the zebras to migrate? These are just some of the many questions which I am looking to answer through this research.

During the last week of July I went with a veterinarian to try and replace the broken GPS collars with new replacement collars. We knew that it would be difficult as the last time we tried to remove collars it took us 8 days to remove 7 collars.

We headed to the pans of the eastern Makgadikgadi first to locate any collared zebra which had yet to migrate. I had tracked 3 collared zebra in this area less than one week before and so was hopeful that we would be able to find them now. During the course of two days and following lots of VHF tracking we located and replaced the collars on the only two collared zebra which we could find. This meant that all of the remaining collared zebra had (I hoped!) to be in the Boteti region to which we headed next.

After stopping countless times in order to scan the area using VHF tracking equipment and many kilometres of off-road driving the remaining 4 zebras with broken GPS collars were located and eventually darted. The thick acacia scrub around the Boteti made things both easier and more difficult at the same time. It was made easier in that we could get closer to the zebra than in the open grasslands where it is difficult to get 50 metres away from the collared zebra. It was more challenging because of the number of bushes and tall grasses which were often between us and the zebra and through which a dart can not travel. Patience, as ever, was the key and we were ultimately successful and were able to replace all of the broken collars.

After the successful darting there are 10 zebras collared in the Makgadikgadi once more and hopefully these collars will remain on the zebra until March 2011. I will keep checking on them each month to see where they are and to make sure that the collars are still working.

If anyone has any comments or queries about the research then please contact me.

Best wishes to you all and thank you for your continued support.