Friday, 3 July 2009

Unseasonal weather


In my last blog entry I mentioned how the dry season had finally begun with all of the zebra migrating west, back to the Boteti region. I spoke to soon. There has been the most rain in June for 100 years which has understandably changed things once again.

June started well as the final GPS collar was deployed onto a zebra within 500 metres of Leroo La Tau. Everything went smoothly and the zebra was back with her harem within 20 minutes of the initial darting. We then began fieldwork in earnest by tracking collared zebra and locating preferred grazing patches to sample. We were able to conduct a number of these sampling sites prior to the rain arriving. We also tried to conduct a 12-hour focal observation on one collared zebra who decided to return to the Boteti waterholes for a drink. In doing so she had to walk through areas of dense acacia which we weren’t able to follow her through and so we had to stop the observation.

Then on June 8th the clouds started to build and I expected rain. However, I expected the usual 2-3mm which usually arrives in early June. Instead we got non-stop rain for 48 hours which prompted the government to issue flood warnings for most of the country. When the rain decided to stop there had been over 100mm in the western Makgadikgadi and over 180mm at Jack’s camp on the east of the Makgadikgadi! One of the most significant effects of this un-seasonal rainfall has been on the local farmers who had successfully harvested their crops but which then got severely damaged in the rain.

The zebra’s, however, decided that the rain was a good thing which they were going to take full advantage of. Within hours of the rain beginning all 10 collared zebra were on the move and migrating east back towards the open grasslands. In the grasslands they are able to graze in areas of plentiful high-quality grass near to pans which are full of water. This can only be a good thing for the Makgadikgadi zebra population but wasn’t really in the script of what should be happening during the dry season here in the Makgadikgadi.

I have adapted my field schedule to accommodate the zebra’s grazing in the east and this means that I am now spending 3 days at a time out in the centre of the national park away from my camp. During these 3 days I am able to collect a significant amount of data on the grazing preferences of zebra as well as conduct behavioural observations and counts.

A typical routine during a 3 day sampling trip is as follows:

Day one:

Rise at around 5:30am and download up-to-date GPS data from the collars so that we know where all of the collared zebra are. We then finish packing the car with the bed rolls, tent, tracking aerials, the fridge and food and anything else that we might need. Make a cup of coffee to drink from a thermal mug on the journey and leave camp before sunrise.

I choose which collared zebra’s I would like to collect samples from prior to leaving and so we head for the last downloaded GPS point for one collared zebra. When we near this point we begin to track the collar using a VHF receiver as the zebra will have moved, but hopefully not too far. Sometimes the zebra may be in a herd of a thousand or more zebra and so identifying the collared zebra can take sometime. After locating the zebra, we identify the area where it is grazing and then sample this area, identifying the grass species present as well as measuring the quantity of available forage. For the rest of the day we repeat this process for 2 or 3 more collared zebra before locating a campsite at sunset.

Day two:

Rise around 5:30am to track and locate a collared zebra before sunrise at 7am in order that we can spend the whole day observing one zebra. It’s currently the middle of winter here in Botswana and so it’s incredibly cold at this time in the morning and the aluminium aerials make you feel even colder.

Once a zebra has been located we then follow this zebra until 6pm, conducting a 5 minute behavioural observation every 20 minutes. During this 5 minute observation period I record the activity that the zebra is exhibiting such as grazing, vigilant, resting, walking, grooming or interacting with other zebra or other animals. If the zebra decides it wants to go somewhere then we need to follow but at a distance where we do not interfere with normal behaviour but where we can still see the zebra. If at anytime we lose the zebra and can not see her for two consecutive 5 minute observation periods then the whole days data collection has to be scrapped.

After conducting the final 5 minute observation at 6pm we head back to where we camped the previous night for a warm meal.

Day three:

Rise around 6am to break camp and locate a collared zebra. Before 9 am it is not possible to conduct grass sampling as there is too much dew on the grass and so we conduct observations on the foraging behaviour of the zebra. We then spend the remainder of the day identifying and sampling the preferred grazing sites of collared zebra as on day one.

Interspersed with the grass sampling we conduct counts of random herds of zebra to record how many adult males, adult females, yearlings and juveniles there are. This allows you to get a good picture of how ‘healthy’ the overall population is. Put simply - if there are lots of yearlings in the population then the number of young zebra surviving to become adult zebra is good and the population is in good health and may be growing.

Around an hour before sunset we set off on the two hour drive back to our main camp here at Leroo La Tau ready for a warm shower.

We then spend two days in camp sorting and entering the data that we have collected before heading back into the park again for another 3 days.

I hope this helps you to understand what we get up to on a daily basis. If you have any questions or comments then feel free to get in touch either via the blog or by email.

Till next time.


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