Downloading data from Hobo loggers
Sometimes you have to take a leap of faith and leave expensive equipment in the field in order to get much needed long-term data. This is what we did last February in a trip to KZN where we made an elevational transect while collecting African clawed frogs for Laurie (see Blog Post here). We placed four loggers at sea level, 1000 m, 2000 m and 3000 m asl. Sadly, the logger at 3000 m asl disappeared very soon after we placed it in a deluge of floods that hit Lesotho in March 2021. That meant that there were still three more loggers out in the field that needed to be retrieved.
Fortunately, with the help of Bongani Ntloko from Letseng mine, we were able to redeploy another Hobo logger into a pond with Xenopus at ~3300 m asl. The results after one year (March to March 2022-23) are amazing.
Firstly, note that the scale on the y-axis only goes up to 20 C, and the water never gets that warm. For most of the year, the water is below 10 C. Only from around mid-October to late-March is the water above 10 C. This means that the frogs in Lesotho are more than half of their year in water less than 10 C. Even in summer, the water still regularly dips below 10 C on a daily basis.
Happily, the logger from 2000 m asl at the Fat Mulberry was retrieved by Marggie and she brought it to Stellenbosch where we could download the data.
This month I made a trip back to KZN to retrieve the outstanding loggers from near Dalton and at Bonamanzi:
The temperature of the water in a dam near Dalton never went below freezing, but it did get quite cold (as well as getting hot in the summer).
Meanwhile at Bonamanzi, the temperature was nearly always above 10 C, and even went above 40 C! Contrast this with Lesotho when the water temperature rarely went above 10 C!
You may remember that Bonamanzi was where we had our traps vandalised by crocodiles. Happily though, you can see that the logger (right) didn't come to the same fate. The logger near Dalton (left) was still tied to the same stone sunk in the dam.
Thanks to friends in Lesotho, we redeployed one of these Hobo devices there. Because you can replace their batteries, they are fantastic and just carry on working. We are hoping that the new logger won't go AWOL!
