Lab publication

25 August 2015

The MeaseyLab produces it's first joint publication. The idea for this study came from finding huge numbers of eggs, tadpoles and frogs in the stomachs of Xenopus.  We then wondered which other species are frog eaters, and under what circumstances does this happen?

Although the study ended up with some more questions, we did find some interesting answers. For example, we found that invasive frogs are more likely to eat frogs than native frogs, and this effect was increased when we ignored the many studies on (mostly Cane) toads. 

Read all about it:

Measey GJ, Vimercati G, de Villiers FA, Mokhatla MM, Davies SJ, Edwards S, Altwegg R. (2015) Frog eat frog: exploring variables influencing anurophagy.PeerJ3:e1204https://dx.doi.org/10.7717/peerj.1204

  Lab  News

Western Leopard Toads are leaping

18 August 2015


Every year, usually in August, Cape Town slows down to assist Western Leopard Toads (WLT: Amietophrynus pantherinus) across the roads. This year, members of the MeaseyLab took time out of their evenings to help toads across the road. The WLT has been a past research favourite, and is currently part of current research projects by Mac and Zishan. Giovanni was leading the way this year as he's interested in using any casualties for comparison with the invasive Guttural Toad.

Thanks to all for turning out, and thanks to Sarah Davies for this image of Alex capturing a shot of an old 'gal.

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Capensibufo rosei on the go

08 August 2015

When toads breed, we're used to hearing a noisy chorus that can be melodic or raucous (depending on your inclination), but what does it sound like when toads with no calls breed? The Cape peninsula mountain toadlet (Capensibufo rosei) has no calling or auditory apparatus. It breeds during the Cape winter and the congregations can be several hundred individuals, but there's no noise. It's no chorus! In fact, seeing hundreds of frogs moving in silence is quite eerie.

 

This male is under 20mm long, and you can see that they are surrounded by strings of eggs that have been laid over the previous days and nights. There's so much to find out about how these animals live, as well as their apparent enigmatic decline. We're doing a lot of work on these animals and starting to get some answers - check out the publications page for more information.

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Coordinate precision errors

07 August 2015

What does it mean when we give lots of decimals behind the degrees?

Many of us have GPS devices which give us locations in decimal degrees, but what do all those decimals really signify and can we rely on them? In the image below, Alex Rebelo has set out a series of increasingly accurate data points (using Kenilworth Race Track in Cape Town as his example). 

You can clearly see here the difference between giving two decimal places and three decimal places is about 1km!

Should you ever give 5 decimal places? Unless you are using a survey GPS, the answer is no. 

Most handheld GPS units can get an accuracy of around 6-8m, so giving 4 decimal places is realistic. For most of our purposes (usually mapping frogs), this accuracy level is fine.

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It's frog time again

07 August 2015

Winter is a busy time in the lab. The frogs start calling and it means that we all have to get out into the field. 

For me, nothing is nicer than spending a day than getting up into the mountain and making a recording of moss frogs. 

Here you see a microphone array, errected to conduct spatially explicit capture recapture. See Stevenson et al  for a recent publication on this method.

Stevenson, B. C., Borchers, D. L., Altwegg, R., Swift, R. J., Gillespie, D. M., & Measey, G. J. (2015). A general framework for animal density estimation from acoustic detections across a fixed microphone array. Methods in Ecology and Evolution, 6(1), 38-48.

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