Thursday, 24 January 2013

Why Druridge Bay needs Warthogs

Birds might seem the obvious carriers for seeds, spores and broken fragments of plants to get from pond to pond, but there may be other means of transport. One of my favourite academic papers* from 2012 about pond ecology is a fine example featuring some rather larger means of dispersal. I know that ”favourite” is not the sort of criterion science is supposed to use in these days of research metrics and impact factors, but let’s leave those cold measures behind and head to the warmth of Africa. Bram Vanshoenwinkel and his colleagues at the University of Leuven in Belgium and in Harare in Zimbabwe knew that many of the large mammals in the African bush needed to drink regularly, moving from pond to pond, often wallowing and caking themselves in mud. What if that mud held seeds of plants or eggs and spores of invertebrates? The buffalo, antelope, warthogs and elephants would be a superb means to get from pond to pond. All you’d have to do to find out was scrape the mud off an elephant. On second thoughts, maybe not. Let the elephant do the scraping for you. So Bram and co collected mud from the trunks of trees from around temporary ponds in the Zimbabwean bush where animals had rubbed and scratched.
Mud was collected from as high as 400 cm up the tree trunks. The mud was then rewetted in the lab, incubated and any animals that hatched out or plants that germinated were identified. The mud spawned a host of different creatures, mostly various water fleas (Cladocera), pea shrimps (Ostraocda) and other more exotic crustaceans of temporary pools such as tadpole shrimps (Triops). Also a few plants including a duckweed (Lemna). Best of all was the spread of mud up and down the tree trunks; there was a distinct pattern with a lot of mud at around 300 cm (elephant scratch height), another clump at 120 cm (rhino and buffalo) and a third at ~60 cm (warthog height). There will be some of you reading this humming songs from the Lion King by now. It is a superb mental picture though, all that rubbing, itching, scratching, wallowing and glooping. Elephants at Druridge is unlikely but cattle, sheep and horses are there in numbers. It is a fair bet that they make effective vectors too. * Vanschoenwinkel, B. et al. (2012) Freshwater Biology, Vol. 56, pp 1606-1619

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