Malcolm Douglas

Tel: 083 233-5264 | Fax: 086 619-5492 | Email: malcolm.enviroskills@gmail.com

Opinions expressed in this newsletter are not necessarily those of Enviroskills or of the editor.Enviroskills is not liable for any errors in information, nor for any actions in reliance thereon.

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Flying in the rain ..I cannot profess to ever having given this issue much thought, but an article I recently readbrought up a random question - how do tiny insects fly in rain? I had always assumed thatin those conditions mosquitoes and midges would simply land and wait for the rain tofinish. Apparently this is not so, and is not even necessary.

Mosquitoes are no match for a falling raindrop, which in our storms can reach massesexceeding 50 times a mozzie’s body weight and which fall at nearly 10 meters per second.One would think that this would deliver a death blow to a mosquito. It does, but only if the mosquito is hit by a dropwhile the insect is safely landed on a solid surface.

David Hu of the Georgia Institute of Technology in Atlanta says that the secret is to roll with the punch. Themosquito’s low mass ensures that when it is hit by a raindrop, it is simply moved in the direction of the drop - forusually about 20 body lengths. This seems pretty obvious, but when you consider that the mosquito endures abouta 100-G acceleration at right angles to its previous flight path, it really is quite amazing. To top that off, the tinyinsect then seems to miraculously shrug off the coating of water and continue on its way. This is the interesting partbut we have not yet learned the trick they use. Studies are being conducted to try and discover how the wings andlegs of small flying insects are able to shed water so quickly and efficiently.

Lonesome George is dead!The last Pinta Island tortoise is dead, leaving the subspecies extinct. Lonesome George was the sole member ofhis type (Chelonoidis nigra abingdoni) since 1972 when he was found on the island despite the subspecies beingconsidered extinct at the time. He spent the remainder of his life in captivity in the hope that a mate for him couldbe found. George was found dead in his enclosure at the Charles Darwin Research Station on Santa Cruz Islandon the 24th June.

Most of the areas islands had big populations of huge Galapagostortoises which provided an excellent source of meat for sailorswho passed through the archipelago. It was simple to load themup into the ship where they would stay alive almost indefinitelyand be conveniently slaughtered when needed. So many werekilled that five of the 15 subspecies recognised are extinct today.Another problem the tortoises faced was the introduction ofgoats, which destroyed the vegetation to such an extent that thetortoises food source was eliminated. It was this that caused thedemise of the Pinta Island subspecies.

Issue 74June 2012

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Enviroskills - Keeping Guides on Target

In the news

Our threatened wetlands

According to the recently released National Biodiversity Assessment 2011 (NBA 2011) wetlands are the mostendangered natural environment in South Africa. The major causes of the decrease being urban sprawl, miningand agriculture. One of the most important contributing factors to the decline of the environment overall is theincrease in alien plants. According to the report, the area covered by alien plants has doubled to 20 millionhectares since the mid 1990’s. If the trend continues, there will be no natural vegetation left in KZN, Gauteng orthe North West by 2050.

In her statement at the time of the report’s release, Edna Molewa said "Failure to protect biodiversity is self-defeating because we are all going to lose in the end, the rural poor being the most affected. This is becausemany of our communities are directly dependent on biodiversity and ecosystems services."

Important new source of atmospheric dust - the Southern Kalahari

Dust rising from various areas of Earth are an important source of micronutrients for ecosystems globally. As anexample, dust rising from the Sahara desert is blown across the Atlantic ocean and has an important effect onthe Amazon jungle. Most large dust sources on earth are found in the northern hemisphere, but it seems that anew source has been identified - the southern Kalahari.

Vast areas of the Kalahari dunefields are now being destabilised by overgrazing and agriculture, leaving largequantities of dust to be raised up into the atmosphere. The interdune dust from that area is rich in iron and islikely to enrich the southern ocean and enhance its productivity. To me this is an example of how a disaster inone area of the world is capitalised on by nature in another. (Source: Environmental Research Letters)

New threat in DRC’s Garamba National Park

African Parks (based in Johannesburg) has announced thatJoseph Kony's Lord's Resistance Army has again movedinto DRC's Garamba National Park where they recentlyengaged in an hour long firefight with field rangers near thepark’s headquarters.

The LRA which is notorious for killing and kidnappingwomen and children, has been an increasing threat sincemoving into the region in recent years to escape theUgandan army. The group is suspected of poachingelephants and has been responsible for firing on aircraftoverflying the region. In April, a secret camp wasdiscovered in the centre of the park where 60 militia hadbeen staying along with several kidnapped women and

children. Non essential staff have been evacuated from the park to prevent a repetition of the tragedy of January2009 when a large force of LRA attacked the headquarters at Nagero and killed 15 park staff and kidnappedtwo children.

“Don't blow it - good planets are hard to find.”

Quoted in Time

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Enviroskills - Keeping Guides on Target

Earth’s nine lives - which one’s are already lost?Earth and nature have been very kind to us humans - at least until now. Our species has been revelling in thefantastic weather of the last 10000 years, not realising that this is the best period of weather EVER to have existedin the planets 3,8 billion year history. Things could always be very different and usually were in the past.

The period of time I refer to is called the Holocene - a very benign time in which the balance of gases, nutrientcycles, water supplies and other important life support systems were kept in narrow and tolerable limits for humans.Many scientists now argue that we have left that epoch and have entered the Anthropocene - the period of earth’shistory that has been most influenced by human activity. What happens now is anyone’s guess.

The pressure brought to bear on the balance of the very systems that supported us to the massive population wehave today are now being stretched in directions that could tip the balance against us in future. A group ofscientists lead by Johan Rockström, (director of the Stockholm Environment Institute in Sweden) sat down someyears ago and came up with a list of these impacted systems that could change the future of our species. Theycame up with nine planetary life-support systems and determined as best they could the extent to which they havebeen overtaxed or not. According to Rockström, the boundaries are “rough, first estimates only, surrounded bylarge uncertainties and knowledge gaps”.

According to the teams estimations, three of the nine support systems are already overtaxed, viz. biodiversity loss,nitrogen fixation and climate change. Of the remaining six, three others are at or approaching the limits althoughthe extent of their influence is not yet understood or known. This means that several of those could already be overthe tolerance limits and we don’t yet know it.

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Enviroskills - Keeping Guides on Target

What is it?

The photo shows a snail’s shell quite obviously, but why is there a covering over the aperture (opening) and what isit made of?

“When a man throws an empty cigarette package from an automobile, he is liableto a fine of $50. When a man throws a billboard across a view, he is richly

rewarded.”

Pat Brown, in Ogilvy on Advertising, 1985

“Lines of arrested growth”Over the years I have been following the scientists debating the temperature of dinosaur blood. At first we were toldthat the “terrible lizards” were ectothermic (cold blooded). Then the majority of palaeontologists started leaningtowards the endothermic (warm blooded) theory. The reasons for supporting the various theories are many, butone of them came under scrutiny recently and has helped further debunk the idea that dinosaurs were coldblooded.

Today it would seem that the majority of expertsconsider dinosaurs to have been endothermic, but anagging element of doubt still remained. This doubtwas raised by something called lines of arrestedgrowth or LAGs. Cold blooded animals that hibernateshow these lines in the makeup of their bones, wherethe bone grows in rings almost like those in a treetrunk. Only cold blooded animals were believed toshow this trait.

To check this notion, scientists analysed the bones of41 mammal species to see if the lines were found ornot. They were - and in all 41 species checked. Thiseffectively knocks down the theory that LAGs occuronly in cold blooded animals, but it still does notcompletely rule out the possibility that dinosaurs werecold blooded.

The study was lead by Meike Koehler of the Catalan Institute of Palaeontology in Barcelona and is published inNature.

Photo: Meike Koehler

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Enviroskills - Keeping Guides on Target

Crossword

Across

2. A tough horny substance being the principalcomponent of the exoskeletons of arthropods (6)

4. The combination of clay, silt and sand particles in asoil is known as an ........ (9)

6. Arising or occurring between different species. (13)

7. (of birds) leaving the nest shortly after hatching. (10)

10. South Africa's national fish (7)

14. Producing living young (not eggs). (10)

16. Largest freshwater fish found in Southern Africa (5)

18. Plant that derives moisture and nutrients from theair and rain; usually grows on another plant but notparasitic on it. (8)

20. An astronomical unit of measurement that derivesfrom "Parallax of one arc second" (6)

21. Projection behind and above a bovid's hoof. (7)

22. (Of plants, antlers and teeth) being shed at the endof the growing period. (9)

23. Plant adapted for life with a limited supply of water;compare hydrophyte and mesophyte. (9)

Down

1. A South American tree that gives Pretoria its othername. Now considered an undesirable alien plant (9)

2. A small horny callus on the inner surface of a horse'sleg. (8)

3. Complex phenolic substances produced by plantsthat affect their palatability and digestibility (7)

5. A horizontal underground stem producing daughterplants at rooted nodes. (7)

8. All the plant life in a particular region. (5)

9. The boundary of the Earth's crust and underlyingmantle (4)

11. Process whereby substances are removed from soilby percolating water. (8)

12. The total mass of living matter in a given unit area(7)

13. The term used to describe the amount of freeforward / backward play a cartridge has in a closed riflechamber. (9)

15. Native to or confined to a certain region. (7)

17. Grass-like or rush-like plant growing in wet placeshaving solid stems, narrow grass-like leaves andspikelets of inconspicuous flowers. (5)

19. A hanging fold of loose skin on the neck of someantelopes and zebras. (6)

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Enviroskills - Keeping Guides on Target

“Misguided” - giraffe colourationI think that guides in South Africa are now thoroughlyconfused about the colouration of giraffes. Male giraffesare supposed to get darker with age according to some.According to others that is just a genetic trait. Which isthe truth?

The reason I brought this up is because of an article Iread about a 33 year long study which now conclusivelyproves that male Thornicroft’s giraffes (from Zambia) dobecome darker with age. This says nothing about thesouthern giraffe that we have here in South Africa, butone is tempted to think that there may be somesimilarities.

A park ranger Phil Berry has been documenting giraffecolouration for 33 years in Zambia’s South Luangwa parkand now Professor Fred Bercovitch from the PrimateResearch Institute and Wildlife Research Centre, KyotoUniversity, Japan, has partnered with him to publish theresults in the Journal of Zoology.

According to their observations, the male giraffe coat startsto darken at around 7 - 8 years of age and becomes much darker over the following 2 years. This they believe, isrelated to the onset of puberty and probably has something to do with increasing levels of testosterone. Thechange is so predictable that it is possible to very accurately age the animal by coat colour alone.

In South Africa, many large and old giraffe bulls do become dark with age - but not all. The giraffes from the drywestern part of their range in the Kalahari and Namibia seem to stay quite pale throughout their lives, perhaps inthe interest of remaining cool. Despite the research conducted on Thornicroft’s giraffe, I don’t think that anythingdefinite can be said regarding progressively darkening colouration within the giraffe species as a whole. The jury isstill out on this one and guides should use this to their advantage. You can keep guests very interested byexplaining and comparing some of the differences and variations found in giraffe colouration. We will never knoweverything.

What is it - AnswerThe image shows a dead land snail (I have no idea the species) that I found under a stone near Gravelotte in the

Limpopo province. The aperture of the snail was completely blocked by astructure called an epiphragm which is designed to keep the snail fromdesiccating during the dry winter months. Most snails produce a mucusepiphragm which is effective at preventing water loss and is used by manyto glue themselves to the substrate as well. This is a common sight in theCape, where snails often climb up wooden fence posts and glue themselvesthere to while away the dry months.

The structure shown here is called a calcareous epiphragm and is muchmore efficient at preventing water loss. It consists of a combination of mucusand calcium carbonate and is actually quite thick. I didn’t measure it, but Iwould guess this one was at least 0,5 mm thick. It makes such a tight sealthat a small hole needs to be left in the “cap” to allow the diffusion of oxygeninto the shell.

This snail must have died of a disease, been burned, parasitised or simplycould not make it through the long dry months.Photo: M Douglas

Here I superimposed two photographs taken at the same place,using the same settings and not moving the camera to try capturethe scale of a giraffe bull compared to a six foot tall man.