Tswaing Meteorite Crater

View of the Tswaing Meteorite Crater from the crater's rim.

On a recent visit to the Tswaing Meteorite Crater (also known as Saltpan) my wife and I were pleasantly surprised at all it has to offer nature lovers. Located approximately 40 km north-northwest of Pretoria (4), the impact crater is anomalously well preserved and home to a wide range of prolific fauna and flora. Due to its value to science and tourism the crater and its immediate surrounds form a protected area open to the public at a small entrance fee.

Impact, Geology and Archaeology:

Roughly 220 000 years ago a moderately sized meteorite hit Southern Africa forming the Tswaing Meteorite Crater. Like many meteorites the ‘Tswaing Meteorite’ was vaporised on impact. It is believed to have been 30-50 m in diameter as it sped to the Earth’s surface at 72000-108000 km/hour (2). The energy released by the impact was roughly equal to that of 1000 nuclear bomb explosions (2). Most, if not all, non-primitive life forms within a radius of about 20 km of the impact site was obliterated (2).

The Meteorite impacted the Nebo granite of the Bushveld Igneous Complex, overturning and tilting various portions of granite. Apart from the crater and structural geology of Tswaing, rapidly deformed quartz and feldspar crystals, as well as melt-breccias formed from the granite bear witness to the colossal impact event (4).

The rim of the crater has an altitude roughly 60 m higher than the surrounding country, while the crater floor lies roughly 120 m below the highest portion of the rim (1). The crater’s basin (i.e. floor) lies below the regional watertable (3). This resulted in the formation of a semi-permanent lake inside the crater, as ground- and rain water tend to flow into the crater basin (3). Due to a higher average rate of evaporation from the lake than the average rate of rain water addition to it, the lake has been saline for many millennia.

The saline character of the lake is responsible for much of the crater’s archaeological significance. Stone Age artefacts have shown that people hunted, gathered and collected salts at Tswaing from roughly 150 000 to 30 000 years before present. In historical times, between 1912 an1956, salt and soda was mined commercially at Tswaing by SA Alkali Ltd..

Biodiversity:

Black-winged Stilts are one of the waterbirds one might encounter at the saline crater lake.

In terms of nature, Tswaing arguably has most to offer birders, though various mammals and numerous trees and plants occur in it. Roughly 260 bird species have been documented within the conservancy (2). This large array of birds can be attributed to the mixture of bio zones within Tswaing. They are Acacia woodland, mixed woodland (crater rim), river and wetland (wetland occurs in the north-eastern sector of the conservancy), areas where grasses dominate and the crater lake with its shores (2). The Acacia and mixed woodland attract species such as Crimson-breasted Shrike, Red-chested Cuckoo (in summer), Burchell’s Coucal, Southern Red-billed Hornbill, Cardinal Woodpecker, Fork-tailed Drongo, Brown-hooded Kingfisher, Pearl-spotted Owlet (2) and Acacia Pied Barbet (2). At the saline crater lake one can expect to see species such as Black-winged Stilt, Cape Teal, Little Grebe, Black-smith Lapwing, Pied Avocet (2) and Three-banded Plover. The wetland in the northeast of the conservancy hosts various Warblers (Willow, Icterine, Garden, Marsh, Great Reed and River), African Rail and African Purple Swamphen, to name a few (2). After high rainfall Harlequin Quail and Dwarf Bittern may visit the wetland (2). A final birding highlight I wish to mention is the African Hawk-Eagle pair that breed within the crater every year (2). The public is strongly urged not to approach the eagle’s nest, as this might interfere with the raptors’ breeding success.

Various small mammals such as rodents, mongoose, hares, genets and Vervet Monkey (2) occur at Tswaing. Larger mammals include Chacma Baboon and introduced antelope such as Impala.

Finally, for those with a passion for botany – many trees in the Tswaing have been tagged with numbers. Lists with the corresponding tree species names can be obtained at the Tswaing Museum (2).

Personal experience:

I’ve only visited the Tswaing Crater once, but the experience has definitely motivated me to want to go again. Upon entering Tswaing the first two birds we saw were Brown-hooded kingfishers, the third species, I believe, was a White-winged Widowbird – both of which you would rarely see in Pretoria. The most prominent birdcall, evident throughout our visit, was that of the Red-chested Cuckoo, which we spotted in flight a handful of times. Other prominent vocals were those of Burchell’s Coucals and Arrow-marked Babblers.

Upon entering Tswaing the first two birds we saw were Brown-hooded kingfishers...

The environment within Tswaing, especially near the crater, seemed healthy and thriving. Walking in-and-around the crater evoked a feeling of being in a remote part of Africa. This feeling was probably due to elevated humidity, pristine woodland, and the strange geomorphology of the crater.

One thing I want to do differently if I visit Tswaing again in summer – is to take lots of mosquito repellent. As soon as we started descending into the crater, we started loosing blood!

Access, facilities and costs:

The Tswaing Crater is open to the public from 07:30-16:00 everyday (2). Entrance costs R15 per adult and R20 per car (optional) and is payable at the Tswaing Museum. One may leave one’s car at the museum and enter Tswaing on foot. The entrance to Tswaing is located roughly 200 m north of the museum along the M35. Obtaining a permit for one’s car gives one access to a limited portion of the conservancies’ road network - enabling one to drive up to near the crater’s rim. A clearly marked hiking trail exists, for which a map is given on the information brochure obtained at the museum. The full length of the trail is 7.2 km (2). Day visitors can make use of the picnic area which includes braai facilities and toilets (2). Finally, camping and chalets are available at Kgotla Camp (2). For more information phone 012 790 2302.

Conclusions:

The Tswaing Crater is a must-see for Gauteng nature lovers, especially to those that enjoy birdwatching. Being only about 40 km from Pretoria – visitors from our Capital City could easily do just a morning- or afternoon visit. Visitors from further a field would probably do best to make a day-visit of Tswaing, or to sleep over at Kgotla Camp.

Denni Raubenheimer
dennirau@yahoo.com

References:

1) Brandt, D. and Reimold, W.U. (1995). The geology of the Pretoria Saltpan impact structure and the surrounding area. South African Journal of Geology, 98 (3), 287-304.

2) Marias, E. and Peacock, F. (2008). The Chamberlain Guide to Birding Gauteng. Mirafra Publishing, Cape Town. – 384pp.

3) McCaffrey, L.P. and Harris, C. (1996). Hydrological impact of the Pretoria Salt Pan crater, South Africa. Journal of African Earth Sciences, 23 (2), 205-212.

4) Partridge, T. C., Demenocal, P. B., Lorentz, S. A., Paiker, M. J. and Vogel, J. C. (1997). Orbital forcing of climate over South Africa: a 200,000-year rainfall record from the Pretoria Saltpan. Quarternary Science Reviews, 16, 1125-1133.

Austen Roberts and Pretoria Botanical Gardens

Nature oases within large cities’ limits might be prone to unnatural elements, but, as is the case with the Austen Roberts Bird Sanctuary and the Pretoria National Botanical Gardens, may offer a wealth of natural beauty. And though the fauna in such havens might be aware of human activity around them, they often continue with their required daily activities as if we were not there.

1) Austen Roberts Bird Sanctuary

This White-faced Duck was photographed through one of the viewing holes in the wall built along the path leading to the Sasol Hadeda Hide.

The Austen Roberts Bird Sanctuary is located on the site of an old clay quarry in the suburb of Nieuw Muckleneuk and was established in 1958. Though it apparently took a while for a wide variety of birds to start roosting and/or abiding in the sanctuary, it soon became a refuge and prime foraging site to a large number of bird species.

Biodiversity:
More than 160 species have been recorded in the sanctuary and in addition to birds some antelope (Common Duiker and Blesbok) and Leopard Tortoises call the sanctuary home. Slender Mongoose, though not confined to the sanctuary, is also often seen. Some of the birds one is likely to encounter are Blue Crane, Sacred Ibis, White-faced Duck, Knob-billed Duck, Yellow-billed Duck, Egyptian Goose, Little Grebe, Reed Cormorant, African Darter, Black Crake, Warblers (Lesser Swamp, Little Rush and Willow), Southern Masked Weaver, Thick-billed Weaver and Village Weaver. Kingfishers are common (Pied, Giant and Brown-hooded) and various elusive species, such as the Black-crowned Night Heron and Little Bittern, might also be seen.

This female Giant Kingfisher took a breather on a tree adjacent to the Sanctuary’s main dam and next to the walkway leading to the Sasol Hadeda Hide.

Access and facilities:
The general public may not venture into the sanctuary itself, but can view it either from the walkways that follow the sanctuary’s fence, from the Blue Crane Restaurant, which borders and overlooks much of the sanctuary and from the Sasol Hadeda Hide. The walk around the fence may sound dull, but a number of small dams are located close to the fence and one is sure to see a good number of bird species and some antelope if one walks around the whole perimeter. The Blue Crane Restaurant allows a good view over the sanctuary’s main dam, especially from its top deck. With a pair of binoculars one can utilize the restaurant’s vantage point to the full, although the view itself is scenic and many birds should be well within range to observe without optical aid. If one is a birder then a visit to Austen Roberts is not complete without making use of the Sasol Hadeda Hide. This hide is well designed with a walkway leading to the hide that largely conceals the visitor from birds. Furthermore, this walkway also has eye-level gaps in its concealing wall that allow for intimate close-up views of a number of ducks and other birds. The hide itself looks out onto a small stream on side, an embayment fringed by reeds and much of the sanctuary’s main dam. Look out for Warblers and Black Crake around the hide and upon entering and leaving the hide scan the nearby trees that fringe the dam for Kingfishers. Another feature of the sanctuary is the small museum located between the restaurant and hide. It features displays of a number of birds preserved by taxidermy and would be enjoyed by most children, though adults (like myself) are not exempt.

The birds, and certain antelope like the Common Duiker, in the reserve are quite habituated to humans, which allows for close views and many photo opportunities. Whether one is a serious birder and/or nature photographer or just a nature lover, the Austen Roberts Bird Sanctuary has something to offer. Its tranquillity and beauty allow the mind to escape from the hustle and bustle of surrounding suburban Pretoria.

2) Pretoria National Botanical Gardens
Apart from being a nice picnic spot, the Pretoria National Botanical Gardens offers access to patches of bush of pristine flora and a healthy diversity of birdlife. Situated near the N1-N4 interchange, the gardens were established in 1946 and span a large area of 76 hectares. A quartzite ridge runs through the gardens and separates its southern and northern portions. Apart from the woodland biozone defined by the ridge, portions of natural grassland occur, while the remainder of the gardens is composed of a mosaic of mini-gardens, all having different themes, and lawns that are interspersed with trees.

When the fig trees that grow on the quartzite ridge that runs through the gardens develop ripe figs one is likely to find the beautiful African Green Pigeon along with various other frugivores gorging themselves on these fruit.

Biodiversity:
The botanical gardens are home to a wide spectrum of life, from plants and trees to reptiles, amphibians, mammals and birds. Roughly 200 species of birds have been recorded and one may well be surprised to encounter species you might not expect well within Pretoria such as Crimson-breasted Shrike, Acacia Pied Barbet, African Green Pigeon and in summer Grey-headed Kingfisher. A mammal rather ubiquitous on the quartzite ridge is the Rock Hyrax (Dassie) and if you’ve never seen these large rodents in a tree – this is a common spectacle in the gardens. I have not seen any, but I’m sure mongoose, genets and various snakes are also resident in the gardens. Finally, I wouldn’t be doing the gardens due honour by neglecting to mention its floral diversity. More or less 1000 and 500 species of flowering plants and trees occur in the gardens, respectively. The gardens’ diversity in trees is impressive considering that it accounts for more than half of our indigenous tree species. Furthermore, many of the trees occurring in the gardens are labelled - displaying their common and scientific names.

As well as lawns interspersed with trees and woodland areas, the gardens contain large patches of grassland that provide ideal conditions for many flowering plants, as well as prime foraging grounds for Spotted Thick-knee and the like.

Access & facilities:
The botanical gardens are open year-round from 08:00-18:00. Adults pay R18.00 for a day’s entrance and students R10. Facilities include a visitor’s centre, an environmental education centre, a restaurant overlooking a small dam and ablution facilities. Note that the restaurant’s entrance is outside the gardens - fringing the gardens’ main parking area. Finally, the South African National Biodiversity Institute’s head office is located inside the gardens and has a commended bookstore.

So, whether one is in the mood for a picnic, a short hike, birding or just nature, the Pretoria Botanical Gardens offers a wide spectrum of natural beauty and diversity at an affordable price.

Denni Raubenheimer

PS: In writing this article I consulted ‘The Chamberlain Guide to Birding Gauteng’, a desirable book to any Gauteng birder.

Pretoria: Rietvlei Nature Reserve

The first three places in Pretoria that I would recommend for nature lovers are Rietvlei Nature Reserve, the Pretoria Botanical Gardens and Austen Roberts Bird Sanctuary. It must be noted though, that the latter two cater more for bird lovers and bird photography. Also worth note, and by no means inferior, except arguably to Rietvlei, are Roodeplaatdam Nature Reserve and the Magaliesberg Mountain Range. Finally, for those seeking a relaxing walk through nature or to do some birdwatching in Pretoria East, the Fearie Glen Nature Reserve is a very affordable option. Please note that the series of articles I am writing on the nature areas in and around Gauteng will be limited to ones I have personally visited.

Rietvlei Nature Reserve is situated on the eastern outskirts of Pretoria adjacent to, and southwest of, the R50 to Delmas. One of the features of this roughly 4000 ha reserve is its wide range of mammals, ranging from mice and mongoose to black wildebeest, white rhino and a pair of cheetahs. The reserve also boasts a wide range of birds (roughly 280 species have been observed), including water-affinite species like African Fish Eagle, Kingfishers (Giant, Malachite, Pied and Half-collared are common) and Goliath Heron, a whole host of water birds and grassland species such as Korhaans (Northern Black, Barrows and Blue), Orange-throated Longclaw and African Grass Owl.

Grasslands, marshes, gently undulating hills and two dams dominate the landscape. Luckily the network of roads and 4 hides allow visitors excess to almost every nook and cranny of the reserve. Until recently there were only three hides, one at each of the dams and the other along the Vlei Route downstream of Marais Dam. The reserve’s new hide is situated on the eastern side of the Rietvlei Dam, roughly southeast of the camping area. In my opinion it is by far the best hide. It looks out onto a small island which hosts breeding colonies of Reed- and White-breasted Cormorant and allows the visitor a 270º viewing range. Grey-headed gulls, Reed-knobbed Coots, Little Grebes and African Darters are some species usually within sight. Furthermore, there are reedbeds on both sides of the hide that together with a half-drowned dead tree a few metres from the hide attract a number of birds, and offer Kingfishers desirable perches.

Another birding and photography hotspot is at the small bridge just downstream of the Marais Dam along the Vlei Route. Here my wife and I have had the opportunity to photograph Black-shouldered Kite and Malachite Kingfisher and I have read in more than one source that it is prolific for sightings of not only Malachite Kingfishers but also Pied-, Giant-, and Half-collared Kingfishers.

Visitors may enter the reserve between 05:30 and 17:00 in summer (Sept.-Mar.) and between 06:00 and 16:00 in winter. Entrance is R35.00 per person, but no fee is charged for children under the age of 12. The reserve offers accommodation in the form of two overnight huts, as well as camping in a separate portion of the reserve. Please note that the camping fee does not include entrance to the other part of Rietvlei. Finally, guided hikes and game drives are also available to the public.

All in all Rietvlei is a jewel of Pretoria that is well maintained and managed. It offers a wide variety of fauna and natural beauty in close range of the Pretoria CBD at prices affordable to the average Joe.

In my next entry I will be discussing the Pretoria Botanical Gardens and Austen Roberts Bird Sanctuary.

Denni Raubenheimer
dennirau@yahoo.com

PS: In writing this article I consulted ‘The Chamberlain Guide to Birding Gauteng’, a desirable book to any Gauteng birder. To view more photos like those shown on this blog go to www.wildlifestockimage.com.

Gauteng: In and Around

Gauteng. Economic and industrial hub of South Africa. Probably the Province most synonymous with the rat race. With all the development and industry associated with this region, what does it still have to offer nature lovers? In my opinion, still quite a lot.

The following entrees to this blog will be focused on the nature reserves, wilderness areas and nature oases in and close to Gauteng. Being based in Pretoria I will start off with “Jacaranda Stad” and her surrounds and by the end I hope to have done justice to a still beautiful Province.

Please feel free to suggest locations in and nearby Gauteng that you would like to be discussed, or to comment on your experience of such places.

Denni

My first blog entry..
What an amazing year this has been so far. One of the foremost reasons for this has been that my wife and I have been spending so much time in nature. Furthermore, we have been privileges enough to capture some of the beauty we have witnessed on “film” (or rather memory cards).

There are so many subjects that can be discussed on a wildlife photography blog. Some that I have in mind are sharing our experience of various nature reserves, wilderness areas, etc., discussing environmental issues and posting interesting facts about some of our photographic subjects.

Wildlife photography is such a rewarding activity. I hope that the passion my wife and I have formed for this discipline/art form/whatever you want to call it will contribute towards increasing people’s love and admiration for nature and in the long-term towards nature conservation.

To visit our wildlife stock photography website go to www.wildlifestockimage.com.

Denni Raubenheimer