Showing posts with label Antelopes. Show all posts
Showing posts with label Antelopes. Show all posts

Monday, 4 December 2023

Evidence for Late Pleistocene net-hunting in southern Somalia.

Humans have been farming for about 12 000 years, a period which was preceded by hundreds of thousands of years of living a hunter/gatherer existence. It is logical to assume, therefore, that the social networking skills which made modern civilization possible developed largely before the event of farming. The advent of specialist hunting techniques such as net-hunting, which require advanced planning and co-operation between groups of hunters, and which can produce large amounts of meat in single events, are thought to have been a significant step in the development of Human social networks, connected to the emergence of social hierarchies and concepts of land ownership.

The lifestyle of Homo sapiens in East Africa from our emergence as a species onwards has been heavily investigated for decades, although curiously, despite the importance placed on the role of hunting as a driver of Human evolution by many early archaeologists, the techniques used to hunt have been relatively neglected, with an assumption that big game hunting was the dominant behaviour. Recent studies, however, have suggested that while big game hunting was important on the grassy plains of East Africa, in the coastal forests of the region, remote capture devices, such as snares, traps, or nets, used to target small Animals have been important for at least 125 000 years.

Given that such methods are thought to be closely associated with the emergence of social networks, the nature these hunting practices, and the ways in which they evolved over time, must be seen as an important part of the Human story. Examination of Later Stone Age sites in the semi-arid environment of southern Somalia, have shown that nets were being used to intensively hunt Dwarf Antelopes between about 26 000 and about 6000 years ago.

In a paper published in the journal Archaeological and Anthropological Sciences on 2 December 2023, Mica Jones of the School of Archaeology at the University of Oxford, presents the results of a study of Animal bones from the Late Pleistocene Guli Waabayo rock shelter in the Buur Heybe inselberg cluster, and the implications of this for the use of net-hunting by the Later Stone Age hunter/gatherers of the area.

Inselbergs are hills made from hard volcanic rock, which persists when other deposits are eroded away, typically forming elongate structures. In Somalia such structures are known as 'buurs', and in the inter-riverine region of southern Somalia, where rainfall is typically between 400 mm and 600 mm per year, clusters of these buurs can help to trap nutrient-rich soils and collect rainwater in pools and ponds, providing favourable habitats for a range of Plants and small Animals.

A previous study of the Rife Range Site at Buur Hakaba found that Later Stone Age hunters there specialised in hunting Dwarf Antelope, probably with nets, leading to the development of a more sedentary lifestyle and the holding of territories in the Early-to-Middle Holocene, a period of increased rainfall. However, the small number of remains recovered from this site, combined with an absence of dates, limits the usefulness of this study. The Guli Waabayo rock shelter at Buur Heybe, about 25 km to the northeast of Buur Hakaba, has yielded a much more extensive collection of Animal remains, combined with a series of robust dates, covering a period of 20 000 years, potentially enabling a good test site for hunting practices in the region before the start of the Holocene.

Map of inter-riverine southern Somalia with locations of the Buur Heybe and Buur Hakaba inselberg clusters. Jones (2023).

More than a hundred rock shelters and other archaeological sites have been identified in the inter-riverine region of southern Somalia since the 1930s. However, only three of these sites have been subject to any organised excavation work. The Gogoshiis Qabe site was excavated in the 1940s by the Italian archaeologist Paolo Graziosi. In the 1950s British archaeologist John Desmond Clark investigated the Guli Waabayo and Rife Range sites, establishing that there was a degree of cultural continuity between the two. Following Clark's activities, no further organised archaeological work was carried out in the region until the 1980s, when Steven Brandt and the Buur Ecological and Archaeological Project returned and carried out further excavations at all three sites. These excavations were brought to an abrupt halt with the onset of the Somali Civil War in 1989, although, with the consent of the Somali Academy of the Arts and Sciences, much of the excavated material was exported to the US, where it has been held in the collections of several institutions. 

Jones examined the material brought back from Guli Waabayo to establish the identity of the small Antelope bones present; these had previously all been assigned to the genus Madoqua (Dik Diks), but this is not the only genus of small Antelopes in the Horn of Africa, and, since different Antelope have different ecologies, the identity of these bones has implications for the techniques which would have been effective when hunting them. Next Jones looked at the overall assemblage, and calculated the proportion of remains coming from each type of small Mammal, and then the proportion of each age-set within the overall sample.

Studying hunting methods used to on large prey can be achieved by looking at the weapons involved, or the use and modification of the landscape by the hunters, such as cliff jumps or kite structures. However, the study of how small game is hunted requires less direct approach, as such Animals are often captured with snares, nets, or traps made from perishable materials such as plant fibres, wood, or leather. In order to address this Zooarchaeologists have developed methods of analysing the ways in which people in the past hunted small game, based upon analysis of the variety of remains.

The composition of collections of small Animal remains will vary depending on the hunting method used. Studies conducted in places where net-drives (driving Animals into net traps) are still used, such as the Congo Basin, Australia, and the southwestern United States, has shown that this method will tend to target only one or two species, but will trap almost all members of those species within the target area. This method is most useful for targeting small Animals in forested, bushy or rocky habitats. Pursuit hunting and setting of individual traps such as snares both tend to produce a more diverse range of prey, which will be reflected in the bone assemblage left behind. 

Furthermore, while net hunting captures individuals of all ages, both snare hunting and persuit hunting tend to produce a high proportion of remains from a single age group, since the young of small Animals generally lack the weight to trigger snares designed for adult Animals, and Humans hunting with bows or clubs will generally take a higher proportion of slower, juvenile Animals.

The excavations carried out at Guli Waabayo comprised 11 one metre by one metre pits, each excavated to a depth of 2.5 m. These uncovered a sequence of three Middle Stone Age/Later Stone Age technologies, although, the lower part of the exposed sequence could not be dated due to an absence of Animal remains. Dates were obtained from Ostrich shell fragments for the upper 1.5 m of the sequence, demonstrating at least sporadic occupation of the shelter from 26 000 to 6000 years ago. Two distinct Later Stone Age technologies could be seen within the sequence, the Eibian, which was used during the arid Marine Isotope Stage 2 from about 29 000 to about 14 500 years ago, and the Bardaale, used in the wetter African Humid Period from about 14 500 to about 6000 years ago.

Analysis of the faunal remains found at Guli Waabayo showed that Later Stone Age hunters across the Pleistocene/Holocene boundary targeted a diverse range of game, including large and small Mammals, Birds, Reptiles, and Fish, although they had a clear preference for Mammals massing less than 20 kg. This preference for small Mammals seems to have increased slightly in the African Humid Period, although this change in climate appears to have made relatively little difference to the site's occupants, probably because the African Humid Period was a lot less pronounced in southern Somalia than in other areas.

Of the bones present at Guli Waabayo, 3104 could be identified as coming from small Mammals, with 2111 identifiable to a lower taxonomic level. Of these 1263 have previously been identified as coming from Dwarf Antelope, with the assumption that they originated from Dik Dik. However, this assumption was never actually put to the test, and there is another form of Dwarf Antelope present in the Horn of Africa, the Suni, Neotragus moschatus.

Jones selected all of the first phalanges assigned to Dwarf Antelopes in the Guli Waabayo collection, and compared them to first phalanges from Dik Dik and Suni in the collection of the Field Museum in Chicago. The size ranges of the first phalanges did not overlap, and all of the specimens from the Guli Waabayo collection conformed with the Dik Dik form, although it was not possible to tell which species of Dik Dik they belonged to.

The Dik Dik genus, Madoqua, first appears in the fossil record in the Miocene. There are four living species within the genus, Madoqua guentheriMadoqua saltiana, and Madoqua piacentinii are endemic to the Horn of Africa, while the fourth, Madoqua kirkii is found from Somalia south to Tanzania and eastern Uganda, as well as on the west coast of Southern Africa in Namibia and Angola. All species favour rocky environments with low thicket vegetation, with the inselbergs of southern Somalia providing an excellent environment, that today supports a large population of Dik Dik, which live in monogamous pairs, with each pair occupying and defending a territory with an area of about 1 km².

A Salt's Dik Dik, Madoqua saltiana, in the wild. David Castor/Wikimedia Commons.

Dik Dik are not widely hunted in Africa today, although in places they are targeted for their meat and skins, which are used to make gloves and cloaks. The Hadza people of northern Tanzania occasionally hunt Dik Dik with bows and arrows, while the Mukogodo people, who lived in the area around Mount Kenya in the eighteenth century are believed to have hunted Dik Dik both with snares and by stalking. 

Modern Somali pastoralists have been recorded to chase down Dik Dik, which seems surprising, given that these Dwarf Antelopes can reach speeds of about 42 km per hour, but is possible because they are so reluctant to leave their territories that they will often run around the perimeter when chased, allowing much slower Human pursuers to keep them in sight until they become exhausted and are easily captured. In the 1940s and 1950s several agropastoralist groups in Somalia were reported to capture Dik Dik in net hunts.

During these hunts, the men used nets about 5 m in length, strung between 2 m long poles. These nets would be used to create semi-circular traps, into which Dik Dik could be driven by men and Dogs, before being dispatched with bows and arrows, a methodology which could conceivably have been used by Later Stone Age hunters in the same region.

Having established the Small Antelope remains at Guli Waabayo came from Dik Dik, Jones next sorted the remains into age groups, based upon examination of complete and partial tooth rows, as well as loose lower 3rd molars and 4th premolars. The dental aging of modern Dik Dik has not been extensively studied, but it was still possible to separate the remains into juvenile, older juvenile, adult, and older adults, based upon the relative eruption and wear seen in the teeth. 

Madoqua mandibles of different age sets from Guli Waabayo. Jones (2023).

Dik Dik remains dominated the faunal assemblage at Guli Waabayo in both Marine Isotope Stage 2 and the African Humid Period. Roughly twice as many remains assignable to Madoqua were found in Marine Isotope Stage 2 selection as in the African Humid Period selection, but this was also true of other Animals present, ab probably reflects the fact that Marine Isotope Stage 2 lasted about 14 000 years, while the African Humid Period lasted only about 6000 years. Nevertheless, the proportion of the assemblage made up by Dik Dik bones did increase, from 55.2% in Marine Isotope Stage 2, to 71.9% in the African Humid Period.

Small Mammal frequencies from Guli Waabayo, presented as % (number of identifiable specimens). Abbreviations: MIS 2, marine isotope stage 2; AHP, African humid period; ka. thousand years ago. Jones (2023).

In both intervals, the age-profile of the Dik Dik remained fairly constant, with all age groups present, but adults making up almost half of the assemblage in both cases, while the other three age groups each made up between 13.3% and 21.3% of the assemblage, although Jones notes that the sample size is very small for the African Humid Period, which may mask greater variation than is recorded.

Dik-dik mortality profiles from Guli Waabayo, presented as % (minimum number of individuals). Abbreviations: MIS 2, marine isotope stage 2; AHP, African humid period; ka, thousand years ago. Jones (2023).

There was a relatively high proportion of Carnivore remains in both Marine Isotope Stage 2 (4.4%) and the African Humid Period (5.4%). This could potentially indicate that the site had at times been occupied by Carnivores (for example Hyenas), and that they would have been responsible for some of the other remains present. Signs of such denning behaviour are considered to include juvenile Carnivore bones, gnaw marks on the bones of other Animals. Of 88 identified small Carnivore bones present in the total collection from Guli Waabayo, only three had unfused epiphyses (two from indeterminate Carnivores and one from a small Felid). In addition a mandible was identified with an erupting third molal (a sign that it came from a juvenile Animal), which could be assigned to a Dwarf Mongoose, Helogale sp.. No bones could be attributed to juvenile medium or large Carnivores, such as Hyenas or Lions, and no neonatal Carnivore bones of any type were found. A single Dik Dik bone from Marine Isotope Stage 2 showed signs of gnawing, but this was clearly by a Rodent Three Dik Dik bones from the African Humid Period also showed signs of gnawing, with two of these again clearly having been gnawed by Rodents. Conversely, none of the Dik Dik bones showed signs of butchery with tools, although this would not typically be expected with the bones of an Animal this small. Signs of burning, another clear indicator of a Human predator, were found on 12.3% of the Marine Isotope Stage 2 Dik Dik remains, and 7.8% of the African Humid Period Dik Dik bones.

Jones's investigation confirmed that Later Stone Age hunters had extensively targeted Dik Dik, small territorial Bovids, during both Marine Isotope Stage 2 and the African Humid Period, something in line with previous research at the site. However, unlike previous researchers, Jones did not concentrate on the toral diversity of remains at the site, but specifically upon the most abundant item, the Dik Dik, with a view to understanding the importance of these Antelopes to Later Stone Age hunting communities in the area. The evidence strongly suggests that the people here became specialist hunters of Dik Dik during the arid Late Pleistocene. 

This is different to the pattern observed at the Riffle Range Site, where a specialisation in net-hunting of Dik Dik appears to have developed during the African Humid Period, alongside a more general shift towards a more settled lifestyle and the permanent holding or territory by Later Stone Age groups. At Guli Waabayo the proportion of Dik Dik among the Animal remains increased in the African Humid Period, suggesting that they became a more important resource during this time, but they were clearly already a major prey species in Marine Isotioe Stage 2. This suggests that the change in climate did not provoke a major change in hunting methods or other behaviours at Guli Waabayo. This raises the possibility that the apparent change in behaviour at the Riffle Range Site 12 000 years ago may be actually indicate that the site was only sporadically inhabited prior to this, or simply that earlier remains have not been preserved. An increase in usage of the Riffle Range Site during the Holocene appears to be the more likely scenario, but why that should be is unclear.

The hunters of Guli Waabayo appear to have taken far more Dik Dik than any other Animal, even similar sized small Mammals, such as Hares or Hyraxes. Thus suggests that they had developed a specialised hunting technique which enabled them to reliably capture large numbers of Dik Dik, bur which did not work as readily on other prey. Furthermore, the Dik Dik remains have a distinct age profile, with all age groups present but adults being the most abundant. Based upon studies of modern Dwarf Antelope hunters, the most likely explanation for this is that communal net drives were used to target Dik Dik on a regular basis, but that other hunting methods were also used to catch other prey.

The selection of faunal remains present at Guli Waabayo makes it likely that both snare and pursuit hunting were also practiced, but the large proportion of Dik Dik in the remains cannot be explained by this. Snares will tend to target a range of Animals of the same size, including small Carnivores, which are present in the Guli Waabayo assemblage, but do not tend to capture juvenile Animals, which are typically too small to trigger them. Had snares been the primary hunting method at Guli Waabayo, then the overall assemblage of Animals would have been more varied, without any single species dominating, and juvenile Dik Dik would have been largely absent. Pursuit hunting, in contrast, tends to produce a far higher proportion of juvenile Animals, which are easier to run down, but again does not tend to produce an assemblage dominated by a single species. 

The bone assemblage from Guli Waabayo was accumulated over thousands of years, making it unlikely that all of the Dik Dik remains there are the result of a single hunting method. Nevertheless, it does appear likely that net hunting played a significant role in the life of Later Stone Age hunters in the region.

The most egalitarian hunter/gatherer societies tend to invest little effort in the manufacture of material goods. However, as societies become more complex, an increasing emphasis is placed upon resource management, and delayed-return technologies, which ensure the future supply of food. Such technologies include both devices used to store food, and to capture Animals for consumption, and are in turn associated with a decrease in mobility, with groups tending to remain in one place for longer. In environments with strong seasonal variations in the availability of food, this can lead to the development of flexible political systems or large resource-sharing networks. 

The Holocene Kansyore people of the Lake Victoria Basin are known to have used pottery and Fish weirs d to exploit seasonal Fish stocks, a specialization which resulted in long-term occupation of sites, and presumably a sense of ownership of those sites. The connection between subsistence, land use, and technology during earlier periods in East Africa is less clear, although the specialisation in hunting Dik Dik in the pre-Holocene Later Stone Age at Guli Waabayo suggests that these people had developed a lifestyle in Marine Isotope Stage 2 which was tied to long term resource management within a single environment, and the use of specialist equipment, in the form of nets, which would have required considerable investment in time to construct and maintain.

The traditional view of Late Pleistocene hunters in East Africa has been one of highly mobile groups which placed an emphasis on the hunting of large game. However, the evidence from s coastal and forested regions suggests that small game may have been a far more important resource than was previously thought, to at least some groups of hunter/gatherers. The use of delayed-return hunting technologies, such as snares, traps, or nets, would have allowed more settled populations in coastal and forested environments, enabling a diversity of survival strategies to survive alongside one another in East Africa during the Late Pleistocene. The evidence for specialist Dik Dik hunting at Guli Waabayo adds to this understanding, giving an example of a community surviving in a semi-arid environment by adopting a more settled lifestyle and a specialist method of hunting.

Most hunting methods target one Animal at a time, but net drives can trap numerous Animals at the same time, potentially leading to surpluses of meat following the hunt. Among modern communities which practice net hunting in the Congo Basin, hunts are typically communal activities, involving men, women, and children, and the re-enforcement of social bonds. In Australia the organisation of net-hunts has been associated with the emergence of political hierarchies, while in the southwestern US the organisation of communal net hunts for Rabbits has been associated with both forming co-operative bonds between different groups, and the establishment of temporary leaders.

No direct evidence of netting has been found at Guli Waabayo, however, the pattern of remains suggests that the hunters here were using communual net-drives to capture large numbers of Dik Dik during the Later Stone Age. Such hunts would likely have resulted in considerable amounts of meat becoming available at certain times, enabling the surplus to be shared among large extended communities.

If this were the case, then Dik Dik hunting would have enabled large communal gatherings, promoting social cohesion between groups and promoting further co-operation. However, the faunal data is not enough in itself to make many assumptions about these ancient societies, and further analysis of Human burials from Guli Waabayo and Gogoshiis Qabe, combined with studies of lithic tools from these sites and the Riffle Range Site, should help us gain a better understanding of these ancient East African communities.

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Sunday, 1 April 2018

Poaching in the Kakum Conservation Area of Ghana.

Tropical forests have come under unprecedented threat in recent decades, with wildlife populations threatened by both the felling of forests and hunting. To remedy this, many countries have introduced protected areas such as national parks within areas of tropical forests, within which the hunting or harvesting of wild animals and plants is strictly controlled or completely forbidden. Unfortunately, such schemes are typically imposed by central governments without any input from local communities that have lived in, and extracted resources from, these forests for centuries or more. This can mean that such communities suddenly find traditional sources of income and sustenance are suddenly forbidden, whereas any income from the new reserves typically goes into central government coffers, creating an sense of alienation, and a subsequent reluctance to cooperate with park schemes.

In a paper published in the Journal of Threatened Taxa on 26 February 2018, Edward Debrah Wiafe of the Department of Environmental and Natural Resources Management at the Presbyterian University College in Akropong-Akuapem, Ghana, presents the results of a 13 month study of poaching in the Kakum Conservation Area of southern Ghana.

The Kakum Conservation Area comprises the Kakum National Park, with an area of 210 square kilometres, and the Assin Attandanso Resource Reserve, covering 150 square kilometres. These were originally created during the colonial period (1931 and 1937 respectively), in order to protect the watershed that supplied the Cape Coast region, and to provide a source of timber. Establishing forest parks for the benefit of the timber industry might seem slightly contradictory, but in Britain, the colonial power in Ghana at the time, all natural forests vanished centuries ago, and with timber coming from managed and protected woodlands harvested on a rotational basis, with trees being left to grow for decades unmolested; unprotected areas tend to be rapidly converted to arable production, which produces a crop every year. The forests at Kakum were home to a number of local communities, which relied on the forests to provide them with resources through hunting and gathering, and occasionally some artisanal gold and clay mining, but little timber harvesting is thought to have occurred before the forest parks were created.

A raised walkway in the Kakum National Park; a popular attraction with tourists that provides a useful source of hard currency. Nicola Chiappi/Wikimedia Commons.

Today the area is protected by Wildlife Protection Rangers armed with G.P.S. units, compasses, grid maps and riffles, who enforce strict rules prohibiting anybody from hunting any animal or removing any plant from the reserve without express written permission, effectively making all hunting illegal. The reserve is home to a number of protected Mammals and Birds including African Elephant, Loxodonta africana, Maxwell’s Duiker, Philantomba maxwellii, Black Duiker, Cephalophus niger, Bongo, Tragelaphus eurycerus, Lowe’s Monkey, Cercopithecus lowei, Olive Colobus, Procolobus verus, Black and White Colobus, Colobus vellerosus, and Yellowbilled Turaco, Tauraco macrorhynchus. It is also home to 53 Human communities, who are now reliant on subsistance farming.

Wiafe collected data on arrests made by Wildlife Protection patrols between November 2012 and November 2013, including the number of arrests, the time of poaching equipment they were using and the numbers and types of animals they were caught with.

In November 2012 the patrols arrested two poachers, armed with snares and shotguns, and in possession of one Maxwell’s Duiker, 27 Rats and two live Pangolins. In December 2012 three poachers were arrested, armed with shotguns and in possession of ne Maxwell’s Duiker and two Pangolins.

A Maxwell’s Duiker, Philantomba maxwellii, considered to be Least Concern under the terms of the International Union for the Conservation of Nature's Red List of Threatened Species and hunted by poachers in the Kakum Conservation Area of Ghana. Paul Cools/iNaturalist/ICUN Red List.

In January 2013 the patrols arrested one poacher, armed with a shotgun, and in possession of two Maxwell's Duiker, one Lowe's Monkey, and one Spot-nosed Monkey. In February one poacher was arrested, in possession of snares and two Maxwell's Duiker, one Royal Antelope, one Tree Squirrel and a Potto. In march 2013 a single poacher was apprehended, armed with a shotgun and in possession of one Maxwell's Duiker and one Lowe's Monkey. In April 2013 no poachers were arrested.

A Lowe's Monkey, Cercopithecus lowei, in the Mole Game Reserve in Ghana. This species is again considered to be of Least concern under the terms of the ICUN's Red List, and is hunted in the Kakum Conservation Area of Ghana. Peter Strong/Wikimedia Commons.

In May 2013 four poachers were arrested, armed with shotguns and in possession of five Maxwell's Duiker, two Royal Antelope, two Lowe's Monkeys, and one Spot Nosed Monkey. In June no poachers were apprehended again, while in July 2013 three poachers were arrested, in possession of shotguns and having killed two Maxwell's Duiker, one Lowe's Monkey and one Elephant.

African Elephant, Loxodonta africana, in the Kakum National Park. The species is considered to be Vulnerable under the terms of the ICUN's Red List. Kakum National Park.
 
In August 2013 the patrols arrested one poacher, armed with a shotgun and in possession of one Royal Antelope, one Flying Squirrel, one Lowe's Monkey, one Olive Colobus, and one live Pangolin. No poachers were apprehended in September or October 2013, while in November 2013 another single poacher was arrested, this time armed with a shotgun and and in possession of one Maxwell's Duiker, two Lowe's Monkeys and two live Pangolins.

A Long-tailed Pangolin, Uromanis tetradactyla, in the Kakum National Park. One of three Pangolin species in the area, all of which are considered to be Vulnerable under the terms of the ICUN's Red List. Lars Peterson.

During the time of the study 69 animals were recovered by Wildlife Protection Rangers in the Kakum National Park, including 29 Rodents, 19 Antelope, 13 Primates, seven Pangolins, and an Elephant. Of these eight belonged to species considered to be Vulnerable under the terms of the ICUN's Red List of Threatened Species (the Pangolins and the Elephant) one belonged to a species considered to be Near Threatened (the Olive Colebus), while the remainder belonged to species considered to be of Least Concern. This pattern did not vary notably from that in areas where hunting is not illegal.

The favoured weapon of the Poachers was clearly the shotgun, which Wiafe notes is the weapon most conservationists would prefer to see used, as it is a discriminating weapon which allows hunters to only take the animals they want, unlike snares which are more random. This is not always the case in protected reserves, as the sound of shotguns can attract the attention of patrols, however in this instance the hunters reported preferring shotguns as they enable them to target animals in the tree canopy. However the Wildlife Rangers also reported sometimes finding fencing around paths in the reserves, directing animals to snares outside the bounds of the protected area.

See also...

http://sciencythoughts.blogspot.co.uk/2018/03/cheirogaleus-grovesi-new-species-of.htmlhttp://sciencythoughts.blogspot.co.uk/2018/01/calculating-role-of-pleistocene-refugia.html
http://sciencythoughts.blogspot.co.uk/2017/11/image-of-elephant-human-conflict-wins.htmlhttp://sciencythoughts.blogspot.co.uk/2017/11/pongo-tapanuliensis-new-species-of.html
http://sciencythoughts.blogspot.co.uk/2017/10/elephants-kill-four-rohingya-refugees.htmlhttp://sciencythoughts.blogspot.co.uk/2017/10/unsustainable-chocolate-production.html
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Saturday, 6 January 2018

Calculating the role of Pleistocene refugia in explaining the distribution of modern Duiker populations.

Although not affected by extensive glaciations during the Pleistocene, Africa is thought to have had periods of much cooler and drier climate which correspond the the glaciations in Eurasia and North America. During these periods the tropical forests which cover much of West and Central Africa are thought to have shrunk into a series of refugia, smaller forest patches from which forest species spread to cover the remainder of the area in warmer and wetter periods. Many modern groups of animals and plants have distributions that are thought to derive from these refugia, with species, subspecies or populations thought to have derived from different refugia still having distinct distributions within modern continuous forests. However examination of the various groups of animals and plants found in African forests appear to suggest different numbers of refugia, with different studies suggesting different numbers of refugia providing different origins for modern populations in the same regions.

In a paper published in the journal BMC Evolutionary Biology on 6 September 2017, Stephan Ntie of the Department of Biology at the Université des Sciences et Techniques de Masuku, and the Department of Biological Sciences at the University of New Orleans, Anne Davis, also of the Department of Biological Sciences at the University of New Orleans, Katrin Hils of the Cheetah Conservation Fund and the Institute for Evolution and Ecology at the University of Tübingen, Patrick Mickala, also of the Department of Biology at the Université des Sciences et Techniques de Masuku, Henri Thomassen, also of the Institute for Evolution and Ecology at the University of Tübingen, Katy Morgan, also of the Department of Biological Sciences at the University of New Orleans, Hadrien Vanthomme of the Département Ecologie et Gestion de la Biodiversité at the Muséum National d’Histoire Naturelle, Mary Gonder of the Department of Biology at Drexel University, and Nicola Anthony, once again of the Department of Biological Sciences at the University of New Orleans, describe the results of a study into the populations of modern Duikers, Cephalophinae, in modern West-Central African rainforests, with a view to understanding if this distribution derives from Pleistocene refugia.

Duikers are small-to-medium-sized Antelope found in dense forests in sub-Saharan Africa. The group is thought to have originated in the Miocene, and is composed of specialist browsers (feeding on leaves, shoots and fruits) rather than grazers (feeding on grass) like other Antelope. There are currently sixteen species of Duiker, split into three genera, many of which have overlapping ranges, but which are able to co-exist due to different ecological roles and diets.

A Bay Duiker, Cephalophus dorsalis, photographed slightly outside the Akanda National Park in Gabon in July 2012. Lyse Primault/Wikimedia Commons.

Studies of other groups suggest there were probably four refugia in the West-Central Africa region, the Gulf of Guinea Refugia in the volcanic mountains between Cameroon and Nigeria, the South-western Cameroon Refugia in coastal Cameroon to the south of the Sanaga River, the Equatorial Guinea and northern Gabon Refugia in the coastal forests spanning the borders between Equatorial Guinea and Gabon and the Southern Gabon Refugia to the south of the Ogooué River in Gabon.

In order to assess the distribution of modern Duiker populations in the region, Ntie et al. collected samples of Duiker dung from the Cross River National Park in Nigeria, the Takamanda National Park, Campo Ma’an National Park, and Lobéké National Park in Cameroon, the Monte Alén National Park, Monte Mitra, and Bioko Island in Equatorial Guinea, the Monts de Cristal National Park, Birougou National Park, Gamba Complex of Protected Areas and Minkébé National Park in Gabon, the Nouabelé Ndoki National Park in the Republic of Congo, the Mbaéré-Bodingué National Park in the Central African Republic, and the Salonga National Park in the Democratic Republic of Congo. In addition museum specimens from the Mount Nimba Strict Nature Reserve in Guinea, Cape Province in South Africa, the Dja Faunal Reserve, and area around the town of Bamenda in Cameroon, Lefini Reserve, Odzala National Park and area around Brazzaville in the Republic of Congo, Mbaéré-Bodingué National Park in the Central African Republic, area around Mitzic in Gabon, and area around Kisangani in the Democratic Republic of Congo

These samples were analysed for traces of mitochondrial DNA (mtDNA). Because mitochondrial DNA is found in the mitochondria, organelles outside the cell nucleus, it is passed directly from mother to child without being sexually recombined each generation, enabling precise estimations of when individuals shared common ancestors, at least through the female line (it is also possible to trace direct ancestry through the male line, using DNA from the Y chromosome, which is passed directly from father to son without sexual recombination), enabling Ntie et al. to determine the species of Duiker that produced each stool, and sort the samples into discrete lineages with common ancestry within each species.

A Blue Duiker, Philantomba monticola. Derek Keats/Wikimedia Commons.

Ntie et al. were able to recover mtDNA from six species of Duiker, the Bay Duiker, Cephalophus dorsalis, the Peter's Duiker, Cephalophus callipygus, the Yellow-backed Duiker, Cephalophus silvicultor, the Black-fronted Duiker Cephalophus nigrifrons, the White-bellied Duiker Cephalophus leucogaster, and the Blue Duiker, Philantomba monticola, plus the Water Chevrotain, Hyemoschus aquaticus and the Sitatunga Tragelaphus spekii, which are ecologically similar Ruminants. However, only three species, the Bay Duiker,the Peter's Duiker and the Blue Duiker, were found in more than three locations, preventing the inclusion of any of the other species in the study.

Stool samples from the Bay Duiker were found at all areas except Cross Rivers in Nigeria and Cape Province in South Africa. However, there appeared to be no clear population structure within this species, suggesting that individuals of this species range widely between locations, and that if they ever were restricted to refugia all traces of this have long since been overwritten by breeding migration between populations.

Both the Peter's Duiker and the Blue Duiker were also present in most locations (neither was found in Guinea and the Peter's Duiker was also absent in Cape Province and the Central African Republic). In both these species two distinct lineages appeared to be present, with populations in Nigeria and northern Cameroon apparently separate from all other populations.

A Peter's Duiker, Cephalophus callipygus, in the Campo Ma’an National Park in Cameroon. Wikimedia Commons.

This strongly suggests that the Peter's Duiker and the Blue Duiker were reduced to at least two separate populations during the Pleistocene glaciations, one in the Gulf of Guinea Region and one to the south; though it cannot be determined if these southern populations were restricted to single forest fragments, or were found in more than one fragment but able to move between them (Duiker cannot survive and reproduce for long periods in open grassland, but are certainly capable of crossing it).

See also...

http://sciencythoughts.blogspot.co.uk/2016/10/understanding-ancestry-of-european-bison.htmlhttp://sciencythoughts.blogspot.co.uk/2016/01/ammotragus-lervia-diet-of-barbary-sheep.html
http://sciencythoughts.blogspot.co.uk/2016/01/mapping-distribution-of-southern-pudu.htmlhttp://sciencythoughts.blogspot.co.uk/2015/12/capreolus-constantini-roe-deer-from.html
http://sciencythoughts.blogspot.co.uk/2015/02/the-genetic-diversity-and-distribution.htmlhttp://sciencythoughts.blogspot.co.uk/2014/07/a-highly-specialized-musk-ox-from-late.html
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Saturday, 10 August 2013

How fencing the Tibetan prairies is effecting the endangered Przewalski’s Gazelle.

The Przewalski’s Gazelle (Procapra przewalskii) is a species of high altitude adapted Antelope, which formerly ranged across much of northwestern China and Inner Mongolia. It is now restricted to a small area around Qinghai Lake on the Tibetan Plateau, with a population comprising about 400 individuals, divided into six populations which apparently do not interbreed. The species was reduced to this level by hunting, but after being placed on the ICUN Red List of Threatened Species, China introduced laws to protect the Gazelles and hunting is now thought to be rare. However the population has continued to decline, causing conservationists to look for other forms of human activity that may be harming the animals recovery. The species is currently considered to be Endangered by the ICUN, but is only just above the Critically Endangered Level.

In a paper published in the June 2013 edition of the Chinese Science Bulletin, ZhangQiang You of the Key Laboratory of Animal Ecology and Conservation Biology at the Institute of Zoology at the Chinese Academy of Sciences, the University of Chinese Academy of Sciences and Mianyang Normal University, ZhiGang Jiang and ChunWang Li, also of the Key Laboratory of Animal Ecology and Conservation Biology, and  David Mallon of the Antelope Specialist Group at the ICUN and the Department of Biology, Chemistry and Health Science at Manchester Metropolitan University, discuss the results of a long term study into the effects of livestock fencing on the remaining populations of Przewalski’s Gazelle.

Three male Przewalski’s Gazelles near Qinghai Lake on the Tibetan Plateau. Coke & Som Smith.

You et al. examined three populations of Gazelles, at Hudong-Ketu and Yuanzhe, where livestock fences have been introduced, and at Kuaierma, which remains unfenced. The study was based upon direct observation rather than radio tagging, due to the conservation status of the animals. Livestock fences have spread across much of the prairie-land of northern China, Inner Mongolia and the Tibetan Plateau in recent decades, with a 2002 study estimating that 70% of the area had been fenced.

It was found that animals in the fenced areas occupied much smaller territories than those in the unfenced areas, and roamed over lower distances each day. They also grazed without breaks fro shorter periods, and spent considerable amounts of their time walking along the fences. The Gazelles were capable of leaping the fences, but apparently did not often choose to do so. Deaths were recorded from animals becoming entangled in the fences, and predation by Wolves was higher in the fenced areas, suggesting that the fences presented a significant obstacle to the movement of the Gazelles.

Current distribution status of the Przewalski’s gazelle around Qinghai Lake in northwest China. There are six populations: Gonghe (GH), Gangcha (GC), Bird Island (BI), Hudong-Ketu (HD-KT), Yuanzhe (YZ) and Kuaierma (KM). You et al. (2013).


You et al. conclude that livestock fences present a significant threat to the long-term survival of Przewalski’s Gazelle, and note that previous studies have suggested that the fences also have a similar effect on populations of the Mongolian Wild Ass (Equus hemionus) and Tibetan gazelle (Procapra picticaudata). They suggest that an integrated sustainable grassland management scheme needs to be developed for the Central Asian grasslands in order to prevent a series of extinctions of the large Ungulates of the region.


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