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Sedimentary Structures Generated by Hippopotamus amphibius in a Lake-margin Wetland, Ngorongoro Crater, Tanzania


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Large mammals, especially Hippopotamus amphibius, have created a distinctive set of traces in a spring-fed freshwater wetland on the margin of the saline-alkaline crater lake in the Ngorongoro Crater, Tanzania. It is comprised of a ∼30 m diameter zone of deep (<2m) bioturbation due to hippo wallowing, surrounded by dendritic to radial hippo trails 1–5 m wide and <0.5 m deep, infilled with organic-rich mud. These trails narrow and thin as they grade into trackways on the lake flat. Tracks and trackways of more terrestrial mammals, such as bovids and equids, are found in the lake flat muds surrounding the hippo-dominated area. Associations of sedimentary structures such as these are important indicators of paleoenvironmental conditions where they are preserved in the sedimentary record, due to the strong affinity of Hippopotamidae for freshwater environments.
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Sedimentary Structures Generated
by Hippopotamus amphibius in a
Lake-margin Wetland, Ngorongoro
Crater, Tanzania
Department of Geological Sciences, Rutgers University, Piscataway,
NJ 08854-8066
PALAIOS, 2002, V. 17, p. 212–217
Large mammals, especially Hippopotamus amphibius,
have created a distinctive set of traces in a spring-fed fresh-
water wetland on the margin of the saline-alkaline crater
lake in the Ngorongoro Crater, Tanzania. It is comprised of
30 m diameter zone of deep (
2m) bioturbation due to
hippo wallowing, surrounded by dendritic to radial hippo
trails 1–5 m wide and
0.5 m deep, infilled with organic-
rich mud. These trails narrow and thin as they grade into
trackways on the lake flat. Tracks and trackways of more
terrestrial mammals, such as bovids and equids, are found
in the lake flat muds surrounding the hippo-dominated
area. Associations of sedimentary structures such as these
are important indicators of paleoenvironmentalconditions
where they are preserved in the sedimentary record, due to
the strong affinity of Hippopotamidae for freshwater envi-
Large vertebrates long have been recognized as impor-
tant agents in shaping the geomorphology of their terres-
trial environments and the character of associated sedi-
ments (Laporte and Behrensmeyer, 1980). One of the dif-
ficulties in understanding the nature of large mammal-
substrate interactions in the geologic past is the general
lack of extant species similar in size to the megafauna of
the ancient past. Therefore, inferences based on modern-
process observations have been limited to those faunas,
typically in Africa, that can be observed today in natural
settings (Cohen et al., 1993).
Of the extant large mammals, perhaps the most nearly
infaunal is Hippopotamus amphibius, which is known for
conducting wholesale excavation of sediment in a variety
of environmental settings (McCarthy et al., 1998). These
organismsare particularly important inclosed-basinlake-
margin settings, where low topographic gradients and
strong geochemical gradients allow mammal activities to
affect the local hydrology, geochemistry, and vegetation
(Deocampo and Ashley, 1997; Deocampo, 2001). In thedry
lands of East Africa, Hippopotamusamphibius tends to fo-
cus activity in fresh water bodies and wetlands (Kingdon,
1979). Understanding the nature of the interactions be-
* Present address: Department of Mineral Sciences, National Museum
of Natural History, Smithsonian Institution, MRC 119, Washington,
DC 20560-0119
tween hippos and their substrates, and the resultingsedi-
mentary records, can provide important information on
the paleoenvironments and paleoecology of analogous an-
cient settings.
The purpose of this paper is to describe the set of sedi-
mentary traces associated with the activities of modern
vertebrates, especially Hippopotamus amphibius,onthe
margin of Lake Makat, in the Ngorongoro Crater, Tanza-
nia. The low-gradient lake margin is in a protected natu-
ral setting with a population of hippopotamus; hence, this
providesa basis for understanding what waslikelyamuch
more widespread phenomenon in the Cenozoic.
Ecological Setting
The Ngorongoro Crater is the ;19 km diameter caldera
ofa large volcano that collapsedin the Crater Highlands of
northern Tanzania about 2 million years ago (Hay, 1976).
The internally drained modern caldera surface (Fig. 1) is
characterized by a wide range of environmental settings
anda diverse floraland faunalassemblage (Herlocker and
Dirschl, 1972; Anderson and Herlocker, 1973; Estes and
Small, 1981; Kabigumila, 1993). Ngorongoro is well
known for its large populations of non-migratory large
mammals,including plains animals such as zebraand wil-
debeest, forest dwellers such as waterbuck, and notable
carnivores such as lion and leopard. Vertebrate activity
tendsto follow seasonal patterns,with largemammalpop-
ulations dispersed during wet times, and concentrated
aroundpastures and water sourcesduring the dryseasons
(Estes and Small, 1981; Deocampo et al., 1998).
Although it is relatively small, the Mti Moja spring, lo-
cated on the northeast shore of the saline-alkaline Lake
Makat (Fig. 1; UTM coordinates 0783064E, 9648057N), is
an important focus of large-mammal activity in the area
(Table 1). The spring is a major source of potable water in
thecenter of the Crater,farfromthe springs, streams,and
wetlands near the Crater wall (Deocampo and Ashley,
1999). Groundwater erupts at the base of an eroding cliff
and flows for about 100 m toward the lake in a restricted 2
m wide, ,50 cm deep channel (Fig. 2). Once reaching the
lower-gradient lake flat, water spreads out, feeding a com-
plex of lightly vegetated marsh-and-hippopotamus habi-
tat. The most distal spring waters, about 600–800 m away
from the source, are highly saline brines that do not sup-
port any rooted vegetation (Deocampo, 1997; Deocampo
and Ashley, 1999).
Mti Moja was visited repeatedly during July and Au-
gust, 1995–2000. When lake waters were low (1995–1997,
2000), maps of spring-water distribution and geomorphic
features were created by a combination of electronic total
station, differentially-corrected global positioning system,
and tape-and-compass. Daytime hippo activity was ob-
served on foot from distances ranging from 20–1000 m, for
timespans up to several hours; nocturnal observations
were logistically not possible. Because hippo activity out-
side pools generally is limited to the night, the actual cre-
ation of structures was not observed directly. However,
hippo structures clearly were associated with occupied
hippo pools and identifiable hippo tracks. Conductivity
FIGURE 1—Location of the study area.
TABLE 1—Large vertebrate animals observed within 100 m of Mti Moja spring, northeast shore of Lake Makat, NgorongoroCrater, Tanzania,
Common name Species name
Herbivores Buffalo (Cape)
Gazelle (Grant’s)
Gazelle (Thompson’s)
Syncerus caffer
Gazella granti
Gazella thomsoni
Alcelaphus buselaphus cokii
Hippopotamus amphibius
Rhinoceros (Black)
Zebra (Common)
African Elephant (faeces)
Struthio camelus
Diceros bicornis
Phacochoerus aethiopicus
Connochaetes taurinus
Equus burchelli boehmii
Loxodonta africana
Carnivores Cheetah
Fox (Bat-Eared)
Hyena (Spotted)
Acinonyx jubatus
Otocyon megalotis
Crocuta crocuta
Canis mesomelas
Panthera leo
and pH of surface waters were measured in situ by elec-
tronic meter. Organic carbon content was estimated by
loss-on-ignition for one hour at 550 C (Lewis and Mc-
Conchie,1994), well below the experimentally-determined
threshold for significant structural water loss for Ngoron-
goro clays (Deocampo, 1997). Associated geomorphology,
sedimentology, and aqueous geochemistry of the wetland
will be reported elsewhere (Deocampo, in press).
Hippopotamus traces
Hippo activity is centered within pools for most of the
daytime hours (Fig. 3A). Hippos lie partially submerged
within these shallow pools (5–15 m across, ,2 m deep),
wallowing and interacting with others in their group
(Kingdon,1979). Although these activities do involve some
movement and churning of the substrate (Wolanski and
Gereta, 1999), more significant substrate reworking oc-
curs as hippos move in and out of the pools at night. Dur-
ing these movements, the hippo bodies easily plow
through saturated muddy sediment. Repeated nocturnal
forays by hippos from their daytime wallows to evening
grazing pastures have created a ;100-m-long dendritic
network of trails originating in the wallowing pools (Fig.
3B-D). These trails, created as the hippos forcibly move
through saturated mud, measure 1–5 m across and ;0.5
m deep, and are infilled with organic-rich mud. The trails
commonly have elevated mud levees on their margins,
which were squeezed above the lakeflat surface by the
passage of the hippos, and then dried in place (Fig. 3E).
The largest trails are those closest to the pools, reflecting
the repeated usage of these over time; the more distal
trails may be used less frequently, depending on the des-
tination of the hippos, which may change with time. The
trails become exposed and mudcracked as the surface wa-
ter coverage shrinks during the dry season, and the abun-
dance of organic carbon content is reduced, although it is
still much higher than that of surrounding mudflats (Ta-
ble 2).
As the trails emerge onto drier land, they become shal-
lower and grade into recognizable tracks and trackways
(Fig. 3D). Whereas some of the trails adjacent to the pools
are a few meters across, the distal ends of the trails are
commonly the width of a single hippo as they emerge onto
dry land. Spring water at Mti Moja flows into the hippo
pools and then continues onto the mudflats, following the
hippo trails. The distal ends of the Mti Moja trails com-
monly contain highly saline and alkaline waters (Fig. 2),
and efflorescent crusts of evaporite minerals may form in
thesesettings (Deocampo and Ashley,1999). A mapof sur-
face water coverage during the dry seasons of 1995–2000
showsthat this distribution maychangeovertime (Fig.2).
Where these trails occur in a more stable setting, such as
adjacent to a large pool, long-term repeated usage contin-
ues to enlarge the trails, and they can be visible from long
distances (Fig. 3F).
FIGURE 2—Mti Moja spring surface water distribution and geochemistry. (A) Local map showing the distribution of surface water and major
vertebrate traces at the lake-margin Mti Moja and spring-fed wetland. The central area of hippo pools grades into surrounding areasof hippo
trails, which then grade into the trackfields created by a diversity of vertebrates on the mudflats. The area was flooded by lake water during
1998–1999 and was accessible from the east again in 2000. (B) Graph showing steep geochemical gradient produced by downstreamevap-
oration of springwaters during 1995. The freshest waters are adjacent to the springhead and in the area of hippo pools, while themost saline
and alkaline waters are found in the distal ends of the hippo trails and in puddles on the mudflats (Deocampo and Ashley, 1999).
Other Vertebrate Traces
Other large mammals have a significant impact on the
Mti Moja system. Most notable aside from hippotamus is
the Cape buffalo (Syncerus caffer), which also createswal-
lows. These tend to be smaller than hippo wallows (2–3 m
wide, ,0.5 m deep), and they lack the kind of trail thatare
created by the hippopotamus. The buffalo also seem to
preferthe moist ground slightlyupslope fromthe fully sat-
urated lake-flat muds, although this may be due to hippo
defense of their wallowing pools.
The many bovids and equids that visit Mti Moja spring
also generate traces. These are generally trackfields; in-
dividual trackways are indistinguishable due to their
great number. These are best seen in the slightly saturat-
ed mudflats that the animals cross to access the freshwa-
ter-spring source. Although many of these animals roll on
their backs both for cleaning and dusting, such behavior is
generallyon dry mudflats;hence, theydo notproduce wal-
lowing structures. Where they traverse marshland, how-
ever, they may bioturbate sediment with their legs up to
;1 m deep, and they can produce a step up to 50 cm tall
marking the boundary between a dry, resistant ledge and
wet marshy sediment. Such activity is restrictedgenerally
to areas such as the first 100 m of the Mti Moja channel
(Fig. 2A), where the saturated area may be crossed easily.
Impacts of Hippopotamus amphibius
The flow of water from the Mti Moja spring onto the
Lake Makat mudflats is affected strongly by hippopota-
mus trails, in large part due to the low hydraulic conduc-
tivity of the clay-rich substrate. Changes over time in the
distribution of the trails may be related to changes in pre-
ferred upland grazing pastures. This flow of spring waters
through hippopotamus trails is similar to the effect ob-
served in the Okavango Delta, where channel location is
influenced strongly by hippos (McCarthy et al., 1992,
1998). Such a pattern is likely to be seen in any setting
with a substrate soft enough to allow deformation by hip-
popotamus torsos.
A zoning in traces is evident at Mti Moja, withhippopot-
amus dominating the environment. At the core of the sys-
tem is an area with hippo pools characterized by the deep-
est bioturbation profiles, freshest water, and organic-rich
sediment.This reflects the persistent concentration of hip-
po activity within the pools throughout the day, and per-
haps also for much of the night. Immediately adjacent to
the pools is the area of dense trails, some with dendritic
patterns, created by movements in and out of the pools.
These are widest adjacent to the pools, where the trails
converge, and they spread out in the direction of travel to
grazing pastures. At Mti Moja, these directions are gener-
ally shore-parallel, as may be expected because the saline-
alkaline lake is not preferred hippopotamus habitat. The
distal ends of these trails narrow, to perhaps one hippo-
potamus width, and they shallow, before emerging onto
dry land. Surrounding the area of hippo trails is an
ephemerally wet area characterized by buffalo wallows
and ungulate trackfields. The depth of bioturbation in
theseareas is less thantheothers, with a greater diversity
of evident traces.
Some general characteristics of the Mti Moja lake-mar-
gin spring wetland can be applied to paleoenvironmental
FIGURE 3—Examples of large sedimentary structures created by
Hippopotamus amphibius
. (A) Active hippo pool occupied by two individuals,
with a trail in the foreground and surrounding trackfields on the mudflats in the background. (B) A dendritic trail originating in thepool atupper
left, with branches diverging off the trunk in both directions. (C) Hippo’s view of a dried trail burrowed into the mudflat. Geological hammerfor
scale at right. (D) A hippo trail as it emerges onto what was drier land at the time of the trail’s creation. (E) Close-up of mud levee on the
margin of the hippo trail shown in C. Geological hammer for scale at bottom. (F) View from the Crater rim (;600 m above the floor) of a hippo
trail emerging from the Lerai Hippo Pool, on the south edge of Ngorongoro Crater. Black dots at the bottom of the picture are wildebeestand
problems. The first one is the hippopotamus trail itself—
this structure has not been recognized widely, but it may
be a common feature of lake-margin deposits, such as in
thePlio-Pleistocene Olduvai basin (Deocampoand Ashley,
1997; Ashley et al., 2000). Seen in outcrop, certain U-
shapedstructures that are about1m deep and 1–5 mwide
are possibly hippopotamus trails. These may be infilled
with either organic-rich sediment, as at Mti Moja, or pos-
sibly by lacustrine muds if the wetland is flooded by lacus-
trinetransgression. A biological origin forthese structures
is likely when evidence such as massive infill texture, fine
grainsize, a lack ofscourortool marks, and perhaps agra-
TABLE 2—Estimates of organic carbon content in Mti Moja lake-flat
wetlands based on loss-on-ignition analysis.
Sample site Sample weight
(g) Organic carbon
(wt %)
Hippo pool margin
Hippo pool margin
Hippo trail
Hippo trail
dational contact argue against fluvial incision and chan-
nelization. In high-energy settings such as the Okavango,
the distinction may be more difficult to make because hip-
po trails later may become fluvial channels (McCarthy et
al., 1992; 1998). As in modern settings, the depth and
width of excavation of these trails may be reduced with
distance from the core of the hippopotamus habitat.
The second aspect of hippopotamus bioturbation that
may be useful in paleoenvironmental interpretation isthe
zoning of traces that is apparent in the modern setting.
The deepest bioturbation profile is observed in the core
pool/wallow area, with trails emerging from it dendritical-
ly or radially, depending on local hydrology. These trails
generally become narrower toward nearby pasturelands,
not downslope toward the lake. Surrounding deposits con-
tain evidence for shallower bioturbation and smaller trac-
es, such as tracks and trackways. Surrounding deposits
also have a higher diversity of traces, because hippopota-
mus activity in the core pool area can obliterate the traces
of other animals.
Indryland basins, traces such as theseare importantin-
dicators of freshwater conditions, as they represent fo-
cused biological activity dependent on freshwater in an
arid setting (Deocampo and Ashley, 1997). This provides a
basis for interpreting high-resolution aspects of analogous
paleoenvironments, such as in arid-land basins of East Af-
rica during the Pleistocene. Such structures also may be
identified in the more distant geologic past, becausemem-
bers of Hippopotamidae have preferred relatively fresh
aquatic environments since at least the late Miocene
(Kingdon, 1979). The morphology of fossil species, such as
Hippopotamus gorgops, suggests that members of this ge-
nus were even more aquatic than extant species (Coryn-
don, 1976; Stuenes, 1989). Prior to the evolution of the
Hippopotamidae, other large semi-aquatic organisms may
have occupied a similar ecological niche, and exhibited a
similar pattern of interaction with the substrate.
Large mammals, especially Hippopotamus amphibius,
can create a systematic pattern of traces in arid lake-flat
settings, largely controlled by the localized availability of
fresh surface water. This is characterized by a central bio-
turbation zone extending up to 2 m deep, with dendritic or
radial trails leading out of the wallows up onto drier
ground. Trails are 1–5 m wide, ,0.5 m deep, and infilled
with organic-rich sediment. They narrow and become
shalloweras they emerge ontodrier ground andgrade into
trackways. Other vertebrate trackways, such as buffalo
wallows and other ungulate trackways and trackfields,
may be recorded surrounding the area of hippo-dominated
activity. Sets of traces such as these are important indica-
tors of freshwater conditions in dryland basins due to the
strong affinity of Hippopotamus amphibius for relatively
fresh water. These features can provide important evi-
dence for paleoenvironmental reconstructions of arid
lands during the Neogene and, perhaps, also in the more
distantgeological past, for ecologicallysimilar paleofauna.
Sincere thanks to the Tanzanian Commission on Sci-
ence and Technology and the Ngorongoro Conservation
Area Authority for permission to conduct this research,
and to C. Liutkus, L. Moruo, and A. Tlaa, for able field as-
sistance. Thanks to the Geological Society of America, Sig-
ma Xi- the Scientific Research Society, the Exploration
Club, and the Olduvai Landscape Paleoanthropology Pro-
ject (NSF Archaeology BNS-9000099, SBR-9601065,SBR-
9602478 and EAR-9903258) for support. This paper bene-
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... On the other hand, hippos are gregarious and travel in groups with adults that weigh between 1000 kg and 1500 kg in a network of partially submerged trails that are used daily for hippo traffic moving from daytime pools to night time grazing areas 74,75 . These trails, between 0.5 m and 1 m wide and 0.5 m to 1 m deep, lead away from the wetlands and criss-cross adjacent terrain, representing significant topography in this otherwise flat terrain 52,74 . In the BBRB tracksite, a multi-aged group of artiodactyls moved across several well-developed trails of 1 m-1.5 m wide and 0.1 m -0.3 m depth, which represented a significant impact on the substrate (Fig. 5). ...
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We present a new locality with at least 880 vertebrate tracks found at the top of a limestone bed from the lower Miocene Tudela Formation (Spain). The trampled surface was formed by artiodactyls that crossed a muddy carbonate accumulated under the influence of water level variations in a palustrine environment. The tracks reflect different types of morphological preservation. The well-preserved tracks have tetradactyl digit impressions caused by both manus and pes, and are the type series of a new artiodactyl ichnotaxon, Fustinianapodus arriazui ichnogen. nov. and ichnosp. nov. The rest of the tracks, which are not as well preserved, are didactyl and were classified as undetermined artiodactyl tracks. According to their preservation, morphology, size, arrangement and orientation, we propose that this tracksite is the product of a social behaviour, particularly gregariousness, of a multi-age group of artiodactyls ~19 Ma ago. The morphologic and palaeoecologic data presented here suggest that the trackmakers were a group of anthracotheres with a livelihood similar to current hippos. They crossed, periodically, a fresh water palustrine area along some preferential pathways (trails).
... The hierarchical cluster analysis revealed that the area had three large herbivore functional groups. The first group comprised ecosystem engineers such as elephant (Mosepele et al. 2009, Sidle & Ziegler 2010 and hippopotamus (McCarthy et al. 1998, Deocampo 2002, McCauley et al. 2015. The third group comprised megaherbivores such as giraffe and buffalo, while the middle group contained small herbivores such as duiker and impala. ...
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covers broad environmental areas of ecology, agriculture, forestry, agro-forestry, social science, economics, water and energy, climate change, planning, land use, pollution, strategic and environmental assessments and related fields. The journal addresses the sustainable development agenda of the country in its broadest context. It publishes four categories of articles: Section A: Research articles. High quality peer-reviewed papers in basic and applied research, conforming to accepted scientific paper format and standards, and based on primary research findings, including testing of hypotheses and taxonomical revisions. Section B: Research reports. High quality peer-reviewed papers, generally shorter or less formal than Section A, including short notes, field observations, syntheses and reviews, scientific documentation and checklists. ABSTRACT Functional diversity is a component of biodiversity that includes the range of roles that organisms perform in communities and can explain and predict the impact of organisms on ecosystems. Mudumu National Park is an important ecosystem that acts as a wildlife corridor for migratory fauna moving between Botswana, Namibia, Angola and Zambia. Thus, a thorough understanding of the functional diversity of large herbivores would assist with the management of the park. The present study examined large herbivore species contribution to total large herbivore biomass; dominant species' functional similarities; and whether or not functional diversity is affected by increasing distance from the Kwando River. A total of twenty-two roads were selected that provided good coverage of the park and were surveyed using the line transect distance sampling method. All large herbivores seen on either side of the transects were identified to species level and recorded. The hierarchical cluster analysis in SPSS was used to classify the herbivores into functional groups. Only a small number of species were found to be dominant in both numbers and biomass. Furthermore, dominant species were found to be functionally distinct, and functional dominance changed with respect to season and distance from the river.
... Since adult hippos can weigh up to 3 tons (Eltringham 1999;Kingdon 2015), their behavior and body mass have a great impact on the hydrological network morphology. Hippos affect vegetation composition both by selectively grazing so that the so-called 'hippo lawns' develop and by producing dung in such a way that it is widely spread around (McCarthy et al. 1998;Deocampo 2002;Mosepele et al. 2009;. The changes are overall positive for birds and herbivores (Boisserie and Gilbert 2008) and by implication for hominins. ...
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Single-carcass sites of Lower and Middle Pleistocene age have attracted much attention since they were first recorded. They have been the focus both of science and of museum displays, with reconstructions of “hominins-feasting-on-a-carcass” purposefully illustrating a major step in human evolution. Here we report the Acheulean site Gombore II-2 in the upper Awash Valley of Ethiopia, dating to 0.7 Myr. In the 1970s, due to the presence of hippo remains, the site was published as a single-carcass butchering site. New excavations revealed an ichnosurface displaying animal and human footprints associated with bones and lithics. Subsequent studies of lithic and faunal remains of recent and past excavations as well as archive studies show that Gombore II-2 represents one of the earliest sites with hominin-hippo interaction. The hippo remains belong to a minimum of three carcasses, at least one of them butchered by hominins and subsequently ravaged by hyenas. However, instead of single carcasses exploited on the spot, evidence suggests the existence of a living floor where butchering episodes were performed through time, possibly transporting portions from scavenging sites at a distance. Gombore II-2 thus provides unique insight into planning capacities and control over the environment probably by early representatives of Homo heidelbergensis.
... The wetlands are maintained by groundwater seepage, springs and runoff. Wetland hydro geomorphology is modified by wetting and drying cycles, herbivores (Laws, 1968;Murray-Rust, 1972;McCarthy et al., 1998;Deocampo, 2002), and anthropogenic modifications (Murray-Rust, 1972;Rapp et al., 1972;Payton et al., 1992). Hydrology, topography, pedology, lithology, vegetation, and land-use types and intensities (Poesen et al., 2010) control surface channeling, uphill gullying and erosion. ...
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This study presents a multidisciplinary perspective for understanding environmental change and emerging socio-ecological interactions across the Amboseli region of southwestern Kenya. We focus on late Holocene (<5,000 cal yr. BP) changes and continuities reconstructed from sedimentary, archeological, historical records and socio-ecological models. We utilize multi-disciplinary approaches to understand environmental-ecosystem-social interactions over the longue durée and use this to simulate different land use scenarios supporting conservation and sustainable livelihoods using a socio-ecological model. Today the semi-arid Amboseli landscape supports a large livestock and wildlife population, sustained by a wide variety of plants and extensive rangelands regulated by seasonal rainfall and human activity. Our data provide insight into how large-scale and long-term interactions of climate, people, livestock, wildlife and external connections have shaped the ecosystems across the Amboseli landscape. Environmental conditions were dry between ~5,000 and 2,000 cal yr. BP, followed by two wet periods at ~2,100–1,500 and 1,400–800 cal yr. BP with short dry periods; the most recent centuries were characterized by variable climate with alternative dry and wet phases with high spatial heterogeneity. Most evident in paleo and historical records is the changing woody to grass cover ratio, driven by changes in climate and fire regimes entwined with fluctuating elephant, cattle and wild ungulate populations moderated by human activity, including elephant ivory trade intensification. Archeological perspectives on the occupation of different groups (hunter-gatherers, pastoralists, and farmers) in Amboseli region and the relationships between them are discussed. An overview of the known history of humans and elephants, expanding networks of trade, and the arrival and integration of metallurgy, livestock and domesticated crops in the wider region is provided. In recent decades, increased runoff and flooding have resulted in the expansion of wetlands and a reduction of woody vegetation, compounding problems created by increased enclosure and privatization of these landscapes. However, most of the wetlands outside of the protected area are drying up because of the intensified water extraction by the communities surrounding the National Park and on the adjacent mountains areas, who have increased in numbers, become sedentary and diversified land use around the wetlands.
Natural disturbances remove biomass from wetlands. In extreme cases, they also remove the substrate. Natural disturbances tend to increase biological diversity in wetlands. Fire is a common natural disturbance. Along rivers, bank erosion and sedimentation produce a diversity of habitat types. Animals may also create natural disturbance: hippopotamus and alligators are two examples. Wetland plants have many means of recovering from natural disturbances. Humans often reduce natural disturbances, and this leads to many undesirable changes, including invasion by woody plants.Keywords Natural disturbance Biomass Fire Peat MeandersRivers Erosion Hippopotamus Alligators Animal trails Seeds Rhizomes
Humans evolved in the dynamic landscapes of Africa under conditions of pronounced climatic, geological and environmental change during the past 7 million years. This book brings together detailed records of the paleontological and archaeological sites in Africa that provide the basic evidence for understanding the environments in which we evolved. Chapters cover specific sites, with comprehensive accounts of their geology, paleontology, paleobotany, and their ecological significance for our evolution. Other chapters provide important regional syntheses of past ecological conditions. This book is unique in merging a broad geographic scope (all of Africa) and deep time framework (the past 7 million years) in discussing the geological context and paleontological records of our evolution and that of organisms that evolved alongside our ancestors. It will offer important insights to anyone interested in human evolution, including researchers and graduate students in paleontology, archaeology, anthropology and geology.
Vertebrate ichnology is being revolutionised by the ease with which 3D data can be acquired and there is an increased focus on developing analytical tools and approaches that allow hypothesis driven testing. This revolution is not without its detractors, but is perhaps more advance than the use of 3D data in forensic science. In this chapter we first consider the role of 3D data in the formal classification of tracks and the review some of the challenges associated with demonstrating co-association while interpreting track assemblages. This is followed by four case studies based on the research work of the authors.
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A biogenic mechanism is proposed that produces a diagnostic geochemical signature of perennial spring-fed wetlands in arid basins, especially the saline and alkaline volcanic basins of East Africa. Respiration by vegetation and decay of organic matter within marshes in Ngorongoro Crater, Tanzania, locally increases aqueous PC02. The resulting lowered pH inhibits the precipitation of calcite and decreases the rate of silica dissolution. Steep geochemical gradients are produced. These are represented mineralogically by siliceous biomineralization within the perennial marsh and carbonate precipitation in surrounding ephemeral wetlands, mudflats, and lacustrine environments. As a test of this model of geochemical sedimentation, the mineralogy of the early Pleistocene Siliceous Earthy Claystone of Oldupai Gorge is consistent with its interpretation as a paleo-spring wetland deposit. Because such deposits are expressions of the paleo-water table, this approach has potential applications in many studies of basin paleohydrology, paleoclimatology, paleoecology, and archaeology.
We studied mammal and bird track formation at the northern edge of Lake Manyara, Tanzania, to develop models for interpreting fossil tracks and trackways. Lake Manyara is a closed-basin, alkaline lake in the East African Rift System. The area has a high vertebrate diversity, allowing us to investigate tracks in an environment similar to that of many ancient track-bearing sequences. Three study sites, two on mud flats adjacent to the lake margin and a third on a delta floodplain, provided contrasting environments in which to assess the types of biological data that can potentially be extracted from fossil trackways. Our censuses of mammals and their tracks revealed that most species that occur within the study area leave a track record, and that common species leave abundant tracks, although numbers of trackways are not proportional to numbers of individuals. Logarithmic increases in track sampling area yield a linear increase in the proportion of both the medium and large-sized local mammals represented in a track record. Transect vs. area mapping methods produced different censusing results, probably because of differences in monitoring periods and areal coverage. We developed a model of expected track production rates that incorporates activity budget and stride length data in addition to abundance data. By using these additional variables in a study of diurnal birds, we obtained a much better estimator relating track abundance to trackmaker abundance than that provided by census data alone. Proportions of different types of tracks predicted by the model differ significantly from the observed proportions, almost certainly because of microenvironmental differences between the censusing and track counting localities. Censuses of fossil tracks will be biased toward greater numbers of depositional-environment generalists and away from habitat-specific species. Trackways of migratory animals were dominantly shoreline-parallel, whereas trackways of sedentary species were more variable. A strong shoreline-parallel environmental zonation at the Alkaline Flats site exerted an influence on trackmaker distribution patterns, initial track formation, and track preservation. Variations in habitat usage by different species, as well as species abundance and directionality of movement, were all important in determining the number of preservable tracks a species produced within a given environmental zone. Fossil trackways are time-averaged, although over entirely different temporal scales than are bones. Unlike bones, tracks are not space-averaged. Therefore, wherever possible, fossil track and bone studies should be used to complement each other, as they provide fundamentally different pictures of paleocommunities. Tracks provide “snapshot” views of localized assemblages of organisms useful in reconstructing autecological relationships, whereas bones yield a broader image of a local fauna in which seasonal and microenvironmental variation are more commonly smoothed out.
Environmental analysis of the Pliocene-Pleistocene Koobi Fora Formation reveals many vertebrate footprints and trackways in fluvial and lake-margin strata. Examination of tracks and game trails in similar modern Kenyan environments, and comparison with those in older sediments, indicate characteristics useful for their recognition elsewhere. Preservation is best in mud and sand interbeds of medium thickness where the animal foot punches out a plug of coherent surface sediment (usually mud) and presses it into underlying units of contrasting lithology (usually sand). Thicker and less coherent muds simply mold the foot. -from Authors
(1) Ngorongoro Crater in Tanzania, a caldera some 20 km across, is well known for its exceptionally large and varied population of permanently resident game animals. This remarkable population is associated with a variety of vegetation types. (2) This paper describes the major soil groups of the caldera and demonstrates the strong influence of these on the vegetation types, so illustrating in turn the dependence of the animal population on the diversity of soils. (3) A toposequence of seven major soil groups is found: saline-alkali soils at the lowest levels, mineral hydromorphic soils on lower slope colluvium, topomorphic vertisols in depressions, lithomorphic vertisols and brown calcareous soils on mid-slopes, eutrophic brown soils and weakly acid ferruginous tropical soils on upper slopes. (4) Other soils described are four poorly or imperfectly drained lacustrine and alluvial complexes on the crater floor and an excessively drained lithosolic creep complex on the wall. (5) The major vegetation types, mapped in Fig. 1 and related to the soil features in Fig. 2, include swamp and woodland but are mostly different types of grassland. (6) The weathering/leaching balance is mainly dependent on drainage, and influences textural, mineralogical, structural and nutrient differences. (7) The species composition, height, cover and rooting depth of the grasslands reflect soil aeration and soil reaction: these factors in turn mainly vary with drainage and topography. (8) Though man and animals affect the vegetation by burning and grazing, the influence of soil is thought to be predominant. (9) Utilization of vegetation seems to be dependent on palatability, stickiness of the soils when wet, seasonal behaviour of game and cover for predators. (10) The seasonal grass production and grazing sequence ensure that a reasonable supply of fodder is nearly always available. This makes possible the large, varied and essentially non-migratory animal population.
The revised taxonomy of the subfossil hippopotami of Madagascar suggests that of the hitherto described four species, only two are valid. Lectotypes of these two species, Hippopotamus lemerlei Grandidier and H. madagascariensis Guldberg, are designated and the species are redescribed. Cranial features suggest differences in functional anatomy and ecology between these two species. The short and deep glenoid fossa together with the lateral wear facets of the incisors in H. lemerlei indicate restricted lateral movements of the mandible, while the long and shallow glenoid fossa and the horizontally worn incisors of H. madagascariensis demonstrate extensive lateral mobility. The long, narrow skull of H. lemerlei, with its elongated facial portion and short postorbital part, points to an amphibious mode of life; while the proportions of the more robustly built skull of H. madagascariensis indicate a mainly terrestrial habit. Tip-to-tip occlusion of the incisors, a posterior groove in the upper canines, and double-rooted first premolars are present in H. madagascariensis, but not in H. lemerlei. Since the two Madagascan species are closely related, these features cannot be used as distinguishing characteristics on the generic level. The ancestral form(s) of the Madagascan hippopotami is not known, but H. amphibius, with its well-developed aquatic adaptations, seems to be a possible ancestor. Like many other fossil hippopotami from isolated islands, the two Madagascan species are dwarfs.
Information on large herbivore populations and movements within the Ngorongoro Crater and surrounding grasslands is taken from the results of thirty-three censuses undertaken between 1964 and 1978. Data show that wildebeest, with an annual average of over 14,000 animals, form over two-thirds of the large herbivore population. Crater carrying capacity is discussed in relation to rainfall in the crater and on surrounding hills and slopes. It is suggested that inflowing water from the Crater Highlands controls carrying capacity and that rainy season water levels and dry season burns control seasonal movements. The relatively constant population size of wildebeest and zebra is due to periodic net emigration. In conclusion it is argued that the crater does not function as an isolated island and that the survival of viable wildlife populations depends on land use on the adjacent grassland habitats. Des informations sur les populations et les mouvernents des grands herbivores dans le cratère du Ngorongoro et les savanes avoisinantes sont basées sur les résultats de 33 recensements réalisés entre 1964 et 1977. Ces données montrent que les gnous, avec une moyenne annuelle de plus de 14000 animaux, forment plus des 213 de la population des grands herbivores. La capacité de charge du cratère est analysée en relation avec les chutes de pluie locales, sur les crêtes et les versants des alentours. On suggère que l'écoulement des eaux en saison sèche dans le cratère régit la capacité de charge et que les quantités d'eau en saison des pluies et les feux en saison sèche régissent les déplacements saisonniers. Les tailles des populations relativement constantes des gnous et des zèbres sont dues è I'emigrationpériodiquenette. En conclusion, il est démontré que le cratère ne fonctionne pas comme un îlot isolé et que la survie de ses populations dépend du sort des milieux de savane adjacents.
ABSTRACTA study of the avulsion of a major distributory channel on the alluvial fan (22 000 km2 in area) of the Okavango River in northern Botswana has revealed that channels serve as arterial systems distributing water which sustains large areas of permanent swamp. The channels are vegetatively confined. A primary channel, defined here as a channel which receives water and sediment directly from the fan apex, aggrades vertically as a result of bedload deposition. The rate of aggradation increases downchannel and may exceed 5 cm yr−1 in the distal reaches. Rapid aggradation is associated with a decline in flow velocity. This initiates a series of feedback mechanisms involving invasion of the channel by aquatic plants which trap floating plant debris, further reducing flow rate and causing the channel water surface to become elevated, thereby increasing rate of water loss from the channel, accelerating blockage and aggradation. The channel ultimately fails. Enhanced water loss from the channel promotes the growth of flanking swamp vegetation, which confines the failing channel. Increased flow through the swamp erodes pre-existing hippopotamus trails, producing a secondary channel system which overlaps but does not connect directly to the failing reach of the primary channel. The region of failure of the primary channel migrates upstream, accompanied by headward propagation of the secondary channel system. The swamp distal to the failed primary channel dessicates and is destroyed by peat fires. Secondary channels are stable and not prone to blockage. Comparison with avulsions described in other river systems indicates that the influence of plants in the Okavango River system is exceptionally strong.