Conservation and economic benefits of a road around the Serengeti

No abstract available

Range expansion of the globally Vulnerable Karamoja apalis Apalis karamojae in the Serengeti ecosystem

This study was funded by the Rufford Maurice Laing Foundation, the Canadian Natural Sciences and Engineering Research Council and Frankfurt Zoological Society.The underlying causes of change in geographic range size are less well understood in African birds than in north temperate species. Here, we examine factors associated with range expansion in the Karamoja apalis (Apalis karamojae), a globally Vulnerable warbler confined to north-east Uganda, north-central Tanzania and southern Kenya. In Tanzania, it was originally known only from the Wembere Steppe, but since 1993 (and possibly as early as 1983) has extended its range into the Serengeti ecosystem, c. 140 km to the north, reaching southern Kenya by 2004. Changes in the warbler's range within the Serengeti have broadly reflected a cyclical change in the density of its main habitat, Acacia drepanolobium woodland, which was low in the 1970s, high during the 1980s and 1990s, and declined in the early 2000s. Karamoja apalis records in the Serengeti showed a 5 year time lag behind A. drepanolobium density, which was in turn negatively correlated with the area of grassland burnt 10 years earlier. Previous studies in the Serengeti have also linked Acacia regeneration to changes in grazing pressure, as increasing wildebeest (Connochaetes taurinus) numbers have reduced the volume of combustible material present, and hence the frequency of damaging 'hot burns'. We conclude that this globally threatened warbler appears to have benefited from changes in ungulate populations in the Serengeti, which have influenced burning intensity and hence tree regeneration. The warbler's range now appears to be declining, however, following a recent reduction in the density and annual survival of A. drepanolobium in the northern Serengeti.Resume Les causes sous-jacentes du changement de la taille d'une distribution geographique sont moins bien connues pour les oiseaux africains que pour les especes du nord tempere. Nous examinons ici des facteurs lies a l'expansion de l'aire de repartition de l'apalis de Karamoja Apalis karamojae, un sylviide classe comme Vulnerable au niveau mondial, confine au NE de l'Ouganda, au centre-nord de la Tanzanie et au sud du Kenya. En Tanzanie, on ne le connaissait a l'origine que dans la steppe de Wembere mais depuis 1993, et peut-etre meme des 1983, il a etendu son aire de repartition dans l'ecosysteme du Serengeti, environ 140 km plus au nord, et atteint le sud du Kenya en 2004. Les changements de l'aire de repartition de ce sylviide dans le Serengeti refletent largement un changement cyclique de la densite de son habitat principal, la foret d'Acacia drepanolobium, qui etait faible dans les annees 1970, forte pendant les annees 1980 et 1990, et qui a diminue au debut des annees 2000. Les rapports sur l'apalis de Karamoja au Serengeti montrent un retard de cinq ans par rapport a l'evolution de la densite d'A. drepanolobium, elle-meme etant negativement liee a la zone de prairie brulee 10 ans plus tot. Des etudes anterieures faites au Serengeti lient aussi la regeneration des acacias aux changements de la pression du paturage, etant donne que le nombre croissant de gnous, Connochaetes taurinus, a reduit le volume des matieres combustibles restantes et donc la frequence des feux trop chauds qui causent beaucoup de degats. Nous concluons que cet oiseau menace au niveau mondial semble avoir beneficie des changements des populations d'ongules au Serengeti, qui ont influence l'intensite des feux et donc la regeneration des arbres. L'aire de repartition de ce sylviide semble pourtant en train de se reduire suite a une recente reduction de la densite et de la survie annuelle d'A. drepanolobium dans le nord du Serengeti.PostprintPeer reviewe

Protected areas as biodiversity benchmarks for human impact: agriculture and the Serengeti avifauna.

Protected areas as biodiversity benchmarks allow a separation of the direct effects of human impact on biodiversity loss from those of other environmental changes. We illustrate the use of ecological baselines with a case from the Serengeti ecosystem, Tanzania. We document a substantial but previously unnoted loss of bird diversity in agriculture detected by reference to the immediately adjacent native vegetation in Serengeti. The abundance of species found in agriculture was only 28% of that for the same species in native savannah. Insectivorous species feeding in the grass layer or in trees were the most reduced. Some 50% of both insectivorous and granivorous species were not recorded in agriculture, with ground-feeding and tree species most affected. Grass-layer insect abundance and diversity was much reduced in agriculture, consistent with the loss of insectivorous birds. These results indicate that many species of birds will become confined to protected areas over time. We need to determine whether existing protected areas are sufficiently large to maintain viable populations of insectivorous birds likely to become confined to them. This study highlights the essential nature of baseline areas for assessing causes of change in human-dominated systems and for developing innovative strategies to restore biodiversity

Range expansion of the globally Vulnerable Karamoja apalis Apalis karamojae in the Serengeti ecosystem

The underlying causes of change in geographic range size are less well understood in African birds than in north temperate species. Here, we examine factors associated with range expansion in the Karamoja apalis (Apalis karamojae), a globally Vulnerable warbler confined to north-east Uganda, north-central Tanzania and southern Kenya. In Tanzania, it was originally known only from the Wembere Steppe, but since 1993 (and possibly as early as 1983) has extended its range into the Serengeti ecosystem, c. 140 km to the north, reaching southern Kenya by 2004. Changes in the warbler's range within the Serengeti have broadly reflected a cyclical change in the density of its main habitat, Acacia drepanolobium woodland, which was low in the 1970s, high during the 1980s and 1990s, and declined in the early 2000s. Karamoja apalis records in the Serengeti showed a 5 year time lag behind A. drepanolobium density, which was in turn negatively correlated with the area of grassland burnt 10 years earlier. Previous studies in the Serengeti have also linked Acacia regeneration to changes in grazing pressure, as increasing wildebeest (Connochaetes taurinus) numbers have reduced the volume of combustible material present, and hence the frequency of damaging 'hot burns'. We conclude that this globally threatened warbler appears to have benefited from changes in ungulate populations in the Serengeti, which have influenced burning intensity and hence tree regeneration. The warbler's range now appears to be declining, however, following a recent reduction in the density and annual survival of A. drepanolobium in the northern Serengeti.ResumeLes causes sous-jacentes du changement de la taille d'une distribution geographique sont moins bien connues pour les oiseaux africains que pour les especes du nord tempere. Nous examinons ici des facteurs lies a l'expansion de l'aire de repartition de l'apalis de Karamoja Apalis karamojae, un sylviide classe comme Vulnerable au niveau mondial, confine au NE de l'Ouganda, au centre-nord de la Tanzanie et au sud du Kenya. En Tanzanie, on ne le connaissait a l'origine que dans la steppe de Wembere mais depuis 1993, et peut-etre meme des 1983, il a etendu son aire de repartition dans l'ecosysteme du Serengeti, environ 140 km plus au nord, et atteint le sud du Kenya en 2004. Les changements de l'aire de repartition de ce sylviide dans le Serengeti refletent largement un changement cyclique de la densite de son habitat principal, la foret d'Acacia drepanolobium, qui etait faible dans les annees 1970, forte pendant les annees 1980 et 1990, et qui a diminue au debut des annees 2000. Les rapports sur l'apalis de Karamoja au Serengeti montrent un retard de cinq ans par rapport a l'evolution de la densite d'A. drepanolobium, elle-meme etant negativement liee a la zone de prairie brulee 10 ans plus tot. Des etudes anterieures faites au Serengeti lient aussi la regeneration des acacias aux changements de la pression du paturage, etant donne que le nombre croissant de gnous, Connochaetes taurinus, a reduit le volume des matieres combustibles restantes et donc la frequence des feux trop chauds qui causent beaucoup de degats. Nous concluons que cet oiseau menace au niveau mondial semble avoir beneficie des changements des populations d'ongules au Serengeti, qui ont influence l'intensite des feux et donc la regeneration des arbres. L'aire de repartition de ce sylviide semble pourtant en train de se reduire suite a une recente reduction de la densite et de la survie annuelle d'A. drepanolobium dans le nord du Serengeti.</p

Landscape-level movement patterns by lions in western Serengeti: comparing the influence of inter-specific competitors, habitat attributes and prey availability

Background: Where apex predators move on the landscape influences ecosystem structure and function and is therefore key to effective landscape-level management and species-specific conservation. However the factors underlying predator distribution patterns within functional ecosystems are poorly understood. Predator movement should be sensitive to the spatial patterns of inter-specific competitors, spatial variation in prey density, and landscape attributes that increase individual prey vulnerability. We investigated the relative role of these fundamental factors on seasonal resource utilization by a globally endangered apex carnivore, the African lion (Panthera leo) in Tanzania’s Serengeti National Park. Lion space use was represented by novel landscape-level, modified utilization distributions (termed “localized density distributions”) created from telemetry relocations of individual lions from multiple neighbouring prides. Spatial patterns of inter-specific competitors were similarly determined from telemetry re-locations of spotted hyenas (Crocuta crocuta), this system’s primary competitor for lions; prey distribution was derived from 18 months of detailed census data; and remote sensing data was used to represent relevant habitat attributes. Results: Lion space use was consistently influenced by landscape attributes that increase individual prey vulnerability to predation. Wet season activity, when available prey were scarce, was concentrated near embankments, which provide ambush opportunities, and dry season activity, when available prey were abundant, near remaining water sources where prey occurrence is predictable. Lion space use patterns were positively associated with areas of high prey biomass, but only in the prey abundant dry season. Finally, at the broad scale of this analysis, lion and hyena space use was positively correlated in the comparatively prey-rich dry season and unrelated in the wet season, suggesting lion movement was unconstrained by the spatial patterns of their main inter-specific competitors. Conclusions: The availability of potential prey and vulnerability of that prey to predation both motivate lion movement decisions, with their relative importance apparently mediated by overall prey abundance. With practical and theoretical implications, these results suggest that while top carnivores are consistently cognizant of how landscape features influence individual prey vulnerability, they also adopt a flexible approach to range use by adjusting spatial behaviour according to fluctuations in local prey abundance.Other UBCNon UBCReviewedFacult

Bird community responses to changes in vegetation caused by increasing large mammal populations in the Serengeti woodlands

Context: The increase in density of large tree species, Vachellia robusta and V. tortilis, in the Serengeti Ecosystem of Tanzania has resulted in a decline of small tree species Senegalia senegal, V. hockii, Commiphora spp. This change has occurred since the late 1970s, a consequence of an increase in wildebeest following the extirpation of rinderpest, which reduced the dry grass fuel for fires, resulting in low fire frequencies. Change in tree species raises the question of whether there are indirect consequences for the avifauna that depend on the large trees for food and nesting. Aims: To determine how an increase in large mammals could influence diversity and distribution of avifauna communities in the Serengeti ecosystem woodlands. Methods: Data used to estimate changes in density of large and small trees were measured by Point Centre Quarter (PCQ). Bird species were recorded in 19 small-tree sites and 18 large-tree sites in the Serengeti National Park. Richness of bird guilds was calculated in the two habitat complexes (small and large trees), and the ‘rarefaction’ method was used to assess the difference in richness in habitats of the study area. Mean abundance for each species was calculated over the total number of sites for each habitat and compared using the Wilcoxon Rank Sum test to examine how the abundance of avifauna changes with each habitat type. Key results: There was an increase in the density of large trees in some areas in which they have replaced the original small trees. Such changes have resulted in greater richness of hole nesters and bark feeders, and a greater abundance of large-hole nesters and gleaner bird species. Conclusions: Because the increase in tree density was caused by an increase in large mammals, we conclude that this increasing mammal population is indirectly increasing richness and abundance of birds using the trees. Implications: Understanding the influence of large mammal populations on bird distributions has important conservation implications because the Serengeti ecosystem is classified as an important, endemic bird area

Evaluating the protection of wildlife in parks: the case of African buffalo in Serengeti

Human population growth rates on the borders of protected areas in Africa are nearly double the average rural growth, suggesting that protected areas attract human settlement. Increasing human populations could be a threat to biodiversity through increases in illegal hunting. In the Serengeti ecosystem, Tanzania, there have been marked declines in black rhino (Diceros bicornis), elephant (Loxodonta africana) and African buffalo (Syncerus caffer) inside the protected area during a period when there was a reduction of protection through anti-poaching effort (1976–1996). Subsequently, protection effort has increased and has remained stable. During both periods there were major differences in population decline and recovery in different areas. The purpose of this paper is to analyse the possible causes of the spatial differences. We used a spatially structured population model to analyze the impacts of three factors—(i) hunting, (ii) food shortage and (iii) natural predation. Population changes were best explained by illegal hunting but model fit improved with the addition of predation mortality and the effect of food supply in areas where hunting was least. We used a GIS analysis to determine variation in human settlement rates and related those rates to intrinsic population changes in buffalo. Buffalo populations in close proximity to areas with higher rates of human settlement had low or negative rates of increase and were slowest to recover or failed to recover at all. The increase in human populations along the western boundary of the Serengeti ecosystem has led to negative consequences for wildlife populations, pointing to the need for enforcement of wildlife laws to mitigate these effects

Supplement 1. R code for computer simulation model of time dynamics of predator and two prey species shown in Fig. 1.

<h2>File List</h2><div> <a href="Rcode_for_model_simulations_Figure_1.txt">Rcode_for_model_simulations_Figure_1.txt</a> (md5: 338340b55f076dac7ccd48545c681460)</div><h2>Description</h2><div> <p>This R code text file simulates time dynamics of predator and two prey species to produce the outcomes shown in Fig. 1 of the paper. State variable names and parameters are exactly as depicted in the text. The code is straighforward and carefully annotated to explain objectives of each section. </p> </div