Lake Manyara National Park Research Articles

The contribution of community-based conservation models to conserving large herbivore populations

In East Africa, community-based conservation models (CBCMs) have been established to support the conservation of wildlife in fragmented landscapes like the Tarangire Ecosystem, Tanzania. To assess how different management approaches maintained large herbivore populations, we conducted line distance surveys and estimated seasonal densities of elephant, giraffe, zebra, and wildebeest in six management units, including three CBCMs, two national parks (positive controls), and one area with little conservation interventions (negative control). Using a Monte-Carlo approach to propagate uncertainties from the density estimates and trend analysis, we analyzed the resulting time series (2011–2019). Densities of the target species were consistently low in the site with little conservation interventions. In contrast, densities of zebra and wildebeest in CBCMs were similar to national parks, providing evidence that CBCMs contributed to the stabilization of these migratory populations in the central part of the ecosystem. CBCMs also supported giraffe and elephant densities similar to those found in national parks. In contrast, the functional connectivity of Lake Manyara National Park has not been augmented by CBCMs. Our analysis suggests that CBCMs can effectively conserve large herbivores, and that maintaining connectivity through CBCMs should be prioritized.

Mathematical modelling Treponema infection in free-ranging Olive baboons (Papio anubis) in Tanzania

Yaws is a chronic infection caused by the bacterium Treponema pallidum susp. pertenue (TPE) that was thought to be an exclusive human pathogen but was recently found and confirmed in nonhuman primates. In this paper, we develop the first compartmental ODE model for TPE infection with treatment of wild olive baboons. We solve for disease-free and endemic equilibria and give conditions on local and global stability of the disease-free equilibrium. We calibrate the model based on the data from Lake Manyara National Park in Tanzania. We use the model to help the park managers devise an effective strategy for treatment. We show that an increasing treatment rate yields a decrease in disease prevalence. This indicates that TPE can be eliminated through intense management in closed population. Specifically, we show that if the whole population is treated at least once every 5-6 years, a disease-free equilibrium can be reached. Furthermore, we demonstrate that to see a substantial decrease of TPE infection to near-elimination levels within 15 years, the whole population needs to be treated every 2-3 years.

Population dynamics of the Manyara monkey (Cercopithecus mitis manyaraensis) and vervet monkey (Chlorocebus pygerythrus) in Lake Manyara National Park, Tanzania.

Estimating population densities and their trends over time is essential for understanding primate ecology and for guiding conservation efforts. From 2011 through to 2019, we counted two guenon species during seasonal road transect surveys in Lake Manyara National Park: the Tanzania-endemic Manyara monkey Cercopithecus mitis manyaraensis (International Union for Conservation of Nature and Natural Resources, IUCN, Red List category of "endangered") and the vervet monkey Chlorocebus pygerythrus (Red List category of "least concern"). To account for imperfect detectability, we analysed the data in a line distance sampling framework, fitted species-specific detection functions, and subsequently estimated seasonal densities. To test for seasonal differences and yearly trends in the species-specific density estimates, we fitted generalized additive models. Seasonal point density estimates fluctuated considerably during the 9years (2011-2019) of our study, ranging from 3 to 29 individuals km for Manyara monkeys and from 19 to 83 individuals km for vervet monkeys. Densities of both taxa did not differ seasonally, and we did not detect marked directional population trends. Our study illustrates the utility and limitations of line distance sampling for long-term primate monitoring. Beyond informing primate ecology and management, our results highlight the conservation importance of Lake Manyara National Park for primate conservation.

Road-based line distance surveys overestimate densities of olive baboons.

Estimating population density and population dynamics is essential for understanding primate ecology and relies on robust methods. While distance sampling theory provides a robust framework for estimating animal abundance, implementing a constrained, non-systematic transect design could bias density estimates. Here, we assessed potential bias associated with line distance sampling surveys along roads based on a case study with olive baboons (Papio anubis) in Lake Manyara National Park (Tanzania). This was achieved by comparing density estimates of olive baboons derived from road transect surveys with density estimates derived from estimating the maximum number of social groups (via sleeping site counts) and multiplying this metric with the estimated average size of social groups. From 2011 to 2019, we counted olive baboons along road transects, estimated survey-specific densities in a distance sampling framework, and assessed temporal population trends. Based on the fitted half-normal detection function, the mean density was 132.5 baboons km-2 (95% CI: 110.4–159.2), however, detection models did not fit well due to heaping of sightings on and near the transects. Density estimates were associated with relatively wide confidence intervals that were mostly caused by encounter rate variance. Based on a generalized additive model, baboon densities were greater during the rainy seasons compared to the dry seasons but did not show marked annual trends. Compared to estimates derived from the alternative method (sleeping site survey), distance sampling along road transects overestimated the abundance of baboons more than threefold. Possibly, this overestimation was caused by the preferred use of roads by baboons. While being a frequently used technique (due to its relative ease of implementation compared to spatially randomized survey techniques), inferring population density of baboons (and possibly other species) based on road transects should be treated with caution. Beyond these methodological concerns and considering only the most conservative estimates, baboon densities in LMNP are among the highest across their geographic distribution range.

Female post-copulatory behavior in a group of olive baboons (Papio anubis) infected by Treponema pallidum.

Pathogens exert a profound and pervasive cost on various aspects of primate sociality and reproduction. In olive baboons (Papio anubis) at Lake Manyara National Park, Tanzania, genital skin ulcers, caused by the bacterium Treponema pallidum subsp. pertenue, are associated with increased female mating avoidance and altered male mating patterns at a pre-copulatory and copulatory level. Beyond this, mating is also comprised of post-copulatory interactions among sexual partners (i.e., copulation calls, darting [post-copulatory sprint away from the male], and post-copulatory grooming). In baboons, female post-copulatory behavior is hypothesized to incite male-male competition, promote subsequent copulations, and/or strengthen the bonds between the mating pairs. Due to a higher reproductive burden (i.e. pregnancy, lactation, infant rearing), females should avoid proceptive behavior after mating to decrease further exposure to potential pathogens. To investigate whether the presence of genital skin ulcers has an impact at the post-copulatory level, we analyzed 517 copulation events of 33 cycling females and 29 males with and without genital skin ulcers. The occurrence of female post-copulatory behaviors was not altered by genital skin ulcerations in males. Similar to other baboon populations, females in our study group were more likely to utter copulation calls after an ejaculatory copulation. The likelihood of darting was higher after ejaculatory copulations and with the presence of copulation calls. Post-copulatory grooming (i.e., occurring within 15 seconds after a copulation) was not frequently observed. Our results indicate that despite the presence of conspicuous signs of disease, female post-copulatory behavior was not affected by the genital health status of the males. This indicates that in our study group, infection cues caused by T. pallidum subsp. pertenue play a major role before and during mating, but not after mating. The post-copulatory behavior of females is most likely affected by physiological or evolutionary constraints other than sexually transmitted infections.

Camera-trap data do not indicate scaling of diel activity and cathemerality with body mass in an East African mammal assemblage.

Diel activity patterns of animal species reflect constraints imposed by morphological, physiological, and behavioral trade‐offs, but these trade‐offs are rarely quantified for multispecies assemblages. Based on a systematic year‐long camera‐trap study in the species‐rich mammal assemblage of Lake Manyara National Park (Tanzania), we estimated activity levels (hours active per day) and circadian rhythms of 17 herbivore and 11 faunivore species to determine the effects of body mass and trophic level on activity levels and cathemerality (the degree to which species are active throughout the day and night). Using generalized least squares and phylogenetic generalized least squares analyses, we found no support for the hypothesis that trophic level is positively associated with activity levels. We found no support for activity levels to scale positively with body mass in herbivores or to differ between ruminants and nonruminants; in faunivores, we also did not detect relationships between body mass and activity levels. Cathemerality was positively associated with activity levels but did not scale significantly with body mass. Overall, our findings caution against trophic level or body mass‐associated generalized conclusions with regard to diel activity patterns.

Hunter-Gatherers in context: Mammal community composition in a northern Tanzania landscape used by Hadza foragers and Datoga pastoralists.

In many regions of sub Saharan Africa large mammals occur in human-dominated areas, yet their community composition and abundance have rarely been described in areas occupied by traditional hunter-gatherers and pastoralists. Surveys of mammal populations in such areas provide important measures of biodiversity and provide ecological context for understanding hunting practices. Using a sampling grid centered on a Hadza hunter-gatherer camp and covering 36 km2 of semi-arid savannah in northern Tanzania, we assessed mammals using camera traps (n = 19 stations) for c. 5 months (2,182 trap nights). In the study area (Tli’ika in the Hadza language), we recorded 36 wild mammal species. Rarefaction curves suggest that sampling effort was sufficient to capture mammal species richness, yet some species known to occur at low densities in the wider area (e.g. African lions, wildebeest) were not detected. Relative abundance indices of wildlife species varied by c. three orders of magnitude, from a mean of 0.04 (African wild dog) to 20.34 capture events per 100 trap-nights (Kirk’s dik dik). To contextualize the relative abundance of wildlife in the study area, we compared our study’s data to comparable camera trap data collected in a fully protected area of northern Tanzania with similar rainfall (Lake Manyara National Park). Raw data and negative binomial regression analyses show that wild herbivores and wild carnivores were generally detected in the national park at higher rates than in the Hadza-occupied region. Livestock were notably absent from the national park, but were detected at high levels in Tli’ika, and cattle was the second most frequently detected species in the Hadza-used area. We discuss how these data inform current conservation efforts, studies of Hadza hunting, and models of hunter-gatherer foraging ecology and diet.

Attitudes of local leaders towards wildlife conservation in village areas in southern Ngorongoro Conservation Area, Karatu District, Tanzania

Understanding attitudes of local leaders towards conservation issues in village areas surrounding protected areas is vital for the success of sustainable biodiversity conservation. This is because of the need of designing effective conservation programs outside protected areas and to reduce resource-based conflicts involving local communities and protected areas. Twenty villages in Karatu district located between Ngorongoro Conservation Area (NCA) and Lake Manyara National Park (LMNP) were chosen for this study. The data were collected using semi-structured questionnaires administered to 133 local leaders in 20 villages. Findings indicated that attitudes of local leaders towards conservation in the village areas were positive. We observed that 90.3% of the village government members and 50% of the chairpersons considered charcoal making as detrimental to the environment and insignificant to the development of their villages. Majority of the respondents (80.0%) rated that village environmental conservation bylaws are having inadequate penalties for offenders in dealing with the current state of rapid environmental deterioration in village lands. The position of a leader was an important predictor as 87.4% of village chairpersons and 70.0% of the village government members were positive towards conservation in village lands. The implication of the results could be linked to conservation initiatives outside protected areas and understanding the attitudes and securing the support of local leaders. Key words: Environmental conservation, Ngorongoro Conservation Area, wildlife conservation, local communities, protected areas.

Wildlife population trends as indicators of protected area effectiveness in northern Tanzania

Abstract Protected areas are the cornerstone of biodiversity conservation, yet the relative effectiveness of different conservation models is often unknown. Here, we describe seasonal population densities and associated annual population changes of ten wildlife species (elephant, giraffe, zebra, wildebeest, waterbuck, warthog, Grant’s gazelle, impala, Thomson’s gazelle, and Kirk’s dik-dik) in four protected areas in northern Tanzania over eight years and test two hypotheses: (1) annual wildlife population changes are positively correlated with conservation status; and, (2) relationships between annual population changes and protected area status are mediated by species’ body mass. We carried out wildlife surveys from late 2011 to the end of 2018 and estimated wildlife densities in a line distance sampling framework. The majority of species occurred at high densities in fully protected areas, and larger-bodied species occurred at low densities or were absent in the least protected area. We estimated annual species- and area-specific population changes with generalized linear mixed effects that accounted for seasonal variation in this ecosystem. Using multi-model comparisons, we did not find evidence that annual population changes were correlated with body mass. However, species- and area-specific population changes appeared to vary by species and area, but were not consistently associated with protection status. Wildlife populations in Tarangire National Park and two human-dominated areas showed mainly stable or positive population trends, whereas wildlife populations in Lake Manyara National Park appeared to decline during the study period. This ecosystem- and long-term monitoring indicates apparent context-dependent differences in protected area performance within one ecosystem and exemplifies the need for, and challenges of, long-term monitoring in protected areas to guide effective conservation.

Relative abundance and activity patterns explain method-related differences in mammalian species richness estimates

Species richness and species-specific occupancy are key variables for biodiversity monitoring. While there are many field techniques to assess presence of mammalian species, their relative performance and cost effectiveness can be affected by biological variables that are related to availability (relative abundance, diurnal activity) or by traits that are related to visibility (body size, coloration, habitat selection) of a species. We conducted four transect surveys, driven during daytime hours and continuous monitoring with camera traps over a 16-week period in Lake Manyara National Park, Tanzania. Transect and camera-trap surveys yielded estimates of 20 and 38 mammalian species, respectively. In absolute terms, diurnal vehicle transects were less costly than camera trapping, but in relative terms (cost/species), camera trapping was more cost effective. Logistic regression showed that mammal species with reduced availability (low relative abundance and low proportion of diurnal activity) were less likely to be detected during diurnal line-transect surveys. Species-specific detection probabilities and occupancy estimates were lower during transect surveys compared to the camera-trap survey. Similar to differences in naive species occupancy, method-related differences in modeled detection probabilities were positively correlated with relative abundance. Results suggest that factors influencing availability of a species explain method-related differences in detection probabilities and species richness estimates.

Occurrence of trypanosome infections in cattle in relation to season, livestock movement and management practices of Maasai pastoralists in Northern Tanzania.

African animal trypanosomosis (AAT) is a parasitic disease considered to be one of the greatest constraints to cattle production in Tanzania. There is insufficient information on seasonal occurrence of AAT and management practices in Monduli District of the Maasai Steppe ecosystem to guide and prioritize AAT control programs. A cross-sectional survey was undertaken in 10 randomly selected villages of Monduli District. Information on seasonal animal movements, including wildlife interaction, and AAT management practices was gathered using a standardized questionnaire with 130 pastoralists. Blood samples were collected from a total of 960 cattle, in wet and dry seasons. An entomological survey was also undertaken in the dry season. Polymerase chain reaction targeting the internal transcribed spacer 1 (ITS1) was used for parasite identification in cattle blood and in tsetse flies. The overall apparent prevalence of AAT in cattle was 5.8% (95% CI of 4.1-8.3) and 4.2% (95% CI of 2.7-6.3) during wet and dry reasons, respectively. Trypanosoma vivax was the most common species identified in cattle. All tsetse flies (n = 426) collected were trapped in Esilalei village which is in close proximity to Lake Manyara National Park. Tsetse fly infection status was determined to be 7.0%; (CI 95% of 4.9-9.8%) with nearly 50% of infections due to T. congolense. All 130 cattle owners reported that they could easily recognize AAT and the majority (75%) identified the most prominent clinical signs. Nearly all owners (98.5%) identified that tsetse flies were responsible for AAT transmission. All cattle owners (100%) reported the use of trypanocides for AAT treatment, while 2.3% reported to also use herbal medicine. The trypanocides, Novidium® and Berenil®, were the most frequently reported commercial drugs and were used by 42% of cattle owners. Vector control by hand spraying was reported by the majority (90.8%) of cattle owners, while dipping and deployment of insecticide-impregnated targets were reported by few cattle owners (16.2% and 5.4%, respectively). The majority of cattle owners (83.1%) reported to move cattle away from home villages during the dry season with many migrating to areas in close proximity to wildlife parks. This study confirms the presence of circulating pathogenic trypanosomes in tsetse flies which continue to pose a threat to Maasai cattle. The seasonal movement of cattle during the dry season was associated with more clinical cases of cattle trypanosomosis. This study demonstrates the need to strengthen surveillance and control strategies for AAT.

Long‐term population dynamics in a multi‐species assemblage of large herbivores in East Africa

AbstractWildlife population declines in Africa are widespread. However, species‐specific population trends and dynamics in mammal community composition have rarely been described over long time periods. To describe population trends of 13 large herbivore species in Lake Manyara National Park (Tanzania) from 1959 to 2016 and to discover whether the herbivore community structure changed, we used general additive models and additional statistical methods to detect structural changes in the time series. Population dynamics were non‐linear and population growth rates were not correlated with precipitation anomalies. Relatively steep population declines of three megaherbivores occurred during the 1980s and early 1990s, resulting in severe reductions in African elephant and buffalo populations and the local extinction of black rhinoceros. These declines coincided with reported peaks of illegal hunting of these species and expansion of agriculture at the periphery of the park. Population densities of elephant and buffalo seem to have stabilized in recent times, yet have not recovered to previous densities. In contrast, eight species (giraffe, zebra, waterbuck, wildebeest, warthog, impala, bushbuck, and baboon) have apparently fared well (similar or higher densities in most recent compared to first decade), despite having undergone substantial fluctuations over the past 58 yr. Population fluctuations in these species were likely caused by disease outbreaks, heavy bush encroachment, and reduced competition with buffalo. Possibly, declines in megaherbivore densities (mainly elephants) facilitated bush encroachment. Albeit grazers are still dominating in the herbivore community, the proportion of browsers is currently increasing, likely encouraged by dense vegetation in the shrub layer in large parts of the park. Overall, herbivore biomass density has declined by ~40% compared to the baseline estimate in the first decade of the time series. Our analyses and ancillary information provide evidence that this overall decline in the herbivore assemblage was triggered by human‐induced reductions in megaherbivore population densities during the 1980s, either through excessive poaching, insularization of the park, or both. Likely, this had cascading and interacting effects on the vegetation structure and the herbivore assemblage. Thus, legacy effects of ineffective megaherbivore conservation efforts 30 yr ago are likely still affecting the ecology of this national park.

Olive baboons' (Papio anubis) response towards crowned eagles (Stephanoaetus coronatus) at Lake Manyara National Park.

In this paper we report on two encounters between olive baboons (Papio anubis) and crowned eagles (Stephanoaetus coronatus) at Lake Manyara National Park, northern Tanzania. During these encounters olive baboons responded by giving alarm calls and all infants and juveniles rushed down from trees seeking cover under bushes or close proximity to adult conspecifics. In one of the events, alarm calls from banded mongoose (Mungos mungo) and rock hyraxes (Procavia capensis) most likely triggered alarm calling of vervet monkeys (Chlorocebus pygerythrus) which in turn prompted baboons to respond with alarm calls as well. In both observations, adult male baboons took the lead in climbing trees, threatening the eagle (staring, yawning, ground slapping) and chasing it away. The reaction of the baboons suggests that crowned eagles pose a threat at least for juvenile baboons at Lake Manyara National Park.

Sex‐obsessed or just sociable? Non‐copulatory displays in the hamerkop

Sex‐obsessed or just sociable? Non‐copulatory displays in the hamerkop

Flies and Yaws: Molecular Studies Provide New Insight

Flies and Yaws: Molecular Studies Provide New Insight

Temporal gland secretion in African elephants (Loxodonta africana)

The underlying causes of temporal gland secretion (TGS) in African elephants are not well understood. In order to better understand TGS predisposing factors, we assessed TGS in relation to a suite of intrinsic and environmental variables in free ranging elephants. TGS monitoring was done in fully protected areas of Lake Manyara National Park (LMNP) and Tarangire National Park (TNP) and Manyara Ranch (MR), a semi-protected multiple use area. Using a hierarchical modeling approach that accounted for the nested data structure, we found that TGS was mainly associated with elephant-specific variables. The likelihood of TGS increased with elephant age. Female elephants were more likely to show TGS than male elephants. In larger groups, females were less likely to have TGS, whereas the likelihood for TGS increased with group size in male elephants. This information enhances our understanding of TGS, and its importance as physiological marker.

Isolation of Treponema DNA from Necrophagous Flies in a Natural Ecosystem

BackgroundRecently, the World Health Organization launched a campaign to eradicate the tropical disease yaws, caused by the bacterium Treponema pallidum subsp. pertenue; however, for decades researchers have questioned whether flies act as a vector for the pathogen that could facilitate transmission. MethodsA total of 207 fly specimens were trapped in areas of Africa in which T. pallidum-induced skin ulcerations are common in wild baboons; 88 flies from Tarangire National Park and 119 from Lake Manyara National Park in Tanzania were analyzed by PCR for the presence of T. pallidum DNA. FindingsWe report that in the two study areas, T. pallidum DNA was found in 17–24% of wild-caught flies of the order Diptera. Treponemal DNA sequences obtained from many of the flies match sequences derived from nearby baboon T. pallidum strains, and one of the fly species with an especially high prevalence of T. pallidum DNA, Musca sorbens, has previously been shown to transmit yaws in an experimental setting. InterpretationOur results raise the possibility that flies play a role in yaws transmission; further research is warranted, given how important understanding transmission is for the eradication of this disfiguring disease.

Tarangire revisited: Consequences of declining connectivity in a tropical ungulate population

The hyper-abundance of migratory wildlife in many ecosystems depends on maintaining access to seasonally available resources. In Eastern and Southern Africa, land-use change and a loss of connectivity have coincided with widespread declines in the abundance and geographic range of ungulate populations. Using photographic capture-mark-recapture, we examine the historical pattern of loss of connectivity and its impact on population trends in a partially migratory wildebeest population in northern Tanzania. To estimate abundance, we use a novel modeling approach that overcomes bias associated with photo misidentifications. Our data indicate (1) diminished connectivity within and between seasonal areas as a result of human activities, (2) a reduction in the overall population size compared to historical numbers, with high variability over time, (3) the continued use of highly constrained movement corridors between the three main seasonal ranges, (4) higher recruitment in the non-migratory subpopulation (Lake Manyara National Park) than in other areas of the ecosystem, and (5) an increase in the relative abundance of resident to migrant wildebeest. Recent conservation efforts to protect seasonal habitat and to enforce anti-poaching policies outside protected areas have likely helped stabilize the population, at least temporarily, but we caution that several key vulnerabilities remain.

Wildlife Induced Damage to Crops and Livestock Loss and how they Affect Human Attitudes in the Kwakuchinja Wildlife Corridor in Northern Tanzania

Human-wildlife conflict is a major issue for conservationists due to crop-damage and livestock depredation by wild animals, causing local farmer’s economic loss resulting into deepening of poverty. This study assesses wildlife induced damage. A total of 250 households were randomly interviewed by the use of questionnaires in three villages (Kakoye, Minjingu and Olasiti) in the Kwakuchinja wildlife corridor, northern Tanzania. Annually loss of 383 kg of crops per household was reported in the study area, or US $ 154 per household annually. Most destruction was done by elephants. Depredations of livestock were estimated to on average 2.2 (US $ 106) livestock annually. This loss affects farmers economically as well as that they are spending time in guarding livestock from predators. Cattle were mostly attacked by lions and spotted hyenas while goats and sheep were attacked by spotted hyenas and leopards. These losses lead to retaliatory killing of carnivores. Wildlife induced damage to crops and livestock were worsened by people encroaching into the borders of protected areas and destroying wildlife habitats. Households close to the boundary of the Tarangire and Lake Manyara National Park incurred greater losses from crop and livestock depredation. There should be provision of conservation educations to communities bordering protected areas to practice sustainable agriculture and income generating projects that are conservation friendly.

Validation of Serological Tests for the Detection of Antibodies Against Treponema pallidum in Nonhuman Primates

There is evidence to suggest that the yaws bacterium (Treponema pallidum ssp. pertenue) may exist in non-human primate populations residing in regions where yaws is endemic in humans. Especially in light of the fact that the World Health Organizaiton (WHO) recently launched its second yaws eradication campaign, there is a considerable need for reliable tools to identify treponemal infection in our closest relatives, African monkeys and great apes. It was hypothesized that commercially available serological tests detect simian anti-T. pallidum antibody in serum samples of baboons, with comparable sensitivity and specificity to their results on human sera. Test performances of five different treponemal tests (TTs) and two non-treponemal tests (NTTs) were evaluated using serum samples of 57 naturally T. pallidum-infected olive baboons (Papio anubis) from Lake Manyara National Park in Tanzania. The T. pallidum particle agglutination assay (TP-PA) was used as a gold standard for comparison. In addition, the overall infection status of the animals was used to further validate test performances. For most accurate results, only samples that originated from baboons of known infection status, as verified in a previous study by clinical inspection, PCR and immunohistochemistry, were included. All tests, TTs and NTTs, used in this study were able to reliably detect antibodies against T. pallidum in serum samples of infected baboons. The sensitivity of TTs ranged from 97.7-100%, while specificity was between 88.0-100.0%. The two NTTs detected anti-lipoidal antibodies in serum samples of infected baboons with a sensitivity of 83.3% whereas specificity was 100%. For screening purposes, the TT Espline TP provided the highest sensitivity and specificity and at the same time provided the most suitable format for use in the field. The enzyme immune assay Mastblot TP (IgG), however, could be considered as a confirmatory test.