Mpala Research Center and Wildlife Foundation

ABSTRACTThe Grévy's zebra, an endangered species native to Kenya and southern Ethiopia, has been the target of sustained conservation efforts in recent years. Accurately monitoring Grévy's zebra populations is essential for ecologists to evaluate ongoing conservation initiatives. Recently, in both 2016 and 2018, a full census of the Grévy's zebra population was enabled by the Great Grévy's Rally (GGR), a citizen science event that combines teams of volunteers to capture data with computer vision algorithms that help experts estimate the number of individuals in the population. A complementary, scalable, cost‐effective and long‐term Grévy's population monitoring approach involves deploying a network of camera traps, which we have done at the Mpala Research Centre in Laikipia County, Kenya. In both scenarios, a substantial majority of the images of zebras are not usable for individual identification due to ‘in‐the‐wild’ imaging conditions—occlusions from vegetation or other animals, oblique views, low image quality and animals that appear in the far background and are thus too small to identify. Camera trap images, without an intelligent human photographer to select the framing and focus on the animals of interest, are of even poorer quality, with high rates of occlusion and high spatiotemporal similarity within image bursts. We employ an image filtering pipeline incorporating animal detection, species identification, viewpoint estimation, quality evaluation and temporal subsampling to compensate for these factors and obtain individual crops from camera trap and GGR images of suitable quality for re‐ID. We then employ the local clusterings and their alternatives (LCA) algorithm, a hybrid computer vision and graph clustering method for animal re‐ID, on the resulting high‐quality crops. Our method processed images taken during GGR‐16 and GGR‐18 in Meru County, Kenya, into 4142 highly comparable annotations, requiring only 120 contrastive same‐vs‐different‐individual decisions from a human reviewer to produce a population estimate of 349 individuals (within 4.6 of the ground truth count in Meru County). Our method also efficiently processed 8.9M unlabelled camera trap images from 70 camera traps at Mpala over 2 years into 685 encounters of 173 unique individuals, requiring only 331 contrastive decisions from a human reviewer.

The need for targeted restoration in regions where ecosystem integrity has become compromised is now widely recognised. Local community views, alongside those of other stakeholders, should be incorporated into transparent decision-making to ensure conservation/restoration activities are successful. We used a structured decision-making approach, working with stakeholders and local communities, to pose and answer the following question for Kenya’s Central Highlands: “what future land-use options [2030] are feasible for the study region, which is most preferable, how does this vary between different stakeholder groups, and what values drive these preferences?”. We engaged with 51 individuals from six stakeholder groups (Big Farms, Conservationists, Counties, Forest Users, Pastoralists, Smallholders). As individuals, the stakeholders held significantly different values for provisioning, cultural, regulation and maintenance ecosystem services. However, following consensus-building activities within the six groups, shared values and perspectives emerged. The future land-use option of habitat conservation/restoration was preferred by the majority of stakeholder groups, although one (Big Farms) favoured increased plantation forestry. Water resource management was also prioritised consistently. By using structured decision-making, we demonstrate that ecosystem restoration is compatible with the views and values of smallholders and forest users, as well as those with a direct interest in conservation. Structured decision-making processes can facilitate stakeholders with disparate views to work towards a consensus regarding future land-use options, aiding environmental planning and implementation.

Abstract Fire and herbivory interact to alter ecosystems and carbon cycling. In savannas, herbivores can reduce fire activity by removing grass biomass, but the size of these effects and what regulates them remain uncertain. To examine grazing effects on fuels and fire regimes across African savannas, we combined data from herbivore exclosure experiments with remotely sensed data on fire activity and herbivore density. We show that, broadly across African savannas, grazing herbivores substantially reduce both herbaceous biomass and fire activity. The size of these effects was strongly associated with grazing herbivore densities, and surprisingly, was mostly consistent across different environments. A one‐zebra increase in herbivore biomass density (~100 kg/km 2 of metabolic biomass) resulted in a ~53 kg/ha reduction in standing herbaceous biomass and a ~0.43 percentage point reduction in burned area. Our results indicate that fire models can be improved by incorporating grazing effects on grass biomass.

Abstract The population size and conservation status of wildlife in post‐conflict areas is often uncertain. In Mozambique, decades of armed conflict resulted in large‐scale wildlife population depletion with limited conservation and research opportunities. The African leopard (Panthera pardus) is a large carnivore with great ecological and economic significance, yet their population status is largely unknown within Mozambique. Using camera trapping in conjunction with robust spatially explicit capture‐recapture modeling, we estimated leopard density in 2021 for Coutada 11, a wildlife management area in the postwar Zambezi Delta landscape of central Mozambique. Leopard density was relatively low (1.57 ± 0.37 SE [latent‐mixture‐model] and 1.84 ± 0.41 [sex‐mixture‐model] leopards/100 km2), occurring in the bottom fourth of 161 range‐wide leopard densities, and similar to those from semiarid and human‐dominated landscapes. Prey‐based carrying capacity estimates suggested that leopard density should be at least twice as large. Despite a recent and substantial reduction in poaching activity, evidence of snared leopards indicates that sustained bushmeat poaching, combined with sustainable, but additional legal offtake is suppressing leopard population recovery. This study provides important baseline insight into leopard population density in Mozambique and joins mounting evidence indicating that anthropogenic pressures limit large carnivore populations which is of major national and global concern. We suggest long‐term monitoring of this leopard population to determine trends over time and implement effective conservation interventions in response to population changes. This population clearly has the capacity to recover if hunting quotas are reduced to account for illegal offtake and, more importantly, if anti‐poaching efforts are redoubled to reduce unsustainable anthropogenic mortality of leopards.

Abstract Wildlife tagging provides critical insights into animal movement ecology, physiology, and behavior amid global ecosystem changes. However, the stress induced by capture, handling, and tagging can impact post-release locomotion and activity and, consequently, the interpretation of study results. We analyzed post-tagging effects on 1585 individuals of 42 terrestrial mammal species using collar-collected GPS and accelerometer data. Species-specific displacements and overall dynamic body acceleration, as a proxy for activity, were assessed over 20 days post-release to quantify disturbance intensity, recovery duration, and speed. Differences were evaluated, considering species-specific traits and the human footprint of the study region. Over 70% of the analyzed species exhibited significant behavioral changes following collaring events. Herbivores traveled farther with variable activity reactions, while omnivores and carnivores were initially less active and mobile. Recovery duration proved brief, with alterations diminishing within 4-7 tracking days for most species. Herbivores, particularly males, showed quicker displacement recovery (4 days) but slower activity recovery (7 days). Individuals in high human footprint areas displayed faster recovery, indicating adaptation to human disturbance. Our findings emphasize the necessity of extending tracking periods beyond one week and particular caution in remote study areas or herbivore-focused research, specifically in smaller mammals.

The Pregnancy Compensation Hypothesis (PCH) posits that sex differences in the mammalian immune system reflect the effects of selection on female immunity during pregnancy, during which increased immunomodulation is required to reduce immune responses to the fetus, while maintaining the ability to respond to pathogens. In humans, fewer pathogens and lower parity in urban, industrialized environments has been suggested to leave female immune systems under-stimulated, creating an evolutionary mismatch which exacerbates sex differences in immunity and increases female autoimmune disease risk. Yet, robust tests of this mismatch hypothesis have not been conducted. Here, we first confirmed a sex-bias in autoimmune disease prevalence in a large dataset of individuals from the United Kingdom (UK Biobank). Second, we asked whether sex differences in immune function are affected by shifts toward urban, lower-parity lifestyles in a single population (the Turkana people of northwest Kenya). We found that lifestyle alters sex differences in immune cell type proportions, but not in gene expression levels. Contrary to expectations from the PCH, parity did not predict immune physiology. We then tested for generalizable trends across natural fertility mammalian populations versus urban humans (data from Turkana, NHANES, GTEx, Batwa and Bakiga, yellow baboons, and macaques). We did not find consistent relationships between lifestyle and sex-biases in immune biomarkers or between parity and the same immune outcomes. Indeed, we found that parity predicts autoimmune disease risk in the opposite direction than expected from the PCH, with higher parity associated with higher autoimmune disease risk while adjusting for relevant socioeconomic variables in the UK Biobank. Taken together, our work suggests that while sex clearly influences immune physiology and disease risk in urban settings, these effects are not easily explained by an evolutionary mismatch. Future work addressing how sex interacts with lifestyle change to generate disease is needed.

ABSTRACTMovement is a key part of life for both solitary and group-living animals. In solitary animals, the energetic costs of making large displacements can be mitigated by energetically efficient strategies—specifically faster, straighter movements. However, little is known about whether moving as part of a collective enhances or limits the ability for individual group members to express such strategies. Drawing on 6 years of population-level high-resolution (1Hz) GPS tracking of group-living vulturine guineafowl (Acryllium vulturinum), we detected 886 events from 94 tagged individuals where their groups made large displacements, shifting their home ranges in response to changing environmental conditions. We contrasted these movements with data with 94 large displacement events by 19 lone, dispersing individuals. Our results suggest that individuals moving as part of group can significantly reduce their energetic cost of transport when making large displacements (15.5% reduction relative to their normal daily ranging behaviours) by increasing the speed and straightness of their movements. However, even during their most-efficient movements, individuals in groups could not achieve or maintain the same increases in speed that others could when moving alone, resulting in significantly limited efficiency gains (solitary individuals were 34.9% more efficient than individuals in groups). Overall, this study provides evidence for a substantial, and previously hidden, energetic cost arising from collective movement.

Abstract Mutualisms between plants and ants are common features of tropical ecosystems around the globe and can have cascading effects on interactions with the ecological communities in which they occur. In an African savanna, we assessed whether acacia ants influence nest site selection by tree-nesting birds. Birds selected nest sites in trees inhabited by ant species that vigorously defend against browsing mammals. Future research could address the extent to which hatching and fledging rates depend on the species of ant symbiont, and why ants tolerate nesting birds but not other tree associates (especially insects).

Abstract Although rhinoceros conservation efforts are focused on anti‐poaching and combating wildlife trade, infectious diseases are an increasing threat to both free‐ranging and captive rhinoceros populations. Among these, clostridial infections with Clostridium perfringens, Paeniclostridium sordellii, and Clostridium novyi have caused acute disease in black and white rhinoceroses, characterized by a high mortality rate within very brief time spans. The acute nature, as well as limited knowledge of epidemiology, diagnosis, and management, make clostridial diseases an important threat to rhinoceros conservation. This article reviews historical cases of clostridial disease in rhinoceros with the aim of formulating a clearer understanding of the disease's epidemiology and using this information to make recommendations for its management in free‐ranging rhinoceroses. Acute colic and sudden death in rhinoceroses, together with necropsy findings of segmental hemorrhagic enteritis, should lead towards a tentative diagnosis of enteric clostridial disease, although detection and identification of specific toxins are required for a definitive diagnosis. Our findings indicate the need for further research into clostridial disease dynamics in wildlife species and provide the basis for this research in rhinoceroses.