Spatiotemporal Mechanisms of the Coexistence of Reintroduced Scimitar-Horned Oryx and Native Dorcas Gazelle in Sidi Toui National Park, Tunisia

Examining the distribution patterns and spatiotemporal niche overlap of sympatric species is crucial for understanding core concepts in community ecology and for the effective management of multi-species habitats within shared landscapes. Using data from 26 camera-traps, recorded over two years (December 2020-November 2022), in Sidi Toui National Park (STNP), Tunisia, we investigate habitat use and activity patterns of the scimitar-horned oryx (n = 1865 captures) and dorcas gazelle (n = 1208 captures). Using information theory and multi-model inference methods, along with the Pianka index, we evaluated the habitat characteristics influencing species distribution and their spatial niche overlap. To delineate daily activity patterns, we applied kernel density estimation. Our findings indicate minimal spatial overlap and distinct environmental factors determining suitable habitats for each species. Furthermore, we found significant temporal niche overlaps, indicative of synchrony in daily activity patterns, with both species showing peak activity at dawn and dusk. Our results indicated that oryx and gazelle differ in at least one dimension of their ecological niche at the current density levels, which contributes to their long-term and stable coexistence in STNP.

Relative abundance of grazing and browsing herbivores is not a direct reflection of vegetation structure: Implications for hominin paleoenvironmental reconstruction

The diet of fossil herbivores inferred from enamel stable carbon isotopes is often used to make paleoenvironmental reconstructions. While many studies have focused on using environmental indicator taxa to make paleoenvironmental reconstructions, community-based approaches are considered to provide a more complete picture of paleolandscapes. These studies assume that the diet and relative abundance of herbivores are related to the areal extent of different vegetation types on the landscape. Here, we quantitatively test this assumption in 16 modern ecosystems in eastern and southern Africa with a wide range of woody vegetation cover. We conducted a landscape-level spatial analysis of vegetation patterns using a published land cover data set and computed landscape metrics. We compiled data on relative abundance and diet of herbivores inferred from carbon isotope studies for all large herbivores in these ecosystems. We found that despite differences in the total areal extent of different vegetation types, numerous sizable patches of each vegetation type are available in most ecosystems. However, despite variation across the ecosystems examined, grazers are typically the most abundant herbivores even in sites that have a higher proportion of forest and shrub cover. This indicates that the diet and relative abundance of herbivores is not a simple reflection of the total areal extent of vegetation types available on the landscape. The higher proportion of grazers observed in these ecosystems is a result of multiple factors including habitat heterogeneity, differences in biomass turnover rate between grasses and woody vegetation, resource partitioning, and the advantages of group living in open environments. Comparison of diet and relative abundance of herbivores in modern ecosystems to fossil herbivore assemblages shows that very different vegetation regimes can support similar herbivore assemblages. This study has significant implications for paleolandscape reconstructions and cautions against a simplistic wooded vs. grassland paleoenvironmental interpretations based on fossil herbivore assemblages.

Development of an apparatus for evaluating the visual and olfactory discrimination ability of cattle under controlled target visibility

Ungulates visually and olfactorily discriminating between vegetation patches in grasslands often encounter restriction of target visibility due to light intensity changes; however, little is known about their performance in such a context. We developed and tested an apparatus for evaluating the visual and olfactory discrimination ability of cattle under controlled target visibility, focusing on the discrimination at a short distance. The apparatus was designed to contain a discrimination target under a sliding cover of variable light transmission levels and behind a vent of a fixed size and aperture so as to control the visibility of the target (14-100% restrictions) while ensuring a constant level of odor. Twelve Japanese Black cows were allowed to choose between two apparatuses presenting a pair of targets: green forage versus empty, green forage versus dead forage, or green forage versus green-dead mixture. Cows rapidly learned to slide open the cover to reach the selected target, consistently chose the green forage against the alternative except against the green-dead mixture under 100% visual restriction, and remembered the reaching procedure for at least 16 days. The results indicate the usefulness of the apparatus for assessing close visual and olfactory discrimination ability of cattle in detail.

Relative importance of senses in forage discrimination by cattle depends on the sensory contrast between the discrimination targets: a preliminary study

The ability of ungulates to discriminate among vegetation patches depends largely on the senses of vision, olfaction, tactility, and gustation. However, little is known about how ungulates rely on the respective senses in response to varying patch characteristics. This study aimed to evaluate how relative importance of senses in patch discrimination by cattle is affected by the sensory contrast between the discrimination targets. Five Japanese Black cows were allowed to choose between two forage patches from a distance of about 1 m. Two combinations of forage patches were used: one was a pair of green and dead forages of bahiagrass (BG) with clear mutual contrast in appearance and odor, and the other was a pair of green forages of BG and cogongrass (CG) with visual and olfactory resemblance. Cows preferably located and ate the green BG as the first choice (Type 1), or as the second choice after touching (Type 2) or further biting (Type 3) the alternative in error. Overall, Type 1 accounted for a high above-chance proportion of 0.94 in the green BG vs. dead BG discrimination, indicating the primary importance of vision and olfaction. By contrast, in the green BG vs. green CG discrimination, Type 1 remained at the chance level of 0.55 with proportions of 0.17 for Type 2 and 0.28 for Type 3, indicating the primary importance of tactility on the muzzle and in the mouth. The context-specific importance of the four senses in patch discrimination represents an adaptive mechanism of animals foraging in grasslands.

Spatio-Temporal Changes in Wildlife Habitat Quality in the Greater Serengeti Ecosystem

Understanding habitat quality and its dynamics is imperative for maintaining healthy wildlife populations and ecosystems. We mapped and evaluated changes in habitat quality (1975–2015) in the Greater Serengeti Ecosystem of northern Tanzania using the Integrated Valuation of Environmental Services and Tradeoffs (InVEST) model. This is the first habitat quality assessment of its kind for this ecosystem. We characterized changes in habitat quality in the ecosystem and in a 30 kilometer buffer area. Four habitat quality classes (poor, low, medium and high) were identified and their coverage quantified. Overall (1975–2015), habitat quality declined over time but at rates that were higher for habitats with lower protection level or lower initial quality. As a result, habitat quality deteriorated the most in the unprotected and human-dominated buffer area surrounding the ecosystem, at intermediate rates in the less heavily protected Wildlife Management Areas, Game Controlled Areas, Game Reserves and the Ngorongoro Conservation Area and the least in the most heavily protected Serengeti National Park. The deterioration in habitat quality over time was attributed primarily to anthropogenic activities and major land use policy changes. Effective implementation of land use plans, robust and far-sighted institutional arrangements, adaptive legal and policy instruments are essential to sustaining high habitat quality in contexts of rapid human population growth.