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Brown MB, Fennessy JT, Crego RD, Fleming CH, Alves J, Brandlová K, Fennessy S, Ferguson S, Hauptfleisch M, Hejcmanova P, Hoffman R, Leimgruber P, Masiaine S, McQualter K, Mueller T, Muller B, Muneza A, O'Connor D, Olivier AJ, Rabeil T, Seager S, Stacy-Dawes J, van Schalkwyk L, Stabach J. Ranging behaviours across ecological and anthropogenic disturbance gradients: a pan-African perspective of giraffe ( Giraffa spp .) space use. Proc Biol Sci 2023; 290:20230912. [PMID: 37357852 PMCID: PMC10291724 DOI: 10.1098/rspb.2023.0912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Accepted: 05/26/2023] [Indexed: 06/27/2023] Open
Abstract
Animal movement behaviours are shaped by diverse factors, including resource availability and human impacts on the landscape. We generated home range estimates and daily movement rate estimates for 149 giraffe (Giraffa spp.) from all four species across Africa to evaluate the effects of environmental productivity and anthropogenic disturbance on space use. Using the continuous time movement modelling framework and a novel application of mixed effects meta-regression, we summarized overall giraffe space use and tested for the effects of resource availability and human impact on 95% autocorrelated kernel density estimate (AKDE) size and daily movement. The mean 95% AKDE was 359.9 km2 and the mean daily movement was 14.2 km, both with marginally significant differences across species. We found significant negative effects of resource availability, and significant positive effects of resource heterogeneity and protected area overlap on 95% AKDE size. There were significant negative effects of overall anthropogenic disturbance and positive effects of the heterogeneity of anthropogenic disturbance on daily movements and 95% AKDE size. Our results provide unique insights into the interactive effects of resource availability and anthropogenic development on the movements of a large-bodied browser and highlight the potential impacts of rapidly changing landscapes on animal space-use patterns.
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Affiliation(s)
- Michael Butler Brown
- Giraffe Conservation Foundation, PO Box 86099, Eros, Windhoek, Namibia
- Smithsonian National Zoo and Conservation Biology Institute, Conservation Ecology Center, 1500 Remount Rd, Front Royal, VA 22630, USA
| | | | - Ramiro D. Crego
- Smithsonian National Zoo and Conservation Biology Institute, Conservation Ecology Center, 1500 Remount Rd, Front Royal, VA 22630, USA
| | - Christen H. Fleming
- Smithsonian National Zoo and Conservation Biology Institute, Conservation Ecology Center, 1500 Remount Rd, Front Royal, VA 22630, USA
- Department of Biology, University of Maryland, College Park, MD, USA
| | - Joel Alves
- Wildscapes Veterinary & Conservation Services, Hoedspruit, South Africa
| | - Karolina Brandlová
- Faculty of Tropical AgriSciences, Czech University of Life Sciences Prague, Kamycka 129, 16500 Prague, Czechia
| | | | - Sara Ferguson
- Giraffe Conservation Foundation, PO Box 86099, Eros, Windhoek, Namibia
| | - Morgan Hauptfleisch
- Biodiversity Research Centre, Namibia University of Science and Technology, 8 Johann Albrecht Street, Windhoek, Namibia
| | - Pavla Hejcmanova
- Faculty of Tropical AgriSciences, Czech University of Life Sciences Prague, Kamycka 129, 16500 Prague, Czechia
| | - Rigardt Hoffman
- Giraffe Conservation Foundation, PO Box 86099, Eros, Windhoek, Namibia
| | - Peter Leimgruber
- Smithsonian National Zoo and Conservation Biology Institute, Conservation Ecology Center, 1500 Remount Rd, Front Royal, VA 22630, USA
| | - Symon Masiaine
- Conservation Science & Wildlife Health, San Diego Zoo Wildlife Alliance, San Diego, CA, USA
| | - Kylie McQualter
- Centre for Ecosystem Studies, School of Biological Earth and Environmental Sciences, University of New South Wales, Kensington, NSW, 2052, Australia
| | - Thomas Mueller
- Senckenberg Biodiversity and Climate Research Centre and Department of Biological Science, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Ben Muller
- Wildscapes Veterinary & Conservation Services, Hoedspruit, South Africa
| | - Arthur Muneza
- Giraffe Conservation Foundation, PO Box 86099, Eros, Windhoek, Namibia
| | - David O'Connor
- Smithsonian National Zoo and Conservation Biology Institute, Conservation Ecology Center, 1500 Remount Rd, Front Royal, VA 22630, USA
- Senckenberg Biodiversity and Climate Research Centre and Department of Biological Science, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Adriaan Jacobus Olivier
- Department of Conservation Ecology and Entomology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
| | | | | | - Jenna Stacy-Dawes
- Conservation Science & Wildlife Health, San Diego Zoo Wildlife Alliance, San Diego, CA, USA
| | - Louis van Schalkwyk
- Office of the State Veterinarian, Department of Agriculture, Land Reform and Rural Development, Kruger National Park, Skukuza, South Africa
- Department of Migration, Max Planck Institute of Animal Behavior, Radolfzell, Germany
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa
| | - Jared Stabach
- Smithsonian National Zoo and Conservation Biology Institute, Conservation Ecology Center, 1500 Remount Rd, Front Royal, VA 22630, USA
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Assessing the Impact of Wildlife on Vegetation Cover Change, Northeast Namibia, Based on MODIS Satellite Imagery (2002–2021). SENSORS 2022; 22:s22114006. [PMID: 35684629 PMCID: PMC9185244 DOI: 10.3390/s22114006] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 05/03/2022] [Accepted: 05/09/2022] [Indexed: 02/05/2023]
Abstract
Human–wildlife conflict in the Zambezi region of northeast Namibia is well documented, but the impact of wildlife (e.g., elephants) on vegetation cover change has not been adequately addressed. Here, we assessed human–wildlife interaction and impact on vegetation cover change. We analyzed the 250 m MODIS and ERA5 0.25° × 0.25° drone and GPS-collar datasets. We used Time Series Segmented Residual Trends (TSS-RESTREND), Mann–Kendall Test Statistics, Sen’s Slope, ensemble, Kernel Density Estimation (KDE), and Pearson correlation methods. Our results revealed (i) widespread vegetation browning along elephant migration routes and within National Parks, (ii) Pearson correlation (p-value = 5.5 × 10−8) showed that vegetation browning areas do not sustain high population densities of elephants. Currently, the Zambezi has about 12,008 elephants while these numbers were 1468, 7950, and 5242 in 1989, 1994, and 2005, respectively, (iii) settlements and artificial barriers have a negative impact on wildlife movement, driving vegetation browning, and (iv) vegetation greening was found mostly within communal areas where intensive farming and cattle grazing is a common practice. The findings of this study will serve as a reference for policy and decision makers. Future studies should consider integrating higher resolution multi-platform datasets for detailed micro analysis and mapping of vegetation cover change.
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Irob K, Blaum N, Baldauf S, Kerger L, Strohbach B, Kanduvarisa A, Lohmann D, Tietjen B. Browsing herbivores improve the state and functioning of savannas: A model assessment of alternative land-use strategies. Ecol Evol 2022; 12:e8715. [PMID: 35342616 PMCID: PMC8931791 DOI: 10.1002/ece3.8715] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 12/26/2021] [Accepted: 01/27/2022] [Indexed: 11/21/2022] Open
Abstract
Changing climatic conditions and unsustainable land use are major threats to savannas worldwide. Historically, many African savannas were used intensively for livestock grazing, which contributed to widespread patterns of bush encroachment across savanna systems. To reverse bush encroachment, it has been proposed to change the cattle-dominated land use to one dominated by comparatively specialized browsers and usually native herbivores. However, the consequences for ecosystem properties and processes remain largely unclear. We used the ecohydrological, spatially explicit model EcoHyD to assess the impacts of two contrasting, herbivore land-use strategies on a Namibian savanna: grazer- versus browser-dominated herbivore communities. We varied the densities of grazers and browsers and determined the resulting composition and diversity of the plant community, total vegetation cover, soil moisture, and water use by plants. Our results showed that plant types that are less palatable to herbivores were best adapted to grazing or browsing animals in all simulated densities. Also, plant types that had a competitive advantage under limited water availability were among the dominant ones irrespective of land-use scenario. Overall, the results were in line with our expectations: under high grazer densities, we found heavy bush encroachment and the loss of the perennial grass matrix. Importantly, regardless of the density of browsers, grass cover and plant functional diversity were significantly higher in browsing scenarios. Browsing herbivores increased grass cover, and the higher total cover in turn improved water uptake by plants overall. We concluded that, in contrast to grazing-dominated land-use strategies, land-use strategies dominated by browsing herbivores, even at high herbivore densities, sustain diverse vegetation communities with high cover of perennial grasses, resulting in lower erosion risk and bolstering ecosystem services.
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Affiliation(s)
- Katja Irob
- Freie Universität BerlinTheoretical EcologyInstitute of BiologyBerlinGermany
| | - Niels Blaum
- Plant Ecology and Nature ConservationUniversity of PotsdamPotsdamGermany
| | - Selina Baldauf
- Freie Universität BerlinTheoretical EcologyInstitute of BiologyBerlinGermany
| | - Leon Kerger
- Freie Universität BerlinTheoretical EcologyInstitute of BiologyBerlinGermany
| | - Ben Strohbach
- Agriculture and Natural Resources SciencesNamibia University of Science and TechnologyWindhoekNamibia
| | - Angelina Kanduvarisa
- Agriculture and Natural Resources SciencesNamibia University of Science and TechnologyWindhoekNamibia
| | - Dirk Lohmann
- Plant Ecology and Nature ConservationUniversity of PotsdamPotsdamGermany
| | - Britta Tietjen
- Freie Universität BerlinTheoretical EcologyInstitute of BiologyBerlinGermany
- Berlin‐Brandenburg Institute of Advanced Biodiversity Research (BBIB)BerlinGermany
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Lee AT, Macray MB, Ryan PG, Alexander GJ. Tortoise mortality along fence lines in the Karoo region of South Africa. J Nat Conserv 2021. [DOI: 10.1016/j.jnc.2020.125945] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Inter-Seasonal Time Series Imagery Enhances Classification Accuracy of Grazing Resource and Land Degradation Maps in a Savanna Ecosystem. REMOTE SENSING 2020. [DOI: 10.3390/rs12010198] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In savannas, mapping grazing resources and indicators of land degradation is important for assessing ecosystem conditions and informing grazing and land management decisions. We investigated the effects of classifiers and used time series imagery—images acquired within and across seasons—on the accuracy of plant species maps. The study site was a grazed savanna in southern Kenya. We used Sentinel-2 multi-spectral imagery due to its high spatial (10–20 m) and temporal (five days) resolution with support vector machine (SVM) and random forest (RF) classifiers. The species mapped were important for grazing livestock and wildlife (three grass species), indicators of land degradation (one tree genus and one invasive shrub), and a fig tree species. The results show that increasing the number of images, including dry season imagery, results in improved classification accuracy regardless of the classifier (average increase in overall accuracy (OA) = 0.1632). SVM consistently outperformed RF, and the most accurate model and was SVM with a radial kernel using imagery from both wet and dry seasons (OA = 0.8217). Maps showed that seasonal grazing areas provide functionally different grazing opportunities and have different vegetation characteristics that are critical to a landscape’s ability to support large populations of both livestock and wildlife. This study highlights the potential of multi-spectral satellite imagery for species-level mapping of savannas.
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Pirie TJ, Thomas RL, Fellowes MDE. Game fence presence and permeability influences the local movement and distribution of South African mammals. AFRICAN ZOOLOGY 2017. [DOI: 10.1080/15627020.2017.1410074] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Tara J Pirie
- People and Wildlife Research Group, School of Biological Sciences, University of Reading, Reading, Berkshire RG6 6AJ, UK
- Ingwe Leopard Research, Lydenburg, South Africa
| | - Rebecca L Thomas
- People and Wildlife Research Group, School of Biological Sciences, University of Reading, Reading, Berkshire RG6 6AJ, UK
- School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK
| | - Mark DE Fellowes
- People and Wildlife Research Group, School of Biological Sciences, University of Reading, Reading, Berkshire RG6 6AJ, UK
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Sianga K, Van Telgen M, Vrooman J, Fynn RW, Van Langevelde F. Spatial refuges buffer landscapes against homogenisation and degradation by large herbivore populations and facilitate vegetation heterogeneity. KOEDOE: AFRICAN PROTECTED AREA CONSERVATION AND SCIENCE 2017. [DOI: 10.4102/koedoe.v59i2.1434] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
Environmental heterogeneity across savanna landscapes, including different seasonal resources at different distances to water, may play a critical role in maintaining the size and diversity of wildlife populations and the sustainability of their resource base. We investigated whether extensive landscapes with functionally diverse seasonal resources and large waterless regions can mediate the effect of herbivory on plant composition, structure and diversity. Vegetation composition, structure and richness in two different vegetation types (mopane and sandveld woodland) at three distance zones (0 km – 5 km, 10 km – 15 km and > 20 km) from the permanent water of the Okavango Delta and Linyanti Swamps were surveyed. We modelled vegetation response of the most abundant species to herbivory in relation to distance from permanent water, and included fire frequency as a covariate. Trees favoured by elephants during the dry season occurred typically as immature, pollarded populations within 5 km of permanent water sources while mature tall populations of these species were found far from water (> 10 km – 15 km). Similarly, short high-quality grazing grasses were higher in abundance within 5 km of permanent water, whereas taller high-quality perennial grasses peaked in abundance beyond 20 km from permanent water. Trends in herbaceous richness with distance from water were contingent upon vegetation type, while tree richness did not change with distance from water. Spatial refuges in waterless regions of landscapes facilitate the creation of heterogeneity of vegetation structure, composition and richness by large herds of mammalian herbivores. Therefore, the extension of herbivore dry season foraging range, for example, by the creation of artificial water points (AWP) in backcountry woodlands, could seriously undermine the resilience of landscapes to herbivory by reducing the availability of spatial refuges. Consequently, it reduces the resilience of herbivore and predator populations that depend on these spatial refuges. We strongly advise that future scientific work, and management and policy actions should be focused on the identification and sustaining of these spatial refuges in wildlife areas.Conservation implications: Management and policy actions should be focused on the identification and sustainability of spatial refuges in wildlife areas. Too many AWP in backcountry woodlands could undermine the resilience of landscapes to herbivory by reducing the proportion of landscapes beyond 15 km from permanent water.
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Hermoso V, Januchowski-Hartley SR, Linke S. Systematic planning of disconnection to enhance conservation success in a modified world. THE SCIENCE OF THE TOTAL ENVIRONMENT 2015; 536:1038-1044. [PMID: 26254022 DOI: 10.1016/j.scitotenv.2015.07.120] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 07/24/2015] [Accepted: 07/24/2015] [Indexed: 06/04/2023]
Abstract
Maintaining spatial-temporal connectivity for conservation is necessary to allow the persistence of ecological processes and the biodiversity they sustain. However, conservation practice in human-modified environments can also benefit from prescribed disconnection through the implementation of barriers. Barriers, such as fences or dams, and buffer zones can be a cost-effective way of addressing threats caused by a globally connected world, such as the propagation of invasive species and diseases, creating refuge areas for native biodiversity and helping reduce economic losses caused by native wildlife or invasive species. Despite the global attention that disconnection has received, no clear framework exists to guide the allocation of barriers for conservation management. Here we propose that the implementation of barriers for conservation should be systematically planned, considering ecological trade-offs for multiple species (easing threats vs. interruption of ecosystem processes) and socio-economic cost-benefits (implementation cost vs. reduced human-wildlife conflicts), rather than using ad-hoc opportunistic criteria or accommodating conservation needs for individual species. Such a systematic approach is necessary to ensure both socially acceptable and ecologically effective use of disconnections as a conservation tool and ideally planned across different realms so co-benefits or trade-offs can be accounted for. However, any implementation of disconnection for conservation should be cautiously considered if uncertainty in effectiveness of the barrier and ecological impacts to other species are high. We also suggest the need for improved approaches to monitoring to learn from previous successes and failures. Our recommendations should guide the systematic evaluation and allocation of barriers to help enhance the value of this conservation tool in the face of increasing propagation of threats worldwide. However, new tools and collaborative frameworks across different realms are needed to help stakeholders make better informed decision.
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Affiliation(s)
- Virgilio Hermoso
- Centre Tecnologic Forestal de Catalunya, Crta. Sant Llorenc de Monunys, Km 2, 25280 Solsona, Lleida, Spain; Australian Rivers Institute and Tropical Rivers and Coastal Knowledge, National Environmental Research Program Northern Australia Hub, Griffith University, Nathan, Queensland, 4111, Australia.
| | | | - Simon Linke
- Centre Tecnologic Forestal de Catalunya, Crta. Sant Llorenc de Monunys, Km 2, 25280 Solsona, Lleida, Spain
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Miranda M, Cristóbal I, Díaz L, Sicilia M, Molina-Alcaide E, Bartolomé J, Fierro Y, Cassinello J. Ecological effects of game management: does supplemental feeding affect herbivory pressure on native vegetation? WILDLIFE RESEARCH 2015. [DOI: 10.1071/wr15025] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Context Supplemental feeding of large mammalian herbivores is a common management tool mainly aimed at promoting healthy populations and at increasing productivity and trophy sizes. Such management measure may indirectly affect herbivore effects on plant communities through altered foraging patterns. The quantification of the ecological effects of large herbivore management is important for designing holistic management and conservation programs. Aims Here we aimed at quantifying the ecological effects of supplemental feeding of Iberian red deer, Cervus elaphus hispanicus, on the composition of and on the browsing effects on Mediterranean woody plant community. Methods An experiment was set up in a hunting rangeland located in central Spain, where female deer were kept in enclosures with either exclusive access to natural forages or with additional ad libitum access to a nutritionally rich concentrate. The experiment also included a control area where deer were absent. Key results We observed significant differences in browsing impacts among the supplemented, non-supplemented and control areas, and such effect varied for the different plant species. Plant species which nutritional content complemented that of fodder were more highly consumed, for instance, Erica spp., which digestible fibre content is higher and N content lower than that of provided fodder. The presence of deer and the concentrate supplied, instead, did not influence the relative abundances of shrub species. Conclusions Artificial supplemental feeding provided to ungulates led to increased browsing on plant species which nutritional composition complemented that of the supplement provided. Implications So as to alleviate herbivory impact on all shrubs, we suggest that composition of supplemental feeding should adjust both to the natural forage availability and quality and to ungulate requirements across seasons.
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