Using N-mixture models to estimate abundance and temporal trends of black rhinoceros (Diceros bicornis L.) populations from aerial counts

Inaccurate estimates of animal populations may lead to flawed management interventions, therefore, it is essential to understand the status and population trend of a species in order to plan its management efficiently. Aerial surveys are considered a useful method for estimating the population size of large conspicuous animals inhabiting large areas, but raw count data from aerial surveys usually underestimate population sizes due to imperfect detection. The use of N-mixture models with aerial count data provides a useful tool to estimate the population sizes while taking detection probability into account. As a study case we used aerial surveys conducted for monitoring black rhinoceros (Diceros bicornis) in Madikwe Game Reserve and Pilanesberg Nature Reserve (South Africa) during 1999–2015, and we analysed data with a dynamic extension of the N-mixture model. We estimated 0.078–0.098 and 0.139–0.142 individuals/km2, respectively, and we found evidence for density dependence in both reserves with a carrying capacity of 0.122 (0.102–0.142) individuals/100 km2. Based on simulations used to assess precision of the estimates, root-mean-square error model (RMSE) estimates was significantly smaller than those for the raw maximum counts. The N-mixture models provide a promising approach to estimate population size, trends and demographic characteristics of large conspicuous mammals such as black rhinoceroses. Such analysis can provide estimates that are more accurate than raw counts. In addition, use of model covariates that affect a species' population parameters can provide useful information for their conservation and management.Jose Jimenez is funded by Plan TIFIES (Spanish Action Plan against illegal trafficking and international poaching of wild species). Ministerio para la Transición Ecológica. Government of Spain.Peer reviewe

Factors predicting habitat use by leopards in human-altered landscapes

SUPPLEMENTARY DATA SD1.—Univariate analyses results for male and female leopard occurrence probability at the fine and large spatial scales.Transformed landscapes caused by human activity leave remnant patches of natural habitat for wildlife. The persistence of species in the face of such transformation depends on individuals’ ability to adapt to novel habitat, and to secure resources and reproductive opportunities despite habitat alterations. The leopard, Panthera pardus, is the last free-roaming top carnivore in South Africa whose high trophic status and wide-ranging movements make them an effective focal species in conservation planning. Using location data from leopards, we investigated key correlates of habitat selection in human-altered landscapes at two spatial scales. We compared sex-related differences and predicted how conspecific home range locations influenced habitat selection. Leopards avoided human-altered landscapes more strongly at the large spatial scale, where both sexes selected core areas near formally protected areas. Conspecific home range locations had a strong positive effect at both spatial scales for males, while for females, conspecifics explained fine-scale habitat selection by selecting areas near neighboring females. Spatial scale, sex-related differences, and conspecific location play roles in habitat selection for solitary felids and have implications for conservation planning and management. Excluding these factors may result in inappropriate species management policies.Development Bank South Africa, United Nations Environmental Programme, United Nations Development Programme, Green Fund, Global Environmental Facility, Global Environment Facility/Small Grants Programme, Henry and Iris Englund Foundation, National Lotteries Distribution Trust Fund, Mones Michaels Trust, Tamarisk Trust, Timothy Allsop, ABAX Foundation, Table Mountain Fund, Vodacom Foundation, Deutsche Bank Foundation (RSA), Brad Banducci, and Arne Hanson.https://academic.oup.com/jmammalhj2023Mammal Research Institut

Gene flow and population structure of a solitary top carnivore in a human-dominated landscape

While African leopard populations are considered to be continuous as demonstrated by their high genetic variation, the southernmost leopard population exists in the Eastern and Western Cape, South Africa, where anthropogenic activities may be affecting this population's structure. Little is known about the elusive, last free-roaming top predator in the region and this study is the first to report on leopard population structuring using nuclear DNA. By analyzing 14 microsatellite markers from 40 leopard tissue samples, we aimed to understand the populations' structure, genetic distance, and gene flow (Nm). Our results, based on spatially explicit analysis with Bayesian methods, indicate that leopards in the region exist in a fragmented population structure with lower than expected genetic diversity. Three population groups were identified, between which low to moderate levels of gene flow were observed (Nm 0.5 to 3.6). One subpopulation exhibited low genetic differentiation, suggesting a continuous population structure, while the remaining two appear to be less connected, with low emigration and immigration between these populations. Therefore, genetic barriers are present between the subpopulations, and while leopards in the study region may function as a metapopulation, anthropogenic activities threaten to decrease habitat and movement further. Our results indicate that the leopard population may become isolated within a few generations and suggest that management actions should aim to increase habitat connectivity and reduce human-carnivore conflict. Understanding genetic diversity and connectivity of populations has important conservation implications that can highlight management of priority populations to reverse the effects of human-caused extinctions.Carnegie Corporation of New York to the Global Change and Sustainability Research Institute at the University of the Witwatersrand. ABAX Foundation, Henry and Iris Englund Foundation, National Lotteries Distribution Trust Fund, Mones Michaels Trust, Arne Hanson, and Deutsche Bank South Africa Foundation.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)2045-7758hb201

Editorial Animal Ethics and Ecotourism

NoneNon

Simulating rewetting events in intermittent rivers and ephemeral streams: A global analysis of leached nutrients and organic matter

Climate change and human pressures are changing the global distribution and the ex‐ tent of intermittent rivers and ephemeral streams (IRES), which comprise half of the global river network area. IRES are characterized by periods of flow cessation, during which channel substrates accumulate and undergo physico‐chemical changes (precon‐ ditioning), and periods of flow resumption, when these substrates are rewetted and release pulses of dissolved nutrients and organic matter (OM). However, there are no estimates of the amounts and quality of leached substances, nor is there information on the underlying environmental constraints operating at the global scale. We experi‐ mentally simulated, under standard laboratory conditions, rewetting of leaves, river‐ bed sediments, and epilithic biofilms collected during the dry phase across 205 IRES from five major climate zones. We determined the amounts and qualitative character‐ istics of the leached nutrients and OM, and estimated their areal fluxes from riverbeds. In addition, we evaluated the variance in leachate characteristics in relation to selected environmental variables and substrate characteristics. We found that sediments, due to their large quantities within riverbeds, contribute most to the overall flux of dis‐ solved substances during rewetting events (56%–98%), and that flux rates distinctly differ among climate zones. Dissolved organic carbon, phenolics, and nitrate contrib‐ uted most to the areal fluxes. The largest amounts of leached substances were found in the continental climate zone, coinciding with the lowest potential bioavailability of the leached OM. The opposite pattern was found in the arid zone. Environmental vari‐ ables expected to be modified under climate change (i.e. potential evapotranspiration, aridity, dry period duration, land use) were correlated with the amount of leached sub‐ stances, with the strongest relationship found for sediments. These results show that the role of IRES should be accounted for in global biogeochemical cycles, especially because prevalence of IRES will increase due to increasing severity of drying event

CO-MANAGEMENT OF MOOSE IN THE GWICH'IN SETTLEMENT AREA, NORTHWEST TERRITORIES

The Gwich’in of the Northwest Territories play an important role in the management of moose (Alces alces): they have a settled land claim that requires their involvement in wildlife management, they provide valuable traditional knowledge to biologists about moose in an area for which there is little background scientific information, and of the moose harvested, subsistence makes up a majority. A co-management board was established to ensure cooperation between Gwich’in and government agencies in the research and management of renewable resources. Through co-management, there is improved exchange of traditional and scientific knowledge between Gwich’in and agency biologists, there is an increased sense of responsibility for management among Gwich’in, and Gwich’in are more willing to participate in future management activities. Since co-management began in this area, biologists and Gwich’in have design and conducted moose surveys, harvest assessment of Gwich’in hunters, inventory of moose habitat, and documentation of traditional knowledge about moose

Water dependence structures predation risk for large herbivores in insular protected areas

Predator avoidance strategies vary across the ungulate guild. Population-level responses to the presence of large predators to a large extent depend on how well ecological conditions suit the particular predator avoidance strategies of a species. Predation risk from ambush predators, e.g. lions negatively correlates with distance from surface water, but only at scales comparable to the foraging range of lions. Prey species with low surface water requirements spend less time close to surface water, and their predator avoidance revolves around selecting predator-free zones. Arguably, spatial segregation would be further encouraged by competition from water-dependent conspecifics. The scarcity of predator-free zones in confined spaces raises the expectation that they are exposed to a high predation risk relative to species more dependent on surface water. Based on this premise, we argue that lion introductions to insular conservation areas of limited size, compromise diverse ungulate communities. We do an across-species comparison of the long-run population growth of a selection of prey species across fourteen small conservation areas. Study areas are categorised according to those harbouring apex predators (lions) and those that do not. Our findings suggest species differentially respond to the presence of lions, with negative responses biased towards species with low surface water requirements. In smaller conservation areas harbouring lions, reducing surface water frequency might prove key to the successful conservation of water-independent large herbivores.https://link.springer.com/journal/429912023-07-22hj2023Zoology and Entomolog

Rainfall, Temperature, and Forage Dynamics Affect Nutritional Quality of Desert Mule Deer Forage

Forage quality affects physiological condition, population dynamics, habitat use, and distribution of ungulates. We studied how rainfall, temperature, forage biomass, and forage growth are related to water content, crude protein (CP), and in vitro dry- matter digestibility (IVDMD) of some common forage species of desert mule deer (Odocoileus hemionus eremicus Mearns) in the Sonoran Desert, California. We established vegetation transects in desert washes to collect forage samples and to measure forage biomass, growth, rainfall, and temperature on a quarterly basis. Percent water and CP were positively associated with forage growth (P < 0.001) and with rainfall (P < 0.025). There were positive relationships between IVDMD and forage growth (P < 0.001), forage biomass (P < 0.001), and the combination of temperature and rainfall (P < 0.001). These findings suggest that the highest quality landscapes for deer are those with rapidly growing forage where forage water, CP, and IVDMD are greatest. With the quantified relationships between rainfall, temperature, and forage characteristics presented here, the nutritional constituents for deer forage can be predicted.  The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 2020Legacy DOIs that must be preserved: 10.2458/azu_rangelands_v58i4_krausma

Habitat use by a large herbivore guild in a fenced South African protected area

In fenced protected areas with limited opportunities to disperse, resources and constraints vary in space and time, affecting herbivore behaviour. The distribution, availability and quality of resources, burnt areas, and potential inter-specific competition all play a role in sustaining populations of large sympatric African herbivores. We investigated the role of resources, constraints and interspecific relationships on habitat use by three ruminants – black and blue wildebeest (Connochaetes gnou, C. taurinus) and red hartebeest (Alcelaphus buselaphus), and a non-ruminant, plains zebra (Equus quagga), across seasons and in different landscape types in a South African reserve. Black wildebeest, blue wildebeest and red hartebeest preferred the open grassland landscape, with homogeneous vegetation, while zebra favoured the wooded grassland landscape, with more heterogeneous vegetation. Burnt areas and vegetation greenness were important for all species, while elevation represented a constraint for black wildebeest only. The presence/absence of other species was important in shaping landscape use for black and blue wildebeest, and this suggests the possibility of competition. Our findings confirm the importance of heterogeneity and, in particular, the important role of a planned burning regime in maintaining such heterogeneity to sustain multi-species herbivore assemblages in small fenced nature reserves, where competition might arise between species using similar resources.The National Research Foundation of South Africahttp://www.sawma.co.zahj2022Zoology and Entomolog