25 research outputs found
Minimum viable population size: not magic, but necessary
No full textBarry W. Brook, Corey J.A. Bradshaw, Lochran W. Traill and Richard Frankha
50/500 rule and minimum viable populations: response to Jamieson and Allendorf
No full textRichard Frankham, Barry W. Brook, Corey J.A. Bradshaw, Lochran W. Traill and Derek Spielma
Minimum viable puoulation sizes and global extinction risk are unrelated
No full textThe definitive version is available at www.blackwell-synergy.comTheoretical and empirical work has shown that once reduced in size and geographical range, species face a considerably elevated risk of extinction. We predict minimum viable population sizes (MVP) for 1198 species based on long-term time-series data and model-averaged population dynamics simulations. The median MVP estimate was 1377 individuals (90% probability of persistence over 100 years) but the overall distribution was wide and strongly positively skewed. Factors commonly cited as correlating with extinction risk failed to predict MVP but were able to predict successfully the probability of World Conservation Union Listing. MVPs were most strongly related to local environmental variation rather than a species' intrinsic ecological and life history attributes. Further, the large variation in MVP across species is unrelated to (or at least dwarfed by) the anthropogenic threats that drive the global biodiversity crisis by causing once-abundant species to declineBarry W. Brook, Lochran W. Traill and Corey J. A. Bradsha
An aggregative response of the tropical Australian magpie goose (Anseranas semipalmata) to seasonal floodplains
No full textWe describe the spatial aggregation of the magpie goose (Anseranas semipalmata) in relation to the dynamics of the ephemeral floodplains of northern Australia. Past broad-scale studies have linked geese to floodplains dominated by the sedge, Eleocharis dulcis, but the type of response has not been determined, nor the impact of predation on food plants. Moreover, departure thresholds are not known. We develop hypotheses on aggregation and departure and confront these with field data. Thus, from 2005–2007 we established two sites on the floodplains of Kakadu National Park (three 1-ha plots per site, six plots in total) and used for monthly, dry season bird counts. An airboat was used to collect data from each of the six plots, including sedge tubers and measures of water level and soil viscosity. Further, we built exclosures (three per site, six in total) to test the impact of herbivory on E. dulcis. Generalized linear models and information theory were used to test the strength of supporting evidence for alternate hypotheses. Geese showed a clear aggregative response to E. dulcis tubers, were forced to depart following floodplain drying and had a marked impact on E. dulcis tuber density. Despite this, there was no evidence of a negative-feedback mechanism between plant–herbivore populations, suggesting that the system is driven by extrinsic parameters (here rainfall).Lochran W. Traill and Barry W. Broo
Trophy hunting certification
No full textAdaptive certification is the best remaining option for the trophy hunting industry in Africa to demonstrate sustainable and ethical hunting practices that benefit local communities and wildlife conservation
Rainfall and temperature variation does not explain arid species diversity in outback Australia
No full textSteps toward conserving biodiversity should start at understanding the components across spatial scales and a determination of the drivers of these. Here we determine additive species diversity for arid South Australia, based on over 50 years of survey data. Elevation and soil data were sourced through the Australian Government, and climate data from the WorldClim database. Alternative hypotheses relating the effect of climatic and environmental parameters to diversity were tested using generalized linear models and ranked according to information-theoretic statistics. Total species richness for the region was 1824, similar to all arid regions. α-diversity values were low, relative to the contributions made by β-diversity toward total γ-diversity, similar to additive diversity indices for nonarid biomes. There was a lack of statistical support for our hypothesis that regional spatial variation in arid region diversity can be explained by climate topography. Arid South Australian species diversity appears to be largely driven by environmental parameters at the localized scale – beyond the resolution of available survey data. Heterogeneity in habitat, provided by mountainous regions, likely contributes toward the high β-diversity values. Our research is the first application of the additive (not multiplicative) approach toward understanding diversity within arid Australia
Sex differences in home range and habitat use by savannah elephants in Gonarezhou National Park, Zimbabwe
No full textProtected areas (PAs) in southern Africa provide refuge to important megafauna such as the savannah elephant (Loxodonta africana). Sections of these protected areas are often transfrontier conservation complexes, whose objective is to facilitate historic patterns of animal dispersal. Knowledge of megafauna home ranges, habitat use, and dispersal in key PAs can inform vital decision-making for elephant conservation. Location data were derived from satellite collars fitted on 26 savannah elephants from 2016 to 2022 in Gonarezhou National Park, Zimbabwe to investigate seasonal and sex differences in elephants’ home range sizes, home range overlap, and their interaction with environmental variables. Differences in the size of home ranges between sexes in all seasons were not significant. Both male and female elephants had high site fidelity, retaining 60% of their home ranges between consecutive seasons. Only females, possibly tracking forage quality, showed reduced overlap of home ranges between the hot dry and hot wet seasons. Male elephants preferred vegetation types dominated by Colophospermum mopane, whereas females used more diverse upland vegetation types, showing a preference for higher elevations than males over all seasons. In areas where elephant movement is restricted by fences and human settlements, continuous monitoring of elephant space use is recommended, and research dynamics should be taken into account when developing site-specific management plans.
Les zones protégées en Afrique australe représentent des refuges pour une importante mégafaune telle que l’éléphant de savane (Loxodonta africana). Il est fréquent que des sections de ces zones protégées soient des complexes de conservation transfrontaliers, dont l’objectif est de faciliter les schémas de dispersion historiques des animaux. La connaissance des domaines vitaux de la mégafaune, de l’utilisation de leur habitat et de leur dispersion dans des zones protégées clés peut contribuer à des prises de décision essentielles pour la conservation des éléphants. Des données de localisation ont été extraites de colliers émetteurs installés sur 26 éléphants de savane entre 2016 et 2022 dans le parc national de Gonarezhou au Zimbabwe, afin d’étudier les variations éventuelles, selon la saison et le sexe des animaux, sur la surface et le chevauchement de leurs domaines vitaux ainsi que sur leur interaction avec les variables environnementales. Les dimensions des domaines vitaux chez les mâles et les femelles n’ont pas montré de différences significatives, toutes saisons confondues. Tous ont fait preuve d’une grande fidélité au site en conservant 60% de leur domaine vital sur les saisons consécutives. Seules les femelles, probablement en recherche d’une certaine qualité de fourrage, ont présenté un chevauchement plus faible de leurs domaines vitaux entre la saison sèche et la saison humide en période chaude. Les éléphants mâles ont affiché un goût plus prononcé pour un type de végétation dominée par Colophospermum mopane, contrairement aux femelles qui se tournaient vers une végétation d’altitude plus variée, indiquant une préférence pour les hauteurs sur toutes les saisons. Dans les zones où les déplacements des éléphants sont contraints par des clôtures et des installations humaines, nous recommandons une surveillance continue de l’utilisation de l’espace par les éléphants et une prise en compte des résultats lors du développement de plans de gestion de site spécifiques
A global survey of the societal benefits of trophy hunting in Africa
No full textAfrican trophy hunting is controversial. Central to the debate on this practice is whether it may be justified by any broader provisions to African society. These typically include meat supply to poor communities, problem animal control, and the funding of conservation and community development. The societal role of African hunting is as contested as the practice itself, with proponents advocating for the benefits of hunting, while critics point to these being inadequate. Little is known about the role of location and demography in the debate on hunting benefits. Here we circulated an anonymous online survey through our international networks. We asked respondents to indicate which (if any) benefits they thought may justify the practice and whether they supported African trophy hunting, or not. We also collected data on respondent geographic location, age, gender, and employment within conservation. The 5755 responses were analysed using multiple correspondence analysis and provided strong evidence for an association between the level of support/rejection of trophy hunting and potential benefits that were perceived to justify the practice. Funding of wildlife conservation through hunting was the most frequently selected benefit, even among many respondents with a neutral or slightly negative view toward trophy hunting as a practice. Respondents strongly opposed to trophy hunting were more likely to reject all societal benefits of hunting. There was some divergence in views between Africa-based respondents, and those outside of Africa. We suggest that any policy development on African trophy hunting be required to incorporate the views of all African stakeholders
Divergent views on trophy hunting in Africa, and what this may mean for research and policy
No full textOver the past decade, trophy hunting in Africa has seen increased public and scientific interest. Much of that attention has come from outside of Africa, with little emphasis on local views. We circulated an online survey through international networks to explore demographic and regional differences in opinion regards support for African trophy hunting, trophy import bans, and outside funding of conservation estates supported by hunting. We received ∼5700 responses and found that location, demography, and conservation background influenced opinion. African and North American respondents showed (significantly) more support for trophy hunting than respondents from Europe or other areas, as did respondents with conservation backgrounds. Unlike North Americans, Africans supported external subsidies of wildlife areas presently funded by hunting. Many factors affected opinions on African hunting, but respondent location played a major role. Realistic policy on African trophy hunting should thus integrate African perspectives, in particular those of rural communities
Habitat partitioning, and an assessment of habitat suitability using presence data, of a large herbivore communitiy on a Zimbabwean private wildlife reserve
No full textThesis (MFor)--University of Stellenbosch, 2003.ENGLISH ABSTRACT: The factors determining habitat selection of large herbivores, on a private
wildlife reserve in semi-arid southeastern Zimbabwe, were investigated.
Gross vegetative structure, herbaceous composition and topographic
features thought to determine herbivore distribution were measured.
Seasonal variation in resource distribution was considered, and research
therefore extended over an entire year. Herbivore distribution and
ecological niche separation was explained through several important
environmental variables, and potential for inter-specific competition
inferred. Additionally, predictive habitat suitability models were designed
for each of the grazing species in the critical dry season.
Herbivores showed a large degree of niche overlap in both the hotwet
season and the cool-dry season, when food resources were more
plentiful. Niche separation between grazers was pronounced in the hot-dry
season. Herbivore distribution was associated most closely with distance
to water, grass sward height, time since burn, woody plant density and by
the presence of predominant grasses, these being Urochloa
mossambicensis, Panicum maximum, Heteropogon contortus and Digitaria
eriantha. Ecological separation of herbivores by the grasses P. maximum,
H. contortus and D. eriantha was more indicative of associated
environmental variables than feeding niche separation.
A GIS-based analysis, using species presence data and quantitative
coverages of environmental variables, produced maps of gradations of
habitat suitability for grazing species during the dry season.
Results of both analyses were integrated and gave a better
understanding of ecological separation, and possible competitive
interactions, among the large herbivore community on Malilangwe Estate.
Recommendations were made based on the interpretation of findings,
within the context of available management options.AFRIKAANSE OPSOMMING: Die bepalende faktore van habitat seleksie by groot herbivore op ‘n
privaat wildreservaat in semi-dorre suidoos Zimbabwe is ondersoek.
Globale plantegroei stuktuur, kruidagtige samestelling en topografiese
eienskappe wat glo herbivoor verspreiding bepaal, is gemeet. Seisoenale
variasie in hulpbronverspreiding is in ag geneem en dus het navorsing oor
‘n hele jaar gestrek. Herbivoor verspreiding en ekologiese nisskeiding is
verduidelik deur verskeie belangrike omgewingsveranderlikes en die
potensiaal vir interspesifieke kompetisie is afgelei. Boonop is
voorspellende habitat-geskiktheidsmodelle ontwerp vir elk van die
weidingspesies in die krities droë seisoen.
Herbivore toon ‘n hoë graad van nis oorvleueling in sowel die warm,
nat seisoen as die koel, droë seisoen wanneer voedingsbronne meer volop
is. Nis verdeling tussen weidiere was duidelik herkenbaar in die warm,
droë seisoen. Herbivoor verspreiding is meestal geassosieer met die
afstand na die water, die grasveld hoogte, tydperk sedert ‘n brand,
digtheid van houtagtige plantsoorte en met die teenwoordigheid van die
oorheersende grasse, Urochloa mossambicensis, Panicum maximum,
Heteropogon contortus en Digitaria eriantha. Die ekologiese skeiding van
herbivore deur die grasse P. maximum, H. contortus en D. eriantha het
meer gedui op geassosieerde omgewingsveranderlikes as op skeiding van
voedingsnisse.
‘n GIS-gebaseerde analise wat spesie-teenwoordigheidsdata en
kwantitatiewe dekking van omgewingsveranderlikes gebruik, het
klassifikasiekaarte geproduseer van habitatgeskiktheid vir weidiere tydens
die droë seisoen.
Resultate van beide analises is geïntegreer en het ‘n beter begrip
van ekologiese skeiding en moontlike kompeterende interaksies tussen die
groot herbivore gemeenskap op Malilangwe Estate tot gevolg gehad.
Aanbevelings is gemaak, gebaseer op die interpretasie van bevindinge,
binne die konteks van beskikbare bestuursopsies.Master
