The Experts below are selected from a list of 480 Experts worldwide ranked by ideXlab platform
Georgina M Mace - One of the best experts on this subject based on the ideXlab platform.
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modelling parameter uncertainty reveals bushmeat yields versus survival trade offs in heavily hunted duiker Cephalophus spp
PLOS ONE, 2020Co-Authors: Tatsiana Barychka, Drew W Purves, E J Milnergulland, Georgina M MaceAbstract:Reliably predicting sustainable exploitation levels for many tropical species subject to hunting remains a difficult task, largely because of the inherent uncertainty associated with estimating parameters related to both population dynamics and hunting pressure. Here, we investigate a modelling approach to support decisions in bushmeat management which explicitly considers parameter uncertainty. We apply the approach to duiker Cephalophus spp., assuming either a constant quota-based, or a constant proportional harvesting, strategy. Within each strategy, we evaluate different hunting levels in terms of both average yield and survival probability, over different time horizons. Under quota-based harvesting, considering uncertainty revealed a trade-off between yield and extinction probability that was not evident when ignoring uncertainty. The highest yield was returned by a quota that implied a 40% extinction risk, whereas limiting extinction risk to 10% reduced yield by 50%-70%. By contrast, under proportional harvesting, there was no trade-off between yield and extinction probability. The maximum proportion returned a yield comparable with the maximum possible under quota-based harvesting, but with extinction risk below 10%. However, proportional harvesting can be harder to implement in practice because it depends on an estimate of population size. In both harvesting approaches, predicted yields were highly right-skewed with median yields differing from mean yields, implying that decision outcomes depend on attitude to risk. The analysis shows how an explicit consideration of all available information, including uncertainty, can, as part of a wider process involving multiple stakeholders, help inform harvesting policies.
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modelling parameter uncertainty reveals bushmeat yield versus survival trade offs in heavily hunted duiker Cephalophus spp
bioRxiv, 2020Co-Authors: Tatsiana Barychka, Drew W Purves, E J Milnergulland, Georgina M MaceAbstract:Reliably predicting sustainable exploitation levels for many tropical species subject to hunting remains a difficult task, largely because of the inherent uncertainty associated with estimating parameters related to both population dynamics and hunting pressure. Here, we investigate a modelling approach to support decisions in bushmeat management which explicitly considers parameter uncertainty. We apply the approach to duiker Cephalophus spp., assuming either a constant quota-based, or a constant proportional harvesting, strategy. Within each strategy, we evaluate different hunting levels in terms of both average yield and survival probability, over different time horizons. Under quota-based harvesting, considering uncertainty revealed a trade-off between yield and extinction probability that was not evident when ignoring uncertainty. The highest yield was returned by a quota that implied a 40% extinction risk, whereas limiting extinction risk to 10% reduced yield by 50%-70%. By contrast, under proportional harvesting, there was no trade-off between yield and extinction probability. The maximum proportion returned a yield comparable with the maximum possible under quota-based harvesting, but with extinction risk below 10%. However, proportional harvesting can be harder to implement in practice because it depends on an estimate of population size. In both harvesting approaches, predicted yields were highly right-skewed with median yields differing from mean yields, implying that decision outcomes depend on attitude to risk. The analysis shows how an explicit consideration of all available information, including uncertainty, can, as part of a wider process involving multiple stakeholders, help inform harvesting policies.
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the madingley general ecosystem model predicts bushmeat yields species extinction rates and ecosystem level impacts of bushmeat harvesting
bioRxiv, 2020Co-Authors: Tatsiana Barychka, Georgina M Mace, Drew W PurvesAbstract:Traditional approaches to guiding decisions about harvesting bushmeat often employ single-species population dynamic models, which require species- and location-specific data, are missing ecological processes such as multi-trophic interactions, cannot represent multi-species harvesting, and cannot predict the broader ecosystem impacts of harvesting. In order to explore an alternative approach to devising sustainable harvesting strategies, we employ the Madingley General Ecosystem Model, which can simulate ecosystem dynamics in response to multi-species harvesting given nothing other than location-specific climate data. We used the model to examine yield, extinctions, and broader ecosystem impacts, for a range of harvesting intensities of duiker-sized ectothermic herbivores. Duiker antelope (such as Cephalophus callipygus and Cephalophus dorsalis) are the most heavily hunted species in sub-Saharan Africa, contributing 34%-95% of all bushmeat in the Congo Basin. Across a range of harvesting rates, the Madingley model gave estimates for optimal harvesting rate, and extinction rate, that were qualitatively and quantitatively similar to the estimates from single-species Beverton-Holt model. Predicted yields were somewhat greater (around 5 times, on average) for the Madingley model, which would be expected given that the Madingley simulates multi-species harvesting from an initially pristine ecosystem. This match increased the degree of confidence with which we could examine other predictions from the ecosystem model, as follows. At medium and high levels of harvesting of duiker-sized herbivores, there were statistically significant, but moderate, reductions in the densities of the targeted functional group; increases in small-bodied herbivores; decreases in large-bodied carnivores; and minimal ecosystem-level impacts overall. The results suggest that general ecosystem models such as the Madingley model could be used more widely to help estimate sustainable harvesting rates, bushmeat yields and broader ecosystem impacts across different locations and target species.
Evaristus Tsi Angwafo - One of the best experts on this subject based on the ideXlab platform.
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caracteristiques biometriques du cephalophe bleu Cephalophus monticola thunberg 1789 du cameroun
Cameroon Journal of Experimental Biology, 2021Co-Authors: Olivier Miantsia Fokam, Felix Meutchieye, Evaristus Tsi AngwafoAbstract:Dans le but de contribuer a la caracterisation phenotypique du Cephalophus monticola (cephalophe bleu) dans la partie meridionale du Cameroun (trois zones agroecologiques), 22 caracteristiques biometriques ont ete consideres sur 180 cephalophes bleus adultes selectionnes selon la methode opportuniste. L’analyse des donnees s’est faite en utilisant la statistique descriptive a travers le logiciel d’analyse SPSS version 21.0 et XLSAT-Pro version 7.5.2. Il en resulte que les caracteristiques biometriques de la tete ne subissent aucune n’influence des zones agroecologiques. Cependant, l’envergure des cornes (EC) presente une tres grande variation dans la zone V (CV=113,27%) dont la femelle avec un CV=96,55%. Pour ce qui est du tronc, la longueur du corps (LCprs) presente une grande dispersion autour de la moyenne avec des valeurs suivantes (en cm) : (71,78 ± 12,46) ; (69,13 ± 13,66) et (66,53 ± 15,54) respectivement aux zones III, IV et V. De tous les caracteristiques biometriques, la longueur de la queue (LQ), le tour du canon anterieur (TCA) presentent une difference significative (P<0,05). L’analyse en composante principale (ACP) permet de voir le niveau de variabilite genetique du cephalophe bleu a travers les caracteristiques biometriques. Ainsi deux niveaux de variabilite genetiques sont observes selon les axes F1 (46,94%) et F2 (10,81%). Les caracteristiques biometriques etudiees permettraient de differencier les cephalophes bleus dans les trois zones agroecologiques. L’utilisation des outils moleculaires ouvriraient des perspectives de mieux cerner la genetique des populations du cephalophe bleu au CamerounAbstract This study aimed at contributing to the phenotypic characterization of Cephalophus monticola (blue duiker) in 3 agroecological zones of the Southern Cameroon region. A total of 22 morphological data were collected on 180 adult blue duikers and 15 cranial measurements on 60 skulls using the opportunistic approach. Data analyses were performed using the descriptive statistics through the software SPSS version 21.0 and XLSTAT-Pro version 7.5.2. From the findings, it appears that the biometric characteristics of the head were not influenced by the agro ecological factor. However, horn width (HW) presents a large variation in zone V (CV=113.27%) which the female having an CV=96.55%. Concerning the trunk, the Body length (BL) expresses a large dispersion with the respective values (in cm): (71.78 ± 12.46); (69.13 ± 13.66) and (66.53 ± 15.54) respectively to agroecological zones III, IV and V. Three traits, tail length (TL) and fore leg girth (FLG) showed significant differences (P<0.05). The principal component analysis (PCA) displays the level of genetic variability of blue duiker through biometric characters. Then, it was observed two levels of genetic of variability according to the axes F1 (46,94%) and F2 (10,81%). The biometric traits tended to discriminate blue duikers in the three agroecological zones. This could be interesting for further investigations involving molecular tools for population genetics.
Tatsiana Barychka - One of the best experts on this subject based on the ideXlab platform.
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modelling parameter uncertainty reveals bushmeat yields versus survival trade offs in heavily hunted duiker Cephalophus spp
PLOS ONE, 2020Co-Authors: Tatsiana Barychka, Drew W Purves, E J Milnergulland, Georgina M MaceAbstract:Reliably predicting sustainable exploitation levels for many tropical species subject to hunting remains a difficult task, largely because of the inherent uncertainty associated with estimating parameters related to both population dynamics and hunting pressure. Here, we investigate a modelling approach to support decisions in bushmeat management which explicitly considers parameter uncertainty. We apply the approach to duiker Cephalophus spp., assuming either a constant quota-based, or a constant proportional harvesting, strategy. Within each strategy, we evaluate different hunting levels in terms of both average yield and survival probability, over different time horizons. Under quota-based harvesting, considering uncertainty revealed a trade-off between yield and extinction probability that was not evident when ignoring uncertainty. The highest yield was returned by a quota that implied a 40% extinction risk, whereas limiting extinction risk to 10% reduced yield by 50%-70%. By contrast, under proportional harvesting, there was no trade-off between yield and extinction probability. The maximum proportion returned a yield comparable with the maximum possible under quota-based harvesting, but with extinction risk below 10%. However, proportional harvesting can be harder to implement in practice because it depends on an estimate of population size. In both harvesting approaches, predicted yields were highly right-skewed with median yields differing from mean yields, implying that decision outcomes depend on attitude to risk. The analysis shows how an explicit consideration of all available information, including uncertainty, can, as part of a wider process involving multiple stakeholders, help inform harvesting policies.
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modelling parameter uncertainty reveals bushmeat yield versus survival trade offs in heavily hunted duiker Cephalophus spp
bioRxiv, 2020Co-Authors: Tatsiana Barychka, Drew W Purves, E J Milnergulland, Georgina M MaceAbstract:Reliably predicting sustainable exploitation levels for many tropical species subject to hunting remains a difficult task, largely because of the inherent uncertainty associated with estimating parameters related to both population dynamics and hunting pressure. Here, we investigate a modelling approach to support decisions in bushmeat management which explicitly considers parameter uncertainty. We apply the approach to duiker Cephalophus spp., assuming either a constant quota-based, or a constant proportional harvesting, strategy. Within each strategy, we evaluate different hunting levels in terms of both average yield and survival probability, over different time horizons. Under quota-based harvesting, considering uncertainty revealed a trade-off between yield and extinction probability that was not evident when ignoring uncertainty. The highest yield was returned by a quota that implied a 40% extinction risk, whereas limiting extinction risk to 10% reduced yield by 50%-70%. By contrast, under proportional harvesting, there was no trade-off between yield and extinction probability. The maximum proportion returned a yield comparable with the maximum possible under quota-based harvesting, but with extinction risk below 10%. However, proportional harvesting can be harder to implement in practice because it depends on an estimate of population size. In both harvesting approaches, predicted yields were highly right-skewed with median yields differing from mean yields, implying that decision outcomes depend on attitude to risk. The analysis shows how an explicit consideration of all available information, including uncertainty, can, as part of a wider process involving multiple stakeholders, help inform harvesting policies.
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the madingley general ecosystem model predicts bushmeat yields species extinction rates and ecosystem level impacts of bushmeat harvesting
bioRxiv, 2020Co-Authors: Tatsiana Barychka, Georgina M Mace, Drew W PurvesAbstract:Traditional approaches to guiding decisions about harvesting bushmeat often employ single-species population dynamic models, which require species- and location-specific data, are missing ecological processes such as multi-trophic interactions, cannot represent multi-species harvesting, and cannot predict the broader ecosystem impacts of harvesting. In order to explore an alternative approach to devising sustainable harvesting strategies, we employ the Madingley General Ecosystem Model, which can simulate ecosystem dynamics in response to multi-species harvesting given nothing other than location-specific climate data. We used the model to examine yield, extinctions, and broader ecosystem impacts, for a range of harvesting intensities of duiker-sized ectothermic herbivores. Duiker antelope (such as Cephalophus callipygus and Cephalophus dorsalis) are the most heavily hunted species in sub-Saharan Africa, contributing 34%-95% of all bushmeat in the Congo Basin. Across a range of harvesting rates, the Madingley model gave estimates for optimal harvesting rate, and extinction rate, that were qualitatively and quantitatively similar to the estimates from single-species Beverton-Holt model. Predicted yields were somewhat greater (around 5 times, on average) for the Madingley model, which would be expected given that the Madingley simulates multi-species harvesting from an initially pristine ecosystem. This match increased the degree of confidence with which we could examine other predictions from the ecosystem model, as follows. At medium and high levels of harvesting of duiker-sized herbivores, there were statistically significant, but moderate, reductions in the densities of the targeted functional group; increases in small-bodied herbivores; decreases in large-bodied carnivores; and minimal ecosystem-level impacts overall. The results suggest that general ecosystem models such as the Madingley model could be used more widely to help estimate sustainable harvesting rates, bushmeat yields and broader ecosystem impacts across different locations and target species.
Drew W Purves - One of the best experts on this subject based on the ideXlab platform.
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modelling parameter uncertainty reveals bushmeat yields versus survival trade offs in heavily hunted duiker Cephalophus spp
PLOS ONE, 2020Co-Authors: Tatsiana Barychka, Drew W Purves, E J Milnergulland, Georgina M MaceAbstract:Reliably predicting sustainable exploitation levels for many tropical species subject to hunting remains a difficult task, largely because of the inherent uncertainty associated with estimating parameters related to both population dynamics and hunting pressure. Here, we investigate a modelling approach to support decisions in bushmeat management which explicitly considers parameter uncertainty. We apply the approach to duiker Cephalophus spp., assuming either a constant quota-based, or a constant proportional harvesting, strategy. Within each strategy, we evaluate different hunting levels in terms of both average yield and survival probability, over different time horizons. Under quota-based harvesting, considering uncertainty revealed a trade-off between yield and extinction probability that was not evident when ignoring uncertainty. The highest yield was returned by a quota that implied a 40% extinction risk, whereas limiting extinction risk to 10% reduced yield by 50%-70%. By contrast, under proportional harvesting, there was no trade-off between yield and extinction probability. The maximum proportion returned a yield comparable with the maximum possible under quota-based harvesting, but with extinction risk below 10%. However, proportional harvesting can be harder to implement in practice because it depends on an estimate of population size. In both harvesting approaches, predicted yields were highly right-skewed with median yields differing from mean yields, implying that decision outcomes depend on attitude to risk. The analysis shows how an explicit consideration of all available information, including uncertainty, can, as part of a wider process involving multiple stakeholders, help inform harvesting policies.
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modelling parameter uncertainty reveals bushmeat yield versus survival trade offs in heavily hunted duiker Cephalophus spp
bioRxiv, 2020Co-Authors: Tatsiana Barychka, Drew W Purves, E J Milnergulland, Georgina M MaceAbstract:Reliably predicting sustainable exploitation levels for many tropical species subject to hunting remains a difficult task, largely because of the inherent uncertainty associated with estimating parameters related to both population dynamics and hunting pressure. Here, we investigate a modelling approach to support decisions in bushmeat management which explicitly considers parameter uncertainty. We apply the approach to duiker Cephalophus spp., assuming either a constant quota-based, or a constant proportional harvesting, strategy. Within each strategy, we evaluate different hunting levels in terms of both average yield and survival probability, over different time horizons. Under quota-based harvesting, considering uncertainty revealed a trade-off between yield and extinction probability that was not evident when ignoring uncertainty. The highest yield was returned by a quota that implied a 40% extinction risk, whereas limiting extinction risk to 10% reduced yield by 50%-70%. By contrast, under proportional harvesting, there was no trade-off between yield and extinction probability. The maximum proportion returned a yield comparable with the maximum possible under quota-based harvesting, but with extinction risk below 10%. However, proportional harvesting can be harder to implement in practice because it depends on an estimate of population size. In both harvesting approaches, predicted yields were highly right-skewed with median yields differing from mean yields, implying that decision outcomes depend on attitude to risk. The analysis shows how an explicit consideration of all available information, including uncertainty, can, as part of a wider process involving multiple stakeholders, help inform harvesting policies.
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the madingley general ecosystem model predicts bushmeat yields species extinction rates and ecosystem level impacts of bushmeat harvesting
bioRxiv, 2020Co-Authors: Tatsiana Barychka, Georgina M Mace, Drew W PurvesAbstract:Traditional approaches to guiding decisions about harvesting bushmeat often employ single-species population dynamic models, which require species- and location-specific data, are missing ecological processes such as multi-trophic interactions, cannot represent multi-species harvesting, and cannot predict the broader ecosystem impacts of harvesting. In order to explore an alternative approach to devising sustainable harvesting strategies, we employ the Madingley General Ecosystem Model, which can simulate ecosystem dynamics in response to multi-species harvesting given nothing other than location-specific climate data. We used the model to examine yield, extinctions, and broader ecosystem impacts, for a range of harvesting intensities of duiker-sized ectothermic herbivores. Duiker antelope (such as Cephalophus callipygus and Cephalophus dorsalis) are the most heavily hunted species in sub-Saharan Africa, contributing 34%-95% of all bushmeat in the Congo Basin. Across a range of harvesting rates, the Madingley model gave estimates for optimal harvesting rate, and extinction rate, that were qualitatively and quantitatively similar to the estimates from single-species Beverton-Holt model. Predicted yields were somewhat greater (around 5 times, on average) for the Madingley model, which would be expected given that the Madingley simulates multi-species harvesting from an initially pristine ecosystem. This match increased the degree of confidence with which we could examine other predictions from the ecosystem model, as follows. At medium and high levels of harvesting of duiker-sized herbivores, there were statistically significant, but moderate, reductions in the densities of the targeted functional group; increases in small-bodied herbivores; decreases in large-bodied carnivores; and minimal ecosystem-level impacts overall. The results suggest that general ecosystem models such as the Madingley model could be used more widely to help estimate sustainable harvesting rates, bushmeat yields and broader ecosystem impacts across different locations and target species.
Olivier Miantsia Fokam - One of the best experts on this subject based on the ideXlab platform.
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caracteristiques biometriques du cephalophe bleu Cephalophus monticola thunberg 1789 du cameroun
Cameroon Journal of Experimental Biology, 2021Co-Authors: Olivier Miantsia Fokam, Felix Meutchieye, Evaristus Tsi AngwafoAbstract:Dans le but de contribuer a la caracterisation phenotypique du Cephalophus monticola (cephalophe bleu) dans la partie meridionale du Cameroun (trois zones agroecologiques), 22 caracteristiques biometriques ont ete consideres sur 180 cephalophes bleus adultes selectionnes selon la methode opportuniste. L’analyse des donnees s’est faite en utilisant la statistique descriptive a travers le logiciel d’analyse SPSS version 21.0 et XLSAT-Pro version 7.5.2. Il en resulte que les caracteristiques biometriques de la tete ne subissent aucune n’influence des zones agroecologiques. Cependant, l’envergure des cornes (EC) presente une tres grande variation dans la zone V (CV=113,27%) dont la femelle avec un CV=96,55%. Pour ce qui est du tronc, la longueur du corps (LCprs) presente une grande dispersion autour de la moyenne avec des valeurs suivantes (en cm) : (71,78 ± 12,46) ; (69,13 ± 13,66) et (66,53 ± 15,54) respectivement aux zones III, IV et V. De tous les caracteristiques biometriques, la longueur de la queue (LQ), le tour du canon anterieur (TCA) presentent une difference significative (P<0,05). L’analyse en composante principale (ACP) permet de voir le niveau de variabilite genetique du cephalophe bleu a travers les caracteristiques biometriques. Ainsi deux niveaux de variabilite genetiques sont observes selon les axes F1 (46,94%) et F2 (10,81%). Les caracteristiques biometriques etudiees permettraient de differencier les cephalophes bleus dans les trois zones agroecologiques. L’utilisation des outils moleculaires ouvriraient des perspectives de mieux cerner la genetique des populations du cephalophe bleu au CamerounAbstract This study aimed at contributing to the phenotypic characterization of Cephalophus monticola (blue duiker) in 3 agroecological zones of the Southern Cameroon region. A total of 22 morphological data were collected on 180 adult blue duikers and 15 cranial measurements on 60 skulls using the opportunistic approach. Data analyses were performed using the descriptive statistics through the software SPSS version 21.0 and XLSTAT-Pro version 7.5.2. From the findings, it appears that the biometric characteristics of the head were not influenced by the agro ecological factor. However, horn width (HW) presents a large variation in zone V (CV=113.27%) which the female having an CV=96.55%. Concerning the trunk, the Body length (BL) expresses a large dispersion with the respective values (in cm): (71.78 ± 12.46); (69.13 ± 13.66) and (66.53 ± 15.54) respectively to agroecological zones III, IV and V. Three traits, tail length (TL) and fore leg girth (FLG) showed significant differences (P<0.05). The principal component analysis (PCA) displays the level of genetic variability of blue duiker through biometric characters. Then, it was observed two levels of genetic of variability according to the axes F1 (46,94%) and F2 (10,81%). The biometric traits tended to discriminate blue duikers in the three agroecological zones. This could be interesting for further investigations involving molecular tools for population genetics.