An assessment of the medium-term reproductive success of an extralimital white rhinoceros population
- Truter, Anja, Mgqatsa, Nokubonga, Parker, Daniel M
- Authors: Truter, Anja , Mgqatsa, Nokubonga , Parker, Daniel M
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/462570 , vital:76315 , xlink:href="https://doi.org/10.1080/15627020.2022.2132120"
- Description: The white rhinoceros (Ceratotherium simum) is threatened primarily due to continued poaching for its horns. In South Africa, partly to promote the conservation of the species, white rhinos have been introduced into areas where they did not occur historically (i.e. where they are considered extralimital). Few studies have investigated the conservation contribution of extralimital white rhinos to the overall national herd. We aimed to determine whether the white rhinos introduced to a private game reserve in the Eastern Cape province have been successful from a reproductive perspective. We calculated inter-calving intervals, age at first calving, sex ratios of calves, and recruitment rates for white rhinos at a single site between 1992 and 2019. The average net annual population growth rate for the population was 10%, which is higher than the recommended 5% by the Biodiversity Management Plan for white rhinos. Trends in density-dependent parameters such as age at first calving and inter-calving intervals also indicated that the study population is still well below the density at which ecological constraints may manifest. We demonstrate that an extralimital white rhino population in the Eastern Cape can be successful from a reproductive perspective.
- Full Text:
- Date Issued: 2022
An assessment of the medium-term reproductive success of an extralimital white rhinoceros population
- Authors: Truter, Anja , Mgqatsa, Nokubonga , Parker, Daniel M
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/462570 , vital:76315 , xlink:href="https://doi.org/10.1080/15627020.2022.2132120"
- Description: The white rhinoceros (Ceratotherium simum) is threatened primarily due to continued poaching for its horns. In South Africa, partly to promote the conservation of the species, white rhinos have been introduced into areas where they did not occur historically (i.e. where they are considered extralimital). Few studies have investigated the conservation contribution of extralimital white rhinos to the overall national herd. We aimed to determine whether the white rhinos introduced to a private game reserve in the Eastern Cape province have been successful from a reproductive perspective. We calculated inter-calving intervals, age at first calving, sex ratios of calves, and recruitment rates for white rhinos at a single site between 1992 and 2019. The average net annual population growth rate for the population was 10%, which is higher than the recommended 5% by the Biodiversity Management Plan for white rhinos. Trends in density-dependent parameters such as age at first calving and inter-calving intervals also indicated that the study population is still well below the density at which ecological constraints may manifest. We demonstrate that an extralimital white rhino population in the Eastern Cape can be successful from a reproductive perspective.
- Full Text:
- Date Issued: 2022
Goat browsing does not induce physical defences but reduces leaf size in Vachellia trees
- Nzimande, Amanda, Mgqatsa, Nokubonga, Kraai, Unathi M, Tsvuura, Zivanai, Kraai, Manqhai
- Authors: Nzimande, Amanda , Mgqatsa, Nokubonga , Kraai, Unathi M , Tsvuura, Zivanai , Kraai, Manqhai
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/462624 , vital:76320 , xlink:href="https://doi.org/10.1016/j.actao.2022.103818"
- Description: One aspect of plant-herbivore interactions in African savannas is the browsing impact of mammalian herbivores on plants, which may result in induced physical defences (spines) and changes in leaf morphology in trees experiencing intensive browsing. In these savannas, spinescence is considered to have evolved in response to herbivore pressure from large mammals. We assessed the impact of free-ranging domesticated goats on the spines and leaves of Vachellia karroo, V. nilotica and V. tortilis in Msinga, South Africa. We predicted that there would be fewer and smaller leaves, and longer spines occurring below compared to above 1.5 m for all tree species. We further predicted that the outer parts of the tree canopy would have smaller and fewer leaves, as well as more and longer spines compared to the inner part of the canopy. To determine the response of these trees to goat herbivory, 35 trees of each Vachellia species were selected, the number of leaves and spines found on two randomly selected branches below 1.5 m and one above 1.5 m were measured. We found that leaves were fewer and smaller below compared to above 1.5 m. Interestingly, we found the reduced leaf size to be equal to the size of spines below 1.5 m. We also found that V. karroo had more spines below 1.5 m compared to V. tortilis and V. nilotica. Along the branch segments, we found that spines were longer in the most accessible parts of the branch, the outer canopy. This study showed that browsing by goats, unlike wild herbivores, do not induce plant physical defences but rather limit available foliage. We also showed that physical defences (spine density) of Vachellia trees vary. This has implications for management and ecology of rangelands browsed by domestic mammals.
- Full Text:
- Date Issued: 2022
- Authors: Nzimande, Amanda , Mgqatsa, Nokubonga , Kraai, Unathi M , Tsvuura, Zivanai , Kraai, Manqhai
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/462624 , vital:76320 , xlink:href="https://doi.org/10.1016/j.actao.2022.103818"
- Description: One aspect of plant-herbivore interactions in African savannas is the browsing impact of mammalian herbivores on plants, which may result in induced physical defences (spines) and changes in leaf morphology in trees experiencing intensive browsing. In these savannas, spinescence is considered to have evolved in response to herbivore pressure from large mammals. We assessed the impact of free-ranging domesticated goats on the spines and leaves of Vachellia karroo, V. nilotica and V. tortilis in Msinga, South Africa. We predicted that there would be fewer and smaller leaves, and longer spines occurring below compared to above 1.5 m for all tree species. We further predicted that the outer parts of the tree canopy would have smaller and fewer leaves, as well as more and longer spines compared to the inner part of the canopy. To determine the response of these trees to goat herbivory, 35 trees of each Vachellia species were selected, the number of leaves and spines found on two randomly selected branches below 1.5 m and one above 1.5 m were measured. We found that leaves were fewer and smaller below compared to above 1.5 m. Interestingly, we found the reduced leaf size to be equal to the size of spines below 1.5 m. We also found that V. karroo had more spines below 1.5 m compared to V. tortilis and V. nilotica. Along the branch segments, we found that spines were longer in the most accessible parts of the branch, the outer canopy. This study showed that browsing by goats, unlike wild herbivores, do not induce plant physical defences but rather limit available foliage. We also showed that physical defences (spine density) of Vachellia trees vary. This has implications for management and ecology of rangelands browsed by domestic mammals.
- Full Text:
- Date Issued: 2022
Varying degrees of spatio-temporal partitioning among large carnivores in a fenced reserve, South Africa
- Evers, Emma E M, Pretorius, Mariëtte E, Venter, Jan A, Honiball, Terry-Lee, Keith, Mark, Mgqatsa, Nokubonga, Somers, Michael J
- Authors: Evers, Emma E M , Pretorius, Mariëtte E , Venter, Jan A , Honiball, Terry-Lee , Keith, Mark , Mgqatsa, Nokubonga , Somers, Michael J
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/462779 , vital:76334 , xlink:href="https://doi.org/10.1071/WR21045"
- Description: Context The spatio-temporal partitioning of large carnivores is influenced by interspecific competition and coexistence within small, enclosed reserves. Lions (Panthera leo), spotted hyaenas (Crocuta crocuta) and leopards (Panthera pardus) are the three largest African carnivores and have the greatest potential for intra-guild competition, particularly where space is limited.Aim To investigate the spatio-temporal partitioning between lions, spotted hyaenas and leopards in a small (~75 000 ha), enclosed nature reserve, Madikwe Game Reserve (Madikwe), South Africa.Methods We deployed 110 camera traps (baited n = 55 and unbaited n = 55) across Madikwe from 26 August 2019 until 6 May 2020. Von Mises kernel density plots were used to investigate daily temporal partitioning among the three species. A multiple-species, single-season occupancy model was used to investigate daily space use patterns.Key results We found both temporal and spatial exclusion between lions and spotted hyaenas on Madikwe. However, no evidence was found of spatio-temporal partitioning between lions and leopards, and spotted hyaenas and leopards.Conclusions Exploitative and interference competition on Madikwe might be high enough to warrant spatio-temporal partitioning between lions and spotted hyaenas to avoid the negative effects of intra-guild competition. Contrastingly, patterns observed between leopards and both lions and spotted hyaenas preclude the possibility of top-down control by superior carnivores.Implication These findings call for an adaptive management approach, where both carnivore and prey species compositions are constantly monitored. Management strategies such as these will allow for the conservation of valuable resources (i.e. prey species) to ensure the persistence of large carnivore populations across African ecosystems.
- Full Text:
- Date Issued: 2022
- Authors: Evers, Emma E M , Pretorius, Mariëtte E , Venter, Jan A , Honiball, Terry-Lee , Keith, Mark , Mgqatsa, Nokubonga , Somers, Michael J
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/462779 , vital:76334 , xlink:href="https://doi.org/10.1071/WR21045"
- Description: Context The spatio-temporal partitioning of large carnivores is influenced by interspecific competition and coexistence within small, enclosed reserves. Lions (Panthera leo), spotted hyaenas (Crocuta crocuta) and leopards (Panthera pardus) are the three largest African carnivores and have the greatest potential for intra-guild competition, particularly where space is limited.Aim To investigate the spatio-temporal partitioning between lions, spotted hyaenas and leopards in a small (~75 000 ha), enclosed nature reserve, Madikwe Game Reserve (Madikwe), South Africa.Methods We deployed 110 camera traps (baited n = 55 and unbaited n = 55) across Madikwe from 26 August 2019 until 6 May 2020. Von Mises kernel density plots were used to investigate daily temporal partitioning among the three species. A multiple-species, single-season occupancy model was used to investigate daily space use patterns.Key results We found both temporal and spatial exclusion between lions and spotted hyaenas on Madikwe. However, no evidence was found of spatio-temporal partitioning between lions and leopards, and spotted hyaenas and leopards.Conclusions Exploitative and interference competition on Madikwe might be high enough to warrant spatio-temporal partitioning between lions and spotted hyaenas to avoid the negative effects of intra-guild competition. Contrastingly, patterns observed between leopards and both lions and spotted hyaenas preclude the possibility of top-down control by superior carnivores.Implication These findings call for an adaptive management approach, where both carnivore and prey species compositions are constantly monitored. Management strategies such as these will allow for the conservation of valuable resources (i.e. prey species) to ensure the persistence of large carnivore populations across African ecosystems.
- Full Text:
- Date Issued: 2022
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