African Journal of Ecology最新文献

Bush encroachment is increasingly becoming a problem for biodiversity conservation in African savannas. While this invasion by woody vegetation may hamper avian scavengers such as vultures, which primarily search by sight, it may benefit mammalian scavengers that search by smell. This study aimed to examine the ability of nocturnal mammalian and diurnal avian scavengers to locate carcasses at increasing vegetation densities. We successively placed 27 impala (Aepyceros melampus) carcasses five days apart in a 2000 ha fenced game camp that offered an extensive range of woody plant densities. Scavenger arrivals and first feedings were recorded with camera traps. The avian scavengers, mainly white-backed Vultures (Gyps africanus), fed exclusively on carcasses during the day, and mammalian scavengers, predominantly brown hyenas (Parahyena brunnea), fed solely at night. The two guilds thus competed exploitatively without direct interaction between them. For vultures, the time taken to locate a carcass increased with woody plant density. The mean density of woody plants that avian scavengers located carcasses at was 2188 plants/ha, whereas mammalian scavengers located carcasses at appreciably higher densities of 5156 plants/ha. Resource managers need to understand the synergy between maintaining woody vegetation to benefit nocturnal mammalian scavengers and maintaining open savannas to benefit diurnal avian scavengers.

The Manyara tilapia (Oreochromis amphimelas), native to the Saline Rift Valley Lakes (SRVLs) in north-central Tanzania, has recently experienced population declines mainly due to overfishing and severe droughts. This, combined with the introduction of Nile tilapia (O. niloticus), which poses a risk of hybridisation, could potentially erode essential genetic traits necessary for their survival. To address these concerns, our study analysed partial cytochrome oxidase subunit I sequences (627 base pairs) from 139 Manyara tilapia and 79 Nile tilapia specimens collected from the SRVLs to test two hypotheses: (i) whether there is no transfer of mitochondrial DNA between these species, and (ii) whether Manyara tilapia populations in the SRVLs have remained genetically connected despite reported declines. The results revealed six distinct haplotypes for Manyara tilapia and three for Nile tilapia. These haplotypes formed separate clusters for each species, with no shared or closely related haplotypes, indicating limited or no transfer of mitochondrial DNA between them. Additionally, we found evidence of restricted genetic connectivity among Manyara tilapia populations in the SRVLs, with populations in Lakes Manyara and Eyasi displaying limited genetic exchange among themselves and with those in other SRVLs. Our findings highlight the importance of sustained conservation efforts in protected areas around Lake Manyara and Lake Eyasi to safeguard the unique populations of Manyara tilapia in these lakes. However, limited connectivity with other SRVLs suggests that conservation initiatives in these areas may have a limited impact on these lakes. Thus, future efforts should prioritise stocks in Lakes Kindai, Singida and Sulunga, focusing on protecting fish refugia, particularly the rivers connected to these lakes, which serve as critical habitats during the dry season and as important reservoirs for replenishing these populations.

Urban life is associated with dietary shifts in opportunistic predators, such as raptors. This is presumably true in food-poor environments, such as drylands. We investigated this issue in little owls (Athene noctua) inhabiting an arid southern Tunisian area. Using pellet data, we found that coleopterans accounted for 69% of ingested food items. Controlling for prey availability, this coleopteran-based diet was more notable in the urban environment compared to rural areas. We suggest that habitat conditions in the urban areas have increased the catchability of nocturnal coleopterans which were then more exposed to predation by little owls than in rural areas.

Ficus trees play an important role as key species in both ecological and sociocultural networks in Madagascar. This study focused on species of isolated Ficus growing in agricultural areas adjoining a forest corridor linking the Ranomafana and Andringitra National Parks in east-central Madagascar, with the aim of understanding the structural and floristic characteristics of the vegetation regenerating under these Ficus ‘trees outside forests’. Two main aspects were studied: (1) the characteristics of the habitats under the crown of isolated Ficus species (Ficus tiliifolia, Ficus reflexa and Ficus lutea), and (2) the specific structure and composition of the vegetation under these Ficus trees: minimum area, species richness, floristic regularity, diversity and similarity, biological type, vegetation type, proportion of annual and herbaceous species, and seed dispersal methods. The results indicate that each of these three Ficus species has its own community composition. The vegetation under F. reflexa is a shrubby formation dominated by autochorous and zoochorous species located on high slopes with a minimum area of 6–12 m². The vegetation under F. lutea is a highly anthropized herbaceous formation dominated by autochorous species located on high slopes at an altitude of 1150–1200 m, with a southwest exposure and a minimum area that ranges from 6 to 9 m². Under F. tiliifolia, different types of plant formations are found in different topographic positions: herbaceous, shrubby or tree-like, with different modes of seed dispersal.

Protection of nursery areas where newborn survival is successful is critical to recovery of endangered mammals. In Kenya, 2014 to 2022, we surveyed Endangered Masai giraffes (Giraffa camelopardalis tippelskirchi) on the Siria Plateau at Oloirien Group Ranch (OGR) and Oloisukut Conservancy (OC), and in the Rift Valley's Mara Triangle Conservancy (MTC). MTC and OC have high lion densities while OGR does not. Using counts and photographic mark-recapture (PMR), we estimated percentages of newborn (<3 months) and juvenile giraffe calves (<1 year) per adult female and per total giraffes sampled. Cormack-Jolly-Seber models were used to estimate annual survival of giraffes at OGR. The mean percentage of newborn calves: adult female at OGR (~18%) was significantly higher than at OC (3.3%) and MTC (0%). The mean juvenile: adult female percentage at the Siria Plateau sites was 62 ± 12.8% versus 12% in MTC. Total juvenile calves averaged 22% on the plateau, four times higher than MTC (5.3%). At OGR, giraffe survival for all ages and sexes was 0.86, higher than protected areas with lions. Only one female giraffe in 229 used both plateau sites, suggesting independent matrilines. Human-populated savannah next to reserves contributes to giraffe recovery, but nursery areas like OGR need robust protection.

The desert-adapted lions (Panthera leo) of northwest Namibia inhabit arid and semi-arid habitats, primarily within communal conservancy lands, which they share with semi-nomadic pastoralists. Though of considerable conservation interest, no systematic population survey of these lions has previously been attempted. From 6 November 2022 to 6 January 2023, 45 trained surveyors covered approximately 40,000 km² of conservancy and government-managed lands, identifying individual lions by vibrissae (whisker-spot) patterns and other demographic indicators. A systematic whole count, identifying every adult individual, was used to estimate population size. This approach drew upon the local ecological knowledge (LEK) of the Lion Rangers, community conservationists responsible for identifying and monitoring lions in their respective communal conservancies, as well as Regional Services staff of Namibia's Ministry of Environment, Forestry and Tourism (MEFT). The population is estimated between 57 and 60 individual adult lions and 14 cubs; this represents an inferred decrease of 46–60% over the past five years. At 0.11–0.12 lions/100 km², this is the lowest recorded density for a free-ranging, self-sustaining lion population in Africa. Thirty-six female and 21 male lions were found during the survey, yielding a sex ratio of 1 ♀: 0.58 ♂. While the population is considered stable and self-sustaining despite recent declines, human-lion conflict (HLC) remains the primary cause of lion mortality and recent drops in available prey are also concerning. Results serve as a baseline for future surveys, which will be an important part of monitoring this relatively small, widely dispersed population.

Spotted hyaena distribution currently widely encompasses sub-Saharan Africa, apart from the Congo Basin. Formerly described as residents of Gabon but considered extinct, vagrant individuals have been recorded since 2003, but no systematic species presence assessment has been made. Based on records of killed individuals, tracks and camera-trap sightings, we show that not only vagrant individuals are roaming in Gabon, but a small resident population occurs in the North-East of the country. The records collated here formed the basis for spotted hyaenas to be listed as protected in Gabon, were included in the IUCN Red List species' range map update and showcased the importance of large-scale by-catch data analysis in updating species distributions.

The East African lowland honey bee (Apis mellifera scutellata) is reported as an aggressive subspecies of the Western honey bee, but few studies have investigated the impact of its aggressiveness on other insect pollinators. Observations of flower visitors to Vachellia (Acacia) etbaica and interactions between honey bees and other insects were conducted in 2022 in Mpala, Kenya. A total of 873 individual flower visitors were recorded, the most frequent being Hymenoptera, followed by Diptera and Lepidoptera. Honey bees dominated floral resources in the morning and late afternoon. When honey bees encountered other types of insects, they displaced the latter from flowers 100% of the time. This has never been observed in other Western honey bee subspecies, and we recommend further research on these taxa.

Urbanisation continues to increase at an alarming rate and its effects on the natural environment are very profound now more than ever. Moreover, studies on terrestrial urban landscapes seems to be more than that on urban freshwater habitats. Furthermore, studies have shown that the Odonata are effective indicators of the effects of urbanisation on freshwater habitats. However, not much is known about their responses to urbanisation in sub-Saharan Africa, especially given the unique set of conditions that characterise the area. Therefore, this study was conducted to investigate differences in Odonata responses, measured as the proportion of habitat generalists, to three levels of habitat disturbance in the Cape Coast Metropolis of Ghana. Results showed that Phaon camerunensis was a potential indicator of habitat disturbance. Also, differences in habitat disturbance significantly affected Odonata composition. The most important variables that influenced Odonata responses were the individual and interaction effects of altitude and preservation of riparian vegetation. Therefore, conservation strategies that are targeted at reducing the impacts of urbanisation on Odonata must focus on these variables.