Browsing by Author "Underhill, Leslie"
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- ItemOpen AccessA contribution to understanding the primary moult of birds(2023) Scott, Tanya; Underhill, Leslie; Erni BirgitMoult is an essential component of the annual cycle of birds, along with breeding, and, if migratory, migration. The leading statistical model for the analysis of primary moult is the Underhill-Zucchini moult model. It estimates moult parameters (duration, the mean start date and its standard deviation). An objective of this thesis was to assemble all published results which had used the UnderhillZucchini moult and to examine the resulting database for patterns in the timing, duration and synchronisation of moult. A total of 242 analyses of 136 species were found. The initial analysis of the database generated two observations: firstly, that latitude played an important role in determining patterns of primary moult, and, secondly, that the available data were latitudinally, spatially across continents, and taxonomically not representative. These gaps in knowledge were too large to rectify within the confines of a single PhD thesis. The preliminary chapters of the thesis added 18 analyses, for 11 species, and have made a contribution towards representativity. Two of the preliminary chapters make substantive contributions to the methods of undertaking statistical studies of moult. A new moult index, the Relative Duration Index, is introduced. Moult studies are frequently undertaken by combining datasets collected in different years (or different places). This thesis contains the first practical application of a proposed method to identify which of the individual datasets have a large influence of the estimates of the moult parameters. Nine analyses extended the latitudinal range of studies southwards and were based on datasets assembled in New Zealand. These are the first analyses of primary moult using the UnderhillZucchini moult model from this country. For seven species, this thesis undertakes moult studies of a species in both its original country, the United Kingdom, and the country into which it had been introduced, New Zealand. These are the first analyses of primary moult of this kind. Preliminary patterns of moult strategies are discussed. Critical gaps in our understanding of primary moult are identified. Priorities for fieldwork and analysis are described in order that key gaps are filled and a global review of primary moult can be undertaken.
- ItemOpen AccessApplication of a multi-method approach to the stock identification and discrimination of kingklip, Genypterus capensis (Smith, 1847), off the South African coast(2024) Mobara, Ayesha; Underhill, LeslieKingklip, Genypterus capensis, is a marine demersal fish distributed in shelf and slope waters of southern Africa, from Walvis Bay in Namibia to Algoa Bay in South Africa. This commercially important species is caught by demersal trawling and longlines. Whereas previous analyses of population structure in kingklip gave contrasting results, the most recent genetic and genomic analyses have indicated population structure in this species with three genomic clusters observed: one off the central Namibian coast, one off the southern Namibian coast and the South African West Coast, and one off the South African South Coast. The identification and delineation of sub-populations is necessary for effective management of exploited species, and determination of the stock identity of individual fish is most effectively and cheaply done using phenotypic characteristics. To assess whether the two genomically-differentiated stocks off South Africa are phenotypically differentiated, a holistic and integrated multi-method approach that analysed morphological (body and otolith), meristic, otolith elemental composition, and parasitological data of kingklip from the West and South Coast was applied. Nine body morphological (standardised for fish size) and three meristic variables were analysed. For both univariate and multivariate analysis, no significant differences between mature Genypterus capensis from the West and South coasts were observed in any of the 12 characteristics. For immature specimens, significant differences between regions were observed in four morphological (upper jaw, lower jaw, orbital diameter, and interorbital diameter), but not in any meristic characteristics. Univariate and multivariate analyses indicated that four (rectangularity, roundness, ellipticity, and aspect ratio) of the six otolith shape indices calculated showed significant spatial differences in mature specimens. In immature specimens, circularity, form factor, ellipticity, and aspect ratio, showed significant differences when using multivariate analysis, and roundness was also significantly different between regions when using univariate analysis. Elliptical Fourier Analysis of otolith shape was applied utilising 157 harmonics, of which seven in mature specimens, and nine in immature specimens were significantly different between regions. Seventeen elements were measured in kingklip otoliths and of these barium, phosphorus, and nickel showed significant differences between regions in immature but no differences were observed in mature fish. Regional differences in four kingklip parasites (Anisakis sp., Diphyllobothrium sp., Lecithochirium sp., Tentacularia sp.) previously identified as potential biotags were assessed, with univariate analysis indicating a significant difference for Tentacularia sp. for both mature and immature specimens. A Stock Differentiation Index (SDI) indicated weak (SDI = 0.26) spatial structure for mature, and a moderate (SDI = 0.33) spatial structure for immature Genypterus capensis in South African waters. These results indicate that the genomic differentiation of G. capensis off the South African coast does not translate into substantial and spatially differentiated phenotypic variation in mature specimens, however moderate stock delineation is observed in immature samples. This suggests that mixing between the two genomically-differentiated kingklip stocks is lowest for juvenile fish and increases with age, which accords with the hypothesis of separated and localised spawning locations for these two stocks off the West and South coasts of South Africa. That otolith shape indices had the strongest discriminatory power of the characteristics examined in this study suggests that analyses of otolith shape at an early stage inferred via measurement of the shape of the first otolith annulus (laid down when fish are 1-year old) may be a useful phenotypic characteristic for stock identity determination, and further research should be conducted in this regard.
- ItemOpen AccessAssessing conservation measures for five Southern African endemic shark species(2024) Cottrant, Emy; Underhill, Leslie; McCord, MeaghenThe South African coast has one of the greatest diversity of Chondrichthyan species in the world with more than 190 species recorded, including 111 species of sharks. Many of these species are endemic to southern Africa (defined as the coastlines of Namibia, South Africa and Mozambique) but are poorly studied, despite their classifications of concern according to the International Union for the Conservation of Nature (IUCN) Red List. However, South Africa continues its efforts to protect the marine environment with a network of 42 Marine Protected Areas established; the Second National Plan for the Protection of Sharks was published in 2022. Sharks, which are characterized by slow growth and maturity at an advanced age, have undergone a rapid decrease in population sizes due to overfishing and habitat loss since the 1970s. To help fill the knowledge gap on endemic shark species, I used long-term datasets to study movement ecology and behaviour in marine protected areas. Study species are dark shyshark Haploblapharus pictus, puffadder shyshark Haploblepharus edwardsii, pyjama shark Poroderma africanum, leopard catshark Poroderma pantherinum and spotted gully shark Triakis megalopterus. Datasets were composed of non-lethal sampling comprised of mark-recapture, baited remote underwater videos (BRUVs) and acoustic telemetry. Results are then used to assess current protection status of those species and give advice to adapt management policies. The analysis of capture-recapture data made it possible to determine the distribution areas of each species in the study area as well as the differences in the size and location of these areas between different sexes and maturities. The efficacy of an MPA was discussed for the protection of those species, especially relevant for the puffadder shyshark, classified as “Endangered” on the IUCN Red List. Furthermore, a comparison between growth rate of wild and captive pyjama sharks helped assessing if captive data can be transposed to wild population in order to study endangered species. Study of the movements of T. megalopterus along the coasts of the Western Cape revealed that this species does not specifically use marine protected areas, regardless of sex or sexual maturity. This characteristic suggests that in the future, if the population declines, which is a potential consequence of being caught as bycatch in longline fisheries, it would be difficult for this population to recover. We also attempted to classify the different areas used by spotted gully sharks in order to identified priority areas for conservation such as nursery areas. The analysis of the BRUVs revealed that the classic analysis techniques were sometimes not adequate to study the relationships between species. The majority of published analyzes are based on MaxN, an estimate of the abundance of each species, often to estimate the effectiveness of marine protected areas and sometimes by extrapolating on the relationships between species within the food chain. During this project, we tested a new alternative metric (visual co-occurrence) that could be included in future analyzes of this type of video, the goal being to obtain a more refined view of reality and potentially increase knowledge about the role that a specific species plays within the ecosystem. Overall, the combination of the databases analysed during this project made it possible to increase knowledge on five endemic species of South Africa and southern Africa, specifically on their movement and differences between sexes in habitat use. The protection measures in place remain effective in maintaining these populations but, like H. edwardsii, do not allow these species to grow in abundance and thus change their IUCN status. In addition, a potential future decline for these populations due to global warming or anthropogenic impact, causing habitat loss, could be fatal for these species without specific protection measures for each species. Since 2022, several projects aim to increase the area of coastal zone covered by marine protected areas in South Africa, so the results of this study have a direct impact on future conservation and management measures for these species.
- ItemOpen AccessMonkey beetles on the beat: urban monkey beetles reveal opportunities for pollinator habitat management in a South African city(2022) Brom, Peta; Underhill, Leslie; Winter, Kevin; Colville, JonathanAgainst a backdrop of global declines in pollinators, evidence suggests that some guilds thrive in urban landscapes and relatively small interventions can provide habitat support in otherwise inhospitable urban landscapes. Despite this knowledge, there is a paucity of research on urban pollinators in Africa. This gap is noteworthy because Africa is a megadiverse region and southern Africa has three global biodiversity hotspots. This thesis is a first step towards filling the Africa gap. Its ought to do so by investigating urban monkey beetles (Coleoptera: Scarabaeidae: Hopliini) in two ways. Firstly, it relates Hopliini community structure to urban environmental gradients and local habitat composition. This was achieved by using pan traps to sample pollinators at 145 sites during two austral spring seasons in greater Cape Town in 2018 and 2019. The findings are that there were three divergent responses to urban landscape dynamics. 1) Those which exploited the urban environment. 2) Those which did not respond to an urban intensity gradient, but did respond to flower‐richness, 3) Those which preferred larger, less disturbed sites at the edge of the city. Secondly, ways that the management of Public Open Space (POS) and road verges can better support the connectivity of habitats containing endemic geophytes and spring annuals were considered. These flower populations provide breeding and foraging resources to Hopliini and other pollinators. They are an especially important resource to the group who are unable to move through or exploit the urban environment without them (Group 2 above). A mowing suspension was investigated to determine how long the indigenous spring show would take to complete the reproductive cycle and reach seed set. The study took a phenological approach to estimating the duration of the suspension. The findings indicate that mowing should be suspended for spring geophyte patches from the first week of August until after the first week of November. The charismatic Baeometra uniflora can be used as an indicator species for when the season has concluded. Methods of strategic landscaping and interplanting are discussed, noting that the peak flowering season in spring is followed by a lesser abundant summer show.
- ItemOpen AccessMoult strategies of oystercatchers (Haematopidae) in New Zealand, Australia and South Africa(2023) Bate, Taylyn; Underhill, Leslie; Ryan PeterWhile there are a number of studies that have examined the moult strategies of migrant waders (Charadrii), only a few have focused on non-migrant waders. As part of a collection of papers that have analysed moult using the Underhill-Zucchini moult model, we used this method to observe the moult strategies of species within the family Haematopidae. Our data includes a combination of previously acquired ringing data and that which we collected, along with contributions by citizen scientists, in the form of photographic records. The first chapter provides an introduction to the study, placing it within the context of comparable research, and placing moult within the context of the birds' important life stages. Our second chapter focuses on the Australian Pied Oystercatcher Haematopus longirostris, of which we completed a detailed analysis of the wing and feather moult. Within chapters 3-6 we examine the wing moult strategies of the Sooty Oystercatcher H. fuliginosus of Australia, the South Island Pied Oystercatcher H. finschi and Variable Oystercatcher H. unicolor of New Zealand, and the African Oystercatcher H. moquini of South Africa. With no long-distance movements, these oystercatchers are free to devote more time and energy towards other stages in their life cycle: breeding and moult. We identified the moult parameters of start date, standard deviation in start date, duration and end date for each of the five species. We acquired the relative feather masses and used these in the conversion of the moult scores to proportion feather mass grown (PFMG). The final chapter synthesizes the work, consisting of a comparison and identification of the similarities and differences between the species' moult strategies, and possible reasons for these. We approach the conclusion that further research is needed on the strategies of moult for resident waders, and this may be achieved successfully through the use of digital photography. With an expanding knowledge of the parameters of moult, there is opportunity for even more discoveries into these birds' lives, which will have benefits for their conservation.
- ItemRestrictedSurviving off junk: low-energy prey dominates the diet of African penguins Spheniscus demersus at Mercury Island Namibia between 1996 and 2009(2010) Ludynia, Katrin; Roux, J-P; Jones, R; Kemper, J; Underhill, LeslieThe diet of African penguins Spheniscus demersus in Namibia consisted mainly of sardine Sardinops sagax in the 1950s. Since the collapse of pelagic fish stocks in the 1970s, birds fed mainly on bearded (pelagic) goby Sufflogobius bibarbatus, a low-energy prey species. We present diet data for African penguins breeding at Mercury Island, the largest colony for this species in Namibia, between 1996 and 2009. Bearded goby was the main prey item throughout the study period, both in terms of frequency of occurrence (67.8%; SD 31.2) and in terms of mass (59.2%; SD 31.5). Diet composition varied throughout the year as well as between years; birds occasionally fed on a variety of fish species other than bearded goby. In Namibia, poor prey abundance is considered as a major factor contributing to the decline of penguin numbers after the collapse of the sardine stocks. However, bearded goby appears to be relatively abundant along Namibia's southern coast and low prey quality rather than low abundance appears to be a key factor influencing population dynamics of African penguins and other marine top predators in southern Namibia.
- ItemOpen AccessThe breeding ecology and behavioural adaptations of African black oystercatchers in light of climate change(2021) Azaki, Bukola Debola Aderewa; Underhill, Leslie; Cunningham, SusanThis thesis examined how weather conditions and other environmental factors influence the vulnerability of nesting African Black Oystercatchers Haematopus moquini (oystercatchers) to climate and habitat change. I explore, for the first time, the behavioural adaptations used by the species to cope with breeding in a limited strip of beach, between high tides and terrestrial predators, and with little nesting shelter, and their breeding decisions to maximise breeding outcomes. Behavioural and breeding data were collected over three breeding seasons (2016—2018) on Robben Island, South Africa (a site with about 5% of the global population of the species) using time-lapse digital cameras and direct observations. Climate and environmental variables were obtained either through on-site iButton data loggers or from the relevant South African meteorological agencies. The results show that oystercatchers are vulnerable to increasing heat loads as temperature increases. However, oystercatchers used a suite of thermoregulatory behaviours to cope with a wide range of environmental temperatures and decreased the length of their incubation bouts as temperature increased. The proximity of the oystercatchers' breeding site to the ocean appears to contribute significantly to their capacity to cope with increasing heat loads. But such sites potentially expose the oystercatchers to the risk of nest losses to storm surges. Oystercatchers reduced this risk by using habitat selection to optimise the placement of their nests close to the midpoint of the beach, but some were constrained by the narrowness of their territories. Oystercatchers also used the biweekly semilunar spring tide cycle to synchronise the incubation start date of their clutches probably to minimise the number of spring tides that they experience during incubation. Predation was the main cause of oystercatcher nest failure. Surprisingly, Mole Snakes Pseudaspis cana were responsible in all cases where the predator identity was known rather than Kelp Gulls which have historically been suggested to be the main agent. Nest predation probability was influenced by temperature and distance to predator-concealing vegetation and increased as more nests became available, causing a seasonal decline of nest survival. Hence, oystercatcher pairs laying large clutches early in the season were more likely to produce one juvenile in a season. The average number of fledgelings per pair per season was 0.38 and close to that (0.35) required to maintain a stable population. These findings improve our understanding of the breeding ecology and behavioural adaptations of the oystercatchers which might help them to cope with climate change as well as provide new insights on which management decisions and further studies can be based.