Population ecology of Indo-Pacific bottlenose dolphins along the south-east coast of South Africa

In this study, the genetic population structure of the Indo-Pacific bottlenose dolphin (Tursiops aduncus) was assessed across the Agulhas and Natal Bioregions of South Africa. At the same time, the abundance, distribution and habitat use of T. aduncus was investigated using boat-based surveys along 145 km of coastline from Goukamma Marine Protected Area (MPA) to Tsitsikamma MPA along the south-east coast of South Africa (Agulhas Bioregion). Tursiops aduncus habitat preferences were assessed based on locations of sightings and recorded behaviour, and compared with those of the sympatric Indian Ocean humpback dolphins (Sousa plumbea). Strong patterns of differentiation between two sub-populations of T. aduncus were identified using double digest Restriction Site Associated DNA sequencing (ddRADseq). Pairwise FST were significant (p < 0.05) between individuals from the Agulhas and Natal Bioregions and yielded values of 0.033 for all the loci. Resource requirements, specialization and differences in habitat use possibly provided sufficient isolation allowing differentiation between sub-populations of the two ecologically distinct bioregions, despite the lack of any prominent boundary to gene flow. The two identified sub-populations should each be managed as a distinct conservation unit. The abundance estimate of T. aduncus for the study area according to an open population model (POPAN) was 2,295 individuals (95% CI: 1,157 - 4,553). Although closed models were considered inappropriate, such a model was applied for the Plettenberg Bay part of the study area in isolation, to allow for comparison with a previous estimate. The comparison showed a 72.3% decrease in abundance between the two periods: from 6,997 (95% CI: 5,230 - 9,492) in 2002 - 2003 to 1,940 (95% CI: 1,448 - 2,600) in 2014 - 2016. The mean group size also declined from 120 (range: 1 - 500) to 26 (range: 1 - 100). The results highlight the importance of assessing abundance changes at other sites to inform the revision of T. aduncus conservation status in South Africa. Tursiops aduncus were encountered throughout the area. The lowest encounter rate was along rocky and exposed shorelines. These areas were, however, associated with relatively larger group sizes and greater likelihood of travelling behaviour, whereas sandy bottomed areas, where encounter rates were highest (e.g. parts of Plettenberg Bay and the Goukamma MPA), were more likely to be associated with other behaviours (e.g. foraging, socialising). There was a relatively low association of encounters with MPAs, possibly due to the fact that two of the three MPAs in the area (Tsitsikamma and Robberg) were characterised by non-preferred habitat, namely rocky shorelines. Comparison with Sousa plumbea showed similarity in habitat preferences between the species, though S. plumbea also showed an affinity for estuarine habitats. Two areas that were highly utilised by both species were located along Goukamma MPA and the north-east section in Plettenberg Bay including the Keurbooms Estuary. The latter is unprotected and a management measure could be to create a controlled-use zone to reduce disturbance to dolphins there

Abundance of Indo-Pacific bottlenose dolphins (Tursiops aduncus) along the south coast of South Africa

Coastally distributed dolphin species are vulnerable to a variety of anthropogenic pressures, yet a lack of abundance data often prevents data-driven conservation management strategies from being implemented. We investigated the abundance of Indo-Pacific bottlenose dolphins (Tursiops aduncus) along the south coast of South Africa, from the Goukamma Marine Protected Area (MPA) to the Tsitsikamma MPA, between 2014 and 2016. During this period, 662.3h of boat-based photo-identification survey effort was carried out during 189 surveys. The sighting histories of 817 identified individuals were used to estimate abundance using capture-recapture modelling. Using open population (POPAN) models, we estimated that 2,155 individuals (95% CI: 1,873–2,479) occurred in the study area, although many individuals appeared to be transients. We recorded smaller group sizes and an apparent decline in abundance in a subset of the study area (Plettenberg Bay) compared to estimates obtained in 2002–2003 at this location. We recorded declines of more than 70% in both abundance and group size for a subset of the study area (Plettenberg Bay), in relation to estimates obtained in 2002–2003 at this location. We discuss plausible hypotheses for causes of the declines, including anthropogenic pressure, ecosystem change, and methodological inconsistencies. Our study highlights the importance of assessing trends in abundance at other locations to inform data-driven conservation management strategies of T. aduncus in South Africa.Supporting information: Fig S1. Survey tracks along the study area. Table S1. Search effort per section of the study area, year and season. Table S2. Model selection and abundance estimates for T. aduncus obtained from POPAN open population Jolly-Seber models.http://www.plosone.orgpm2020Mammal Research InstituteZoology and Entomolog

Rostrum abnormalities in the endangered Indian Ocean humpback dolphin (Sousa plumbea) in South Africa

SUPPORTING INFORMATION : Appendix 1. Photographs of the abnormal rostrum conditions characterized in this study with corresponding ID number (if available), locality, time, and credits.Morphological abnormalities in wild animals can be indicators of the underlying health of a population and may be determined through routine photographic surveys. Here, we assess unusual rostrum conditions in Indian Ocean humpback dolphins (Sousa plumbea) inhabiting South African coastal waters to understand the rate of prevalence of abnormal rostrums and formulate hypotheses on potential causes. Photographic data were collated from systematic boat surveys and opportunistic sightings, obtained between April 1998 and March 2021 in various regions along the South African coast. Overall, 31 unique individuals were found with abnormal rostrum conditions, varying from slight misalignments to severe wounds and/or aberrant morphologies. In most cases, injuries were likely caused by natural events during the animal's life history such as interactions with sharks and/or reef-associated hunting strategies. Mark–recapture data indicated that individuals had survived with these injuries for up to 10 years. This study reports the highest incidence of rostrum abnormalities in the species. As numbers reflect only those that have survived their injuries, they are considered a minimum estimate. A better understanding of the cause(s) of these injuries is important given the endangered status of this species.National Research Foundation; The Rufford Foundation; The Society for Marine Mammalogy.https://onlinelibrary.wiley.com/journal/17494877hj2023Mammal Research InstituteZoology and Entomolog

Indian Ocean humpback dolphin (Sousa plumbea) movement patterns along the South African coast

1. The Indian Ocean humpback dolphin was recently uplisted to ‘Endangered’ in the recent South African National Red List assessment. Abundance estimates are available from a number of localized study sites, but knowledge of movement patterns and population linkage between these sites is poor. A national research collaboration, the SouSA project, was established in 2016 to address this key knowledge gap. Twenty identification catalogues collected between 2000 and 2016 in 13 different locations were collated and compared. 2. Photographs of 526 humpback dolphins (all catalogues and photos) were reduced to 337 individuals from 12 locations after data selection. Of these, 90 matches were found for 61 individuals over multiple sites, resulting in 247 uniquely, well‐marked humpback dolphins identified in South Africa. 3. Movements were observed along most of the coastline studied. Ranging distances had a median value of 120 km and varied from 30 km up to 500 km. Long‐term site fidelity was also evident in the data. Dolphins ranging along the south coast of South Africa seem to form one single population at the western end of the species' global range. 4. Current available photo‐identification data suggested national abundance may be well below previous estimates of 1000 individuals, with numbers possibly closer to 500. Bearing in mind the poor conservation status of the species in the country, the development of a national Biodiversity Management Plan aimed at ensuring the long‐term survival of the species in South Africa is strongly recommended. At the same time, increased research efforts are essential, particularly to allow for an in‐depth assessment of population numbers and drivers of changes therein. 5. The present study clearly indicates the importance of scientific collaboration when investigating highly mobile and endangered species.This collaborative research project was funded by the South African Network for Coastal and Oceanic Research (SANCOR), the National Research Foundation (NRF), and the University of Pretoria.http://wileyonlinelibrary.com/journal/aqc2019-02-01hj2018Mammal Research Institut

Abundance of Indo-Pacific bottlenose dolphins (Tursiops aduncus) along the south coast of South Africa.

Coastally distributed dolphin species are vulnerable to a variety of anthropogenic pressures, yet a lack of abundance data often prevents data-driven conservation management strategies from being implemented. We investigated the abundance of Indo-Pacific bottlenose dolphins (Tursiops aduncus) along the south coast of South Africa, from the Goukamma Marine Protected Area (MPA) to the Tsitsikamma MPA, between 2014 and 2016. During this period, 662.3h of boat-based photo-identification survey effort was carried out during 189 surveys. The sighting histories of 817 identified individuals were used to estimate abundance using capture-recapture modelling. Using open population (POPAN) models, we estimated that 2,155 individuals (95% CI: 1,873-2,479) occurred in the study area, although many individuals appeared to be transients. We recorded smaller group sizes and an apparent decline in abundance in a subset of the study area (Plettenberg Bay) compared to estimates obtained in 2002-2003 at this location. We recorded declines of more than 70% in both abundance and group size for a subset of the study area (Plettenberg Bay), in relation to estimates obtained in 2002-2003 at this location. We discuss plausible hypotheses for causes of the declines, including anthropogenic pressure, ecosystem change, and methodological inconsistencies. Our study highlights the importance of assessing trends in abundance at other locations to inform data-driven conservation management strategies of T. aduncus in South Africa

Population structure associated with bioregion and seasonal prey distribution for Indo‐Pacific bottlenose dolphins (Tursiops aduncus) in South Africa

Many marine species exhibit fine-scale population structure despite high mobility and a lack of physical barriers to dispersal, but the evolutionary drivers of differentiation in these systems are generally poorly understood. Here we investigate the potential role of habitat transitions and seasonal prey distributions on the evolution of population structure in the Indo-Pacific bottlenose dolphin, Tursiops aduncus, off South Africa's coast, using double-digest restriction-site associated DNA sequencing. Population structure was identified between the eastern and southern coasts and correlated with the habitat transition between the temperate Agulhas (southern) and subtropical Natal (eastern) Bioregions, suggesting differentiation driven by resource specializations. Differentiation along the Natal coast was comparatively weak, but was evident in some analyses and varied depending on whether the samples were collected during or outside the seasonal sardine (Sardinops sagax) run. This local abundance of prey could influence the ranging patterns and apparent genetic structure of T. aduncus. These findings have significant and transferable management implications, most importantly in terms of differentiating populations inhabiting distinct bioregions and seasonal structural patterns within a region associated with the movement of prey resources

Science alone won’t do it! South Africa’s endangered humpback dolphins Sousa plumbea face complex conservation challenges

The Indian Ocean humpback dolphin (Sousa plumbea) is “endangered” with likely less than 500 animals remaining in South African waters. Established in 2016, the SouSA Consortium is a formalised network of scientists and conservationists to combine knowledge and research efforts, and make coordinated decisions with the aim of conserving the species. The first collaborative project collated available photoidentification data in an attempt to refine a national population estimate and investigate movements between research sites. This work was able to identify 250 uniquely marked individuals, with the population divided into the south-coast (Agulhas bioregion) and east-coast (Natal bioregion) populations. Environmental factors almost certainly play a role in the declining numbers of the species in South African waters. However, individual threats and solutions are challenging to identify as the South African marine environment is undergoing significant natural and anthropogenic changes with major shifts in the distribution and numbers of some prey, competitor and predator species. Therefore, we believe that a continued investigation of potential contributing factors and their interaction will take too long, inevitably resulting in another case of documenting extinction. With this in mind, we present the results of a SWOT (Strengths, Weaknesses, Opportunities, and Threats) analysis in an effort to help us identify the next steps to take toward the conservation of humpback dolphins in South African waters. We unanimously conclude that no single cause for the rapid decline of humpback dolphins Frontiers in in South African waters can be identified, and that the cumulative effects of multiple stressors, which are difficult to pinpoint and mitigate, are impacting population numbers. While highlighting the need for continued research, we suggest a shift toward more action-focused conservation efforts, the first concrete steps being the development of a Conservation Management Plan with input from other stakeholders.Gesellschaft zur Rettung der Delphine, the Western Indian Ocean Marine Science Association (WIOMSA), a University of Stellenbosch Sub Committee B Postdoctoral Fellowship and the Marine and Coastal grant of the National Research Foundation (NRF).https://www.frontiersin.org/journals/marine-science#am2022Mammal Research Institut

Investigación, reflexión y acción de la realidad socio-educativa a principios del siglo XXI : vol. III

Consciente de la importancia de la investigación educativa para promover las transformaciones que permitan ofrecer a la sociedad nacional e internacional una educación pertinente y relevante que al mismo tiempo, contribuya con el desarrollo humano, en febrero del 2011 y en el marco de la celebración del 30 aniversario de su fundación, el Instituto de Investigación en Educación (INIE) organiza el II Congreso Internacional de Investigación Educativa: Su Incidencia en la Realidad Social. Los aportes presentados durante este II Congreso Internacional de Investigación Educativa, se han recopilado en la publicación del libro digital: Investigación, reflexión y acción de la realidad socio-educativa a principios del siglo XXI. Estos trabajos tienen por objetivo ofrecer propuestas para repensar la educación y los procesos educativos que se desarrollan en las aulas, así como valorar la importancia de realizar las transformaciones que se requieren a partir de los resultados de las investigaciones

Humpback whale “super-groups” – A novel low-latitude feeding behaviour of Southern Hemisphere humpback whales (Megaptera novaeangliae) in the Benguela Upwelling System

ArticleSouthern Hemisphere humpback whales (Megaptera novaeangliae) generally undertake annual migrations from polar summer feeding grounds to winter calving and nursery grounds in subtropical and tropical coastal waters. Evidence for such migrations arises from seasonality of historic whaling catches by latitude, Discovery and natural mark returns, and results of satellite tagging studies. Feeding is generally believed to be limited to the southern polar region, where Antarctic krill (Euphausia superba) has been identified as the primary prey item. Non-migrations and / or suspended migrations to the polar feeding grounds have previously been reported from a summer presence of whales in the Benguela System, where feeding on euphausiids (E. lucens), hyperiid amphipods (Themisto gaudichaudii), mantis shrimp (Pterygosquilla armata capensis) and clupeid fish has been described. Three recent research cruises (in October/November 2011, October/November 2014 and October/November 2015) identified large tightly-spaced groups (20 to 200 individuals) of feeding humpback whales aggregated over at least a one-month period across a 220 nautical mile region of the southern Benguela System. Feeding behaviour was identified by lunges, strong milling and repetitive and consecutive diving behaviours, associated bird and seal feeding, defecations and the pungent “fishy” smell of whale blows. Although no dedicated prey sampling could be carried out within the tightly spaced feeding aggregations, observations of E. lucens in the region of groups and the full stomach contents of mantis shrimp from both a co-occurring predatory fish species (Thyrsites atun) and one entangled humpback whale mortality suggest these may be the primary prey items of at least some of the feeding aggregations. Reasons for this recent novel behaviour pattern remain speculative, but may relate to increasing summer humpback whale abundance in the region. These novel, predictable, inter-annual, low latitude feeding events provide considerable potential for further investigation of Southern Hemisphere humpback feeding behaviours in these relatively accessible low-latitude waters