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Keywords: cultural transmission; ecology of fear; human-wildlife conflict; livelihood impacts; predator-prey interactions EN cultural transmission ecology of fear human-wildlife conflict livelihood impacts predator-prey interactions 1 5 5 01/04/23 20230101 NES 230101 Killer whales ( I Orcinus orca i ) and white sharks ( I Carcharodon carcharias i ) are marine apex predators that shape prey behavior and even entire ecosystems through direct predation effects and indirect fear effects (e.g., Estes et al., [4]; Heithaus et al., [5]). " Predation on a White Shark (Carcharodon carcharias) by a Killer Whale (Orcinus orca) and a Possible Case of Competitive Displacement." Given the well-documented, predictable year-round presence of white sharks in Mossel Bay (Jewell et al., [7]; Ryklief et al., [13]), the sudden absence of white sharks for several weeks immediately after the predation event supports a flight response by surviving white sharks in the area. [Extracted from the article]

Abstract: 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. 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. 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. 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. The present study clearly indicates the importance of scientific collaboration when investigating highly mobile and endangered species. [ABSTRACT FROM AUTHOR]

The distribution, movements and abundance of highly mobile marine species such as bottlenose dolphins Tursiops truncatus are best studied at large spatial scales, but previous research effort has generally been focused on relatively small areas, occupied by populations with high site fidelity., We aimed to characterize the distribution, movements and abundance of bottlenose dolphins around the coasts of Scotland, exploring how data from multiple sources could be integrated to build a broader-scale picture of their ecology., We reviewed existing historical data, integrated data from ongoing studies and developed new collaborative studies to describe distribution patterns. We adopted a Bayesian multi-site mark-recapture model to estimate abundance of bottlenose dolphins throughout Scottish coastal waters and quantified movements of individuals between study areas., The majority of sightings of bottlenose dolphins around the Scottish coastline are concentrated on the east and west coasts, but records are rare before the 1990s. Dedicated photo-identification studies in 2006 and 2007 were used to estimate the size of two resident populations: one on the east coast from the Moray Firth to Fife, population estimate 195 [95% highest posterior density intervals ( HPDI): 162-253] and the second in the Hebrides, population estimate 45 (95% HPDI: 33-66). Interaction parameters demonstrated that the dolphins off the east coast of Scotland are highly mobile, whereas those off the west coast form two discrete communities., We provide the first comprehensive assessment of the abundance of bottlenose dolphins in the inshore waters of Scotland. The combination of dedicated photo-identification studies and opportunistic sightings suggest that a relatively small number of bottlenose dolphins (200-300 individuals) occur regularly in Scottish coastal waters. On both east and west coasts, re-sightings of identifiable individuals indicate that the animals have been using these coastal areas since studies began. [ABSTRACT FROM AUTHOR]

The sympatric Heaviside's (Cephalorhynchus heavisidii) and dusky dolphins (Lagenorhynchus obscurus) are poorly studied in South Africa and are potentially at risk from anthropogenic threats including fisheries bycatch. As part of a larger study, shore-based observations were made in a small bay (~1000 m wide) in the Western Cape, South Africa, during the summer months of 1999-2001 to gather data on their nearshore movements and behavior. Heaviside's dolphins exhibited a diurnal onshore-offshore migration and the sighting rate varied significantly with time of day and brightness of the moon, with numbers being markedly higher before 12:00 and nearer a full moon. These patterns were presumed to be linked to the vertical migration of their principal prey, juvenile hake Merluccius species and Heaviside's dolphins appeared to be resting and not feeding inshore during the day. Sightings of dusky dolphin showed no predictable variation with time of day but their numbers inshore were significantly lower when upwelllng conditions existed offshore. Larger groups of Heaviside's dolphins (especially groups of four) were more active (leaps, etc.) than smaller groups, but behaviour was not linked to environmental factors. The dissimilar responses to environmental conditions suggest that sympatry in these two species is mediated by niche as well as prey differentiation. [ABSTRACT FROM AUTHOR]

Heaviside's dolphins, Cephalorhynchus heavisidii, are endemic to southwestern Africa, where they are exposed to unknown levels of anthropogenic threats, including inshore set netting. Using photo-ID data collected over 3 yr on the west coast of South Africa, we calculated Chapman's-modified Petersen estimates of the number of distinctive individuals at three spatial scales. Sample sizes were small and recapture rates low resulting in high variance. Total population abundance was extrapolated from the proportion of well-marked animals in the population (14%–17%) with between-year estimates adjusted for mortality using data from Commerson's dolphin. The total population size was calculated as 527 animals (CV = 0.35, CI 272–1,020) in the 1999 study area (20 km of coastline, within season), 3,429 animals (CV = 0.36, CI 1,721–6,828) in the central study area (150 km of coastline, 3 yr), and 6,345 animals (CV = 0.26, CI 3,573–11,267) in the full study area (390 km of coastline, 2 yr). Dolphins fitted with satellite transmitters varied in their use of the inshore photographic study area from 39.5% to 94.7% of transmission days (38–51 total). Given the known or suspected biases in the data, these abundance estimates are likely to be biased downward. [ABSTRACT FROM AUTHOR]

Static acoustic monitoring is a cost-effective, low-effort means of gathering large datasets on echolocation click characteristics and habitat use by odontocetes. Heaviside's dolphins (Cephalorhynchus heavisidii) were monitored using an acoustic monitoring unit, the T-POD, in July 2008 at a site of known high abundance for this species in Walvis Bay, Namibia. The T-POD successfully detected clicks from Heaviside's dolphins, and these clicks were detected in the 120 to 140 kHz frequency range. A distinct diel pattern to the hourly mean inter-click interval was observed, with higher values during daylight hours than at night, suggesting that click trains are produced at faster rates at night time. There was no apparent diel pattern in the proportion of buzz trains produced, however. A diel pattern in click activity was observed, with many more detection-positive minutes per hour recorded between dusk and dawn, and vocalization activity dropping to low levels in the middle of the day. This corresponded with visual observations made on abundance of dolphins in the study area. These results suggest that Heaviside's dolphins use this site primarily during the night. Static acoustic monitoring proved to be an effective technique for monitoring patterns of habitat use by Heaviside's dolphins. [ABSTRACT FROM AUTHOR]