MSc Studies Projects
Completed MSc and BSC studies
Emily Griffiths, University of Wales, Bangor. 2009 Whistle repertoire analysis of the short-beaked common dolphin, Delphinus delphis, from the Celtic Deep and the Eastern Tropical Pacific Ocean
Abstract
Understanding the vocal repertoire of a cetacean species enables us to understand how they interpret their environment and their social interactions. The short-beaked common dolphin Delphinus delphis is one of the most widely distributed dolphins in the world. They emit narrow-band tonal whistles generally between 5-20 kHz, but can range from 1-50 kHz. Whistle characteristics from two geographically separate populations of D. delphis were analyzed and compared: British (from the Celtic Deep and English Channel) and Eastern Tropical Pacific (ETP) communities. The whistle parameters of both populations were measured, external confounding factors assessed to determine how they contributed to variation, and visual whistle contour classification was tested against a quantitative whistle contour classification. The frequencies emitted by British common dolphins were generally found to be more similar and significantly higher than those emitted by dolphins in the ETP (global R=0.043, p<0.001; χ2=44.654, df=1, p<0.001). The different populations also showed differences in their whistle contour composition (χ2=8.535, df=1, p=0.003). Spatial and temporal factors such as water column depth, time of day, year and encounter location were examined and their effects on the common dolphin repertoire were investigated. Encounter location, water column depth and time of day were all found to have a significant influence. The visual classification system used by Ansmann et al. (2007) and the quantitative contour similarity (CS) technique used by McCowan (1995) were both applied to classify whistle contours from the ETP. The CS technique provided a good description (proportions of ascending and descending) of whistle slope tendencies, but ultimately did not identify general or clear whistle contour categories. The different vocal repertoires of the two communities could be attributed to the nature of the different locations, environmental and anthropogenic situational factors. download thesis
Caroline Vestey, University College London. 2009. The influence of ecological factors on groups of bottlenose dolphins (Tursiops truncatus) Cardigan Bay, Wales.
Abstract
Despite being the most studied cetacean there are still many uncertainties concerning the bottlenose dolphin (Tursiops truncatus). Cardigan Bay, Wales has one of the two resident populations of bottlenose dolphins in the UK, the second being in the Moray Firth Scotland. Both populations are protected under European Special Areas of Conservation (SAC) legislation. Understanding why Cardigan Bay supports this population is essential in order to protect them.
The study examined the relationship between groups of bottlenose dolphins and their environment. The group sizes ranged from one to 46 but the majority of groups encountered were of five or less. There were seasonal fluctuations which correspond with an influx of migratory prey into Cardigan Bay. Statistical analysis revealed that of the ecological parameters tested; depth, distance to coast and distance to estuary were the most significant influences on the presence and distribution of groups of bottlenose dolphins in Cardigan Bay. All groups were distributed along the coast line with larger groups being found further into the bay. Calves were found closest to the coast and estuaries and in the shallowest depths, then newborns and juveniles were furthest away. Prey and protection are likely to be the common links and driving forces between these species-habitat relationships.
The study demonstrates that the bottlenose dolphins in all group sizes use the whole bay. This has implications for conservation and SAC protection which currently only extends to two designated areas within Cardigan Bay. A number of interrelated environmental factors were seen to effect the distributions of groups which suggest a multivariate ecosystem approach in required to ensure the health of the bottlenose dolphin population. Protection needs to be extended to the bottlenose dolphins’ prey and to Cardigan Bay in its entirety.
Sarah Baulch, University of York. 2007. Fine-scale spatio-temporal variation and habitat partitioning in bottlenose dolphins and harbour porpoises.
Abstract
Coastally distributed cetacean species face many threats from anthropogenic activities. However, owing to high temporal and spatial variability in the distribution of marine mammals, impacts can be difficult to detect, and long-term monitoring is required to detect changes in populations’ distributions and habitat use. Understanding of these spatio-temporal changes in distribution and abundance of marine mammals is essential for successful conservation and management, as it allows mitigation measures to be targeted to critical times and habitats. Fine-scale variation in the spatial and temporal distribution of bottlenose dolphins and harbour porpoises was examined in Cardigan Bay, West Wales, using acoustic monitoring.
Static omni-directional hydrophones, known as T-PODs, were deployed at ten sites within the bay, for two years, providing a continuous means of monitoring rates of occurrence of both species. Acoustic detections indicated large seasonal changes in the relative abundance of harbour porpoises and bottlenose dolphins in Cardigan Bay and revealed seasonal variation in habitat use within the bay. Both species exhibited consistent seasonal changes in distribution from one year to the next , but relatively little variation in presence between diel periods, though finer-scale temporal variation was evident. In addition, both species displayed fine-scale fluctuations in occurrence over the tidal cycle, consistent across sites, seasons and years. Variation in harbour porpoise and bottlenose dolphin presence over the tidal cycle was strongly negatively correlated. This, in conjunction with differences in seasonal presence, and low rates of co-occurrence despite inter-specific similarities in habitat preferences, provides evidence of fine-scale spatio-temporal habitat partitioning between harbour porpoises and bottlenose dolphins. This is, to our knowledge, some of the first evidence of habitat partitioning between these two species. Not only does this mean that the two species may require different management actions but is particularly interesting considering the marked increase in porpoise deaths as a result of bottlenose dolphin attacks in the last decade, which are suggestive of an increase in inter-specific competition, whether as a result of changes in abundance or distribution of bottlenose dolphins or harbour porpoises, or increased competition for less prey. download thesis
Lauren Beddia, University of Wales, Bangor. 2007. Diurnal behaviour of bottlenose dolphins (Tursiops truncatus) in Cardigan Bay, West Wales.
Abstract
The behaviour of common bottlenose dolphins (Tursiops truncatus) in Cardigan Bay, West Wales, was investigated to assess the daily behavioural budget and identify differences due to years, months, group size and seasonality. The kernel ranges were also estimated using the Animal Movement extension in ArcView 3.3, so as to identify the 50% (core areas) and 95% (home ranges) Utilization Distribution (UD), within Cardigan Bay, and then compared between years and for presence of calves. Boat-based visual surveys were conducted from 2001-07 during 435 survey days, resulting in 1,469 sightings of bottlenose dolphins exhibiting particular behavioural states. Focal animal follows were conducted during line-transect and ad-libitum surveys. The following behaviours were considered: travelling, feeding, socializing, resting, and others - such as bow-riding or leaping. Groups were defined as an aggregation of dolphins within 100 metres, with the majority of the individuals engaged in similar activities.
During the study period, travelling and feeding comprised over 85% of the dolphins’ diurnal budget, followed by ‘others,’ resting and socializing. No difference was found in the budgets of groups with calves present compared to those without calves. Single individuals spent more time feeding while groups greater than 11 individuals spent more time travelling and socializing, and more time was spent feeding during the end of the study season compared with early in the season. The dolphins used the space within their home range non-uniformly, with core areas varying with behaviour types, stage of the season, and presence of calves. However, there was a significant overlap of the core areas for all behaviours and for the presence of calves. These findings provide important information concerning the spatial use of Cardigan Bay by this population of bottlenose dolphins. download thesis
Nicola Ruston, University of Central Lancashire. 2007. Observations of bottlenose dolphins (Tursiops truncatus) behavioural changes in relation to boat presence in Cardigan Bay, Wales.
Abstract
The bottlenose dolphins’ habitat brings them in close contact with humans all over the world. There is growing concern over the effect of disturbance by boat traffic to dolphin behaviour and movement. This project investigated the changes in behaviour and movement patterns that took place when bottlenose dolphins came into close contact with various types of boats. The site was on a 60 meter high headland, in New Quay (Cardigan Bay SAC, Wales), to allow the best possible view point for observations of both the boat and dolphin behaviour. The study took place over a four week period in June/July 2007, with 23 positive days for sighting. Behaviour of the dolphins in the absence of boats was recorded every 3 minutes after the first initial sighting until the dolphins disappeared. A similar process was followed during an encounter between a boat and dolphin(s). The behaviours of the dolphins and boats were categorised before the investigation started to allow easy recognition of behaviours. A theodolite was used to track and visually analyse any effect the boats may have had on the movement and behaviour of the dolphins and allow the data to be graphically represented, using a Pythagoras cetacean tracking program.
The results showed obvious relationships between the dolphins’ behaviours and the presence and behaviour of specific boats. Overall, there were 57 dolphin sightings and 49 dolphin-boat encounters; 89% of the dolphin boat encounters showed a significant change in dolphin behaviour. Many of the encounters showed relationships that underline specific behaviours observed from the dolphins and how their behaviour changes depending on boat type and the manner at which they approach an individual. Observing the impact of how dolphins react to vessels will aid in the management of boats and the conservation of bottlenose dolphins within Cardigan Bay’s designated SACs.
Sharon Bond, University of Wales, Bangor. 2006. The use of T-PODs to identify echolocation behaviour in bottlenose dolphins (Tursiops truncatus) in New Quay Bay, Wales
Abstract
The odontocete echolocation system has evolved as a dynamic and specialized process for spatial orientation and the detection and localisation of prey, thus optimizing the chances of survival in an aquatic environment. This study was carried out primarily to explore the possibility of using T-POD acoustic data as a means of identifying the echolocation behaviour of bottlenose dolphins in New Quay Bay, Wales. Dolphins were monitored through land-based visual surveys from May to September 2006, and observations were compared to corresponding click train parameter data collected with two T-POD units deployed in the study area. It was found that click trains produced by foraging dolphins had both significantly lower mean inter-click intervals and train durations, and a significantly higher number of clicks, than those emitted by dolphins observed in the behavioural states of traveling and foraging/traveling. These findings were applied to T-POD data collected in the study area throughout the year, revealing both significant diel and monthly variation in the number of foraging click trains acoustically detected.
The secondary aim of this investigation was to broadly determine the influence of directionality, group size, distance and behavioural state on T-POD detection rates. The collective evaluation of data obtained over the study period indicated that a combination of these variables had an effect on T-POD detection rates. However, further work is required to determine the extent to which each of these factors influences acoustic detection rates, and how environmental variables may also contribute to the detection of echolocating dolphins with T-PODs. It was concluded that if the limitations of using T-PODs are accepted, the methodology employed in this study has the potential to monitor long-term changes in dolphin behaviour. Consequently, such monitoring could provide a method for monitoring fine-scale temporal changes in habitat use. download thesis
Natalie Bush, University of Wales, Bangor. 2006. Spatial use by common dolphins in relation to habitat features in the Celtic Sea.
Abstract
The Short-beaked common dolphin, Delphinus delphis, is frequently observed off the south-west coast of England and Wales during spring and summer. Two-day acoustic and visual (line-transect) surveys were conducted once a month from May to August 2004-06 in the St. George’s Channel. The aim was to determine any significant differences between the two survey techniques in relation to environmental features. During 2004-06, a total of 142 acoustic and 220 visual encounters were detected. Data collected from acoustic and visual encounters were separately analysed and then later compared. 5 7.8% of all acoustic encounters were not associated with a visual sighting within the same timescale; however within this, 28.9% of acoustic contact occurred within five minutes of a sighting. Vocalisation strength was categorised into weak, medium and strong signals which significantly differed in accordance with whether a sighting was detected. Significant positive correlations were observed between group size and acoustic encounter duration, and acoustic encounter duration and the number of sightings per acoustic encounter. A Geographical Information System and remotely-sensed satellite data were used as tools to investigate spatio-temporal distribution of the common dolphin in relation to fixed variables, i.e. depth, and non-fixed variables, i.e. sea surface temperature, surface chlorophyll-a concentration and frontal systems. A significant positive correlation with depth and a significant negative correlation with chlorophyll-a concentration were identified in relation to the distribution of D. delphis. In 2006, D. delphis were thought to be associated with the highly productive Celtic Sea front, an oceanographic feature which forms at the boundary between the Celtic and Irish Seas. Dolphins appeared to be distributed in waters south of the front where the sea surface temperature was warmer. Depth and chlorophyll-a were considered as variables which influenced the dolphins’ prey which subsequently influenced the distribution of D. delphis. download thesis
Edita Magileviciute, University of Wales, Bangor. 2006. Social networks of bottlenose dolphins in Cardigan Bay, Wales.
Abstract
The social structure of a population is a fundamental component of its biology and ecology. Mating strategies, foraging techniques and the ability to explore surrounding environment are closely related to the network of relationships between individuals. In the present study network analytical techniques, developed for the analysis of human sociality, were employed to construct and investigate bottlenose dolphins’ social networks in Cardigan Bay. Pooled data social network for the 5-yr period (2001-2006) was moderately dense (ρ = 0.60) with a high number of direct ties among individuals (k = 27.48). The variability of properties in annual networks indicated the dynamics of relationships. Divisions within networks were detected, and could have been influenced by the degree of homophyly of the preferred companionships, while sex of individuals did not seem to play a significant role in association patterns. However, these findings were considered with caution due to the low number of individuals with known sex, age and kin relatedness in this population. Highly central individuals positioned on the boundaries of network components were identified. Their importance was discussed in relation to the transfer of information and spread of disease.
Analysis of spatial distribution of bottlenose dolphins revealed areas around Mwnt, Ynys Lochtyn and New Quay as being centres of activity for the majority of sampled population in this study. Known ranges calculated for the network components showed overlap in the area usage, and extended travel further north from the Cardigan Bay SAC. Increased effort in the north of Cardigan Bay resulted in the identification of new individuals.
Epidermal skin abnormalities (lesions) were categorized, and their prevalence examined in regards to the topology of individuals in the network. Non random frequencies of lesion distribution found in network components prompted strong recommendations towards more detailed future investigation on the severity of these markings in different age/sex groups and their link to the environmental variables. Network approach was found to be useful in exploring social structure of this population.
The potential to combine such characteristics as individual position in the network, spatial distribution and skin anomalies by incorporating them into the analysis highlighted the efficiency of this technique to further our knowledge in understanding the processes and consequences of a social organization. Furthermore, it pointed to the importance of network of relationships be considered in defining management and conservation guidelines for this, and other cetacean populations. download thesis
Eleanor Stone, University of Wales, Bangor. 2006. A fine-scale study investigating the temporal and spatial use of New Quay bay, Wales, by bottlenose dolphins.
Abstract
This study is an investigation into the use of a small bay by a coastal bottlenose dolphin population. New Quay Bay is a shallow, sheltered bay, which has been frequented by dolphins since at least the 1920’s. Using land-based observations, dolphin presence was recorded between May and September in 2004, 2005 and 2006. In addition, more detailed information about the numbers of animals, their behaviour and habitat use was collected in 2006. A digiscope system was also tested during 2006, for the purpose of taking dolphin photo-identification images.
Dolphins were found to be present in an average of 29.6% of 15-minute observation intervals, although there was significant monthly variation, with an increased presence later in the year. This increase was due to greater numbers of animals in the area, coupled with an increase in group size at this time. Nevertheless, the majority of sightings were of single individuals, with a mean group size in all three years of only 1.8 animals. Tidal state was shown to have a strong influence on dolphin presence, with an increase during the ebb stage.
Dolphins were found to use the bay predominantly for feeding, with this behavioural state being observed 71.1% of the time. Feeding was shown to occur primarily in two areas at either side of the bay, with the majority of travelling behaviour being across the bay between the two feeding spots. The digiscope was successfully used to take photo-identification images of dolphins, but the quality of images was highly dependent on the range and behaviour of animals and the sea conditions. New Quay Bay is thus an important area for bottlenose dolphins, especially as a feeding hotspot, and continued monitoring of this area is necessary for the management of the Cardigan Bay bottlenose dolphin population. download thesis
Lucy Alford, University of Wales, Bangor. 2006. Bottlenose dolphin and harbour porpoise presence and foraging patterns in relation to tidal cycle, height of tide, lunar activity and strength of current.
Abstract
Ten cetacean click detectors (T-PODs) were deployed at set locations within the Cardigan Bay SAC. From sounds recorded between March 2005 and February 2006, bottlenose dolphin and harbour porpoise click trains were determined to allow for investigation into the occurrence and foraging activity of the two species. In doing so, the study would build on current knowledge of use of the SAC by these two species using both visual and acoustic methods. Clear patterns in occurrence were determined, with bottlenose dolphin abundance reaching a maximum in September and October 2005, and harbour porpoises in December 2005. Spatial shifts between T-POD locations were not detected, however. Occurrence was further influenced by the spring/neap tidal cycle with bottlenose dolphins showing a trend of increased detection with increased tidal height and harbour porpoises a trend of decrease. It was assumed that changes in abundance were most likely related to prey availability. Using click train characteristics to determine those trains involved specifically in foraging, two peaks in foraging activity were revealed. The first occurred during the late summer and early autumn, but was only observed at offshore Aberporth. A second peak occurred during winter months at the majority of T-POD locations and was believed to be a consequence of increased foraging requirements, declines in prey abundance or due to a reduction in boat activity. The analysis of foraging clicks did not distinguish between bottlenose dolphins and harbour porpoises, and so it was not possible to link foraging to a particular species. Foraging was found to be unrelated to time of day at the majority of locations, although nocturnal foraging was revealed at Cardigan Island and offshore Aberporth. Tidal state was further found to affect foraging activity, with most foraging occurring during the first half of the ebb or first half of the flood. Velocity did not appear to affect foraging activity. download thesis
Saana Isojunno, University of Jyvaskyla, Finland. 2006. Harbour porpoise distribution in the Cardigan Bay Special Area of Conservation.
Abstract
Small-scale habitat use of harbour porpoise was investigated using non-intrusive land-based watches in the southern part of Cardigan Special Area of Conservation, where relatively little such data had been previously available. Previous research has indicated that local porpoise abundance may respond to several oceanographic and bathymetric features, substrate type, and anthropogenic point sources. Using geographic information system software, this study confirms that harbour porpoise habitat use can be site-specific even at a small scale.
Two hypotheses were tested: 1) that sightings are distributed non-randomly in the study area and 2) if sighting clusters exist, they can be related to environmental variables. To test the first hypothesis, the nearest neighbour-method was used in ArcGIS. Whereas sighting rates did not differ from one vantage point to another, the average observed distance between sightings was found to be significantly lower than expected distance, indicating clustering at a finer scale. Sighting densities were mapped and 467 individual sightings related to maps of sediment type and bathymetry. Sighting rates, and average individual counts per 15-minute interval were treated as indices of abundance. Sighting rates increased towards the end of the two-month study period in July. Sighting rates were lower and transiting behaviour more frequent around the Teifi Estuary than at the other four studied sites. Of environmental variables, sighting rates and clustering tended to be higher during ebb tide and in the afternoon. Staying behaviour and associations with birds were also more frequent during ebb tide. The highest sightings frequency was found at depths of 16-20 m. Sightings also tended to be aggregated around steeper slopes. Most sightings were situated over cobbles with sand/silt and either sparse or moderate but short turf. These patterns are likely to relate to prey availability, which would be of interest for future study and management of the species’ habitats. download thesis
Ina Ansmann, University of Wales, Bangor. 2006. Acoustic behaviour and whistle characteristics of common dolphins (Delphinus delphis) in the Celtic Sea.
Abstract
Cetaceans have adapted to life underwater by developing specialised hearing and echolocation abilities, as well as a communication system that is largely based on acoustic signals. Part of the vocal repertoire of many delphinid odontocetes are narrowband tonal whistles used mainly for communication. The aim of this study was to describe the whistle repertoire of short-beaked common dolphins, Delphinus delphis, recorded in the Celtic Sea off South Wales between May and August, 2005. Comparisons between acoustic and visual detection rates during these surveys showed that acoustic surveying can increase the chances of detecting common dolphins compared to visual methods alone, especially if group size was small and animals were far away from the vessel. However, even though group size was correlated to whistle density, the regression was not strong enough to reliably predict the number of animals based on acoustic data alone. The whistles recorded were classified into six broad categories and thirty sub-types, of which simple upsweeps and downsweeps were the most common. Furthermore, the parameters duration, inflections, steps and various frequency variables were measured. Whistle parameters varied with behavioural context, group size and between encounters. The whistle repertoire of Celtic Sea common dolphins was compared to that of D. delphis from the western approaches of the English Channel, recorded during a WDCS/Greenpeace survey between January and March, 2004. The relative abundances of the broad whistle categories did not differ between the two locations, but most whistle parameters were significantly different. Almost all frequency parameters measured were higher for English Channel whistles, which supports the possibility that these may be two distinct populations of short-beaked common dolphins. The English Channel dolphins may have shifted the frequencies of their vocalisations up to avoid masking by low-frequency ambient noise produced by high levels of vessel traffic in this area. download thesis
Evonne Amblin, University of Plymouth. 2006. Environmental factors affecting the distribution of short-beaked common dolphins (Delphinus delphis) of the Celtic Deep.
Abstract
The short-beaked common dolphin (Delphinus delphis) is widey distributed in warm temperate and tropical waters of the Atlantic and Pacific Oceans. The objective of this study was to investigate the ocean variables that may be correlated with the distribution of the short-beaked common dolphin in the Celtic Deep. Sightings data from 1993 to 2004 were examined with respect to sea surface temperature (SST), salinity, depth, slope, and distance from land. The distribution of common dolphin sightings in the Celtic Deep study area was non-random in relation to the environmental parameters. None of the envirnmetal parameters exhibited a consistently significant effect on the distribution of common dolphins in the Celtic Deep; rather, combination of parameter acted together to produce favourable environmental conditions for the species. The relationship of common dolphin distribution to the environment may reflect prey distributions, i.e. factors which concentrate prey may only secondarily affect the distribution of common dolphins. Feeding in areas where prey are concentrated would improve foraging efficiency and therefore common dolphins would be expected to aggregate in such areas.
Juliana Castrillon, University of Javeriana, Colombia. 2006. Estimating the population size and long-term residence of bottlenose dolphins (Tursiops truncatus) in Cardigan Bay SAC.
Abstract
The bottlenose dolphin (Turpsiops truncatus) Cardigan Bay population has been protected since 1992, although the management plan was implemented only in 2001. Nonetheless, how the population size has responded to these strategies since then has not been evaluated. In order to achieve this goal the population size was calculated from 2003 to 2005, and compared with information collected in the past. Data collected during Sea Watch Foundation surveys were used to estimate T. truncatus abundance. The population size was estimated assuming a close population, using photo-identification data and mark-recapture method with (Mth) model. Most of the sampled individuals in the population were catalogued as frequent and common, showing that the population is likely to be resident, with 40% of the marked animals seen during two consecutive years (high capture frequency). Non statistical difference was found in the estimated population size between 2003 and 2005, although there was an increment in the population size of 16% during that period. Data suggest a growing population in the last sixteen years, which in part can be due to conservation strategies, although this hypothesis needs to be confirmed. download thesis
Ronan Hickey, University of Wales, Bangor. 2005. Comparative study of bottlenose dolphin whistles in the southern Cardigan Bay SAC and in the Shannon Estuary.
Abstract
In previous studies, comparisons of whistle characteristics between geographically isolated populations of delphinid species have revealed variation between locations. The waters of Britain and Ireland are home to three known resident populations of bottlenose dolphins: Cardigan Bay (Wales), the Shannon Estuary (Ireland) and the Moray Firth (Scotland). This study compared the rate, repertoires and characteristics of whistles of two of these populations: Shannon Estuary and Cardigan Bay. Comparisons between years, groups and different group sizes were also carried out within the Shannon Estuary population. Cardigan Bay whistles were collected actively on-board Sea Watch survey vessels using a deployed hydrophone, while Shannon Estuary whistles were collected passively via a fixed hydrophone. Whistles were compared using a series of quantitative parameters and sorted into categories using contour shape. Overall, 1882 whistles were analyzed throughout the course of this study. The vast majority were collected in the Shannon Estuary. A total of 32 different whistle categories were described, of which 21 were observed in both populations, 8 were exclusive to the Shannon Estuary, and 1 was exclusive to Cardigan Bay. The average duration of whistles from the Shannon Estuary population was found to be longer than whistles from Cardigan Bay. The average starting, ending, maximum, minimum, and mean frequency of whistles from Cardigan Bay were significantly higher than Shannon Estuary whistles. However, there was no statistical difference in the whistle rate between the populations. Variations in whistle parameters and frequency of occurrence of whistle categories were also observed in comparisons within the Shannon Estuary population. Whistle rates increased with increasing group size. On a side note, dolphins in the Shannon Estuary were observed to exhibit cyclic behaviour, which was influenced by tidal times. Dolphins were most commonly encountered during the mid ebb tide. The differences observed in the whistle characteristics between the two populations could be representative of behavioural, environmental, or morphological differences between the Cardigan Bay and Shannon Estuary populations. Further research is required to expand upon the results of this study before the variance in whistle characteristics of Cardigan Bay and the Shannon Estuary populations can be fully understood.
Kate Lewis, University of Wales, Bangor. 2005. Habitat use, behaviour and site fidelity of grey seals along the Ceredigion Heritage Coast.
Abstract
Grey seals were sighted from visitor passenger boat trips within all ten zones of the Ceredigion Marine Heritage Coast between New Quay and Ynys Lochtyn in 2004 and 2005, demonstrating their presence along the coastline within the Cardigan Bay SAC. Environmental variables, collected via such trips, and direct observations from Bird’s Rock, a designated Site of Special Scientific Interest, were analysed using univariate and multivariate methods, to investigate whether a particular factor influenced grey seal haul-out behaviour. Although tide, time of day, adjusted air temperature and disturbance primarily influenced haul-out behaviour at Bird’s Rock, it is evident that a complex dynamic of intrinsic and extrinsic factors interact to determine haul-out behaviour. Potential human-induced disturbance was investigated by logging grey seal-vessel interactions observed during direct visual surveys at Bird’s Rock. Vessel traffic appeared not to induce short-term behavioural responses in the majority of seals present, suggesting that vessels which were abiding by the Ceredigion Marine Conservation Code of Conduct did not disturb seals in the short-term. Although infrequent, research vessels abiding and canoes violating the Code of Conduct resulted in seals permanently modifying their behaviour and/or escaping Bird’s Rock. Given that long-term effects of vessel disturbance are unknown, this study supports the need for further investigation. Photo-identification of grey seals encountered along the Ceredigion coastline exhibited a degree of intra-seasonal and inter-annual site fidelity, particularly to Bird’s Rock and Cwmtudu, a pupping beach. 52% of individuals were re-sighted at least twice within the initial season photographed. One bull (ID 015) was encountered in three successive years (2003-2005), whereas a female (ID 007) known to have pupped at Cwmtudu in 2003 was re-sighted there in August 2005. Furthermore, grey seals at Bird’s Rock exhibited a preference for specific haul-out rocks at Bird’s Rock. Finally, direct observation revealed that education of tourists remains paramount in maintaining the protection of grey seals along the Ceredigion Marine Heritage Coast. The continuation of a precautionary approach to management within this area is required. download thesis
Neal Reay, University of Wales, Bangor. 2005. Estimating the g(0) in linear surveys of harbour porpoise, bottlenose dolphins and grey seals.
Abstract
With the current shift in management strategies towards the use of Marine Protected Areas (MPAs) to conserve species of marine mammals and their habitats, there comes the need for accurate, annual abundance estimates of species within MPAs to gain insight as to the species status, and the effectiveness of particular management approaches. Line-transect surveys used to estimate marine mammal abundance assume that detection on the track-line is unity (g(0)=l), which is rarely the case for marine mammals. If not accounted for, abundance estimates will be negatively biased by a factor proportional to the true value of g(0). Dual platform, line-transect surveys were conducted over three consecutive summers (2003-2005) within Cardigan Bay SAC to estimate g(0) for bottlenose dolphins, grey seals and harbour porpoises. Environmental covariates were recorded with each sighting to allow for the inclusion of covariates in the analysis and so reduce the effect of detection bias. Data from the 2003 and 2004 surveys were pooled due to low sample size. Analysis using DISTANCE 5.0 revealed g(0) (NB: significant covariates are given in brackets) for bottlenose dolphins to be 0.705 (group size) in the 2003-04 surveys, and 0.941 (group size, sea state, and observer experience) in the 2005 surveys. Estimates of g(0) for grey seals were 0.815 (no significant covariates) for the 2003/04 surveys, and 0.934 (observer experience) for the 2005 surveys. Estimates of g(0) for harbour porpoises were 0.728 (group size) for the 2003/04 surveys, and 0.811 (group size) for the 2005 surveys. The study revealed that g(0) varied greatly between species and between years, with variations in sample size and surveys conditions greatly affecting estimates. In conclusion, researchers should always calculate g(0) for each survey and incorporate as many covariates as possible to reduce detection bias. download thesis
Mercedes Reyes-Zamudio, University of Wales, Bangor. 2005. Acoustic behaviour of bottlenose dolphins (Tursiops truncatus): a comparison between T-POD and visual surveys.
Abstract
T-PODs are acoustic data loggers that detect echolocation clicks from harbour porpoise (Phocoena phocoena) and bottlenose dolphin (Tursiops truncatus). In the past, T-POD research has focused mainly on harbour porpoises. This study aimed to investigate T-POD performance when studying bottlenose dolphins by: measuring the detection range and detection probability in the presence of dolphins, and investigating the possibility of identifying particular dolphin behaviours from T-POD data. Two TPODs were deployed for a period of six weeks (27th June - 8th August, 2005), at two different locations (Mwnt and New Quay, Cardigan Bay Special Area for Conservation, West Wales). At each location visual observations were undertaken using theodolites to calculate the distance between T-POD and dolphins, and to observe their behaviour. Comparisons between data obtained with T-PODs and simultaneous visual observations showed that the maximum T-POD detection range of bottlenose dolphin clicks was 650m. When the dolphins were present within this range, the T-PODs only detected them 11 percent of the time, and there was a significant negative correlation between distance and the T-POD detection probability, with a sharp decline in detection rate beyond 300 m. In addition, the detection probability varied with dolphin behaviour so that dolphins that were feeding had a significantly higher probability of being detected by the T-POD than dolphins that were travelling. T-POD data showed that dolphins that were feeding emitted click trains with significantly higher numbers of clicks, and had significantly lower inter-click intervals than travelling dolphins, suggesting that click trains with high numbers of clicks (< 30) and low minimum inter-click intervals (< 350 s) signify feeding behaviour in T-POD data. This could be a first step to using T-PODs to provide information on any spatio-temporal patterns of feeding.
Rebecca Walker, University of Wales, Bangor. 2005. Bottlenose dolphin distribution within the Cardigan Bay.
Abstract
Abstract is not available
Jennie Lamb, University of Wales, Bangor. 2004. Relationships between bottlenose dolphins (Tursiops truncatus), environmental variables and boat traffic; visual and acoustic surveys in New Quay Bay.
Abstract
The use of New Quay Bay, within the Cardigan Bay candidate Special Area of Conservation, by the resident bottlenose dolphins (Tursiops truncatus) was investigated by visual and acoustic means. A land-based visual survey conducted from May 1st to August 7th 2004 and a T-POD acoustical survey conducted from June 14th to August 7th 2004 were used to investigate which natural factors affect the presence of the dolphins and also the possible impact of boat traffic in this area. A total of 497 hours of visual data and 1077 hours of acoustic data were collected. Comparisons of the two data sets were made to determine any potential differences between the two techniques. Both bottlenose dolphin presence and boat traffic were found to peak in August. Dolphin presence throughout the day varied inversely with boat traffic. Peak use of the bay by dolphins was at midnight, whereas greatest boat traffic was observed at 1pm. The tidal cycle was significantly correlated with bottlenose dolphin presence, indicating greater presence during the ebb phase of the tide as compared to the flood phase. The reaction of dolphins during boat interactions varied significantly. Most encounters resulted in the dolphin either changing its behaviour or disappearing from view. Fast moving boats such as motor boats and speed boats appeared to cause greatest disturbance to the animals. Visual and acoustic methods revealed broadly similar patterns in most instances. The combined use of both techniques compensated to an extent for the drawbacks inherent to each survey. Precautionary measures such as codes of conduct for marine vessels may help to reduce disturbance experienced by bottlenose dolphins and other marine wildlife, due to increased boat activity in the area. Further study is necessary to determine any long term impacts of disturbance caused by boat traffic. download thesis
Rob Lott, University of Wales, Bangor. 2004. Social structure of bottlenose dolphins (Tursiops truncatus) in Cardigan Bay.
Abstract
This work sought to investigate group sizes, social associations and the resident patterns of bottlenose dolphins (Tursiops truncatus) in the Cardigan Bay candidate Special Area of Conservation using boat-based photo-identification surveys. The present study is the first in which an analysis of the social associations of bottlenose dolphins in Cardigan Bay has been undertaken. A total of 222 surveys were made from 2001-2004, which resulted in 537 encounters. 83% of all encounters werewith animals in groups rather than alone. Group size varied significantly between years and ranged from singletons to 42 animals. The mean group size over all years was 5.85 ±5.89 (median = 4). Some individually identified dolphins were photographed in the study area in successive seasons and years and appear to be seasonally resident in Cardigan Bay. Moreover, certain individuals exhibited a preference for core areas within the cSAC. However, these areas are not considered to be ‘home ranges’ of the dolphins as it is thought all animals leave the cSAC on occasion. Associations were studied using half-weight association indices and cluster analysis. In addition, temporal analyses of association patterns were made plotting changes in the standardised reassociation rate over time. Selection criteria were based on the number of times an individual was sighted during the 2003 study period. The social organisation was characterised by relatively fluid association patterns, with little stability over periods longer than a few days though some longer-term companions were evident. Permutation tests revealed non-random associations and the presence of preferred and/or avoided companions. Both males and females interacted with a large number of other individuals and there were significantly stronger associations between certain male pairs. The long-term site fidelity demonstrated by certain animals in this study highlights the fact that photo-identification monitoring needs a good geographical spread and greater effort will provide significant value in assessing the bottlenose dolphins’ future management needs. download thesis
Andrew Scullion, University of Wales, Bangor. 2004. Short-beaked common dolphin, Delphinus delphis, whistles: Is whistle density, a reliable Form of measuring group size?.
Abstract
Conservation biology and management’ has become an ever increasingly used phrase in marine mammal science over the past 20 years; monitoring the changes in cetacean population sizes, distribution, and their anthropogenic causes are key areas of conservation. The Short-beaked common dolphin, Delphinus delphis, found in waters around the United Kingdom and Republic of Ireland has come under increasing threat from industrial fishing operations, pollution and vessel disturbance. Current estimates of D.delphis population size in the Celtic Deep (UK) range between 23,000 and 249,000 animals, with other estimates suggesting 100,000 animals off the UK and French coasts. Recent acoustic developments have suggested that sound can be used to estimate the number of animals in a dolphin school. Using the Short-beaked common dolphin as an example, this vessel-based study uses acoustic recordings in conjunction with visual sightings data from the Celtic Deep, UK. D.delphis whistle density (whistles per minute) was regressed against dolphin group size to produce a mathematical model , which was then used to predict the whistle density for dolphin schools containing up to 80 animals. The results presented here are compared with those previously reported for two dolphin species. Suggestions are made as to the future development of this technique into a viable method of assessing dolphin group size acoustically. The 414 whistles recorded for this study were also analysed and classified into 20 distinct whistle categories based on contour shape and duration; three categories comprised 44.2% of all whistles recorded. The descriptive frequency (maximum, minimum, start, end, mean, and median) and duration parameters of the categories are presented, and compared with those of previous D.delphis acoustic reviews. Whistles ranged in frequency from 3.37 - 20.982 kHz and lasted between 0.0169 and 2.1482 seconds in duration. Download thesis