Paul M. Thompson

ESTIMATING SIZE AND ASSESSING TRENDS IN A COASTAL BOTTLENOSE DOLPHIN POPULATION

We used a case study of a coastal bottlenose dolphin population to present a framework for determining the number of individuals present and assessing the likely time scale over which trends in abundance may be determined. Such a framework is appropriate for animal species that possess natural markings sufficient for individual recognition, and may be valuable in the development and implementation of management and monitoring programs for vulnerable populations. Population abundance was estimated using mark–recapture methods applied to photoidentification data. This experiment was designed to minimize violation of method assumptions so as to allow use of the most parsimonious model for analysis. The data were examined critically to investigate mark–recapture assumptions, while analytical methods and data were selected to minimize and, where necessary, account for violations. The estimated number of animals with long-lasting marks from left and right side estimates were 73 ± 12 and 80 ± 11 individuals, res...

Molecular scatology: the use of molecular genetic analysis to assign species, sex and individual identity to seal faeces

Seals and commercial fisheries are potential competitors for fish and cephalopods. Research into the diet of British seal species has been based on conventional dietary analyses, but these methods often do not allow assignment of species identity to scat samples. We present a protocol for obtaining DNA from seal scat (faecal) samples which can be used in polymerase chain reactions to amplify both nuclear and mitochondrial DNA. This can provide a method of identifying the species, sex and individual identity of the seal, from a particular scat sample. Combined with conventional dietary analyses these techniques will allow us to assess sources of variation in seal diet composition.

Habitat use by bottlenose dolphins : seasonal distribution and stratified movement patterns in the Moray Firth, Scotland

This study investigated the distribution of a population of bottlenose dolphins Tursiops truncatus resident in the Moray Firth off north-eastern Scotland. Results add to existing information from studies in tropical areas to provide a better understanding of area use in this species. Boat-based surveys and photo-identification techniques were used to study the distribution and movements of individually recognizable dolphins over a 3-year period. Dolphins were seen in all months of the year, but there were consistent seasonal fluctuations in the number of individuals present. Numbers were low in winter and spring and peaked in summer and autumn. Dolphins were seen throughout the survey area but were concentrated in three regions. Each had similar topographic features being centred on deep, narrow channels subject to strong tidal flows. Area use by dolphins changed with season. The outer part of the inner Moray Firth study area was used for most of the year and areas closer to the head of the firth were used seasonally. The summer increase in numbers of dolphins in the inner Moray Firth was not simply due to incomers diluting an already resident population. Instead, there was a stratified movement of all individuals. This persistent geographical stratification suggests that competition between individuals or social groupings may shape spatial distribution in this population. Individuals exhibited rapid movements across the populations range. For instance, one individual was sighted at locations 190 km apart within a 5-day period. In terms of conservation, the high use of areas at the mouths of the inner firths warrants special attention. Furthermore, the stratification patterns amongst dolphins suggest that individuals do not move freely within the inner Moray Firth and therefore may be unable to move away from localized disturbance or pollution.

Senescence rates are determined by ranking on the fast-slow life-history continuum

Comparative analyses of survival senescence by using life tables have identified generalizations including the observation that mammals senesce faster than similar-sized birds. These generalizations have been challenged because of limitations of life-table approaches and the growing appreciation that senescence is more than an increasing probability of death. Without using life tables, we examine senescence rates in annual individual fitness using 20 individual-based data sets of terrestrial vertebrates with contrasting life histories and body size. We find that senescence is widespread in the wild and equally likely to occur in survival and reproduction. Additionally, mammals senesce faster than birds because they have a faster life history for a given body size. By allowing us to disentangle the effects of two major fitness components our methods allow an assessment of the robustness of the prevalent life-table approach. Focusing on one aspect of life history - survival or recruitment - can provide reliable information on overall senescence.

Lagged effects of ocean climate change on fulmar population dynamics.

Environmental variation reflected by the North Atlantic Oscillation affects breeding and survival in terrestrial vertebrates, and climate change is predicted to have an impact on population dynamics by influencing food quality or availability. The North Atlantic Oscillation also affects the abundance of marine fish and zooplankton, but it is unclear whether this filters up trophic levels to long-lived marine top predators. Here we show by analysis of data from a 50-year study of the fulmar that two different indices of ocean climate variation may have lagged effects on population dynamics in this procellariiform seabird. Annual variability in breeding performance is influenced by the North Atlantic Oscillation, whereas cohort differences in recruitment are related to temperature changes in the summer growing season in the year of birth. Because fulmars exhibit delayed reproduction, there is a 5-year lag in the populations response to these effects of environmental change. These data show how interactions between different climatic factors result in complex dynamics, and that the effects of climate change may take many years to become apparent in long-lived marine top predators.

Assessing underwater noise levels during pile-driving at an offshore windfarm and its potential effects on marine mammals

Marine renewable developments have raised concerns over impacts of underwater noise on marine species, particularly from pile-driving for wind turbines. Environmental assessments typically use generic sound propagation models, but empirical tests of these models are lacking. In 2006, two 5MW wind turbines were installed off NE Scotland. The turbines were in deep (>40m) water, 25km from the Moray Firth Special Area of Conservation (SAC), potentially affecting a protected population of bottlenose dolphins. We measured pile-driving noise at distances of 0.1 (maximum broadband peak to peak sound level 205dB re 1microPa) to 80km (no longer distinguishable above background noise). These sound levels were related to noise exposure criteria for marine mammals to assess possible effects. For bottlenose dolphins, auditory injury would only have occurred within 100m of the pile-driving and behavioural disturbance, defined as modifications in behaviour, could have occurred up to 50km away.

SEASONAL AND SEX-RELATED VARIATION IN THE ACTIVITY PATTERNS OF COMMON SEALS (PHOCA VITULINA)

SUMMARY (1) Radio-telemetry was used to study common seal activity patterns around Orkney, and to assess the degree of individual, seasonal and sex-related variation in haul-out behaviour in 1984-86. (2) During the summer, both males and females hauled-out regularly, in a marked diurnal pattern, but there were differences in other aspects of their haul-out behaviour. (3) Males showed a marked change in their haul-out behaviour at the beginning of moult. At this time, they hauled-out every day and, consequently, male behaviour became more synchronous. The change in behaviour of the male followed in 1985 was closely related to changes in abundance at the haul-out site that he used over this period. (4) In contrast, females showed no sign of a similar change in behaviour at the beginning of moult, but appeared to spend more of their time at sea after lactation. (5) During the winter, seals appeared to spend more time in offshore waters, although they regularly returned to the inshore study area to haul-out. At this time of year there was no marked diurnal haul-out pattern. (6) There was a high degree of individual variation in the effect of the tidal cycle on activity patterns, which appeared to be related to tide-related changes in food and habitat availability. Overall, however, the tidal cycle had less effect on haul-out behaviour in summer, when strong circadian patterns were more important. (7) The variations in activity patterns found in this study are discussed in relation to seasonal changes in feeding activity and the demands of breeding and moult.

Phenological sensitivity to climate across taxa and trophic levels

Differences in phenological responses to climate change among species can desynchronise ecological interactions and thereby threaten ecosystem function. To assess these threats, we must quantify the relative impact of climate change on species at different trophic levels. Here, we apply a Climate Sensitivity Profile approach to 10,003 terrestrial and aquatic phenological data sets, spatially matched to temperature and precipitation data, to quantify variation in climate sensitivity. The direction, magnitude and timing of climate sensitivity varied markedly among organisms within taxonomic and trophic groups. Despite this variability, we detected systematic variation in the direction and magnitude of phenological climate sensitivity. Secondary consumers showed consistently lower climate sensitivity than other groups. We used mid-century climate change projections to estimate that the timing of phenological events could change more for primary consumers than for species in other trophic levels (6.2 versus 2.5–2.9 days earlier on average), with substantial taxonomic variation (1.1–14.8 days earlier on average).

Changes in the distribution and activity of female harbour seals during the breeding season: implications for their lactation strategy and mating patterns

Adult female harbour seals from NE Scotland were radio-tracked to follow changes in their distribution and activity during the breeding season. Seals foraged up to 45 km from haul-out sites, but females with pups restricted their range markedly during the early part of the lactation period. However, foraging trips resumed before the expected weaning date, indicating that female harbour seals do not fast throughout lactation. The duration of the period that females spent inshore with young pups was positively related to female body size, suggesting that the speciessmall size may demand that they feed to maintain lactation. Foraging in late lactation results in females becoming highly dispersed during the mating period and it is clearly uneconomic for males to monopolize females

Evidence for infanticide in bottlenose dolphins: an explanation for violent interactions with harbour porpoises?

Most harbour porpoises found dead on the north–east coast of Scotland show signs of attack by sympatric bottlenose dolphins, but the reason(s) for these violent interactions remains unclear. Post–mortem examinations of stranded bottlenose dolphins indicate that five out of eight young calves from this same area were also killed by bottlenose dolphins. These data, together with direct observations of an aggressive interaction between an adult bottlenose dolphin and a dead bottlenose dolphin calf, provide strong evidence for infanticide in this population. The similarity in the size range of harbour porpoises and dolphin calves that showed signs of attack by bottlenose dolphins suggests that previously reported interspecific interactions could be related to this infanticidal behaviour. These findings appear to provide the first evidence of infanticide in cetaceans (whales, dolphins and porpoises). We suggest that infanticide must be considered as a factor shaping sociality in this and other species of cetaceans, and may have serious consequences for the viability of small populations.