Individual and geographical variation in display behaviour of male harbour seals in Scotland

Studying variations in behaviour at the individual or population level enables insight into the reproductive strategies within a species. We examined individual and geographical variation in the vocal and dive behaviour of male harbour seals, Phoca vitulina, which is associated with aquatic mating. This display behaviour was recorded in the Moray Firth, Scotland, from July 1994 to 1997, and in Orkney, Scotland, during July 1998. One vocalization type was apparent in the Moray Firth and two in Orkney. Time parameters (total and pulse duration) varied between males in the population in the Moray Firth. We used both frequency and time parameters in a discriminant analysis, which showed that 73.2% of individual male vocalizations could be correctly classified; 94.6% of male vocalizations from the Moray Firth and Orkney could be correctly classified according to their geographical areas. Therefore, vocal variation was greater between geographical areas than between individuals. No individual variation was apparent between dive and surface interval durations. However, individuals varied significantly in the percentage of short surface intervals. Male harbour seals showed substantial variability in the parameters affecting their vocal and dive behaviour during the mating season. We suggest that these variations may be indicative of adaptations to varying environmental challenges influencing the reproductive strategies of discrete populations. Copyright 2000 The Association for the Study of Animal Behaviour.     

Surface temperature patterns in seals and sea lions: A validation of temporal and spatial consistency

We assessed infrared thermography (IRT) as a tool for evaluating spatial and temporal surface temperature patterns in juvenile female harbor seals (Phoca vitulina, n=6) and adult female Steller sea lions (Eumetopias jubatus, n=2). Following a technical assessment of the influence of environmental parameters on the specific camera to be used, we identified regional and seasonal variability of surface temperatures. Variation was observed in several seasonal transitions (winter, reproductive, molt) in ten monitored body regions. Spatially and temporally consistent thermal patterns in the shoulder, axillae, foreflipper and hindflipper suggest thermal windows in both species.     

Increasing numbers of harbour seals and grey seals in the Solent

Harbour seals (Phoca vitulina) and grey seals (Halichoerus grypus) both occur within the UK, but display regional contrasting population trends. While grey seals are typically increasing in number, harbour seals have shown varying trends in recent decades following repeated pandemics. There is a need for monitoring of regional and local populations to understand overall trends. This study utilized a 20‐year dataset of seal counts from two neighboring harbours in the Solent region of south England. Generalized additive models showed a significant increase in the numbers of harbour (mean 5.3–30.5) and grey (mean 0–12.0) seals utilizing Chichester Harbour. Conversely, in Langstone Harbour there has been a slight decrease in the number of harbour seals (mean 5.3–4.0). Accompanying photographic data from 2016 to 18 supports the increase in seal numbers within Chichester Harbour, with a total of 68 harbour and 8 grey seals identified. These data also show evidence of site fidelity of harbour seals in this area, with almost a quarter of animals resighted within the past three years. Overall, this long‐term study indicates an increasing number of both harbour and grey seals within the Solent. However, more research is required to identify the drivers of this trend.     

Vocalizations and movements suggest alternative mating tactics in male bearded seals

We combined observations of individual male bearded seal, Erignathus barbabus, behaviour at sea with acoustic localization techniques to investigate their reproductive strategies. Data on trill vocalizations and dive behaviour were collected over consecutive years during the seals' mating season in Svalbard, Norway. Males showed stereotypical dive and vocal displays, with clear individual variation. Acoustic localization provided at-sea locations for 17 males based on variation in trill parameters. Kernel home range analyses showed that 12 individuals displayed at set locations (95% kernels=0.27-1.93 km²) and five other males displayed within considerably larger geographical areas (95% kernels=5.31-12.5 km²). Males that used the set locations maintained single discrete core areas (50% kernels), while males with large areas moved between multiple core areas. Movement patterns of males suggest that those with small areas patrolled aquatic territories, while those that used larger areas appeared to ‘roam’. Territorial males showed little spatial overlap, while roaming males overlapped substantially with both territorial and other males' areas. Territorial males had significantly longer trills than roamers. We suggest that trill duration may be a useful indicator of male ‘quality’. Territorial male bearded seals may be ‘successful’ individuals while roaming males may be younger animals or males in poorer condition that are unable to maintain an aquatic territory. Our data on underwater vocalizations and movements of male bearded seals thus provide evidence for the use of alternative mating tactics in this species.Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.      

Geographical and temporal patterns of lemming population dynamics in Fennoscandia

There is a long-lasting debate in ecology on cyclicity. synchrony and time lags of lemming population fluetuations. We have analysed 137 yr of previously published population data on the Norwegian lemming Lemmus lemmus in ten geographic regions of Fennoscandia. The dominating pattern was synchronous 4-yr cycles. There was no support for the hypothesis of a north-south gradient in cycle length. However, we found periods of prolonged interruptions in the cyclicity, which were more eommon in northern areas. We found a high degree of synchrony between regions, with only a weak relationship to distance. The observed pattern in lemming population dynamics was more consistent with effects from extrinsic factors, such as climate, than intrinsic factors, such as dispersal.     

An assessment of population size and distribution of harbour seals in the Republic of Ireland during the moult season in August 2003

The status of Ireland's harbour seal Phoca vitulina vitulina population is poorly understood. The most recent national population estimate dates back to the breeding season in 1978 and did not cover the entire coastline. Reliable up-to-date information on the abundance and distribution of harbour seals in Ireland is necessary to assess the conservation status of the species and for the effective identification, management and monitoring of special areas of conservation required for harbour seals under the EU Habitats Directive. To provide comprehensive current information on Ireland's harbour seal population, a geographically extensive survey was conducted along the coastline of the Republic of Ireland during the species' annual moult in August 2003. This complemented a similar survey of Northern Ireland, which was conducted in 2002. Using thermal imaging technology, haul-out groups of harbour seals and grey seals Halichoerus grypus were identified from the air, aerial-counts were obtained and compared with simultaneous ground-count data from selected sites. Harbour seal distribution recorded during the 2003 moult season was concentrated in the south-west, west and north-west of the country. This national survey yielded a minimum population estimate for the Republic of Ireland of 2905 harbour seals, delivering an effective baseline for current and future population research.     

Age- and sex-specific mortality patterns in an emerging wildlife epidemic: the phocine distemper in European harbour seals

Analyses of the dynamics of diseases in wild populations typically assume all individuals to be identical. However, profound effects on the long-term impact on the host population can be expected if the disease has age and sex dependent dynamics. The Phocine Distemper Virus (PDV) caused two mass mortalities in European harbour seals in 1988 and in 2002. We show the mortality patterns were highly age specific on both occasions, where young of the year and adult (>4 yrs) animals suffered extremely high mortality, and sub-adult seals (1-3 yrs) of both sexes experienced low mortality. Consequently, genetic differences cannot have played a main role explaining why some seals survived and some did not in the study region, since parents had higher mortality levels than their progeny. Furthermore, there was a conspicuous absence of animals older than 14 years among the victims in 2002, which strongly indicates that the survivors from the previous disease outbreak in 1988 had acquired and maintained immunity to PDV. These specific mortality patterns imply that contact rates and susceptibility to the disease are strongly age and sex dependent variables, underlining the need for structured epidemic models for wildlife diseases. Detailed data can thus provide crucial information about a number of vital parameters such as functional herd immunity. One of many future challenges in understanding the epidemiology of the PDV and other wildlife diseases is to reveal how immune system responses differ among animals in different stages during their life cycle. The influence of such underlying mechanisms may also explain the limited evidence for abrupt disease thresholds in wild populations.     

Daily patterns of courtship and mating behavior in the male Japanese quail

Crowing behavior was monitored constantly in male Japanese quail housed singly over 30 successive days. The photoperiod was 16h of light and 8 h of dark. A daily pattern in crowing was observed in which the frequencies were elevated in the afternoon and at the beginning of darkness. However, peak crowing occured 2 h prior to the onset of light. These rhythms were highly correlated among individuals and extremely repeatable over the sequential days of observation.In a second experiment, males which were paired with females were observed for frequencies of crowing, courtship, and mating behavior during the lighted portion of the day. In this experiment, the same photoperiod (16L:8D) was maintained. Paired males exhibited a daily pattern in crowing similar to that observed in the singly housed males. The frequency of mating was the highest between 1200 and 1300 h and lowest at 1400 h. Mating success was highest at midday, as were the number of males exhibiting mating behavior. These diurnal patterns in sexual behavior may depend on environmental cues such as photoperiod, which, in turn, may stimulate endocrine triggers.     

Geographical variation in the mating system of the dusky pipefish (Syngnathus floridae)

Differences among populations in the intensity of sexual selection resulting from distinct genetic mating systems can lead to divergent morphological evolution and speciation. However, little is known about how genetic mating systems vary between populations and what factors may contribute to this variation. In this study, we compare the genetic mating systems of two geographically distinct populations of the dusky pipefish (Syngnathus floridae), a species characterized by polygynandry and male pregnancy, from the Atlantic Coast of Virginia and the Gulf Coast of Florida. Our results revealed significant interpopulation variation in mating and reproductive success. Estimates of the opportunity for selection (I), the opportunity for sexual selection (I(s)) and the Bateman gradient (beta(ss)) were higher among males in the Florida population than in the Virginia population, suggesting that sexual selection on males is stronger in the Florida population. The Virginia population is larger and denser than the Florida population, suggesting that population demographics may be one of many causal factors shaping interpopulational mating patterns. This study also provides evidence that the adult sex ratio, operational sex ratio, population density and genetic mating system of S. floridae may be temporally stable over timescales of a month in the Florida population. Overall, our results show that this species is a good model for the study of mating system variation in nature and that Bateman's principles may be a useful technique for the quantitative comparison of mating systems between populations.     

Geographical and temporal patterns of cyanobacterial assemblages in the Danube Delta lake complexes

Hydrobiologia - Danube Delta shallow lakes experience cyanobacteria blooms that can negatively affect the aquatic ecosystem. Although there are several studies on Danube Delta cyanobacteria, little...     

Modelling spatial patterns in harbour porpoise satellite telemetry data using maximum entropy

The distribution of harbour porpoises in EU waters is poorly understood, and modelled predictions of their distributions could inform the strategic spatial planning of future exploitation of the marine environment to avoid potential conflicts. We analysed satellite telemetry data from 39 harbour porpoises Phocoena phocoena in inner Danish waters using a modelling tool rooted in maximum entropy: Maxent. Maxent does not require absence data and has been shown to be effective for data characterised by small sample size, sampling bias and locational errors. For each season we used an iterative bootstrapping procedure to randomly select among the most precise records from each of the 39 tagged individuals, and ran Maxent on pooled records based on explanatory environmental variables hypothesised to serve as good proxies for harbour porpoise prey abundance. Among our environmental variables, distance to coast and bottom salinity had the most explanatory power, and their response shapes were relatively consistent across most seasons. The predictive power of the models (assessed by ROC‐AUC) ranged from 0.70 to 0.86 within seasons. The southern Kattegat, the Belt Seas, most western part of the Baltic Sea and the Sound were predicted to have relatively high probabilities of occurrence across seasons. In contrast, the central part of Kattegat and the Baltic Sea south and east of Limhamn and Darss Ridge consistently showed low probabilities of occurrence. Areas with the lowest probabilities of occurrence were generally characterised by high predictive uncertainty. Our methods have implications for the analyses of satellite tagged animals in terrestrial and marine environments. By coupling a bootstrapping procedure with Maxent we circumvented some of the statistical challenges presented by satellite telemetry data to generate spatial predictions within the inner Danish waters.     

Sampling spatial and temporal variation in soil nitrogen availability

There are few studies in natural ecosystems on how spatial maps of soil attributes change within a growing season. In part, this is due to methodological difficulties associated with sampling the same spatial locations repeatedly over time. We describe the use of ion exchange membrane spikes, a relatively nondestructive way to measure how soil resources at a given point in space fluctuate over time. We used this method to examine spatial patterns of soil ammonium (NH⁺ ₄) and nitrate (NO⁻ ₃) availability in a mid-successional coastal dune for four periods of time during the growing season. For a single point in time, we also measured soil NH⁺ ₄ and NO⁻ ₃ concentrations from soil cores collected from the mid-successional dune and from an early and a late successional dune. Soil nitrogen concentrations were low and highly variable in dunes of all ages. Mean NH⁺ ₄ and NO⁻ ₃ concentrations increased with the age of the dune, whereas coefficients of variation for NH⁺ ₄ and NO⁻ ₃ concentrations decreased with the age of the dune. Soil NO⁻ ₃ concentration showed strong spatial structure, but soil NH⁺ ₄ concentration was not spatially structured. Plant-available NH⁺ ₄ and NO⁻ ₃ showed relatively little spatial structure: only NO⁻ ₃ availability in the second sampling period had significant patch structure. Spatial maps of NH⁺ ₄ and NO⁻ ₃ availability changed greatly over time, and there were few significant correlations among soil nitrogen availability at different points in time. NO⁻ ₃ availability in the second sampling period was highly correlated (r = 0.90) with the initial soil NO⁻ ₃ concentrations, providing some evidence that patches of plant-available NO⁻ ₃ may reappear at the same spatial locations at irregular points in time. Received: 20 February 1998 / Accepted: 23 November 1998     

Nest‐site fidelity in parental male bluegill Lepomis macrochirus: spatial patterns and the influence of prior mating success

A 4 year mark–recapture study examined the pattern of nesting site fidelity of parental‐type male bluegill Lepomis macrochirus. The study results indicated that iteroparous male L. macrochirus choose new nest sites near their own previously used sites. The scale of site fidelity varied, but generally males choose to renest within shoreline areas rather than specific or exact nest locations (94% within‐year, 86% among‐years). Iteroparous males also displayed no preference to nest in proximity to neighbouring males from previous colonies to suggest social fidelity. Contrary to expectation, manipulating males' reproductive success had no significant effect on the pattern or scale of male reproductive site fidelity.     

Climate-driven spatial and temporal patterns in peatland pool biogeochemistry

Peatland pools are freshwater bodies that are highly dynamic aquatic ecosystems because of their small size and their development in organic-rich sediments. However, our ability to understand and predict their contribution to both local and global biogeochemical cycles under rapidly occurring environmental change is limited because the spatiotemporal drivers of their biogeochemical patterns and processes are poorly understood. We used (1) pool biogeochemical data from 20 peatlands in eastern Canada, the United Kingdom, and southern Patagonia and (2) multi-year data from an undisturbed peatland of eastern Canada, to determine how climate and terrain features drive the production, delivering and processing of carbon (C), nitrogen (N), and phosphorus (P) in peatland pools. Across sites, climate (24%) and terrain (13%) explained distinct portions of the variation in pool biogeochemistry, with climate driving spatial differences in pool dissolved organic C (DOC) concentration and aromaticity. Within the multi-year dataset, DOC, carbon dioxide (CO₂), total N concentrations, and DOC aromaticity were highest in the shallowest pools and at the end of the growing seasons, and increased gradually from 2016 to 2021 in relation to a combination of increases in summer precipitation, mean air temperature for the previous fall, and number of extreme summer heat days. Given the contrasting effects of terrain and climate, broad-scale terrain characteristics may offer a baseline for the prediction of small-scale pool biogeochemistry, while broad-scale climate gradients and relatively small year-to-year variations in local climate induce a noticeable response in pool biogeochemistry. These findings emphasize the reactivity of peatland pools to both local and global environmental change and highlight their potential to act as widely distributed climate sentinels within historically relatively stable peatland ecosystems.     

Happily together forever: temporal variation in spatial patterns and complete lack of territoriality in a promiscuous rodent

The availability of resources, their effect on population density and territoriality, and the ways in which these factors are interwoven with mating systems are important determinants of small mammal space use. It is often difficult to study these patterns in an integrated way, however, especially because long-term data are needed but not readily available. In this paper, we investigate effects of population density, season and breeding status on home range patterns of the promiscuous rodent Mastomys natalensis using monthly capture-mark-recapture data collected over 17 years in a 3-ha grid. Home ranges were estimated using minimum convex polygons bounded by trap locations, and home range overlap and visitation rates were calculated as a measure of territoriality. As higher population densities coincide with increased resource availability, we predicted that home range sizes would correlate negatively with density. Furthermore, as M. natalensis is promiscuous and population densities are generally high, we predicted that territoriality would be low, and home range overlap would therefore be high. Contrary to expectations the home ranges of female adults increased with population density, although those of male adults and subadults followed the expected decrease. Home range overlap and visitation rates were generally high, and increased significantly with population density. More importantly, they were never lower than those of simulated datasets consisting of randomly moved home ranges. These results therefore suggest that M. natalensis displays a complete lack of territoriality that is rarely seen in small mammals but still meets predictions based on knowledge of density and mating system.     

Mating system and reproductive success in eastern Pacific harbour seals

Harbour seals sometimes breed along inland travel corridors where females become clustered in space and time and males establish underwater acoustic display territories similar to terrestrial arenas known as resource-based leks. Under these conditions, we predicted that higher levels of polygyny would be observed than has been previously reported for this species mating in open coast environments without travel corridors. Reproductive success (RS) of 70 males was measured using 20 microsatellite DNA loci and likelihood-based paternity analysis of 136 offspring collected over 3 years. Most males were assigned either zero or one paternity with 80% confidence. The greatest number of pups assigned to one male in a season was two. Variance in RS was higher for males than females (which are biologically limited to one offspring per year) indicating low to mild polygyny. In addition, distributions of relatedness values among pups within year classes did not differ significantly from a simulated distribution with R = 0, indicating that half-siblings were uncommon. Overall, polygyny levels were low relative to terrestrial pinniped mating systems and similar to observations from a harbour seal population along an open coast. Due to large confidence intervals associated with our results, we cannot rule out the hypothesis that a travel corridor might increase the degree of polygyny skew relative to that observed in open coast environments. Habitat appeared to influence male strategies as the most successful males in open coast environments patrolled offshore, while the most successful male in this study defended a territory along the travel corridor.     

Geographical variation in the spatial synchrony of a forest-defoliating insect: isolation of environmental and spatial drivers

Despite the pervasiveness of spatial synchrony of population fluctuations in virtually every taxon, it remains difficult to disentangle its underlying mechanisms, such as environmental perturbations and dispersal. We used multiple regression of distance matrices (MRMs) to statistically partition the importance of several factors potentially synchronizing the dynamics of the gypsy moth, an invasive species in North America, exhibiting outbreaks that are partially synchronized over long distances (approx. 900 km). The factors considered in the MRM were synchrony in weather conditions, spatial proximity and forest-type similarity. We found that the most likely driver of outbreak synchrony is synchronous precipitation. Proximity played no apparent role in influencing outbreak synchrony after accounting for precipitation, suggesting dispersal does not drive outbreak synchrony. Because a previous modelling study indicated weather might indirectly synchronize outbreaks through synchronization of oak masting and generalist predators that feed upon acorns, we also examined the influence of weather and proximity on synchrony of acorn production. As we found for outbreak synchrony, synchrony in oak masting increased with synchrony in precipitation, though it also increased with proximity. We conclude that precipitation could synchronize gypsy moth populations directly, as in a Moran effect, or indirectly, through effects on oak masting, generalist predators or diseases.