As clear as day: nocturnal activity differs from diurnal activity in a temporally constrained capital breeder

Time-activity budgets are fundamental to behavioural studies, allowing examination of how individuals allocate their time, and potentially energy, and how these patterns vary spatially and temporally and in relation to habitat, individual identity, sex, social status and levels of anthropogenic disturbance. Direct observations of animal behaviour, especially in the wild, are often limited to daylight hours; therefore, many activity budgets relate to diurnal activity only, or assumptions are made about nocturnal activity. Activity budgets have been a key component of many behavioural and energetics studies of breeding grey seals (Halichoerus grypus, Fabricius, 1791), and yet very little is known about nocturnal activity of grey seals, and a general, implicit assumption of no significant change from day to night seems to pervade the literature. Here we use a combination of high resolution digital video and thermal imaging video camera to follow known individual grey seal mothers from day into night to examine activity patterns during lactation. We show distinct differences in nocturnal activity budgets relative to diurnal activity budgets. Mothers spent significantly more time resting with a reduction of time spent in the alert and comfort move behavioural categories during nocturnal periods. It is clear that diurnal time-activity patterns of breeding female grey seals cannot be extrapolated to represent activity across a 24-hour cycle. These considerations are particularly critical in studies that aim to use time-activity budgets as proxies for energy budgets

Variability in individual rates of aggression in wild gray seals: fine-scale analysis reveals importance of social and spatial stability

Aggressive interactions are costly for individuals in time, energy, or physical damage, and in polygynous mating systems, there is high variability in the rates and intensity of aggression across individuals and within breeding seasons. However, examinations into the drivers of this variability are often conducted in isolation, in non-wild systems, or the predictor variables in question, for example, dominance, are averaged across large spatial, social, or temporal scales. The aim of this study was to adopt a fine spatial and temporal scale approach to investigate the factors associated with inter-individual variation in aggression in wild, breeding male gray seals within three consecutive breeding seasons. To do this, we fit models examining if the daily frequency of aggression and probability of escalated aggression for males was best explained by factors such as dominance score, proximity to competitors or females, local social stability, and the occurrence of stochastic environmental events. Stability of neighbor identities was the strongest correlate of reduced male aggression. Dominance status did not correlate with aggression at the daily scale, with the exception of one period after a natural disturbance to the breeding colony where dominant males had relatively reduced rates of aggression. These findings emphasize the importance of local social stability in explaining inter-individual variation in aggression in a wild population and suggest that factors associated with aggression are context dependent in relation to the natural environment. Furthermore, we highlight the utility of a fine temporal scale and incorporating spatial parameters when investigating variability in aggression in wild systems

Personality, density and habitat drive the dispersal of invasive crayfish

There is increasing evidence that personality traits may drive dispersal patterns of animals, including invasive species. We investigated, using the widespread signal crayfish Pacifastacus leniusculus as a model invasive species, whether effects of personality traits on dispersal were independent of, or affected by, other factors including population density, habitat, crayfish size, sex and limb loss, along an invasion gradient. Behavioural traits (boldness, activity, exploration, willingness to climb) of 310 individually marked signal crayfish were measured at fully-established, newly-established and invasion front sites of two upland streams. After a period at liberty, recaptured crayfish were reassessed for behavioural traits (newly-established, invasion front). Dispersal distance and direction of crayfish movement, local population density, fine-scale habitat characteristics and crayfish size, sex and limb loss were also measured. Individual crayfish exhibited consistency in behavioural traits over time which formed a behavioural syndrome. Dispersal was both positively and negatively affected by personality traits, positively by local population density and negatively by refuge availability. No effect of size, sex and limb loss was recorded. Personality played a role in promoting dispersal but population density and local habitat complexity were also important determinants. Predicting biological invasion in animals is likely to require better integration of these processes

Finescale topographical correlates of behavioural investment in offspring by female grey seals, Halichoerus grypus

Grey seals breed colonially on substrates ranging from ice to rocky or sandy beaches. Clear differences in seal behaviour patterns exist among such broad classes of breeding habitat. However, finer scale topographical variation is likely to influence individual behaviour with consequences for pupping success. We examined topographical influences on the behaviour of breeding female grey seals by quantifying topography at a subseal size resolution. Using submetre resolution digital terrain models of two sites within a rocky breeding colony, we compared site topography in relation to observed differences in female behaviour at these sites. Females at both sites preferred breeding close to water (standing pools or sea) and frequently commuted between their pups and water. Topographical models indicated that one site was more costly for seals in terms of their locations and movements within the site. This was due to a lack of low-elevation land adjacent to the main access points from the sea and the reduced availability of pools. Females at this site showed reduced pup attendance and an increase in energetically costly behaviours, whilst females at the lower-cost site spent more time interacting with their pups and resting. These topographically induced behavioural differences are likely to affect the quantity and quality of pup provisioning by mothers and influence individual pupping site selection. Less costly sites are likely to be colonized preferentially and by larger, older and more dominant females, potentially generating finescale spatial heterogeneity in female quality within the breeding colony

A physically motivated index of sub-grid scale pattern.

Earth Observation data on land surface properties such as albedo are typically collected at a pixel resolution of 1 km or less. Global climate models, on the other hand, are constrained by current limits on computing power to run at a grid box resolution of 10 km or more. This mismatch in spatial scales means that large amounts of pixel-scale information are condensed into a small number of grid-box-scale summary statistics before use in global climate models. Subgrid-scale patterns in land surface properties may have a significant effect but the summary statistics currently in use, such as the grid box mean and grid box variance, are insensitive to the spatial arrangement of pixels. To address this gap in the information available to global climate models we define here a new grid-box-scale summary statistic, the Laplacian pattern index, that is sensitive to the spatial arrangement of pixels. This dimensionless index is based on the mean-squared value of the Laplacian filter del(2) within the grid box and is motivated by the physics of diffusive heat transport. We investigate the value of the index in some simple cases and show that it is a measure of the local correlation structure within a grid box. This allows us to generate random grid boxes in which the index takes ( on average) a prescribed value. The Laplacian pattern index is designed to be a useful measure of subgrid-scale pattern in numerical climate models, but can be used as a measure of pattern in any two-dimensional array of real-valued data