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opencc-by-4.0May 2020View details →

Weddell seal diving data from the Weddell Sea (2011)

These data comprise locations and dive metrics from 19 adult Weddell seals (Leptonychotes weddellii) instrumented in February 2011 with telemetry devices. These devices were Sea Mammal Research Unit Conductivity-Temperature-Depth Satellite Relay Data Loggers. These are animal-attached loggers that are manufactured and programmed by the Sea Mammal Research Unit Instrumentation Group at the University of St Andrews, Scotland. Ethical approval for this work was obtained from the University of St Andrews Animal Welfare and Ethics Committee, and from the corresponding committee at the British Antarctic Survey. This dataset is linked to the manuscript Photopoulou et al. 2020 "Sex-specific variation in the use of vertical habitat by a resident Antarctic top predator" Proceedings of the Royal Society B (http://dx.doi.org/10.1098/rspb.2020.1447) and a preprint on bioRxiv (https://doi.org/10.1101/2020.06.15.152009). The data are structured in long format, so that each row in the dataset represents an observation. The columns in the data are as follows. ID: This a factor variable identifying each individual seal. It has 19 levels. sex: This is a character variable identifying the sex of the seal, either "F" or "M" for female and male. source: This is a factor variable identifying the type of record. It has three levels "dv", "ho" and "sf" for dive, haulout and surface record respectively.  start_date: This is a date variable (POSIXct) that gives the date and time of the beginning of an observation in UTC time. end_date: This is a date variable (POSIXct) that gives the date and time of the end of an observation in UTC time. local_start_date: This is a date variable (POSIXct) that gives the local date and time of the beginning of an observation at the geographic location of the seal. end_end_date: This is a date variable (POSIXct) that gives the local date and time of the end of an observation at the geographic location of the seal. fg_lon: This is a numeric variable and gives the longitude of the seal at the local end time of each record. This is the product of fitting a statistical model to the observed ARGOS location data, taking account of the error class. This is not the originally observed location. The model used was a continuous time state-space model implemented in the R package foieGras by Ian Jonsen and Toby Patterson (2019) foieGras: Fit Continuous-Time State-Space and Latent Variable Models for Filtering Argos Satellite (and Other) Telemetry Data and Estimating Movement Behaviour. R package version 0.4.01. <https://cran.r-project.org/package=foieGras> fg_lat: This is a numeric variable and gives the latitude of the seal at the local end time of each record. This is the product of fitting a statistical model to the observed ARGOS location data, taking account of the error class. This is not the originally observed location. The model used was a continuous time state-space model implemented in the R package foieGras by Ian Jonsen and Toby Patterson (2019) as above in fg_lon. hour: This is a positive integer variable giving the hour of the day at the local end date. week: This is a positive integer variable giving week of the year at the UTC end date. DURATION: This is a positive integer variable that gives the duration of the record in seconds. MAX_DEP: This is a positive continuous variable that gives the maximum depth (m) visited during a record. This is only zero for haulout records. hunt_secs: This is a positive integer variable that gives the total number of seconds spent in hunting behaviour as calculated using methods developed by Heerah et al. (2019) Validation of dive foraging indices using archived and transmitted acceleration data: The case of the Weddell seal. Frontiers in Ecology and Evolution, 7: 30 and in the supplementary material of Photopoulou et al. (2020) Sex-dependent variation in the use of vertical habitat by a resident Antarctic top predator.  hunt_prop: This is a numeric variable ranging from 0 to 1. It represents the proportion of dive time spent hunting and is calculated as hunt_secs/DURATION for dive records only. hunt_avgdep: This is a positive continuous variable giving the mean depth (m) of hunting behaviour as calculated using methods described above. hunt_mindep: This is a positive continuous variable giving the minimum (shallowest) depth (m) of hunting behaviour, as calculated using methods described above. hunt_maxdep: This is a positive continuous variable giving the maximum (deepest) depth (m) of hunting behaviour, as calculated using methods described above. bathy: This is a negative continuous variable giving the depth (m) of the seal floor at the record's location based on the IBSCO bathymetry dataset Arndt et al. (2013) The International Bathymetric Chart of the Southern Ocean (IBCSO) Version 1.0—A new bathymetric compilation covering circum‐Antarctic waters. Geophysical Research Letters, 40(12): 3111-3117  bathy_std: This is a numeric variable giving the standardised bathymetry value calculated as (bathy-mean(bathy))/sd(bathy). prop_bathy: This is a numeric variable ranging from 0 to 1, giving the proportion of bathymetry reached at the maximum dive depth, calculated as MAX_DEP/bathy. prop_hunt_bathy: This is a numeric variable ranging from 0 to 1, giving the proportion of bathymetry reached at the mean hunting depth, calculated as hunt_avgdep/bathy. dep4ctd: This is a discrete numeric variable diving the depth at which temperature and salinity were extracted from the CTD profile nearest in time to the location of the record. The CTD profile was interpolated at a 10m resolution. psal: This is a positive continuous variable giving the salinity (PSU) at the location of the record, at the depth given by dep4ctd. When there was no hunting, there is an NA. temp: This is a positive continuous variable giving the potential temperature (degrees Celsius) at the location of the record, at the depth given by dep4ctd. When there was no hunting, there is an NA.

opencc-zeroDec 2023View details →

Beneath the Antarctic sea-ice: Fine-scale analysis of Weddell seal (Leptonychotes weddellii) behaviour and predator-prey interactions, using micro-sonar data in Terre Adélie

In this study, we tried to assess: i) whether and how female Weddell seals feed (frequency, depth, duration) during lactation, ii) what is their utilization of a limited foraging area (benthic or pelagic dives) as they are spatially constrained by the presence of their pup, and iii) how can we characterize their foraging dives and the approach/catching phases using new tools providing a more detailed description of their behaviour. Sonar tags were deployed on three breeding female Weddell seals in Terre Adélie (East Antarctica) in November 2019, to study animals' movements and dives at high resolution (3D acceleration, magnetometry, time and depth and GPS location), as well as information on prey and predator-prey interactions using acoustic data.

Figure 2 in Sex-related differences in the postmolt distribution of Weddell seals (Leptonychotes weddellii) in the southern Weddell Sea

Figure 2. Weddell seal tracks created by interpolating estimated dive positions in time. Coastline and contours from Arndt et al. (2013) and bathymetry from ETOPO1 1 Arc-Minute Global Relief Model (Amante and Eakins 2009). Projection: Polar Stereographic. Datum: World Geodetic 1984 (WGS84).

Figure 5 in Sex-related differences in the postmolt distribution of Weddell seals (Leptonychotes weddellii) in the southern Weddell Sea

Figure 5. Resident time (the proportion of dives allocated a resident behavioral state from the state-space model taken from Bestley et al. 2015) for five male and eight female Weddell seals in region A (shallow water in the shelf), region B (deep water Filchner Trough), region C (continental shelf edge), and region D (deep water off the shelf).

Figure 1b in Sex-related differences in the postmolt distribution of Weddell seals (Leptonychotes weddellii) in the southern Weddell Sea

Figure 1b. Four regions categorized by chart contours and bathymetry. Region A is south of 74°200S and <600 m, region B is south of 74°200S and ≥600 m, region C is north of 74°400S and <2,000 m and region D is north of 74°400S and ≥2,000 m. Coastline and contours from Arndt et al. (2013) and bathymetry from ETOPO1 1 Arc-Minute Global Relief Model (Amante and Eakins 2009). Projection: Polar Stereographic. Datum: World Geodetic 1984 (WGS84).

Figure 1a in Sex-related differences in the postmolt distribution of Weddell seals (Leptonychotes weddellii) in the southern Weddell Sea

Figure 1a. Study area showing postmolt range of Weddell seals tagged with CTD-SRDLs during 2011 deployment. Axes include data on both latitude and longitude. Minimum ice extent data from January 2011 and maximum ice extent data from June 2011 (Fetterer et al. 2002). Coastline and contours from Arnt et al. (2013) and bathymetry from ETOPO1 1 Arc-Minute Global Relief Model (Amante and Eakins 2009). Projection: Polar Stereographic. Datum: World Geodetic 1984 (WGS84).

Figure 4 in Sex-related differences in the postmolt distribution of Weddell seals (Leptonychotes weddellii) in the southern Weddell Sea

Figure 4. Bathymetry in meters associated with each estimated dive position for 9 males and 10 females. Bathymetry data were extracted from ETOPO1 1 Arc-Minute Global Relief Model (Amante and Eakins 2009).

opencc-zeroJun 2023View details →

Data from: Evaluating the importance of individual heterogeneity in reproduction to Weddell seal population dynamics using integral projection models

<ol> <li>Identifying and accounting for unobserved individual heterogeneity in vital rates in demographic models is important for estimating population-level vital rates and identifying diverse life-history strategies, but much less is known about how this individual heterogeneity influences population dynamics.</li> <li>We aimed to understand how the distribution of individual heterogeneity in reproductive and survival rates influenced population dynamics using vital rates from a Weddell seal population by altering the distribution of individual heterogeneity in reproduction, which also altered the distribution of individual survival rates through the incorporation of our estimate of the correlation between the two rates and assessing resulting changes in population growth.</li> <li>We constructed an integral projection model (IPM) structured by age and reproductive state using estimates of vital rates for a long-lived mammal that has recently been shown to exhibit large individual heterogeneity in reproduction. Using output from the IPM, we evaluated how population dynamics changed with different underlying distributions of unobserved individual heterogeneity in reproduction.</li> <li>Results indicate that the changes to the underlying distribution of individual heterogeneity in reproduction cause very small changes in the population growth rate and other population metrics. The largest difference in the estimated population growth rate resulting from changes to the underlying distribution of individual heterogeneity was less than 1%.</li> <li>Our work highlights the differing importance of individual heterogeneity at the population level compared to the individual level. Although individual heterogeneity in reproduction may result in large differences in the lifetime fitness of individuals, changing the proportion of above- or below-average breeders in the population results in much smaller differences in annual population growth rate. For a long-lived mammal with stable and high adult-survival that gives birth to a single offspring, individual heterogeneity in reproduction has a limited effect on population dynamics. We posit that the limited effect of individual heterogeneity on population dynamics may be due to canalization of life-history traits.</li> </ol>

publicDec 2023View details →

Beneath the Antarctic sea-ice: Fine-scale analysis of Weddell seal (Leptonychotes weddellii) behaviour and predator-prey interactions, using micro-sonar data in Terre Adélie

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publicJun 2023View details →

Data from: Evaluating the importance of individual heterogeneity in reproduction to Weddell seal population dynamics using integral projection models

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Figure 3 in Sex-related differences in the postmolt distribution of Weddell seals (Leptonychotes weddellii) in the southern Weddell Sea

Figure 3. Daily speed (distance traveled in km/deployment length in days) for five male and eight female Weddell seals in region A (shallow water in the shelf), region B (deep water Filchner Trough), region C (continental shelf edge), and region D (deep water off the shelf).