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.