DOI: 10.5061/dryad.rv15dv4fg
title: Data from: A marine predator relies on both social cues and frequently updated memory to search for prey

description: Finding scattered resources is a challenge for marine predators, their
 search strategies shaping in turn their response to global changes. Three
 types of search strategies are generally considered: random opportunistic
 search, reliance on conspicuous social cues or long-term individual
 fidelity to predictably productive areas. More complex strategies, namely
 intermediate, composite and/or those varying across time and environmental
 conditions are likely to prevail but are rarely explored. We investigated
 memory strategies in Cape gannets, a marine predator heavily relying on
 social cues, and closely related to the Northern gannet which shows
 long-term individual foraging fidelity. Repeat GPS tracks within seasons
 revealed that two different individuals leaving the colony more than three
 days apart showed random chances to forage in a similar direction, whereas
 within-individuals, birds persisted in a same direction for longer
 timescales, reaching random levels only after ten days, or nine
 consecutive trips. This strategy of transient individual preferences
 within a breeding season was observed in most individuals, every year.
 These results suggest a consistent and complex search strategy mixing
 social cues and private information updated every few days. Our simple
 approach can readily be applied to other central place foragers to better
 understand the evolutionary ecology of search strategies.
description: # Cape gannets monitoring of individual fidelity in foraging direction
 [https://doi.org/10.5061/dryad.rv15dv4fg](https://doi.org/10.5061/dryad.rv15dv4fg) Contains metadata files and codes from which to replicate the analyses and figures presented in the manuscript: "A marine predator relies on both social cues and frequently updated memory to search for prey" (10.1098/rspb.2024.2327). Raw GPS tracking data has already been deposited in a more standardized repository (Seabird Tracking Database: [https://data.seabirdtracking.org/](https://data.seabirdtracking.org/)). In "Data" we provide the main script ("Rscript_CGtracksBI_06_DataAnalyses.R", inside subfolder "Scripts Main analyses") to replicate the analyses and figures of the main text of the manuscript, requiring only the three metadata files deposited here in Dryad as well. We also include in the sub-folder "Supplementary Analyses" another metadata file and a code (Rscript_CGtracksBI_08) to replicate the analyses of the Supplementary Material. In "Software" (via Zenodo) we provide, for information, codes to obtain metadata files from the raw tracking data available in Seabird Tracking Database. These codes can only run from the raw tracking data. ## Description of the data and file structure "BirdIsland_CAGA_MasterFile_2010-2021_ForReplicability" provides data on equipped individuals (bird ID, sex when known, average weight and culmen length, and information about deployment and retrieval of GPS device). "CG_2010-2021_alltracks_summary_final.csv" contains descriptive statistics on each foraging trip recorded, a numbering of consecutive trips by the same individual, and a link to individual bird ID. Descriptions of foraging trips include start date, number of recorded GPS locations, distance and direction at maximum range, trip duration, total distance covered, stats on duration between consecutive locations recorded within the trip, stats on the proportion of recorded locations within 15° or 30° of the direction at max range, stats on the completeness of the record (gaps within the foraging trip, distance from colony on last recorded location and corresponding % of max range distance, ...) and stats on speed calculated across consecutive recorded locations. "CG_2010-2021_allpairsoftracks_final" contains descriptive statistics on all possible pairs of foraging trips in the dataset, and links to both bird ID and trip number ID. Descriptive statistics include angle between directions at maximum range, number of consecutive trips apart (delta-trip, when from the same individual), time between trip departures, and difference in distance at maximum range (warning, not distance between points of maximum range). A R object containing bathymetric information on the Indian Ocean, obtained from NOAA server with the R package marmap is also provided in the "Software" section, to help replicate the map (but raw tracking data is needed to fully replicate Figure 1 of the main text). ## Code/Software 9 scripts for R commands are provided in total, some for information on how we proceeded but that require raw data deposited elsewhere (Seabird Tracking Database), and some (mainly Rscript_CGtracksBI_06) to replicate the analyses of the manuscript from the metadata files provided here. In detail, codes included in "Data" are: \- a homemade function to calculate angular differences between bearings (Diffcap, called by Rscript_CGtracksBI_06), \- 1 script (Rscript_CGtracksBI_06) to perform the analyses reported in the manuscript from the three final metadata files provided here, \- a script (Rscript_CGtracksBI_08) to perform the analyses reported in the supplementary materials using an additional metadatafile ("all.pairs_angle_nnd_emd.csv", in subfolder SupplementaryAnalyses) "Software" additionally contains: \- a script to generate the complex Figure 1 in the manuscript (including a RAM-heavy map: BathyMapIndianOcean), although raw tracks are needed to add them on the map (tracking data available in the Seabird Tracking Database) \- a script to generate the picture of the map legend included in Figure 1 ("ScriptForBathyScale.R") \- 5 scripts presented for information only (Rscript_CGtracksBI_01 to Rscript_CGtracksBI_05), to curate raw tracking data (available in the Seabird Tracking Database) and obtain the metadata provided in "Data", \- a set of scripts (Rscript_CGtracksBI_07, Codes A-S Bonnet-Lebrun for NND-EMD) used to generate the supplementary metadata file ("all.pairs_angle_nnd_emd.csv" in "Data") in order to check that the conclusions remained unchanged with a different way to measure similarity betwen foraging trips, corresponding to analyses presented in the Supplementary Materials of the main publication. More specifically: * Rscript_CGtracksBI_07 calculates mean and median trip directions (to be used instead of direction at max range) from raw GPS tracking data (data available at Seabird Tracking Database, code included here for information only) * Codes A-S Bonnet-Lebrun for NND-EMD were included separately because they use another style of R syntax, required specific work to be merged with the rest of the anayses. They include: * a script to calculate NND and EMD indices of similarity between trips from raw tracking data (code included for information only, raw tracking data available at Seabird Tracking Database) * 2 output csv files ("emd.csv" & "nnd.csv") generated by the above script, respectively reporting EMD and NND for each pairs of trips * a script to generate exploratory figures to interpret results from these other similarity indices (not exploited in the manuscript) * 1csv file ("all.pairs_angle_nnd_emd.csv") merging emd & nnd outputs (mentioned above) with all other metrics calculated in the main three metadatafiles (see details below): in addition to column titles already described for these other metadatafiles, 5 other columns are included at the end: * NND12: NND calculated from locs of trip 1 to nearest locs of trip 2 (in km) * NND21: NND calculated from locs of trip 2 to nearest locs of trip 1(in km) * NND21_no_units: not used * EMD: EMD calculated between trips 1 & 2 (no units) * trips_rel: whether trips 1&2 were from the same or from different individual birds ## Description of column headings & units NAs correspond to cases where the value could not be measured / calculated ### Master metadata One line = one individual equipped on one season | DataFileName | BreedingSeason | IndividualID | AgeGroup | BreedingStatus | Sex | DeploymentDate | DeploymentTime | RetreivalDate | RetreivalTime | TripType | GPSFixRate | CorrespAllTr | Folder\_FileGPS | MeanWeight | CulmenLength | | :--------------------- | :---------------------- | :------------------------------------------------------------- | :----------- | :----------------------------------------------------------------------------------------- | :------------ | :------------------------------ | :------------------------------ | :-------------------------------------- | :-------------------------------------- | :----------------------------------------- | :----------------------------- | :---------------------------------------------------------- | :-------------- | :---------------------------------------------------- | :----------- | | name of raw track file | period december-january | Unique identifier of bird (for that season, not always ringed) | Adult or Juv | Only Guard were kept in analyses: corresponds to young chick guarded by one of the parents | Often unknown | When GPS logger was put on bird | When GPS logger was put on bird | When GPS logger was retrieved from bird | When GPS logger was retrieved from bird | Single or multiple froaging trips recorded | Programmed recording frequency | identifier to make correspondence with other metadata files | not used here | in grams, average of several measures when applicable | in mm | ### All tracks One line = one foraging trip recorded on one individual (often multiple trips per individual; i.e. multiple lines for 1 line in Master metadata file) | id | tr | date | npt | full | distmax.km | distback.perc | tripdur.h | pathlength.km | dtmin | dtmed | dtmean | dtmax | diratmaxrange | propdir15dirmr | propdir30dirmr | idtr | percentmissinggap | lastdist | antelastdist | percentmissingreturndist | backatcol | lastdist.km | spmin.kmh | spmed.kmh | spmax.kmh | spflymed.kmh | clean.tr | | :-------------- | :-------------- | :------------- | :------------------------------- | :----------------------- | :-------------------------- | :-------------------------------------------------------- | :------------------------------------------- | :---------------------------------- | :----------------------------------------------- | :--------------------------------------------------- | :---------------------------------------- | :------------------------------------------- | :------------------------------------------------------------------ | :----------------------------------------------------------- | :----------------------------------------------------------- | :---------------------------------------- | :------------------------------------------------------------- | :------------------------------------------ | :------------------------------------------------- | :----------------------------------------------------------------------------------- | :--------------------------------------------- | :---------------------------------- | :---------------------------------------------- | :--------------------------------------------- | :---------------------------------------------- | :----------------------------------------------------------- | :-------------------------------------------- | | bird identifier | trip identifier | departure date | number of GPS locations recorded | Not Applicable, not used | from colony to furthest loc | % distance relative to max distance for last recorded loc | time difference between departure and return | cumulative distane between all locs | minimum lag between consecutive locs, in seconds | median lag between consecutive locations, in seconds | Mean lag between consec. locs, in seconds | max lag between consecutive locs, in seconds | Direction between colony and furthest location (0° North, 90° East) | % locations of the trip within 15° of direction at max range | % locations of the trip within 30° of direction at max range | trip ID before correction, not to be used | % locs missing given programmed record freq and total duration | distance between last loc and colony, in km | distance between second last loc and colony, in km | % of dist from last recorded loc to colony relative to max range of trip from colony | whether last loc was recorded &lt;3km from colony | distance last locations from colony | minimum speed between consecutive locs, in km/h | median speed between consecutive locs, in km/h | maximum speed between consecutive locs, in km/h | median speed between consecutive locs when &gt;10km/h; in km/h | Trip number (per individual) after correction | ### All pairs of tracks One line = one pair of foraging trips among all pairs possible from AllTracks file | ind1 | ind2 | tr1 | tr2 | DiffAngle\_MRMR | lagtr | lagdt | DiffMR | | :------------------- | :------------------- | :-------- | :-------- | :---------------------------------------------------------------------------------------------------------------------- | :---------------------------------------------------------------------------------------------------------------------------------------------------- | :---------------------------------------------------------------------------------------------------------------------------------- | :-------------------------------------------------------------------------- | | individual ID trip 1 | individual ID trip 2 | Trip 1 ID | Trip 2 ID | Angle difference between directions at maximum range trip 1 - trip 2. Similarity between trips in publication main text | if pair of trips from same individual, number of trips apart (e.g. 2 between trip 2 and trip 4 of this individual)delta trip in publication main text | time elapsed between departure date-time of trip 2 and departure date-time of trip 1, in seconds (delta t in publication main text) | Difference between Max Range trip 2 and Max Range trip 1 (used in Supp Mat) |