Data from: Active crocodiles are less sociable
Data files
Sep 05, 2024 version files 388.99 MB
Abstract
How animals move and associate with conspecifics is rarely random, with a population’s spatial structure forming the foundation on which the social behaviours of individuals form. Studies examining the spatial–social interface typically measure averaged behavioural differences between individuals; however, this neglects the inherent variation present within individuals and how it may impact the spatial-social interface. Here, we investigated differences in among-individual (co) variance in sociability, activity, and site fidelity in a population of wild estuarine crocodiles, Crocodylus porosus, across a 10-year period. By monitoring 118 crocodiles using coded acoustic transmitters and an array of fixed underwater receivers, we discovered that not only did individual crocodiles repeatably differed (among-individual variation) in each behaviour measured, but also in how consistently they expressed these behaviours through time (within-individual variation). As expected, crocodile activity and sociability formed a behavioural syndrome, with more active individuals being less sociable. Interestingly, we also found that individuals that were either more sociable or displayed greater site fidelity were also more specialised (lower within individual variation) in these behaviours. Together, our results provide important empirical evidence for the interplay between spatial, temporal and social individual-level behavioural variation and how these contribute to forming behavioural niches.
README: Data from: Active crocodiles are less sociable
https://doi.org/10.5061/dryad.cfxpnvxcg
We supply the underlying data and R code used in the data analysis and preparation of the manuscript "Active crocodiles are less sociable" which in currently under review in the journal "Philisophical transactions of the Royal Society B".
In this study we quantified the degree of among (behavioural phenotypes) and within-individual (behavioural consistency) variation in sociability, daily activity, and site fidelity for a wild population of estuarine crocodiles Crocodylus porosus. We investigated whether an individual’s behavioural phenotype correlates with their consistency across consecutive tracking months and whether behaviours were correlated at the among-individual level, thus forming behavioural syndromes. We predicted that crocodiles would display both among- and within-individual variation in spatial and social phenotypes. Specifically, we hypothesised that behavioural phenotypes are correlated with behavioural consistency, with more sociable and site-attached individuals being more consistent through time, while more active individuals would be less consistent. Finally, we predicted that an individual’s degree of sociability would be positively correlated with both their daily activity and degree of site fidelity.
Author(s)
Cameron J. Baker 1,2*, Barbara Class 3,4, Ross G. Dwyer 4, Craig E. Franklin 2, Hamish A. Campbell 1, Terri R. Irwin 5, and Céline H. Frère 2 1 Research Institute for Environment & Livelihoods, Charles Darwin University, Darwin, Northern Territory 0815, Australia 2 The School of the Environment, The University of Queensland, Brisbane, Queensland 4072, Australia 3 Ludwig-Maximilians-Universität München, 80539 Munich, Germany 4 School of Science, Technology and Engineering, University of the Sunshine Coast, Sippy Downs, Queensland 4556, Australia 5 Australia Zoo, Steve Irwin Way, Beerwah 4519, Queensland, Australia
*Corresponding author: cameron.baker@cdu.edu.au
Description of the data and file structure
File list
Acoustic_telemetry_data.csv
Behavioural_metrics.csv
Crocodile_metrics.csv
Data_analysis.R
CompDHGLM.rds
File descriptions
Acoustic_telemetry_data.csv - A data frame containing the raw acoustic telemetry data underlying the analysis presented in the manuscript.
- DATETIME: The date and time that an acoustic transmitter was detected at a specific acoustic hydrophone
- TRANSMITTERID: The unique identity of each crocodile
- SENSOR1: The either a temperature or depth recording if a transmitter has that functionality
- UNITS1: The units of the sensor recording from the transmitter
- STATIONNAME: The name of the acoustic hydrophone station that a transmitter was detected at
Behavioural_metrics.csv - A data frame containing the processed crocodile behavioural metrics used in the analysis presented in the manuscript.
- TRANSMITTERID: The unique identity of each crocodile
- Unique_months: The unique year/month combination for each observed value
- Year: The year a value was observed
- Month: The month a value was observed
- Number_associates: The number of tagged conspecifics that a focal individual was observed co-occurring at acoustic hydrophones within a particular month
- Potential_associates: The number of tagged conspecifics detected within the focal individual's social environment. For this study, an individuals social environment was determined as the set of acoustic hydrophones a focal individual was observed within the specific month
- Prop_associations: The proportion of conspecifics an individual was observed associating with (observed associates) over the number of individuals present within their social environment (potential associates) per month. This is the measure of sociability used in the study
- Sex: The sex of the focal crocodile
- Mean_TL: The total length of the focal crocodile. For individuals that were captured across multiple years, their mean total length is used
- Distance: The mean river distance (km) travelled by the focal individual per day. This is the measure of activity used in the study
- Area95: The total area (km2) of the focal individuals' least cost utilisation distribution (lcUD).
- Overlaps: The volume of intersection (VI) between a focal individual's lcUD for the current month and the preceding month. This is the measure of site fidelity used in the study
- Detections: The number of times the focal individual was detected within the acoustic hydrophone array.
- cubed_associates: Prop_associations that has been cube-root transformed to normalise the data for modelling
- cubed_distance: Distance that has been cube-root transformed to normalise the data for modelling
- scale_cube_associates: Cubed_associates that have been standardised for modelling (mean = 0, SD = 1)
- scale_cube_distance: Cubed_distance that have been standardised for modelling (mean = 0, SD = 1)
- scale_mean_TL: Mean_TL that have been standardised for modelling (mean = 0, SD = 1)
Crocodile_metrics.csv - A data frame containing the identity of each tagged crocodiles, along with their sex and total length (TL)
- TRANSMITTERID: The unique identity of each crocodile
- Sex: The sex of the focal crocodile
- Mean_TL: The total length of the focal crocodile. For individuals that were captured across multiple years, their mean total length is used
Missing values are denoted by NA.
Data_analysis.R - A detailed account of the model fitting and downstream analysis presented in the manuscript, along with all the code required to generate each of the figures. It relies on the data objects Behavioural_metrics.csv and Crocodile_metrics.csv as inputs. The code produces a model output which is also provided as CompDHGLM_all_crocs.rds.
CompDHGLM_all_crocs.rds - The model output produced from Data_analysis.R
Please contact the project contributors with any questions or comments regarding the analyses.
Sharing/Access information
The code required to determine the behaviours of interest (sociability, activity, site fidelity) is available from the below locations:
https://github.com/Cameron-J-Baker/Supporting-code-Baker_et-al: Determining crocodile home range and space use
https://github.com/Cameron-J-Baker/Baker_et_al_2023_Ani_Behav: Determining associations between crocodiles
Code/Software
All analyses were completed using R 4.1.0.