DOI: 10.5061/dryad.n2z34tn59
title: Data from: Morphological traits are not consistently related to population size in four migratory caribou populations across North America

description: To develop effective management to maintain or restore populations of
 large herbivores, wildlife managers require sound empirical data on their
 variations in size and associated parameters. Many studies have
 highlighted links between morphological traits of individuals and
 population density; however, less attention has been devoted to whether or
 not morphological traits can reliably inform on population size in years
 when no population estimates are available. We evaluated the relationships
 between three morphological traits (hind foot length, body mass, and body
 fat) and population size interpolated over three decades, for four
 migratory caribou (Rangifer tarandus) herds in northern Canada and Alaska.
 Our sample included 8,865 measurements of 4,473 individuals. We used a
 Bayesian modelling approach to evaluate the relationships between
 morphology and population size across different sex and age classes,
 considering different temporal scales and, when possible, phases of
 population growth or decline. We found that morphological traits were not
 consistently linked to population size. Statistically significant
 relationships existed for some combinations of herd and age classes, but
 weak to absent relationships were more common. Our study suggests that
 morphological traits alone cannot replace data obtained from aerial
 surveys to approximate population size when population trends are unknown.
 We discuss the usefulness of morphological traits to explain population
 size, and recognize their role as complementary metrics to inform the
 management and conservation of large herbivore populations, but conclude
 that generally morphological data should not be used to predict population
 size without prior information on population trends.
description: # Morphological traits are not consistently related to population size in
 four migratory caribou populations across North America
 [https://doi.org/10.5061/dryad.n2z34tn59](https://doi.org/10.5061/dryad.n2z34tn59) This folder contains the data and R codes for the article: \ **Vuillaume, B, Leblond, M, Festa-Bianchet, M and Côté, S (2024) Morphological traits are not consistently related to population size in four migratory caribou populations across North America**\ Comments and requests should be addressed to Barbara Vuillaume: [barbara.vuillaume@univ-lyon1.fr](mailto:barbara.vuillaume@univ-lyon1.fr). All material is free of use, but I would appreciate being told, and this dataset and the matching paper cited if appropriate. ## Description of the data and code ### **File list** ``` Popsize_rawdata.txt Popsize_slop.R Popsize_final_dataset.txt Morpho_rawdata.txt Morphological_data_format.R Morpho_dataset.txt Relationship_analysis.R ``` ### File descriptions #### A - Formatting phase (optional part if you are only interested in the main analyses) `Popsizerawdata.txt` - dataset containing raw data of aerial survey and population estimates from other studies, that will be formatted and transformed in the script `Popsizeslop.R` to be usable in the main analysis of the article. `Popsize_slop.R` - First R code to run. It will allow you to format and transform the raw data from the file `Popsizerawdata.txt`, and produce as output the file `Popsize_final_dataset.txt` that you will need for the main analysis of the article. Precisely, it will create the mean and boundary slopes to inform, in the Bayesian model, the range of possible values for the population size in each year. `Morpho_rawdata.txt` - dataset containing raw data of individual morphological trait measurement for each age class of the four migratory caribou herds studied in our article. This dataset includes other correlated morphological variables to the one we used in the final analyses as we used them to assess the values of the morphological traits of interest in the script `Morphological_data_format.R`. `Morphological_data_format.R` - Second R code to run. It will allow you to format all morphological raw data and adjust their value for measurement date. For each age class of each herd, measurements were spread over the years, at different dates. (1) Metatarsal bone measurement was used to calculate hind foot length value for the individuals that only had the first parameter measured. (2) Eviscerated mass was used to calculate live mass value for the individuals that only had the first type of mass measured. (3) To be able to assess a potential relationship between population size and morphological traits, it was essential to correct each morphological traits of interest with the measurement date. The output of the script is the file `Morpho_dataset.txt`. #### B - Main analysis phase `Popsize_final_dataset.txt` - dataset produced with the script `Popsizeslop.R` and charged in the script `Relationship_analysis.R`. It includes the slopes required to test the relationship between population size and the morphological traits considered in our study. `Morpho_dataset.txt` - dataset produced with the script `Morphological_data_format.R` and charged in the script `Relationship_analysis.R`. It includes the formatted measurements of individual morphological traits used to test the relationship between population size and morphological traits in our study. There are annual hind foot length and body mass, as well as seasonal body mass and body fat for each age class in each of the four herds when applicable. `Relationship_analysis.R` - R code to assess the relationship between morphological traits and population size. This script is conducted with the Riviere George herd (RG) as example, since it is the most complete case with three age classes, data for the three morphological traits, and the longest monitoring period of our four herds. The process being exactly the same for the three other herds, we only provide this example. In the code, we developed all the Bayesian models in detail and the posterior MCMC checks. Note: All of the files must be within your working directory for the analyses to work.  #### C – Variable description Explanation for each variable (column name), abbreviations, and units in the `Popsizerawdata.txt` and `Popsize_final_dataset.txt` files. Population size at a given year is expressed as the number of individuals in the population. For all variables, 'N/A' means that no data are available for the variable considered this year. * Herd = name of the population (RAF: Rivière-aux-Feuilles herd, RG: Rivière-George herd) * Year = year the population size was estimated * as.est = population size estimate from aerial surveys * as.LCI = lower confidence interval of population size from aerial surveys * as.UCI = upper confidence interval of population size from aerial surveys * IPM.est = population size estimate from Integrated Population Model * IPM.LCI = lower confidence interval of population size from Integrated Population Model * IPM.UCI = upper confidence interval of population size from Integrated Population Model * estimate = population size estimate retained for the slope calculation * LCI = lower confidence interval of population size retained for the slope calculation * UCI = upper confidence interval of population size retained for the slope calculation * slope.est = population size derivated from the “estimate” variable using a locally-weighted polynomial regression * slope.LCI = lower confidence interval of population size derivated from the “LCI” variable using a locally-weighted polynomial regression * slope.UCI = upper confidence interval of population size derivated from the “UCI” variable using a locally-weighted polynomial regression   Explanation for each variable (column name), abbreviations and units in the `Morpho_rawdata.txt` and `Morpho_dataset.txt` files. * SEQ = unique number * IDENT = identification for marked individuals ('N/A' = no data available) * ID_LABR = secondary identification for some marked individuals from the Rivière-George herd ('N/A' = not applicable) * AGE = approximate age at measurement (in year) * AGECAT = age category at measurement * HERD = name of the population (RAF: Rivière-aux-Feuilles herd, RG: Rivière-George herd) * YEAR = year the measures were taken * MONTH = month the measures were taken * DAY = day the measures were taken * DATE = date the measures were taken * SEASON = index of the biological season the measures were taken * PERIOD_1 = corresponding year period to the season (1=June, 2=July-August, 3=September-December, 4=January-May) * SEX = sex of the individual (Male VS Fem=female) * MILK = female producing milk (1=yes, 2=no, 'N/A' = not applicable for males and calves otherwise not available) * SUITEE = female with calf (1=yes, 2=no, 'N/A' = not applicable for males and calves otherwise not available) * FOETUS = presence of a foetus (1=yes, 2=no, 'N/A' = not applicable for males and calves otherwise not available) * HFL = raw data of hind foot length (in cm); 'N/A' = no data available * HFL_CORR = corrected hind foot length (in cm) from secondary data source; 'N/A' = no data available * HFL6 = pre-existing hind foot length adjusted for an unknown date (in cm) , not used; 'N/A' = no data available * META = raw data of metatarsal length (in cm); 'N/A' = no data available * META_REGR = metatarsal length calculated by regression from an HFL value between 1983 à 1988 (in cm); 'N/A' = no data available * META6 = pre-existing metatarsal length adjusted for an unknown date (in cm), not used; 'N/A' = no data available * LGTH_TOT = total length of the individual (in cm); 'N/A' = no data available * MASS_VIF = raw data of live body mass of the individual (in kg); 'N/A' = no data available * MASS_CORR = corrected live body mass (in kg) from secondary data source; 'N/A' = no data available * MASS6 = pre-existing body mass adjusted for an unknown date (in kg), not used; 'N/A' = no data available * MASS_EVIS = raw data of eviscerated body mass of the individual (in kg); 'N/A' = no data available * BODYFAT = body fat index of the individual; 'N/A' = no data available * SEAS7 = non-biological season used for analyses (May-August: summer; September-December: early winter; January-April: late winter) * MASS_REG = live body mass (in kg) calculated from eviscerated mass in absence live body mass raw data; 'N/A' = no data available * MASS_i = body mass (in kg) used for analyses. Equal to “MASS_CORR” if it exists, or to “MASS_VIF” if the first does not exist, or to “MASS_REG” if the first two do not exist; 'N/A' = no data available * HFL_REG = hind foot length (in cm) calculated from metatarsal length in absence hind foot length raw data; 'N/A' = no data available * HFL_i = hind foot length (in cm) used for analyses. Equal to “HFL_CORR” if it exists, or to “HFL” if the first does not exist, or to “HFL_REG” if the first two do not exist; 'N/A' = no data available * COHORT = biological year (starting from June to May) the individual was born * JJ = Julian day (starting January 1st of each year) * HFL7 = hind foot length (in cm) we adjusted for the mean Julian date of the year; 'N/A' = no data available * MASS7 = body mass (in kg) adjusted for the mean Julian date of the year; 'N/A' = no data available * MASS8 = body mass (in kg) adjusted for the mean Julian date of the season; 'N/A' = no data available * BODYFAT8 = body fat index adjusted for the mean Julian date of the season; 'N/A' = no data available