Material and Methods
Questionnaire design and
dissemination
A questionnaire was developed to collect information on French pet cats
regarding their personality (five personality traits model) and the
frequency with which their owners observed them bringing home birds and
small mammals (ranging from never to very often, defined as once a week
or more). To control for potential confounding factors, additional
information was gathered on other characteristics of the cats (sex, age,
and breed) and their living conditions (type of dwelling, type of the
area around the dwelling, amount of time spent outdoors). The
questionnaire was hosted online on the Google Form platform.
Households in France with at least one pet cat were targeted through
postings on social media. The survey was anonymous, and no personal
information was collected from the respondents. In the introduction part
of the survey, respondents indicated their consent to participate in the
study. The study complied with the legal requirements in France: as no
personal information was collected, ethics approval was not mandatory,
as was confirmed by the Research Ethics Committee of Paris-Saclay
(Polethis, report from January 4, 2021).
The questionnaire consisted of four sections (Appendix 1). The first
section focused on the cat
characteristics: sex (female, male, unknown), age
(<1 years, 1-2 years,
2-10 years, over 10 years, unknown), breed (Bengal, Birman, British
Shorthair, Chartreux, Maine Coon, Persian, Ragdoll, Savannah, Sphynx,
Siamese, Turkish Angora, non-pedigree, European, other, unknown). Note
that in France “European” means “non-pedigree.” We offered the two
options, because some owners might have been more familiar with one word
than the other. The second section focused on the living conditions of
the cat: type of housing (apartment without balcony, apartment with
balcony, subdivision house, individual house), type of environment
(urban, suburban, or rural area), time spent by the cat outdoors daily
(none, limited [less than 1 hour], moderate [1 to 5 hours], long
[more than 5 hours], all the time [just comes back to eat]),
daily time spent by the owner with the cat (none, limited [less than 1
hour], moderate [1 to 5 hours], long [more than 5 hours]).
The third section involved assessing the personality traits. Litchfield
et al. (2017) determined that the personality profiles of cats are
organized around five factors that represent traits related to
neuroticism, extraversion, agreeableness, dominance, and impulsivity.
Each factor can be evaluated using a list of adjectives that have
varying correlations with the trait in question. In our questionnaire,
to ensure short response times and thus high completion rates (e.g.,
Plowman et al., 2013), we selected 15 of the 52 adjectives used in the
original study of Litchfield et al. (2017). For each of the five
personality traits, we selected three adjectives based on two criteria.
First, we selected adjectives with unequivocal translations in French to
avoid ambiguity for the respondents. Second, we used the factor scores
of Litchfield et al. (2017) for each adjective to select those with a
high correlation with the relevant personality trait and a low
correlation with the four others in order to facilitate the
interpretation of the results. For example, the adjective affectionate
was selected, because it is readily translatable in French and has a
high correlation with the personality trait of agreeableness and a low
correlation with the four other personality traits. In English, we chose
the following 15 adjectives. For neuroticism we chose: shy, calm
(negative loading), and fearful of other cats; for extraversion: smart,
vigilant, and persevering; for agreeableness: affectionate, friendly to
people, and solitary (negative loading); for dominance: bullying,
dominant, and aggressive to other cats; and for impulsiveness:
impulsive, predictable (negative loading), and distractible. Each of
these 15 adjectives was presented to the owners who could choose between
strongly disagree, disagree, neither agree nor disagree, agree, and
strongly agree.
The final section of the questionnaire focused on the prey returned home
as observed by the owners and included
the
reported frequency of return of birds and small mammals (daily, 1-6
times per week, 2-3 times per month, 1-3 times per trimester, 1-3 times
per year, never). At the end of the survey, we added an optional
open-ended question to give the owners the opportunity to add any
comments that they wished to share about their cat and to communicate
any insights that may have been overlooked in the survey (Harland et
al., 2011).
The social network Facebookwas chosen as a channel to disseminate the
questionnaire. This network has a large number of user groups dedicated
to cats, which made it possible to conduct a large-scale study. The
questionnaire was diffused in 23 French-speaking groups from February 9,
2021, to March 14, 2021, which allowed us to collect a total of 3,217
responses. The dataset was deposited in the Mendeley repository [ref
number XX–not available yet].
Data treatment and statistical
analyses
All analyses were conducted using R v.4.2 (http://www.R-project.org). For all
statistical tests, the level of significance was set at 0.05.
Factor analysis of personality structure
To ensure that the personality traits of the cats were reliably
described by the owners, we removed from the analyses the surveys
indicating that the owners did not spend any time with their cat (n =
10) and those with comments that prevented their use to study the
personality traits (e.g., respondent not the cat owner, recently adopted
cat, cat with a major health issue; n = 21). Like all animal species,
cats go through different stages of development, and in juveniles,
personality and predatory behavior are not yet stable (Lowe et al.,
2001). Following Litchfield et al. (2017), we conservatively excluded
cats aged under 1 year (n = 614) from the dataset. Finally, the
responses with missing data in the set of personality adjectives were
also removed (n = 64). The final dataset included 2,508 responses.
We performed exploratory factor analysis on the personality variables
(15 adjectives evaluated by the owners) to first determine the number of
personality traits to be extracted and then estimate the values of each
trait for each cat (Sofroniou et al., 1999). We initially ensured that
the data were suitable for factor analysis using Bartlett’s test of
sphericity, which was significant (P < 0.01), and the
Kaiser-Meyer-Olkin (KMO) criterion, which had an overall value of 0.722
(depending on the authors, a value above 0.5 or 0.6 is considered to
mean that the sampling is adequate). Both indicators thus show that the
data were suitable for factor analysis (Kaiser, 1974; Sofroniou et al.,
1999). To determine the number of factors – here, personality traits –
to extract, we used the empirical Kaiser criterion (see Braeken et al.,
2017 for details) and parallel analysis with principal component
analysis (PCA) (comparing the eigenvalues obtained to those generated
from a Monte-Carlo simulated matrix), which indicated that four factors
should be retained. We therefore choose to retain four factors, and used
maximum likelihood factor analysis to extract them from the 15
adjectives. We obliquely rotated these factors (i.e., correlations
between them were allowed), because personality traits are frequently
correlated, as shown by the existence of personality syndromes. As in
previous studies (e.g., Weiss et al., 2015), to interpret the factors,
we defined salient loadings as those equal to or greater than
|.4|. The four factors that we obtained correspond
approximately a posteriori to Litchfield et al.’s (2017) extraversion
(MR1), dominance (MR2), neuroticism (MR3), and agreeableness (MR4) (see
Results section below).
Breed and personality
We tested the link between breed and personality traits by computing the
Euclidian distance between personality profiles for each pair of cats to
produce a resemblance matrix from which we conducted a nonparametric
(permutational) analysis of variance (permanova; package vegan; Oksanen
et al., 2007) using 999 permutations to test whether personality
profiles differed according to breed. We then performed discriminant
analysis using a non-parametric version of Pillai’s test to evaluate the
significance of the eigenvalues (package ade4; Dray et al., 2007). To
ensure to have enough statistical power, we removed five breeds with
less than 60 individuals (Chartreux, n = 28; Savanah, n = 20; Sphinx, n
= 57, Siamese, n = 49, Turkish Angora, n = 21), leading to a dataset of
2,162 responses. We regrouped the “Non-pedigree” and “European” cats
under the “Non-pedigree” label, as both terms are used to describe the
same type of cat in France (the European Short Hair breed exists but is
extremely rare in France).
Factors influencing owner-reported frequency of prey brought home
To run the subsequent analyses regarding predation, additional responses
were excluded from the previously described dataset: cats living in
apartments with minimal outdoor access as well as cats living in houses
but without daily outdoor access (n = 1217), owners of four or more cats
(Cordonnier et al., 2022) who would supposedly have difficulty
determining which cat brought home which prey (n = 188), incomplete
responses (n = 2), and cats belonging to the Bengal breed (n = 36)
because when the survey was posted on a Bengal cat Facebook group,
several people suggested in the comments that participants give false
answers to questions relating to predation. The final dataset included
719 responses. Since the response variables for reported predation
frequencies were ordered (0: never, 1: 1 to 5 times a year, 2: 5 to 10
times a year, 3: 1 to 3 times a month; 4: once a week or more), two
cumulative logit models (CLMs) were adjusted (McCullagh, 1980), with the
reported frequencies of predation taken as response variables: CLM1:
birds, CLM2: mammals. Each model incorporated 11 predictor variables:
cat sex (0: male, 1: female), cat age (ordinal variable: 0: 1-2 years,
1: 2-10 years, 2: 10 years and older), cat breed (Birman, British
Shorthair, Maine coon, Persian, Ragdoll, non-pedigree), type of housing
(0: in a subdividion, 1: detached home), abundance of natural elements
(tree, bushes, grass, etc.) around the place of residence (0: low, 1:
moderate, 2: high), urban level (rural, suburban, urban), time spent
daily outdoors (0: limited, 1: moderate, 2: long, 3: all the time), and
the four quantitative personality traits (MR1 to MR4). To avoid
potential multicollinearity issues, we ensured that all Variance
Inflated Factors (VIFs) were under the threshold of 2 (O’Brien, 2007).
The two models were fitted using the package ordinal (Christensen,
2015). For both models, we used a stepwise selection by sequential
replacement to identify the subset of variables in the dataset resulting
in the best performing model with the lowest prediction error (Venables
et al., 2002; Hegyi et al., 2015). Wald tests were performed on the
predictor variables. The quality of the model estimates was monitored
using Pearson residuals (package sure; Greenwell et al., 2018). For the
qualitative variables, post-hoc tests (including a Holm correction) were
performed using a self-designed contrast matrix (package lsmeans; Lenth
et al., 2016).