Measuring personality traits in Eurasian red squirrels: A critical comparison of different methods

Abstract

Animal personality, behavioural differences among individuals which are consistent through time and contexts, is generally described by one or more traits. Different methods are used to measure these traits, such as behavioural observations and trapping indices. Comparing several methods allows to validate different tests and to better identify which aspect of an animal's personality is being measured. Here, we measured activity, exploration and immobility of Eurasian red squirrels (Sciurus vulgaris) using observations from the open field test (OFT), and compared them with trappability and trap-diversity indices calculated from capture-mark-recapture data in six independent study sites. Trappability measures the willingness to enter a baited trap (boldness), while trap-diversity can be a proxy for exploration tendency. Our first aim was to test their repeatability, thus their appropriateness as candidate measures of personality traits. Next, we explored the predictions that (i) trappability, measuring boldness, does not correlate with any of the OFT personality traits, since risk-taking cannot be expressed in our arena test; and (ii) trap-diversity correlates with exploration obtained from the OFT. Considering the species ecology and study design, we used multivariate Bayesian models based on different time intervals (session/year) and habitat types (alpine/plain). We found significant repeatabilities for trappability, for trap-diversity and for most OFT personality traits, except exploration in the plain sites. Independently from habitat type or time interval, trappability did not correlate with either activity, exploration or immobility from OFT, thus measuring a different personality axis, which we considered a proxy for boldness. Trap-diversity did not correlate with exploration from OFT, but seems related to a different aspect of red squirrels' exploration tendency. Our study emphasizes that caution is needed when using behaviours from OFT to measure multiple personality traits and that applying extra methods based on animals' responses to trapping can provide reliable proxies for boldness and exploration tendency.

Invading parasites: spillover of an alien nematode reduces survival in a native species

“…We acknowledge that our local survival estimate is influenced by recapture probability and potential dispersal (emigration) of marked animals, but since both annual recapture probabilities and site-fidelity of adult red squirrels are high (for detailed analyses and discussion see Wauters et al 2004, 2008and Santicchia et al 2018b), we are confident that our estimate mostly captures actual survival rather than dispersal. A different source of bias in annual survival estimates could be due to the parasite affecting host behaviour and/or its willingness to enter a trap, measured as trappability (Santicchia et al 2018b(Santicchia et al , 2021. As mentioned above, we indeed found that infection by alien S. robustus reduced host activity, an energetically costly personality trait (Santicchia et al 2020).…”

Linking Behavior, Co-infection Patterns, and Viral Infection Risk With the Whole Gastrointestinal Helminth Community Structure in Mastomys natalensis

“…Trappability is associated with space use in several rodents species (25,30,58) and may therefore suggest that individuals who are more active have a higher risk to become infected due to a larger exposure rate to different infected environments. Nonetheless, the link between exploration, measured in an open field arena and trappability is not always clear or present (108)(109)(110). Vanden Broecke et al (58,79), found no correlation between exploration and trappability in M. natalensis which may suggest that this explanation is not very likely.…”

Personality traits, sex and food abundance shape space use in an arboreal mammal

“…Most animals were trapped both before, during and after space use parameters were determined and some traps in which they were caught were outside the estimated home range area (Santicchia et al 2018). Moreover, we are confident that our standardised methods of pre-baiting traps and seasonally spaced multiple days CMR sessions strongly reduced any potential bias in trappability [see also Michelangeli et al 2016 in delicate skink (Lampropholis delicata); Jolly et al 2019 in grassland melomys (Melomys burtoni)] as discussed in detail in previous studies on red squirrels (Wauters et al 2008;Santicchia et al 2018Santicchia et al , 2020. Future research with the use of GPS-collars, which provide continuous animals' locations and complete movements recordings (e.g.…”

“…Trappability and trap diversity indices derived from standardised Capture-Mark-Recapture (CMR) studies have a moderate to good repeatability and represent reliable measures of the personality traits boldness and exploration in the habitat where the animal settled (Boon et al 2008;Boyer et al 2010;Le Coeur et al 2015;Santicchia et al 2018Santicchia et al , 2019Santicchia et al , 2020. We further refer to "Discussion" regarding possible potential caveats related to the use of these indices.…”

“…We also calculated the core-area/home-range ratio as a proxy of home range structure. For each of these radio-tracked individuals, we used a capture-mark-recapture derived trappability index (as measure of boldness) and trap diversity index (as measure of exploration) (Boyer et al 2010;Santicchia et al 2018Santicchia et al , 2020. We predict that: (1) bolder, more explorative individuals of both sexes will have larger home ranges than shy-less explorative ones, due to frequent excursions further away from the core-area and to react faster to changing environmental situations; moreover, they might also have larger core-areas to increase the areas of intensive foraging; (2) bolder, more explorative individuals will have higher corearea/home range ratio, meaning that they will intensively use a larger proportion of their home range; (3) as a consequence of predictions 1 and 2, core-area overlap of bolder, more explorative squirrels should be higher than for shyer, less explorative ones.…”