Animal personality has been defined as consistent between-individual differences in behaviour maintained over time and/or across ecological contexts. Differences in individual personality are measured through traits such as reaction to potential risks or handling novelty, aggressiveness and sociability. Among vertebrates, individual variation in personality has been demonstrated to affect variation in fitness among animals within a population. One of the effects of personality is its potential role in the transmission of parasites and pathogens: risk-taking behavior, exploration tendency, activity and sociality are all traits that may affect hosts’ exposure to parasites by altering contact rates among individuals and/or increasing chances of encountering infective stages in the environment. The aim of the present study was to investigate the relationship between a personality score and the abundance of macroparasites of Eastern grey squirrels (Sciurus carolinensis) as invasive alien species (IAS) introduced in N. Italy. Invasiveness may be enhanced through the process of enemy-release, that is the absence of important predators and/or parasites in the new range compared to the native range. In fact, grey squirrels from populations in Italy have a reduced macroparasite fauna compared to populations in the native range in North America and, as far as endoparasites are concerned, only one intestinal helminth species occurs with high prevalence and intensity in grey squirrels in Italy: Strongyloides robustus. Here we test the hypothesis that bolder squirrels with a high tendency to explore have a higher abundance of S. robustus than more shy, less exploring individuals. We used capture-mark-recapture data gathered over three trapping sessions in 5 high-quality mixed deciduous woods and park in Piedmont to estimate trappability and trap diversity indices (n = 207). Both indices were strongly correlated: therefore a Principal Component Analysis (PCA) was used to derive a new variable (score of the first component, PC1) as single best estimator of tendency of being bold. Next we used PC1 as boldness score in generalized linear models with abundance of S. robustus as dependent variable. We examined 95 grey squirrel carcasses: 61 out of 95 were infected by S. robustus (prevalence 60 ± 4%). Abundance varied from 0 to 86 helminths per host (mean ± SE = 6.68 ± 1.36) and mean intensity (mI) of S. robustus was 10.4 ± 2.0 helminths per host. Only 15 grey squirrels harboured also other helminth species: Trichostrongylus spp. was found in 13 squirrels (13.7%, mean Intensity ± SE: 3.5 ± 1.0) and in two hosts we found 6 oxyurid nematodes and 1 specimen of cestode, respectively, but these parasites were not included in the analyses. The first, general model on S. robustus infection showed that endoparasite abundance in grey squirrels increased with both the host’s PC1 score and body mass. However, further models showed that PC1 score only affects squirrels’ infection status, with bolder, more explorative individuals having a higher probability of being infected by S. robustus. Conversely, intensity of infection in infected animals did not vary with PC1 score, but was positively affected by host body mass. There was no significant difference between males and females in either of the infection parameters. Hence, our results supported the first, general prediction that bolder, more explorative animals are more heavily infected by S. robustus than shy grey squirrels. However, we also found that host personality mainly influences the probability of acquiring S. robustus, whereas it has no effect on parasite intensity in already infected hosts, which is instead determined by host body mass.

The price of being bold: personality affects endoparasite infection in introduced eastern grey squirrels / S. F., C. Romeo, N. Ferrari, M. A., W. L. A. - In: Atti del IV Congresso nazionale di ecopatologia della fauna / [a cura di] L. Stancampiano, E. Armaroli, R. Viganò, N. Ferrari. - [s.l] : Società Italiana di Ecopatologia della Fauna, 2017 Dec. - ISBN 9788894297300. - pp. 30-30 (( Intervento presentato al 4. convegno Congresso Nazionale di Ecopatologia della Fauna tenutosi a Domodossola nel 2017.

The price of being bold: personality affects endoparasite infection in introduced eastern grey squirrels

C. Romeo
Secondo
;
N. Ferrari;
2017

Abstract

Animal personality has been defined as consistent between-individual differences in behaviour maintained over time and/or across ecological contexts. Differences in individual personality are measured through traits such as reaction to potential risks or handling novelty, aggressiveness and sociability. Among vertebrates, individual variation in personality has been demonstrated to affect variation in fitness among animals within a population. One of the effects of personality is its potential role in the transmission of parasites and pathogens: risk-taking behavior, exploration tendency, activity and sociality are all traits that may affect hosts’ exposure to parasites by altering contact rates among individuals and/or increasing chances of encountering infective stages in the environment. The aim of the present study was to investigate the relationship between a personality score and the abundance of macroparasites of Eastern grey squirrels (Sciurus carolinensis) as invasive alien species (IAS) introduced in N. Italy. Invasiveness may be enhanced through the process of enemy-release, that is the absence of important predators and/or parasites in the new range compared to the native range. In fact, grey squirrels from populations in Italy have a reduced macroparasite fauna compared to populations in the native range in North America and, as far as endoparasites are concerned, only one intestinal helminth species occurs with high prevalence and intensity in grey squirrels in Italy: Strongyloides robustus. Here we test the hypothesis that bolder squirrels with a high tendency to explore have a higher abundance of S. robustus than more shy, less exploring individuals. We used capture-mark-recapture data gathered over three trapping sessions in 5 high-quality mixed deciduous woods and park in Piedmont to estimate trappability and trap diversity indices (n = 207). Both indices were strongly correlated: therefore a Principal Component Analysis (PCA) was used to derive a new variable (score of the first component, PC1) as single best estimator of tendency of being bold. Next we used PC1 as boldness score in generalized linear models with abundance of S. robustus as dependent variable. We examined 95 grey squirrel carcasses: 61 out of 95 were infected by S. robustus (prevalence 60 ± 4%). Abundance varied from 0 to 86 helminths per host (mean ± SE = 6.68 ± 1.36) and mean intensity (mI) of S. robustus was 10.4 ± 2.0 helminths per host. Only 15 grey squirrels harboured also other helminth species: Trichostrongylus spp. was found in 13 squirrels (13.7%, mean Intensity ± SE: 3.5 ± 1.0) and in two hosts we found 6 oxyurid nematodes and 1 specimen of cestode, respectively, but these parasites were not included in the analyses. The first, general model on S. robustus infection showed that endoparasite abundance in grey squirrels increased with both the host’s PC1 score and body mass. However, further models showed that PC1 score only affects squirrels’ infection status, with bolder, more explorative individuals having a higher probability of being infected by S. robustus. Conversely, intensity of infection in infected animals did not vary with PC1 score, but was positively affected by host body mass. There was no significant difference between males and females in either of the infection parameters. Hence, our results supported the first, general prediction that bolder, more explorative animals are more heavily infected by S. robustus than shy grey squirrels. However, we also found that host personality mainly influences the probability of acquiring S. robustus, whereas it has no effect on parasite intensity in already infected hosts, which is instead determined by host body mass.
Settore VET/06 - Parassitologia e Malattie Parassitarie degli Animali
Settore BIO/07 - Ecologia
dic-2017
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/541355
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