How biological invasions affect animal behaviour: a global, cross-taxonomic analysis

1. In the Anthropocene, species are faced with drastic challenges due to rapid, human-induced changes, such as habitat destruction, pollution and biological invasions. In the case of invasions, native species may change their behaviour to minimise the impacts they sustain from invasive species, and invaders may also adapt to the conditions in their new environment in order to survive and establish self-sustaining populations. 2. We aimed at giving an overview of which changes in behaviour are studied in invasions, and what is known about the types of behaviour that change, the underlying mechanisms and the speed of behavioural changes. 3. Based on a review of the literature, we identified 191 studies and 360 records (some studies reported multiple records) documenting behavioural changes caused by biological invasions in native (236 records from 148 species) or invasive (124 records from 50 species) animal species. This global dataset, which we make openly available, is not restricted to particular taxonomic groups. 4. We found a mild taxonomic bias in the literature towards mammals, birds and insects. In line with the enemy release hypothesis, native species changed their anti-predator behaviour more frequently than invasive species. Rates of behavioural change were evenly distributed across taxa, but not across types of behaviour. 5. Our findings may help to better understand the role of behaviour in biological invasions as well as temporal changes in both population densities and traits of invasive species, and of native species affected by them.Funding provided by: Deutsche ForschungsgemeinschaftCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100001659Award Number:We followed the recommendations for literature search by the PRISMA statement for meta-analyses (Moher, Liberati, Tetzlaff, & Altman, 2009). Specifically, we searched the Web of Science (on 30 June 2015 from the institution Freie Universität Berlin in Germany. We searched "All databases", but selected the research areas "Behavioural Sciences", "Genetics Heredity", "Environmental Sciences Ecology", "Plant Sciences", "Biodiversity Conservation", "Zoology" and "Evolutionary Biology". We used the following general search string: Behavio* AND (shift* OR change* OR transition*) AND (alien OR exotic OR introduc* OR invas* OR naturali?ed OR nonindigenous OR non-indigenous OR nonnative OR non-native). This initial search yielded 6,463 studies before and 5,948 studies after duplicate removal. We then scanned the titles and abstracts of these studies to exclude those that did not focus on behavioural change. We reviewed the remaining 524 studies to identify those that fit our criteria of eligibility: (i) one or more specific behaviours were observed to have changed; (ii) the change in behaviour had to be observed either in an invasive species or in a native species now interacting with an invasive species. We defined behaviour as "the internally coordinated responses (actions or inactions) of whole living organisms (individuals or groups) to internal and/or external stimuli, excluding responses more easily understood as developmental changes" (Levitis, Lidicker, & Freund, 2009, p. 103). We found 191 studies from 1990 to 2015 that were eligible according to these criteria. The unit of observation in our study is the individual record of behavioural change, of which there were 360 in total. Some studies documented more than one record of a species' behavioural change or different types of behaviour that changed for one species. Each record documented the behavioural change(s) of one native or invasive species. We extracted the following information for each record: background information (year of publication, title, journal and location of study) type of study (laboratory, field or enclosure) type of evidence (experimental or observational/correlational) type of habitat (aquatic, terrestrial, marine or any combination) focal species, classified as (i) native or invasive and (ii) by taxonomic group, using five vertebrate groups (mammals, birds, reptiles, amphibians, fish) and four invertebrate groups (insects, crustaceans, molluscs, other invertebrates) and species that the focal species interacted with (if any)