Urban Invasion Restructures Locomotor Repertoires: Evidence from Introduced Monk Parakeets (Myiopsitta monachus)

Biological invasions are rarely examined through a locomotor lens, yet they provide a powerful opportunity to understand how organisms adjust movement in response to novel environmental conditions. When locomotion is considered in invasion biology, it is typically evaluated in terms of performance (e.g., speed, endurance, dispersal capacity), with far less attention given to how organisms restructure the behaviors that comprise locomotion itself. Urban environments introduce novel substrate geometries and mechanical challenges, potentially altering not only how animals move, but which behaviors they use. Using previously collected positional behavior data from an introduced population of monk parakeets (Myiopsitta monachus), this study evaluates how locomotor repertoire structure varies across substrate types, with particular emphasis on artificial substrates. Locomotor behavior was quantified as substrate-specific probability distributions and analyzed using complementary metrics of diversity, evenness, behavioral enrichment, and repertoire dissimilarity. Artificial substrates exhibited the highest locomotor diversity and high evenness, indicating a broad and relatively balanced use of locomotor behaviors. In contrast, natural substrates were characterized by lower diversity and greater dominance of specific behaviors. Behavioral enrichment analyses revealed increased use of walking and multiple climbing strategies on artificial substrates, coupled with reductions in aerial transitions (i.e, Flight_short_interbranch) and sidling. Dissimilarity metrics further demonstrated that locomotor repertoires on artificial substrates were qualitatively distinct from those observed in natural contexts. These findings indicate that urban environments drive restructuring of locomotor repertoires rather than simple performance tuning within a fixed behavioral framework. By demonstrating that locomotor behavior itself can shift in response to environmental novelty, this study highlights the importance of integrating behavioral, performance, and morphological perspectives when evaluating adaptation to urban environments and biological invasion.