Aggressive interactions during feeding between native and invasive freshwater turtles

Abstract

The red-eared slider (Trachemys scripta elegans) is a worldwide highly invasive species, currently introduced in most freshwater habitats as a consequence of massive pet trade. In the Iberian Peninsula, this species is competing with and displacing the endangered native Spanish terrapin (Mauremys leprosa). Sliders are considered environmentallyaggressive turtles, capable of threatening or biting other individuals during competitive activities such as feeding. We hypothesized that agonistic behavior of introduced sliders against native terrapins might negatively affect the feeding efficiency of M. leprosa. We compared food ingestion of turtles and aggressive interactions during feeding, under situations of conspecific and heterospecific competition. The amount of food ingested by native and introduced turtles was similar under conspecific competition, but T. scripta ingested a greater percentage of food supplied under heterospecific competition. Also, introduced sliders initiated most of the aggressions observed during feeding activity, and aggression was more frequently directed to heterospecifics. Our results suggest a more aggressive and competitive behavior of introduced T. scripta in vying for food resources, which might contribute to explain the observed displacement of native populations of M. leprosa.

Dietary niche constriction when invaders meet natives: evidence from freshwater decapods

“…This is consistent with the presence of significant interspecific aggression, which we observed repeatedly during the study, causing reductions in foraging efficiency of both species when present together. Such aggressive behaviour between species is frequently greater than aggression with conspecifics (Polo‐Cavia, López & Martín ). Even though both absolute and relative reductions in growth rates were similar for both decapod consumers, crayfish still exhibited positive per capita growth rates in the presence of crabs, whereas crabs generally lost mass in the presence of the invasive crayfish.…”

Interference competition between native Iberian turtles and the exotic Trachemys scripta

“…This high percentage of aggressions directed from T. scripta to M. leprosa suggests that the former is a more aggressive species and dominant over the latter. Furthermore, the percentage of food ingested by M. leprosa under inter-specific competition correlated positively with the level of suffered aggressiveness, thus indicating that daring M. leprosa which incurred in active competition for food were harshly punished by aggressive sliders, whereas shier individuals that displayed a subordinate role were less attacked (POLO-CAVIA et al, 2011). These findings suggest the existence for M. leprosa of a trade-off between feeding efficiency and costs of aggressive competition with T. scripta.…”

“…Food ingestion of M. leprosa and T. scripta were compared in the laboratory under situations of intra-and inter-specific competition, analysing the frequency of aggressive interactions between individual turtles of similar size, and observing that, when the two turtle species were forced to forage together, the access of M. leprosa to feeding resources was severely restricted by T. scripta, which ingested a greater percentage of the supplied food (POLO-CAVIA et al, 2011;Fig. 3).…”

Occurrence patterns of alien freshwater turtles in a large urban pond ‘Archipelago’ (Rome, Italy): Suggesting hypotheses on root causes

“…; Polo‐Cavia et al . ), they exhibit a higher natural resource availability, and consequently a higher probability of medium‐long‐term survival in larger ponds. All the species have a similar ecology.…”