Does the exotic invader turtle, Trachemys scripta elegans, compete for food with coexisting native turtles?

Abstract

Nowadays, established populations of exotic turtles, Trachemys scripta elegans, coexist with native turtles in the wild in southern Spain. We analysed the diet of this exotic species and compared it with the diet of the two native species (Mauremys leprosa and Emys orbicularis) in two ponds. The exotic turtle is an opportunistic omnivore. In one of our study ponds where exotic invasive crayfish were very abundant, adult and juvenile exotic turtles fed mainly on this prey. In the other study pond, juveniles fed mainly on animal matter and adults ate similar proportions of plants and animals. Native turtles also ingested mainly crayfish in the first study pond, but M. leprosa were mainly herbivorous in the second pond. We did not detect strong differences among the diets of the three species. While native species significantly differ in their diets, the exotic turtles did not differ from some groups of native ones. Exotic turtles had the widest range of food, overlapping the food spectra of different age groups of the two native species in both localities. Comparing with previous reports on native turtles diet of the same area, our results did not reveal changes in the diet which could be associated to interactions with exotic turtles, but the observed shift to a higher proportion of animals in the diet in one of the ponds were mainly due to the high abundance of exotic crayfish.

Reproductive Traits Demonstrate How Well the Mediterranean Stripe-Necked Turtle Mauremys leprosa Can Flourish under Highly Degraded–Polluted Conditions

“…Jorgewich-Cohen et al [ 49 ] strongly implicated ecological factors, mainly resource availability on clutch capacity and egg size of chelonian species. The very wide food spectrum of M. leprosa (omnivory with a predominance of carnivory, but also scavenging and coprophagy) allows it to obtain supplies at will in eutrophic and polluted waters [ 8 , 13 , 52 ]. In Boukhmira, several groups of turtles consisting of a few dozen individuals were frequently noted eating the abundant aquatic invertebrates, rushing toward the organic waste freshly thrown by the local inhabitants, and also feeding on the corpses of fish and other vertebrates found on the surface of the stream (Pers.…”

Habitat overlap and body condition in aquatic turtles: are there additive effects between invasive and native species?

“…We expected (hypothesis i) to find some level of habitat partitioning that could explain the presence of the three species within the same basin (Segurado and Figueiredo, 2007;Escoriza, 2018). We also expected (hypothesis ii) that the abundance of the invasive turtle would negatively affect the body condition of the native species both by itself and synergistically with the native species because these turtles widely overlap in their trophic niches (Díaz-Paniagua et al, 2011).…”

A heuristic for innovative invasive species management actions and strategies

“…Exotic freshwater turtles such as the red slider (Trachemys scripta elegans) count among the most invasive species (https://www. nobanis.org/), with potentially major impacts on native species in the wild (Cadi and Joly 2003, Díaz-Paniagua et al 2011, Standfuss et al 2016. They occur in European cities mainly as a result of citizens releasing their pets in neighboring urban parks (Teillac-Deschamps et al 2009), where these pets contribute to relationships between citizens and nature (Teillac-Deschamps et al 2008, Philippot et al 2019.…”