Observations of a novel predatory gull behavior on an invasive ascidian: A new consequence of coastal urban sprawl?

Abstract

Coastal urbanization has a dramatic effect on both terrestrial and marine ecosystems, altering resources such as food or space. Many species have shifted their ranges in response to anthropogenic pressures, resulting in novel species interactions. Here, we report an observation of a novel foraging behavior of the European Herring Gull (Larus argentatus): the capture and consumption of the widespread sea squirt Ciona intestinalis from under floating pontoons in a recreational marina in Ireland. Multiple gulls were observed performing a complex, multi‐step manipulation of several C. intestinalis individuals to remove their cellulose‐based tunic, which remained unconsumed. Further avenues of investigation are discussed, and hypotheses concerning possible ecosystem effects of novel ecological interactions occurring in proliferating artificial environments are presented.

The invasive species Rangia cuneata: A new food source for herring gull (Larus argentatus)?

“…In addition, this smashing method is known for a long time (Oldham, 1930) and occurs worldwide (Cadée, 2001). Moreover, it is worth to note that observation of gulls feeding on NIS species has been already recorded in the literature (Cadée, 2000(Cadée, , 2001(Cadée, , 2008Holman et al, 2019). For instance, Cadée (2000Cadée ( , 2001Cadée ( , 2008 reported herring gulls carrying the NIS Pacific oysters (C. gigas) or the NIS E. directus to high altitude and drop them onto rocks to crack them open and to feed them.…”

“…For instance, Cadée (2000, 2001, 2008) reported herring gulls carrying the NIS Pacific oysters ( C. gigas ) or the NIS E. directus to high altitude and drop them onto rocks to crack them open and to feed them. Similarly, in 2018, Holman et al (2019) observed a new behavior of herring gull feeding on C. intestinalis in a recreational marina in Ireland. In this study, the authors observed a gull diving down below the pontoons and emerging with a sea squirt of the non‐native species C. intestinalis .…”

“…For instance, Cadée (2000Cadée ( , 2001Cadée ( , 2008 reported that the native European herring gulls (Larus argentatus) fed both on the NIS Pacific oysters (Crassostrea gigas) and on the NIS Ensis directus in the Wadden Sea. Finally, Holman et al (2019) highlighted a novel herring gull's foraging behavior on the widespread sea squirt Ciona intestinalis from under floating pontoons in a recreational marina in Ireland.…”