Isotopic niche of New Jersey terrapins suggests intraspecific resource partitioning, and little variability following a major hurricane

Abstract

Diamondback terrapins (Malaclemys terrapin) are sexually dimorphic generalist turtles that inhabit salt marshes and estuaries along the Atlantic and Gulf coasts of the United States. On October 29th, 2012, Hurricane Sandy made landfall in New Jersey, USA, directly impacting terrapin populations inhabiting central and southern Barnegat Bay. To examine potential food web mediated impacts to the terrapin population and their foraging dynamics we examined carbon and nitrogen stable isotope values collected from terrapin tissues (2011, 2015, 2019) and resource taxa (2015, 2019) within Barnegat Bay. Isotopic analysis revealed that mature females had lower carbon and higher nitrogen values than immature females and males with almost no isotopic niche overlap, whereas males and immature females had statistically similar values with overlapping niches. Terrapins and resources collected from island habitats contained higher carbon and nitrogen values than those from mainland habitats, with little overlap in niche between habitats. There were no significant temporal variations detected in either carbon or nitrogen values from terrapins between years, or within each habitat pre- and post-Hurricane Sandy. These findings suggest long-term terrapin foraging dynamics have remained relatively stable, signifying resilience to disturbance events within the study site.

Dietary Niche of Three Omnivorous Turtle Species in a Northern Florida River: Insights from Stable Isotope Analysis

“…Ontogenetic changes in diet have been well-documented in many other turtle species, including Chelonia mydas (L.) (Green Turtle; Morais et al 2014) (Bouchard andBjorndal 2006, Clark andGibbons 1969). Isotope studies have also detected ontogenetic shifts in Apalone ferox Schneider (Florida Softshell Turtle) populations in lakes in northwestern Florida (Aresco et al 2015), as well as in a Malaclemys terrapin terrapin Schoepff (Northern Diamondback Terrapin) population in southern Barnegat Bay, NJ (Denton et al 2023). The more vertical orientation of the ellipse in C. serpentina in our study with its narrower range in carbon values indicates foraging on consistent basal resources, whereas the wider range in nitrogen values may reflect a diet spanning trophic levels (Fig.…”