Skin δ13C and δ15N reveal spatial and temporal patterns of habitat and resource use by free-ranging odontocetes from the southwestern Atlantic Ocean

Trophic ecology and foraging areas of cetaceans sampled in the coastal waters of south-eastern Brazil assessed through skinδ13C andδ15N

“…Similar isotopic values have been observed in S. frontalis and D. delphis from southern Brazil (31-34°S) nearshore (Botta et al, 2012) and oceanic populations (Troina et al, 2020b). Nevertheless, the authors have concluded that despite the relatively high isotopic niche overlap between the oceanic populations of D. delphis and S. frontalis, the fact that they avoid one another (Di Tullio et al, 2016) is a strategy to minimize competition (Troina et al, 2020b). In south-eastern Brazil, data from stomach contents showed overlap in some prey species taken by these toothed whales, although they differed in terms of size-classes and the dominance of species (Melo et al, 2010).…”

“…Despite the geographic overlap in occurrence between S. frontalis and D. delphis (Moreno et al, 2005;Tavares et al, 2010), we found no evidence for overlap in the use of resources, as indicated by the lack of isotopic similarity between these two species. Similar isotopic values have been observed in S. frontalis and D. delphis from southern Brazil (31-34°S) nearshore (Botta et al, 2012) and oceanic populations (Troina et al, 2020b). Nevertheless, the authors have concluded that despite the relatively high isotopic niche overlap between the oceanic populations of D. delphis and S. frontalis, the fact that they avoid one another (Di Tullio et al, 2016) is a strategy to minimize competition (Troina et al, 2020b).…”

Long-Term Consequences of High Polychlorinated Biphenyl Exposure: Projected Decline of Delphinid Populations in a Hotspot for Chemical Pollution

“…Surprisingly, the offshore individuals sampled between 200 and 400 m depth isobath also presented elevated concentrations of PCBs and pesticides, which may be a consequence of their elevated trophic level. 56,65 The main effects of high PCB concentrations include the decrease of immunological parameters such as natural killer cell activity and lymphocyte proliferation 8,11 and may facilitate the establishment of bacterial and viral infections, leading to higher mortality rates by infectious diseases. 10,66 Furthermore, the transference of part of the mother's body burden to the calf can also decrease offspring survival probability 12,14 and trigger hormonal deregulation when combined with other contaminants, such as DDTs.…”

A practical guide on stable isotope analysis for cetacean research

“…This approach has been applied to assess the trophic relationships, habitat, and resource use of fin whales (e.g., Das et al, 2017; Ryan et al, 2013), common bottlenose dolphins Tursiops trucatus (e.g., Santos Carvallo et al, 2015), sympatric coastal (e.g., Teixeira et al, 2020; Young et al, 2017) and oceanic odontocetes (e.g., Troina et al, 2021), to name a few. Additionally, both Layman metrics and SIBER approaches can be combined to evaluate the niche partitioning among populations (e.g., Brotons et al, 2019; Riccialdelli et al, 2017) and species (e.g., Troina et al, 2020b). Swanson et al (2015) advanced ellipse‐based models further by allowing for the inclusion of more than two niche dimensions.…”