Feeding ecology of gray whales inferred from stable-carbon and nitrogen isotopic analysis of baleen plates

Abstract

Stable-carbon and nitrogen isotopic compositions (d 13 C, d 15 N) of baleen plates of two juvenile and four adult gray whales (Eschrichtius robustus) were examined. High variance in isotopic composition of baleen plates was detected among individuals and, unlike other migratory species of baleen whales examined isotopically, d 13 C and d 15 N values of most whales showed no regular oscillations. Only one baleen plate reflected the assumed principal Arctic prey (ampeliscid amphipods) during growth on the summer grounds. The rate of baleen growth inferred for one of the juveniles in the last 5 months of life (4.7 mm/week) was similar to the rate calculated previously for a rehabilitating gray whale calf. Autumn corresponded to the timing of the formation of lowest d 15 N values measured along plates. We estimate that the baleen length in all adult gray whales recorded around a year of information (1.3 ± 0.3; Mean ± SD). This short period of dietary integration precludes long time series analyses in this species and reflects the extensive wear on baleen plates due to benthic foraging.

Signals from the south; humpback whales carry messages of Antarctic sea‐ice ecosystem variability

“…Protocols for BSI analysis are published elsewhere (Eisenmann et al, 2016). In brief, blubber samples were extracted overnight in a 2:1 chloroform:methanol solution to remove any oils and lipids (Caraveo-Patiño, Hobson, & Soto, 2007;Hobson & Schell, 1998) and oven-dried at 58°C. 1-2 mg of clean sample material were weighed into tin capsules for isotope analysis (Caraveo-Patiño et al, 2007).…”

Stable isotope chemistry, population histories and Late Prehistoric subsistence change in the Aleutian Islands

“…Within the context of marine environments, archeologists have used stable carbon isotope analysis to reconstruct the relative contributions of terrestrial versus marine resources to mixed human diets (e.g., Coltrain, 2009;Coltrain et al, 2004;Lovell et al, 1986;McGovern-Wilson and Quinn, 1996 [but see Ambrose et al, 1997]; Parkington, 1988Parkington, , 1991Richards and Hedges, 1999;Sealy, 1986;Sealy and van der Merwe, 1985, 1986, 1988Walker and DeNiro, 1986). This method has also been used to track migration and foraging patterns of several Arctic species including bowhead whale, anadromous fish, migratory waterfowl and pinnipeds (e.g., Bunn et al, 1989;Burton and Koch, 1999;Caraveo-Patiño et al, 2007;Dehn et al, 2007;Hobson, 1987;Hobson and Welch, 1995;Kling et al, 1992;Tamelander et al, 2006;Wada et al, 1991). In the case of human foragers subsisting on marine resources, stable carbon isotope values can also covary with foraging environment.…”

Mercury and stable isotope cycles in baleen plates are consistent with year-round feeding in two bowhead whale (Balaena mysticetus) populations

“…Previous studies have shown that stable isotope ratios along baleen plates provide insight into seasonal movements between feeding grounds (Schell et al 1989a, b;Hobson and Schell 1998;Caraveo-Patiño et al 2007;Bentaleb et al 2011;Ryan et al 2013;Eisenmann et al 2016). For instance, the seasonal shift in stable isotope values evident in Southern right whale (Eubalaena australis) baleen indicates an annual migration over the south Atlantic convergence (Best and Schell 1996).…”