Individual specialization in the foraging habits of female bottlenose dolphins living in a trophically diverse and habitat rich estuary

Rossman, Sam; Ostrom, Peggy H.; Stolen, Megan; Barros, Nélio B.; Gandhi, Hasand; Stricker, Craig A.; Wells, Randall S.

doi:10.1007/s00442-015-3241-6

Cited by 41 publications

(44 citation statements)

References 38 publications

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“…Multivariate modeling framework can accompany other forms of data (i.e., GIS or morphometric data) to enhance analyses of species' niches (Rossman et al. ) and allow ecologists to ask ever more complex questions.…”

Section: Discussionmentioning

confidence: 99%

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Beyond carbon and nitrogen: guidelines for estimating three‐dimensional isotopic niche space

Rossman

Ostrom

Gordon

et al. 2016

Ecology and Evolution

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Isotopic niche has typically been characterized through carbon and nitrogen ratios and most modeling approaches are limited to two dimensions. Yet, other stable isotopes can provide additional power to resolve questions associated with foraging, migration, dispersal and variations in resource use. The ellipse niche model was recently generalized to n‐dimensions. We present an analogous methodology which incorporates variation across three stable dimensions to estimate the significant features of a population's isotopic niche space including: 1) niche volume (referred to as standard ellipsoid volume, SEV), 2) relative centroid location (CL), 3) shape and 4) area of overlap between multiple ellipsoids and 5) distance between two CLs. We conducted a simulation study showing the accuracy and precision of three dimensional niche models across a range of values. Importantly, the model correctly identifies differences in SEV and CL among populations, even with small sample sizes and in cases where the absolute values cannot precisely be recovered. We use these results to provide guidelines for sample size in conducting multivariate isotopic niche modeling. We demonstrate the utility of our approach with a case study of three bottlenose dolphin populations which appear to possess largely overlapping niches when analyzed with only carbon and nitrogen isotopes. Upon inclusion of sulfur, we see that the three dolphin ecotypes are in fact segregated on the basis of salinity and find the stable isotope niche of inshore bottlenose dolphins significantly larger than coastal and offshore populations.

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Section: Discussionmentioning

confidence: 99%

“…; Rossman et al. ). However, until recently methodological approaches for quantitatively defining isotopic niche space were limited to the incorporation of only two isotopes (Swanson et al.…”

Section: Introductionmentioning

confidence: 99%

Beyond carbon and nitrogen: guidelines for estimating three‐dimensional isotopic niche space

Rossman

Ostrom

Gordon

et al. 2016

Ecology and Evolution

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“…Individual specialization of foraging habits has been documented for other generalist consumers, such as coastal cetaceans (Rossman et al. ), sea otters ( Enhydra lutris ) (Estes et al. ), and bears (Deacy et al.…”

Section: Discussionmentioning

confidence: 99%

“…4), suggesting some seals rely more heavily on sockeye salmon (seal 03 and seal 07) and others less so (seal 02 and seal 04). Individual specialization of foraging habits has been documented for other generalist consumers, such as coastal cetaceans (Rossman et al 2015b), sea otters (Enhydra lutris) (Estes et al 2003), and bears (Deacy et al 2016). The food resources produced from within the lake available to seals include abundant juvenile sockeye salmon and a diverse array of resident fishes, all of which would isotopically reflect lake water (Figs.…”

Section: Foraging Ecology Of Iliamna Sealsmentioning

confidence: 99%

“…The differential exploitation of resources among life stages reflects the fact that particular prey sources are needed or preferred during different times (Van Daele et al 2013;Rossman et al 2015a). Similarly, individual foraging behaviors suggests that individuals adopt various feeding strategies in the face of spatially and temporally dynamic prey sources (Estes et al 2003;Rossman et al 2015b;Deacy et al 2016). In both instances, there is an important interaction between foraging strategy, trophic resources, and the role of heterogeneity.…”

Section: Conservation Of Iliamna Sealsmentioning

confidence: 99%

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Isotopes in teeth and a cryptic population of coastal freshwater seals

Brennan

Fernández

Burns

et al. 2019

Conservation Biology

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Human activities threaten the biodiversity of aquatic mammals across the globe. Conservation of these species hinges on the ability to delineate movements and foraging behaviors of animals, but gaining such insights is hampered by difficulties in tracing individuals over their lives. We determined isotope ratios in teeth (87Sr/86Sr, 13C/12C, and 18O/16O) to examine lifelong movement and resource‐use patterns of a unique freshwater population of a wide‐ranging pinniped species (harbor seal [Phoca vitulina]) that resides in Iliamna Lake, Alaska (U.S.A.). This population's potentially unique migratory behavior and use of different trophic resources are unknown. The isotope ratios we measured in teeth showed that seals were born in the lake, remained lifelong residents, and relied principally on resources produced from in the lake, even when seasonally abundant and nutrient‐dense spawning anadromous fish (i.e., sockeye salmon [Oncorhynchus nerka]) were available in the lake. Our results illustrate how serial isotope records in teeth, particularly 87Sr/86Sr ratios, can be used to quantify how coastal mammal populations exploit both freshwater and marine ecosystems. Understanding lifelong patterns of habitat and resource use is essential information when designing effective conservation plans for threatened coastal mammals. We present the Iliamna Lake harbor seals as a unique case study into how isotope records within teeth can help reveal the cryptic ecology of such a population residing in an intact ecosystem. The results also provide critical baseline information for the Kvichak River system, which is facing an uncertain future due to proposed large‐scale industrial development and a rapidly changing climate.

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Large‐scale molecular barcoding of prey DNA reveals predictors of intrapopulation feeding diversity in a marine predator

Voelker

Schwarz

Thomas

et al. 2020

Ecology and Evolution

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Predator–prey interactions are critical in understanding how communities function. However, we need to describe intraspecific variation in diet to accurately depict those interactions. Harbor seals (Phoca vitulina) are an abundant marine predator that prey on species of conservation concern. We estimated intrapopulation feeding diversity (variation in feeding habits between individuals of the same species) of harbor seals in the Salish Sea. Estimates of feeding diversity were examined relative to sex, month, and location using a novel approach that combined molecular techniques, repeated cross‐sectional sampling of scat, and a specialization metric (within‐individual consistency in diet measured by the Proportional Similarity Index (PSi)). Based on 1,083 scat samples collected from five haul‐out sites during four nonsequential years, we quantified diet using metabarcoding techniques and determined the sex of the scat depositor using a molecular assay. Results suggest that intrapopulation feeding diversity was present. Specialization was high over short periods (24–48 hr, PSi = 0.392, 95% CI = 0.013, R = 100,000) and variable in time and space. Females showed more specialization than males, particularly during summer and fall. Additionally, demersal and benthic prey species were correlated with more specialized diets. The latter finding suggests that this type of prey likely requires specific foraging strategies and that there are trade‐offs between pelagic and benthic foraging styles for harbor seals. This differential feeding on prey species, as well as between sexes of harbor seals, indicates that predator–prey interactions in harbor seals are complex and that each sex may have a different impact on species of conservation concern. As such, describing intrapopulation feeding diversity may unravel hitherto unknown complex predator–prey interactions in the community.

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Individual specialization in the foraging habits of female bottlenose dolphins living in a trophically diverse and habitat rich estuary

Cited by 41 publications

References 38 publications

Beyond carbon and nitrogen: guidelines for estimating three‐dimensional isotopic niche space

Beyond carbon and nitrogen: guidelines for estimating three‐dimensional isotopic niche space

Isotopes in teeth and a cryptic population of coastal freshwater seals

Large‐scale molecular barcoding of prey DNA reveals predictors of intrapopulation feeding diversity in a marine predator

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