[MARMAM] New publication on humpback whale stable isotopes

[Jasmin Gross]

Dear Colleagues,

my co-authors and I are pleased to announce the publication of a new manuscript 
in the journal Rapid Communications in Mass Spectrometry:

Groß, J., Fry, B., Burford, M.A., Bengtson Nash, S. (2021). Assessing the 
effects of lipid extraction and lipid correction on stable isotope values (δ13C 
and δ15N) of blubber and skin from southern hemisphere humpback whales. Rapid 
Communications in Mass Spectrometry 35: e9140 https://doi.org/10.1002/rcm.9140


Abstract
RATIONALE The coupled analysis of δ13C and δ15N stable isotope values of 
blubber and skin biopsy samples is widely used to study the diet of 
free-ranging cetaceans. Differences in the lipid content of these tissues can 
affect isotopic variability because lipids are depleted in 13C, reducing the 
bulk tissue 13C/12C. This variability in carbon isotope values can either be 
accounted for by chemically extracting lipids from the tissue, or by using 
mathematical lipid normalisation models.
METHODS This study examines: (1) the effects of chemical lipid extraction on 
δ13C and δ15N values in blubber and skin of southern hemisphere humpback 
whales, (2) whether chemical lipid extraction is more favourable than 
mathematical lipid correction and (3) which of the two tissues is more 
appropriate for dietary studies. Strategic comparisons were made between 
chemical lipid extraction and mathematical lipid correction, and between 
blubber and skin tissue δ13C and δ15N values, as well as C:N ratios. Six 
existing mathematical normalisation models were tested for their efficacy in 
estimating lipid-free δ13C for skin.
RESULTS Both δ13C and δ15N values of lipid-extracted skin (δ13C: -25.57 ‰, 
δ15N: 6.83 ‰) were significantly higher than bulk skin (δ13C: -26.97 ‰, δ15N: 
6.15 ‰). Five of the six tested lipid normalisation models had small error 
terms for predicting lipid-free δ13C values. The average C:N ratio of 
lipid-extracted skin was within the lipid-free range reported in other studies 
while the average C:N ratio of blubber was higher than previously reported.
CONCLUSIONS These results highlight the need to account for lipids when 
analysing δ13C and δ15N values from the same sample. For optimised dietary 
assessments using parallel isotope analysis from a single sample, we recommend 
the use of unextracted skin tissue. d15N values should be obtained from 
unextracted skin, whilst δ13C values may be adequately lipid corrected by a 
mathematical correction.


The publication can be accessed via this 
link
 or feel free to email me for a copy.

Kind regards,
Jasmin

— —
Jasmin Groß (she/her) I PhD Candidate

Southern Ocean Persistent Organic Pollutants Program (SOPOPP)
Centre for Planetary Health and Food Security | School of Environment and 
Science | Griffith University | Nathan Campus, 170 Kessels Road, Nathan QLD 
4111 Australia

HDR Representative on the Griffith Board of Graduate Research I GUPSA Research 
Officer I ANZSCSMM Chapter Head I Young Science Ambassador

Email:  
jasmin.gr...@griffithuni.edu.au
Phone: +61 (0)7 3735 9237
Mobile: +61 (0)491 074 464
Twitter: @jasmin4689

[cid:FB55EE31-E78C-402C-AF1A-CEEAF9511E5E]

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[MARMAM] Humpback whale social structure in northern British Columbia

[Eric Keen]

Colleagues,

On behalf of my co-authors I am pleased to share the following publication:

Wray J, Keen EM, O’Mahony ÉN (2021) Social survival: Humpback whales
(*Megaptera
novaeangliae*) use social structure to partition ecological niches within
proposed critical habitat. PLOS ONE 16(6): e0245409.

Open access: https://doi.org/10.1371/journal.pone.0245409

*Abstract:*
Animal culture and social bonds are relevant to wildlife conservation
because they influence patterns of geography, behavior, and strategies of
survival. Numerous examples of socially-driven habitat partitioning and
ecological-niche specialization can be found among vertebrates, including
toothed whales. But such social-ecological dynamics, described here as
‘social niche partitioning’, are not known among baleen whales, whose
societies—particularly on foraging grounds—are largely perceived as
unstructured and incidental to matters of habitat use and conservation.
However, through 16 years of behavioral observations and
photo-identifications of humpback whales (*Megaptera novaeangliae*) feeding
within a fjord system in the Canadian Pacific (primarily within Gitga’at
First Nation waters), we have documented long-term pair bonds (up to 12
years) as well as a complex societal structure, which corresponds closely
to persistent patterns in feeding strategy, long-term site fidelity
(extended occupancy and annual rate of return up to 75%), specific
geographic preferences within the fjord system, and other forms of habitat
use. Randomization tests of network congruency and clustering algorithms
were used to test for overlap in patterns of social structure and habitat
use, which confirmed the occurrence of social niche partitioning on the
feeding grounds of this baleen whale species. In addition, we document the
extensive practice of group bubble net feeding in Pacific Canada. This
coordinated feeding behavior was found to strongly mediate the social
structure and habitat use within this humpback whale society. Additionally,
during our 2004–2019 study, we observed a shift in social network structure
in 2010–2012, which corresponded with environmental and demographic shifts
including a sudden decline in the population’s calving rate. Our findings
indicate that the social lives of humpback whales, and perhaps baleen
whales generally, are more complex than previously supposed and should be a
primary consideration in the assessment of potential impacts to important
habitat.

Lead author Janie Wray is the corresponding author for this paper:
ja...@bcwhales.org

Best wishes,
Eric Keen
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