Abstract

Cortisol is often used in wildlife health studies and conservation efforts as an indicator of fitness and stressor load, providing some insight into individual and population responses to stressors. Typical methodology for measuring cortisol, however, involves blood sampling which can be invasive, stressful, or unfeasible in free-ranging animals. Recently, alternative matrices for hormone measurements have received a lot of interest, including collection of exhaled breath condensate (blow) from cetaceans. Previous work within our laboratory developed a protocol for blow collection from aquarium belugas (Delphinapterus leucas) and validated use of a commercial enzyme immunoassay to measure cortisol in blow samples.

The purpose of this work was to apply the blow collection methodology during beluga live capture health assessments in Bristol Bay, AK between 2012 and 2014. A collection device, composed of a petri dish and nylon membrane, was held inverted over the blowhole for 2 or 4 repeated exhales during restraint in shallow water. Samples were collected at the onset of examination (pre) as well as just prior to release (post) for all animals. In 2014, intermediate plates were also taken throughout the examination. Blow was recovered from membranes by centrifugation as previously determined, and cortisol was measured using a commercially available EIA from Cayman Chemical. Blow samples from a total of 22 whales from 2012, 2013 and 2014 are included in this study. Initial (pre) samples were taken between 21 and 39 minutes from entanglement and appear to show no effect of body condition, sex or time of day on cortisol values (α = 0.05). Animal length also appeared not to affect the cortisol response, though animals > 161 cm display somewhat smaller responses. Time between pre and post blow samples ranged from 20 to 85 minutes. There was a slight increase in cortisol between pre and post samples, though this was not statistically significant (α = 0.05). In fact, a decrease in cortisol was detected in several animals. However, there was a significant negative correlation between blow sample volume and cortisol content for post samples (p = 0.039), suggesting dilution by water content. Samples taken throughout examination during 2014 suggest variability in individual responses to handling and sampling, and that neither pre nor post samples necessarily represent the peak in cortisol response.

Ongoing work is investigating a way to standardize results and account for variation in water content, which may alter patterns reported here. However, this work does demonstrate the usefulness of blow sampling as a tool to measure the response of belugas to live captures or other procedures. The non-invasive nature of blow sampling means it can be done efficiently and continuously throughout a clinical procedure or research efforts. Furthermore, blow sampling can be applied to populations which cannot be handled directly or for which blood sampling is not feasible. Finally, cortisol data obtained from blow may be useful in determining appropriate neuro-endocrine responses in cetaceans and in future assessments of individual and population responses to disturbances and anthropogenic stressors.

Acknowledgements

This work was funded by Office of Naval Research award #N00014-11-1-0437 (analyses) and Georgia Aquarium (field effort). Sampling occurred under NMML permit #14245 and IACUC # AFSC/NWFC 2012-1. The authors thank the Bristol Bay Marine Mammal Council, as well as Mandy Keogh, Justin Richard and the Bristol Bay Field team.

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