Abstract
The maintenance of robust wild populations and recovery of endangered species are dependent upon the health of individuals within those populations. A variety of methods are available to study the health and physiology of individual whales in the field. These approaches include: evaluation of body and skin condition,4,5 fecal sampling for parasites, disease agents, biotoxins, and pollutants,3 measurement of hormone metabolites in feces and blubber,3,7 and sampling of respiratory vapor (blow) for hormones, microbial organisms and other biochemical indicators2. Using well-studied North Atlantic right whales (Eubalaena glacialis) as a model, we are working on approaches to integrate individual whale health profiles into assessments of population status. Here we present examples of the links between visual health measures and vital population parameters, and present a new modeling approach incorporating health and sightings data to estimate population trends and survival.
Visual assessment has been used to evaluate the health status of individual right whales of concern, and these measures have also been linked with population vital rates.5 A significant decline in body condition and an increase in skin lesions of unknown etiology coincided with a dramatic decline in calving rates in the mid to late 1990's.1,5 Using a Markov chain process we analyzed the relationship between body condition scores and calving in adult females (1980–2009). Females almost never transitioned from resting to pregnant unless body condition was good, indicating that reproduction is contingent on sufficient blubber energy reserves and that this can be evaluated visually.
Body condition scores have also been linked with mortality. Right whales with a sighting gap of 6 years ("presumed dead") had significantly worse body condition than whales known to be living.5 Further, we compared the condition scores of whales that were presumed dead and never sighted again (n = 100) with whales that were eventually resurrected (re-sighted after > 6 years, n = 35). Whales in fair and poor condition at their last sighting were significantly less likely to be "resurrected" than those with good body condition (χ2 = 7.97, p < 0.05). Additionally, of 15 right whales sighted in poor body condition, 14 (93%) are either known or presumed dead, thus poor body condition is a strong predictor of mortality.
As the next step in linking individual and population health, we are incorporating thirty years of right whale health and sightings data into a Hierarchical Bayesian model.8 This model is being developed to make inferences on right whale health and survival integrating both spatial and temporal elements. Ultimately, this model will be useful to follow trends in population health, and it provides a framework for examining the relative impact of different anthropogenic stressors on right whale health and survival.
Acknowledgements
The Office of Naval Research, NOAA Fisheries, and the Northeast Consortium supported this research. Our thanks to the New England Aquarium right whale team and numerous researchers who collected samples, and the North Atlantic Right Whale Consortium for permission to use life history and sightings data. This research was conducted under research permits from the National Marine Fisheries Service, and Scientific Research Permits from Fisheries & Oceans, Canada, under the Canadian Species at Risk Act.
* Presenting author
Literature Cited
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