Health of North Atlantic right whales Eubalaena glacialis over three decades: from individual health to demographic and population health trends

Abstract

Marine mammals are faced with increasing challenges from environmental fluctuation, climate change, and disturbances from human activities. Anthropogenic mortalities have been well documented, but it is difficult to assess the sub-lethal effects of disturbance on the fitness of marine wildlife, and to distinguish these impacts from natural variations in health and reproduction. Here, we used photographic data on body and skin condition, blowhole cyamids, and rake marks, to evaluate the health of North Atlantic right whales Eubalaena glacialis from 1980 to 2008. We applied a hierarchical Bayesian model to these data to estimate the underlying continuous health status of individuals, demographic groups, and the population to characterize health patterns and temporal trends. Visual health scores (scaled from 0 to 100) from 48 560 sighting events were used to estimate the health of 622 identified right whales on a monthly basis. Health in most whales fluctuated between 70 and 90, and health scores of < 60 were observed in whales in poor condition. Health varied by sex, age-class and reproductive state, with the greatest annual variability occurring in actively reproducing females. Calving females had significantly higher health scores than non-calving females, and a steep deterioration in population health coincided with a dramatic decline in calving from 1998 to 2000. Health in all demographic groups and the population declined over the 3 decades of observations. Given the inevitable data gaps that occur in most marine wildlife research, modeling advances such as the one presented here offer a promising approach to assess the complex interactions between biology, ecology, and sublethal anthropogenic disturbance on marine mammals.

Fecal glucocorticoids and anthropogenic injury and mortality in North Atlantic right whales Eubalaena glacialis

“…Extensive survey effort in the NARW calving ground and other habitats enabled identification of the vast majority of calving females, allowing for determination of reproductive status in adult females as either pregnant, lactating, or resting (i.e. non-pregnant, non-lactating) (Browning et al 2010, Rolland et al 2016). …”

“…Paired feces and serum collected from the live-stranded right whale provided comparison of fGCs in 2 matrices in a chronically stressed whale. Serum cortisol and corticosterone in this whale (50.0 and 29.0 ng ml anthropogenic stressors on individuals or populations (Tyack 2008, Fleishman et al 2016, Rolland et al 2016, Williams et al 2016. Concern about the non-lethal effects of human activities has resulted in the development of methods to quantify physiological and pathological responses of non-captive marine mammals (Ayres et al 2012, Rolland et al 2012, Hunt et al 2014a.…”

Body condition changes arising from natural factors and fishing gear entanglements in North Atlantic right whales Eubalaena glacialis

“…As the purpose of this study was to investigate characteristics of body condition changes in right whales, only the body condition parameter was analyzed, based on observations from 1980 to 2011. The collection of visual health data follows the methodology developed for evaluating scars on right whales (Knowlton et al 2012, Schick et al 2013, Rolland et al 2016. Photographs from all sightings of an individual whale were grouped sequentially by right whale habitat region (e.g.…”

“…The methodology used to batch right whale sightings in this study, developed first for evaluation of scarring rates in right whales and extended to the health assessment when the latter technique was developed in 2000, has been utilized in several previously published works (Knowlton et al 2012, Schick et al 2013, Rolland et al 2016). Batches were organized spatially rather than temporally in the development of the methodology in order to examine changes related to habitat conditions.…”

“…There is growing concern about the sublethal impacts of entanglement events on right whales, as well as the cumulative impact of multiple entanglement events on health, reproduction, and survival , Robbins et al 2015, Rolland et al 2016. Recently developed state-space modeling approaches that use visual health data to estimate health over time have been used to examine the impact of health on reproduction (Rolland et al 2016), and offer opportunities to examine impacts of entanglement, including the entanglement severity, duration, and type on right whale health and survival (Schick et al 2013). …”