Studying cetacean behaviour: new technological approaches and conservation applications

Animal behaviour can provide valuable information for wildlife management and conservation. Studying the detailed behaviour of marine mammals involves challenges not faced by most animal behaviour researchers due to the size, mobility and lack of continuous visibility of these animals. We describe several methods developed by marine mammal scientists to study behaviour, primarily of cetaceans, focusing on technological advances: unmanned aerial systems (UAS), satellite-linked telemetry, passive acoustics and multisensor high-resolution acoustic recording tags. We then go on to explain how the data collected by these methods have contributed to and informed conservation actions. We focus on examples including: satellite data informing the interactions between cetaceans and offshore oil and gas development; passive acoustics used to track distributions of several species of cetaceans, including their movements near shipping lanes; and high-resolution acoustic recording tags used to document responses of cetaceans to anthropogenic activities. Finally, we discuss recent efforts to link animal behaviour to individual fitness and, particularly for behavioural disturbances, to population-level consequences, which can be helpful for informing conservation efforts. The infusion of technological advancements into studies of cetacean behaviour combined with emerging analytical techniques brings us to the next 20+ years of studying these animals. These developments will improve our capabilities in areas such as testing whether their behaviour adheres to traditional behavioural theory, and will certainly assist the guiding of conservation efforts

Atlantic Behavioral Response Study: Experimental Design, Analytical Methods, and Preliminary Results

Excerpted from ESOMM - 2018, 6th International Meeting on the Effects of Sound in the Ocean on Marine Mammals The Hague, The Netherlands

Effects of body condition on buoyancy in endangered North Atlantic right whales

Buoyancy is an important consideration for diving marine animals, resulting in specific ecologically relevant adaptations. Marine mammals use blubber as an energy reserve, but because this tissue is also positively buoyant, nutritional demands have the potential to cause considerable variation in buoyancy. North Atlantic right whales Eubalaena glacialis are known to be positively buoyant as a result of their blubber, and the thickness of this layer varies considerably, but the effect of this variation on buoyancy has not been explored. This study compared the duration and rate of ascending and descending glides, recorded with an archival tag, with blubber thickness, measured with an ultrasound device, in free-swimming right whales. Ascending whales with thicker blubber had shorter portions of active propulsion and longer passive glides than whales with thinner blubber, suggesting that blubber thickness influences buoyancy because the buoyant force is acting in the same direction as the animal’s movement during this phase. Whales with thinner layers also used similar body angles and velocities when traveling to and from depth, while those with thicker layers used shallower ascent angles but achieved higher ascent velocities. Such alterations in body angle may help to reduce the cost of transport when swimming against the force of buoyancy in a state of augmented positive buoyancy, which represents a dynamic response to reduce the energetic consequences of physiological changes. These results have considerable implications for any diving marine animal during periods of nutritional stress, such as during seasonal migrations and annual variations in prey availability

Marine Mammal Noise Exposure Criteria: Assessing the Severity of Marine Mammal Behavioral Responses to Human Noise

Major progress has been made since the publication of noise exposure criteria by Southall et al. (2007) in addressing the probability and severity of marine mammal behavioral responses to measured noise exposures. New methodological developments for studying behavioral responses have broadened the spatial, temporal, and population scales of potential disturbance studies and expanded scientific data on responses of marine mammals (or lack thereof) to various human noise exposure scenarios. Experimental and observational studies have substantially expanded the resolution, parameters, and contexts for understanding individual and group responses to discrete noise events. The combined data strongly suggest that efforts to derive simple all-or-nothing thresholds for single noise exposure parameters (e.g., received noise level) and behavioral responses across broad taxonomic and sound categories can lead to significant errors in predicting effects that are fundamentally inconsistent with the probabilistic nature of responses. Differences between species, among individuals, across situational contexts, and with the temporal and spatial scales over which exposures occur lead to variability in the probability and severity of behavioral responses. Studies that account for such factors and the variability they cause can provide far more accurate probability functions for predicting effects and can reduce variabilities related to exposure level and response. To that end, several new approaches are developed here for evaluating response severity in laboratory and field conditions in terms of effects on vital rates. These are applied to selected studies of marine mammal behavioral response to demonstrate their application in more consistently addressing acute exposure contexts for individuals or discrete groups. Needs for new approaches and transparent processes are identified for addressing sustained and/or repeated noise exposures on population scales