Skip to main content

On-animal sound sensors: long-term sound and movement recording tags for studying how environmental noise affects animals

Final Report Summary - ANIMALSOUNDSENSORS (On-animal sound sensors: long-term sound and movement recording tags for studying how environmental noise affects animals)

A vast array of animals use sound to communicate, navigate, find food or detect threats. But while the vocal and hearing capabilities of animals have evolved over millions of years, human activities are altering the soundscape on land and in the sea on a decadal scale. This project examines how animals use sound and respond to noise disturbance. The goals are: (i) to explore how animals incorporate sound information into behavioural decisions, and (ii) to examine how human activities may be disrupting this information flow. Ultimately, I seek to test if noise disturbance changes the behavioral budgets of animals and so has a cumulative impact on fitness. To achieve this requires the development of cutting-edge tag technology for sampling the sounds experienced by animals synchronously with their fine-scale movements over extended intervals. The combination of sound and movement sensors is critical as it enables the quantification of sound exposures and their behavioural consequences. The project has a wide taxonomic focus: comparing animals in the vastly different but closely linked marine, terrestrial and aerial environments increases the power to reveal underlying response mechanisms. The project therefore requires the development of tags that will survive in the deep ocean and others that are light enough to be carried by birds, as well as analytical tools to examine the dense multi-sensor data that these devices collect.
Sound recording tags have been used for some time on marine animals but battery and memory constraints mean that these have a short recording duration and are far too large for birds. A major challenge of the project was therefore to develop low-power electronics and efficient data storage methods. Power consumption was reduced by careful circuit design linked with efficient software while a new lossless sound compression algorithm was developed to greatly increase recording time. Production of tag designs for each environment was aided by creating a precision manufacturing facility enabling rapid iteration and evaluation of prototypes. The resulting miniature tags for marine and terrestrial animals achieve an order of magnitude greater longevity than the state-of-the-art while still sampling the full hearing range of each species. These highly-integrated tags incorporate wideband movement sensors and an innovative fast acquisition GPS. A heartrate sensor and a backscatter sonar have also been prototyped in these tags. These new sensors provide valuable information about stress and habitat quality, respectively, that help interpret responses to sound. Most recently, a highly miniaturized tag with a reduced sensor suite weighing as little as 2g has been developed for bats and birds. Together, these devices represent a step change in animal monitoring technology opening a rich array of opportunities for cross-environment comparative studies.
Versions of the new tags have been deployed on wild seals (two species), porpoises, whales (3 species), and captive deer with studies on river dolphins and hyenas planned for this year. The bird tag has been trialed on captive crows and will be used on wild animals shortly. To analyse the data from these deployments, new processing tools have been developed quantifying noise levels, foraging behaviour and movements. A high-resolution echo processing method has provided unique information about search strategies and predator-prey interactions in echolocating cetaceans resulting in a new paradigm for how these animals hunt. This technique has been used to evaluate prey selection and noise responses in porpoises with implications for interactions with fisheries. New processing methods for movement sensors have been developed to quantify locomotion effort, swimming gaits and to detect foraging in non-echolocating taxa. Taken together, these techniques will deliver unique information about the potential consequences of human-sourced noise on animals providing a strong scientific basis for improved conservation management.

Results from the project have been reported in 23 scientific papers published or in review as well as 4 book chapters. The new tags created during the project are about to be deployed intensively on a range of species so there will be significant on-going scientific impact. The research will benefit society by identifying how human activities can adversely affect animals and so have implications on biodiversity conservation and ecosystem health. Potential end-users include policy makers and regulators who will benefit from knowing the relative contribution of activities to the cumulative exposure of animals enabling evidence-based and appropriate management of the environment. As a specific example from the project, sound tag studies on Brydes whales in New Zealand, have led to a protocol of voluntary speed restrictions for ship traffic in and out of a major harbour in an effort to reduce mortality of these large whales from collisions.

The technology has several commercial applications. Autonomous sound recorders are being used increasingly on land and in the sea to monitor environmental noise and detect animal calls. The sound tags developed here require an order of magnitude less power than conventional sound recorders enabling longer recording times in battery-limited sensors. The technology has already been incorporated into a commercial sound monitor creating an economic opportunity for a small business and I am working with two tag manufacturers to incorporate sound loggers into their products. The technology has also been adapted for use in robotic ocean gliders creating a cost-effective capability for site monitoring, habitat quality assessment, and animal abundance surveys. These sensors may be especially relevant for fulfilling monitoring obligations under the Marine Strategy Framework Directive.

My motivation in moving to Europe has been to establish an inter-disciplinary research group in the development and use of electronics sensors to study animals. This group, now comprising two PhD students and two research assistants, is embedded in a leading centre for marine bioacoustics and biologging at the host institution. There is a strong prospect of continuing support for my position and I am working to expand the cross-disciplinary teaching offered by the department to capitalise on the unique skills therein. An important factor in ensuring long-term stability is external funding. I have been able to attract funding from a diverse range of international sources including the USA, Denmark, Germany and the UK. As an electronics engineer working within biology, teaming is also essential for me and this project has enabled me to develop international collaborations with researchers working with a wide variety of animals. This wide network ensures a growing array of applications for the technology while also fostering my long-term integration into the European research community.

Project website: