Monitoring Ecosystems through Sound: The Present and Future of Passive Acoustics

Post provided by Ella Browning and Rory Gibb

AudioMoth low-cost, open-source acoustic sensor ©openacousticdevices.info

AudioMoth low-cost, open-source acoustic sensor ©openacousticdevices.info

As human impacts on the world accelerate, so does the need for tools to monitor the effects we have on species and ecosystems. Alongside technologies like camera traps and satellite remote sensing, passive acoustic monitoring (PAM) has emerged as an increasingly valuable and flexible tool in ecology. The idea behind PAM is straightforward: autonomous acoustic sensors are placed in the field to collect audio recordings. The wildlife sounds within those recordings are then used to calculate important ecological metrics – such as species occupancy and relative abundance, behaviour and phenology, or community richness and diversity.

The Pros and Cons of Passive Acoustic Monitoring

Using sound to monitor ecosystems, rather than traditional survey methods or visual media, has many advantages. For example, it’s much easier to survey vocalising animals that are nocturnal, underwater or otherwise difficult to see. Also, because acoustic sensors capture the entire soundscape, it’s possible to calculate acoustic biodiversity metrics that aim to describe the entire vocalising animal community, as well as abiotic elements in the environment.

The use of PAM in ecology has been steadily growing for a couple of decades, mainly in bat and cetacean studies. But with sensor costs dropping and audio processing tools improving, there’s currently a massive growth in interest in applying acoustic methods to large-scale or long-term monitoring projects. As very low-cost sensors such as AudioMoth start to emerge, it’s becoming easier to deploy large numbers of sensors in the field and start collecting data. Continue reading

New Associate Editors

Today we are welcoming two new Associate Editors to Methods in Ecology and Evolution: Huijie Qiao (Chinese Academy of Sciences, China) and Veronica Zamora-Gutierrez (Unidad Durango, Mexico and University of Southampton, UK). They have both joined on a three-year term and you can find out more about them below.

Huijie Qiao

Huijie Qiao

Huijie Qiao

“My research is focused broadly on macroecology. I work to clarify the theory and methodology behind ecological niche modelling and species distribution modelling. In this realm, I have worked to improve our understanding of those modelling algorithms that perform best under different model configuration scenarios, and examined how spatial bias affects model outcomes. I have also developed a simulation framework designed to understand the causal mechanisms that structure biodiversity on both long and short timescales in a virtual world.”

Huijie had an article published in last December’s issue of Methods in Ecology and Evolution. In ‘Using data from related species to overcome spatial sampling bias and associated limitations in ecological niche modelling‘ the authors assess how useful it is to integrate occurrence data for closely related species with varying degrees of niche overlap into Ecological niche models of focal species. In recent years, Huijie has also had articles published in Global Ecology and Biogeography, American Naturalist and Ecography.

Veronica Zamora-Gutierrez

Veronica Zamora Gutierrez

Veronica Zamora Gutierrez

“I am an ecologist and my research interests range from mammal´s conservation, bioacoustics and species interactions to ecosystem services in both natural areas and human-dominated landscapes like cities and agroecosistems. At present, my work focuses mainly on bats to answer question related to their importance as pollinators and suppressors of insects’ population, their echolocation behaviour and how global change is and might affect them. Deepening our understanding of these questions is crucial for developing effective conservation strategies in this anthropozoic era.”

In 2016, Veronica was the lead author on ‘Acoustic identification of Mexican bats based on taxonomic and ecological constraints on call design‘ which was published in the September issue of Methods in Ecology and Evolution. The article collated a reference call library for bat species that occur in a megadiverse country (Mexico) and is now freely available. More recently, she has published articles on the effects of climate change on bats and the importance of vertebrate pollinators.

We’re delighted to welcome Huijie and Veronica to the Associate Editor Board and we look forward to working with them over the coming years.

Solo: Developing a Cheap and Flexible Bioacoustic Tool for Ecology and Conservation

Post provided by Robin Whytock

A Solo recorder in the field. ©Tom Bradfer-Lawrence

A Solo recorder in the field. ©Tom Bradfer-Lawrence

Ecologists have long been fascinated by animal sounds and in recent decades there’s been growing interest in the field of ‘bioacoustics’. This has partially been driven by the availability of high-definition digital audio recorders that can withstand harsh field conditions, as well as improvements in software technology that can automate sound analysis.

Sound recordings can be used to study many aspects of animal behaviour in a non-intrusive way, from studying the social dynamics of monkeys or even clownfish to detecting echolocating bats or singing birds. Some species can only reliably be separated in the field by the sounds that they make, such as common and soprano pipistrelle bats. Bat research in general has been revolutionised by commercially available acoustic loggers, with some amazing advances using artificial intelligence to automatically detect bat calls. Continue reading

Midwater Ocean Communities: Sounds Like Siphonophore Soup

Post provided by Roland Proud

How do we know how many fish there are in the ocean? 1000, 1 billion, 1000 billion? We can’t catch them all and count – that’s not practical. Nor can we make observations from Earth-orbiting satellites – light does not penetrate far into the ocean. What we can use is sound.

Sound travels well in water (faster and further than it does in air), so we can use scientific SONAR (echosounders) to produce sound waves and record backscatter from organisms and communities. This provides information concerning their biomass, distribution and behaviour. A recent study used echoes from the mesopelagic zone (200 – 1,000m) to predict global mesopelagic fish biomass to be between 11 and 15 billion tonnes (that’s a lot), suggesting that mesopelagic fish communities could potentially provide global food security.

Mesopelagic Biogeography

In a recent paper, we (the Pelagic Ecology Research Group, PERG at the University of St Andrews) divided the global ocean up into regions based on the properties of echoes from the mesopelagic zone (see below).

10 mesopelagic classes are shown for the open-ocean, echo intensity (a proxy for biomass) increases from blue to red. Coastal zones excluded. Longhurst provinces overlaid. Shapefile here. Proud et al. (2017)

10 mesopelagic classes are shown for the open-ocean, echo intensity (a proxy for biomass) increases from blue to red. Coastal zones excluded. Longhurst provinces overlaid. Shapefile here. Proud et al. (2017)

Continue reading

Listen Up! Using Passive Acoustic Monitoring to Help Forest Elephant Conservation

Post provided by Peter H. Wrege

Forest elephant in Gabon

Forest elephant in Gabon

Heard but not seen, populations of forest elephants (Loxodonta cyclotis) are rapidly declining due to ivory poaching. As one of the largest land mammals in the world, this species is surprisingly difficult to observe in the dense forests of Central Africa, but their low frequency rumbles can be recorded. With the autonomous recording afforded by passive acoustic monitoring (PAM) though, we have a window onto forest elephant ecology and behaviour that’s providing data critical to their conservation and survival.

The diverse ways that PAM can contribute to conservation outcomes is growing and while still underappreciated, the availability of relatively inexpensive recorders, increased power efficiency, and powerful techniques to automate the detection of signals have led to an explosion in use. In 2007 there were only about 20 published papers using PAM techniques, but since then over 400 papers have appeared in peer-reviewed journals.

Spectrogram of two forest elephant rumbles. Horizontal line shows the limit of human hearing.

Spectrogram of two forest elephant rumbles. Horizontal line shows the limit of human hearing.

Essentially, PAM is the automatic recording of sounds in a given environment, often for long periods. The trick, and often greatest challenge, is to find the signals of interest (bird calls, elephant rumbles, gunshots) within the recordings. With these signals we can quantify abundance, occupancy and spatial or temporal patterns of activity. Particularly in landscapes or ecosystems where visual observation is difficult (e.g. oceans, rainforests, nocturnal environments) PAM may be uniquely capable of delivering informative and unbiased data. Because PAM is a relatively new method but of considerable interest across the disciplines of ecology, behaviour and conservation, there is huge interest in refining the sampling and statistical methods needed to deal with the peculiarities of acoustic data. Continue reading

Issue 8.5

Issue 8.5 is now online!

The May issue of Methods is now online!

This issue contains three Applications articles and two Open Access articles. These five papers are freely available to everyone, no subscription required.

MatlabHTK: A software interface to a popular speech recognition system making it possible for non-experts to implement hidden Markov models for bioacoustic signal processing.

 PrimerMiner: The R package PrimerMiner batch downloads DNA barcode gene sequences from BOLD and NCBI databases for specified target taxonomic groups and then applies sequence clustering into operational taxonomic units to reduce biases introduced by the different number of available sequences per species.

 BarcodingR: An integrated software package that provides a comprehensive implementation of species identification methods, including artificial intelligence, fuzzy-set, Bayesian and kmer-based methods, that are not readily available in other packages.

Continue reading

Microphone Backpacks for Individual-level Acoustic Recordings

To understand the factors shaping vocal communication, we need reliable information about the communicating individuals on different levels. First, vocal behaviour should be recorded from undisturbed animals in meaningful settings. Then we have to separate and assign the individuals’ vocalisations. Finally, the precise timing of vocal events needs to be stored.

Microphone backpacks allow researchers to record the vocal behaviour of individual animals in naturalistic settings – even in acoustically challenging environments! In the video below, Lisa Gill, Nico Adreani and Pietro D’Amelio demonstrate the lightweight radio-transmitter microphone backpacks that have been developed and built at the Max Planck Institute for Ornithology, Seewiesen, Department of Behavioural Neurobiology. They show the attachment and setup of this system in detail, evaluate its behavioural effects, and discuss what makes it so useful for studying vocal communication, especially in small animals.

This video is based on the article ‘A minimum-impact, flexible tool to study vocal communication of small animals with precise individual-level resolution‘ by Gill et al.

 

Issue 8.3

Issue 8.3 is now online!

The March issue of Methods is now online!

This issue contains two Applications articles and one Open Access article. These three papers are freely available to everyone, no subscription required.

 Solo: Solo audio recorders are inexpensive, easy to construct and record audible sound continuously for around 40 days. The paper also has a video tutorial explaining how to assemble the required hardware and comes with a companion website with more information.

 The third dimension: A novel design to obtain three-dimensional data on the movements of aquatic organisms at depths of up to 140m. The set-up consists of two synchronised high-speed cameras fixed to two articulated arms and can be used for any underwater applications that require synchronized video recordings of medium- to large-sized animals.

Continue reading

Issue 8.2

Issue 8.2 is now online!

The February issue of Methods is now online!

This issue contains four(!) Applications articles and two Open Access articles. These six papers are freely available to everyone – no subscription required.

 Earth Mover’s Distance: The Earth Mover’s Distance (or EMD) is a method commonly used in image retrieval applications. The authors of this paper propose its use to calculate similarity in space use in the framework of movement ecology. This will be helpful for many questions regarding behavioural ecology, wildlife management and conservation.

 warbleR: The R package warbleR is a new package for the analysis of animal acoustic signal structure. It offers functions for downloading avian vocalisations from the open-access online repository Xeno-Canto, displaying the geographic extent of the recordings, manipulating sound files, detecting acoustic signals or importing detected signals from other software, and much more.

– meteR: The open-source R package, meteR directly calculates all of Maximum entropy theory of ecology’s (METE’s) predictions from a variety of data formats; automatically handles approximations and other technical details; and provides high-level plotting and model comparison functions to explore and interrogate models.

– Noise Egg: The Noise Egg is a device that can produce a low-frequency sound, which can be used as an experimental source of noise both in aquaria and in the field. It was developed to study the effects of noise on communication and behaviour in small aquatic animals; however, it could be used for other purposes, such as testing the propagation of certain frequencies in shallow-water habitats.

Continue reading

Testing the Effects of Underwater Noise on Aquatic Animals

Post provided by Karen de Jong

Most people assume that research equipment is expensive and complicated. But, it doesn’t need to be and the noise egg is a perfect example of this. It consists of a watertight container (as used by scuba divers) and the buzzer from a cellphone and does exactly what it says: it produces low frequency noise. This allows researchers to test the effect of noise on underwater life. It is a small, simple and cheap device that anyone can build.

Why Test Effects of Noise?

A painted goby in front of his nest ©K. de Jong

A painted goby in front of his nest ©K. de Jong

Underwater noise is rapidly increasing due to, for example, boat traffic and offshore wind farms. This can lead to stress for animals and difficulties in communication. Just as people have a hard time communicating in a noisy pub, animals may struggle to get their messages across when background noise is high. A nice description of how animals use sound and how noise may affect this can be found at www.dosits.org

While there is some knowledge on the effect of noise on large aquatic animals, we still know very little about how fish and other small aquatic animals are affected. Such knowledge is vital for management of protected areas. It’s also important to know whether wind farms and boat traffic can affect reproduction in populations of underwater resources such as fish and mussels. The answers to these questions are likely to be species specific, so we’ll need data on a large number of species in different habitats. Continue reading