Sticking Together or Drifting Apart? Quantifying the Strength of Migratory Connectivity

Post provided by Emily Cohen

Red Knot migratory connectivity is studied with tracking technologies and color band resighting. © Tim Romano

Red Knot migratory connectivity is studied with tracking technologies and colour band resighting. © Tim Romano

The seasonal long-distance migration of all kinds of animals – from whales to dragonflies to amphibians to birds – is as astonishing a feat as it is mysterious and this is an especially exciting time to study migratory animals. In the past 20 years, rapidly advancing technologies  – from tracking devices, to stable isotopes in tissues, to genomics and analytical techniques for the analysis of ring re-encounter databases – mean that it’s now possible to follow many animals throughout the year and solve many of the mysteries of migration.

What is Migratory Connectivity?

One of the many important things we’re now able to measure is migratory connectivity, the connections of migratory individuals and populations between seasons. There are really two components of migratory connectivity:

  1. Linking the geography of where individuals and populations occur between seasons.
  2. The extent, or strength, of co-occurrence of individuals and populations between seasons.

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Getting Every Last Bit Out of Dives: Data Abstraction On-board Telemetry Tags

Post provided by THEONI PHOTOPOULOU, MIKE FEDAK, LEN THOMAS and JASON MATTHIOPOULOS

Animal Telemetry for Air-breathing Divers

CTD-SRDL Tags

CTD-SRDL telemetry tags being primed for deployment. ©Theoni Photopoulou

Nowadays animal telemetry tags for air-breathing divers come in all shapes and sizes. In four short decades tags for diving animals have gone from prototypes like the one built by Jerry Kooyman for deployment on Weddell seals – which consisted of a kitchen timer and a roll of graph paper – to a multitude of sophisticated electronic devices, fit for just about any animal or purpose you can think of.

All this progress has meant we can collect more information than ever before and do so remotely. Nevertheless, the lives of most divers remain a well-kept secret. For tags that transmit what they collect (as opposed to those that store data until they’re retrieved), the transmission stage is usually the bottleneck. This has driven the development of energy and time efficient software and data processing.

For a tag like the conductivity-temperature-depth Satellite Relay Data Logger (CTD-SRDL) built by the Sea Mammal Research Unit Instrumentation Group at the University of St Andrews – which was designed to spend months at sea – the problem boils down to one thing. Data are collected at a high resolution on-board the tag amounting to 100kB daily, but only 1kB of this information (at best) can be transmitted to the ground station. Therefore in preparation for transmission, the data need to be chosen carefully, compacted and fitted into several satellite messages of fixed size to ensure that enough useful information is received. Each satellite message can hold up to 248bits of information. To give an idea of how limiting this is, consider that this sentence would (without compaction) take up 896bits! Continue reading

Accompanying Marine Mammals into the Abyss: The Benefits of Electronic Tag Data for Undersea Tracking

Post provided by Christophe Laplanche, Tiago Marques and Len Thomas

1km Deep

Most marine mammal species spend the majority of their lifetime at sea… underwater. Some species (like sperm whales, beaked whales, and elephant seals) can go routinely as deep as 1000m below sea level. To mammals like us, these incredible depths seem uninhabitable. It’s cold, dark, under high pressure (100kg/cm²) and 1km from air! Yet deep-diving marine mammals thrive there and have colonized every deep ocean on the planet. They have developed amazing capabilities for that purpose – including efficient swimming, an advanced auditory system, sonar (in some cases), thermal insulation, extreme breath holding abilities and resistance to high pressure.

How is that possible?

Spending most of their time at depth makes them quite difficult to study. And we have a lot of questions to ask them. How do they balance swimming cost versus food intake? Do they forage cooperatively, in groups? For those with sonar, how does it work? With increasing human activities (oil exploration, military sonar, sea transport, fishing etc.) an important new question arises: how do they cope with us?

Researchers tagging a Cuvier's beaked whale with a DTAG sound tag (soundtags.st-andrews.ac.uk) in the Ligurian Sea (© T. Pusser)

Researchers tagging a Cuvier’s beaked whale with a DTAG sound tag (soundtags.st-andrews.ac.uk) in the Ligurian Sea (© T. Pusser)

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New Tool to Assess Effects of Powerful Man-Made Underwater Sounds

Below is a press release about the Methods paper ‘An interim framework for assessing the population consequences of disturbance‘ taken from the University of St Andrews:

A team of scientists from the University of St Andrews has developed a new desktop tool for assessing the impact of noise from human disturbance, such as offshore wind development on marine mammal populations.

PCOD_PR_imageThe team, led by Prof. John Harwood, have developed the interim Population Consequences of Disturbance (PCoD) framework for assessing the consequences of human induced noise disturbance on animal populations. The study was published yesterday in the journal Methods in Ecology and Evolution.

Changes in natural patterns of animal behaviour and physiology resulting from animals being disturbed may alter the conservation status of a population if the activity affects the ability of individuals to survive, breed or grow. However, information to forecast population-level consequences of such changes is often lacking. The project team developed an interim framework to assess impacts when empirical information is sparse. Crucially, the model shows how daily effects of being disturbed, which are often straightforward to estimate, can be scaled to the duration of disturbance and to multiple sources of disturbance.

“We have developed a novel framework that can be used to broadly forecast the consequences of anthropogenic disturbance on animal populations, which in principal can be applied to a range of marine and terrestrial species and different types of disturbance.” – Dr Stephanie King

One important application for the interim PCoD framework is in the marine industry. Many industries use practices that involve the generation of underwater noise. These include shipping, oil and gas exploration, defence activities and port, harbour and renewable energy construction. Continue reading