Lead image copyright: Guy Stevens

The Manta Trust is pushing the boundaries of manta ray research with the use of ultrasound technology in Laamu Atoll. The use of contactless ultrasound scans to study the reproductive health of reef manta rays (Mobula alfredi) has become a crucial tool in understanding the species' biology and supporting its conservation.

Unlike traditional ultrasound, which requires an animal to be captured or restrained, this technology allows researchers to scan wild manta rays while they are freely swimming. This provides an invaluable opportunity to study their reproductive biology without disturbing them. But getting an ultrasound image of a wild manta is no easy task.

First, there has to be a manta. Then she needs to be female and, ideally, visiting a cleaning station. Once those conditions are met, the real challenge begins. The researcher must approach the manta carefully without disturbing her, hold position in what can be strong current, and bring the ultrasound probe to within around 10 centimetres of her body. The probe itself is only around the width of two fingers and needs to remain almost perfectly still to produce a clear image. And all of this has to happen while the manta is moving. Sometimes there are only a few seconds to get everything right.

The ultrasound technology used in Laamu is the result of a successful collaboration between Ray Rochester, IMV Imaging, Vetsonic (UK) Ltd, the University of Cambridge, Six Senses Laamu, and the Manta Trust. This partnership led to the development of the Duo-Scan:Go Oceanic, a wireless, fully sealed and waterproof ultrasound scanner designed for use underwater. 

The device can display ultrasound images on a smartphone or tablet, allowing researchers to examine the internal structures of wild manta rays in their natural environment. This technology has opened up new opportunities for understanding manta ray reproduction. Manta rays reproduce slowly, and there is still much we do not know about their reproductive biology. Ultrasound can help researchers monitor pregnancy, investigate reproductive maturity and follow the development of pups.

Combined with the long-term photo-identification work carried out by the Manta Trust in Laamu, ultrasound allows researchers to follow individual females and build a much clearer picture of their reproductive lives.

Learning to use the technology has been a gradual process. The Manta Trust team has received specialist training and practical support from Ray Rochester, helping researchers refine their scanning techniques and interpretation of ultrasound images. The first scans were a learning experience, with researchers having to develop the skills needed to read the situation underwater, anticipate the manta's movements and position the tiny probe at exactly the right moment. 

That experience has continued to pay off. One of the most significant breakthroughs came when the team successfully captured an ultrasound image of a developing pup inside Oulaya (M4499). Seeing a manta pup developing inside a wild manta ray on the ultrasound screen is something the team does not take for granted. Sometimes there are obvious external signs that a manta is pregnant. Sometimes, as was the case with Oulaya, there aren't. Being able to look inside and find evidence of a developing pup when there are no visible signs of pregnancy is an incredible result for research.

Ultrasound provides information that simply cannot be gained from observing manta rays from the outside. By combining scans with long-term photo-identification data, researchers can follow individual females and learn more about pregnancy, reproductive maturity, gestation and pup development. With more than 150 reef manta rays documented in Laamu, the ongoing research conducted by the Manta Trust team is providing valuable insights into the reproductive behaviour of this population.

The work also builds on previous research conducted in Laamu, including published research demonstrating the use of underwater contactless ultrasonography to investigate the reproductive activity of manta and devil rays.  As the Manta Trust team continues to develop its ultrasound research, each successful scan adds another piece to the puzzle of manta ray reproduction. The technique may only take a few seconds, but getting those few seconds right can take months or even years of learning.

With continued research, training and collaboration, ultrasound technology will allow the team to make even greater strides in understanding manta ray biology and informing conservation efforts.

For information: 

Manta Trust 

Maldives Underwater Initiative

IMV Imaging

Vetsonic Ltd. 

University of Cambridge

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