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Much like a human fingerprint, every manta ray has a unique pattern of spots on its ventral surface or belly, that remain unchanged throughout that individual’s lifetime. The unique nature of these spots is incredibly helpful for manta scientists, enabling individual mantas to be identified just by photographing their belly’s.
Rowan Virbickas, 2019
Edy Setyawan, 2021
The awesome thing about this technique is that it’s simple, inclusive (literally everyone can get involved) and most importantly it’s non-invasive, promoting respectful and passive interaction.
All of this lovely data can then be used to develop photo-ID databases for all known manta rays within a population. This effective research method has been successfully replicated for all known manta populations around the world.
Mark Erdmann, 2017
This is a slow and steady research tool, that’s value improves with time as more IDs are collected and importantly the number of previously identified mantas, known as re-sightings increase. The more re-sightings collected over the years can reveal migration patterns, critical habitats use i.e. for feeding and breeding, as well as an individual’s life history, such as pregnancies and injuries. All of this information can then be used to recommend and implement sustainable, conservation management for manta rays throughout their population range.
To the trained eye an ID image offers a lot more information about an individual manta then just it’s belly spots. Gender, injuries (and their origin), tail length and hitchhikers i.e. fish that closely associate with mantas such as remora are all important elements to each manta ray’s story.
The target location for getting a good ID shot usually reveals the manta’s gender, which is really important because this information can be used to calculate proportions of males and females in the population. Determining the maturity status i.e. whether an individual is sexually active or not is equally as critical, providing further insight into the populations’ composition and health.
A male’s maturity directly relates to the size and shape of his claspers which can be captured along with his ID. Claspers that are pronounced (easy to spot) and extend past the male’s anal fins are clear signs of sexual maturity. Whereas tiny claspers, that are much harder to spot are found on juvenile or sub adult males.
There are a couple more details to look for when verifying a females maturity status and often requires additional images. The more images available, the more information we have to learn about each manta ray. For this reason when our team encounter a manta, we take numerous images as well as video footage from every possible angle and we strongly encourage our citizen scientists to do the same.
Currently, researchers have to rely on external indicators relating to courtship to confirm a female’s sexual maturity.
Mating scars are a visual record of the female manta ray’s dating history; her scars will fade but traces of them permanently remain. Therefore, mating scars are incredibly useful when determining a female’s maturity and also estimating how long ago she mated.
Fortunately for us, when manta rays mate the male leaves his mark! Mating scars are abrasions caused by the male’s tiny teeth as he holds onto the female whilst they are belly to belly. Apart from a few exceptions, these scars are consistently found on the female’s left wing. Fresh mating scars are pink or red and turn white or black as they age.
Edy Setyawan, 2021
Baby bumps are the next external indicator we look out for after discovering mating scars. Encountering pregnant females gives invaluable insight into the finer details of a population and depending on the stage of pregnancy can also highlight potential pupping ground and nursery areas.
Edy Setyawan, 2021
The advancement of drone technology has revolutionised how data can be collected on some of the world’s most elusive and hard to reach species.
This birds eye view enables researchers to observe their subjects from a whole new perspective, often resulting in never before seen behaviours and interactions that simply are not possible when humans get too close. For our team, using a drone has become an essential means of collecting data on the notoriously elusive and energetic oceanic manta rays of Aotearoa. The ability to passively observe and document manta ray behaviours whilst collecting photo IDs has significantly boosted our knowledge of this historically data deficient population and has dramatically increased the number of mantas in our ID Database!
In addition to a male’s clasper size and a female’s mating scars, the size of a manta ray is literally a HUGE indicator of maturity. Manta rays are measured in meters from one wing tip to the other, commonly known as Disc Width. Obtaining this measurement ranges from difficult to impossible when you are working with hungry manta rays in open ocean. And without something to compare a manta rays size to, visual estimations can’t be considered reliable.
Our team soon realized that our aerial drone could be further utilised to accurately measure a manta ray disc width by introducing an object of known length into the same frame as our chosen manta. With the help of our trusty Manta Ruler and some snazzy drone pilot skills, we can now accurately measure our photo identified mantas! Incorporating size into our photo ID records will over time help to answer some currently unknown questions relating to size at sexual maturity and growth rate.
Irene Middleton, 2019
Sophie Roselt, 2021
Rikako Orzaki, 2021
Steve Hathaway, 2016
Scott Tindale, 2018
Emma Harrison, 2021
Emma Harrison, 2021
Rowan Virbickas, 2019
The Hunters Club, 2021