Manta presentation in Maldives

1. Mantas of the Maldives
Part 1: Introduction to Manta ecology and
distribution
By Dr. Anne-Marie Kitchen Wheeler
Project Founder
Manta Ecology Project

2. Two species of manta ray:
Manta birostris (Walbaum 1792) (MB)
Common name: GIANT or OCEANIC MANTA
Manta alfredi (Krefft 1868) (MA)
common name ALFRED or REEF MANTA
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3. Two species of manta ray:
Manta birostris (Walbaum 1792) (MB)
Common name: GIANT or OCEANIC MANTA
Manta alfredi (Krefft 1868) (MA)
common name ALFRED or REEF MANTA
Another species?
A third species has been proposed which may be a sub-species of MB or
may be a new species by it’s limited range (Marshall et al. 2009).
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4. Two species of manta ray:
Manta birostris (Walbaum 1792) (MB)
Common name: GIANT or OCEANIC MANTA
Manta alfredi (Krefft 1868) (MA)
common name ALFRED or REEF MANTA
Another species?
A third species has been proposed which may be a sub-species of MB or
may be a new species by it’s limited range (Marshall et al. 2009).
Both species are observed in the Maldives however MB is much rarer
(12 vs 2220 individuals recorded Manta Ecology Project database Jan. 2014)
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5. Manta birostris (MB)
Manta alfredi (MA)
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6. Manta birostris (MB)
Manta alfredi (MA)
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7. Manta birostris (MB)
Manta alfredi (MA)
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8. Manta birostris (MB)
Manta alfredi (MA)
2
2
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9. Manta birostris (MB)
2
Manta alfredi (MA)
2
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10. Manta birostris (MB)
Manta alfredi (MA)
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11. Manta birostris (MB)
Manta alfredi (MA)
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12. Manta birostris (MB)
Manta alfredi (MA)
4
4
4
4
4
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13. Manta birostris (MB)
Manta alfredi (MA)
4
4
4
4
4
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14. Manta birostris (MB)
Manta alfredi (MA)
2
2
4
4
TEETH ON:
o UPPER JAW
o LOWER JAW
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4
4
TEETH ON:
o LOWER JAW
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15. Manta birostris (MB)
Manta alfredi (MA)
4
4
4
4
4
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16. Manta birostris (MB)
Manta alfredi (MA)
4
4
4
4
4
?
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17. Manta birostris (MB)
Manta alfredi (MA)
4
4
4
4
4
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18. Manta birostris (MB)
Manta alfredi (MA)
4
4
4
4
4
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19. There are black variants of each species but are exceedingly rare in Maldives
and only black MB have so far been reported. Black MA are common is other
tropical island areas (up to 50% of MAs may be black variant)
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20. There are black variants of each species but are exceedingly rare in Maldives
and only black MB have so far been reported. Black MA are common is other
tropical island areas (up to 50% of MAs may be black variant)
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21. There are black variants of each species but are exceedingly rare in Maldives
and only black MB have so far been reported. Black MA are common is other
tropical island areas (up to 50% of MAs may be black variant)
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22. Manta rays can be individually identified from their ventral markings
Marks in central and abdominal
areas are used to identify individuals
(Kitchen-Wheeler 2010, Marshall et. al 2009)
A trained observed will quickly
appreciate that markings vary
between individuals and that
markings are unique
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23. Manta rays can be individually identified from their ventral markings
Visual identification can be used
instead of tagging or physically
marking individuals
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25. Manta Lifecycle (MA)
The age to which mantas live is still not fully understood but a
Male’ based manta ray known as Brenda is known to be at
least 40 years old.
One of the oldest Mantas in the world?
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26. Manta Lifecycle (MA)
Age and growth studies in other elasmobranchs have been based
on ring (or band) measurements of vertebrae sections
but these have not been found/reported in manta rays.
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27. Manta Lifecycle (MA)
Examples of known longevity of other elasmobranchs in the
wild include the common spiny dogfish Squalus acanthias
(Linnaeus 1758) achieving 65-70 years and grow to 170 cm total
length.
It is likely that manta rays live as long.
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28. Manta Lifecycle
Female mantas give birth to fully formed live young. Examples
born in aquaria measured 1.92-1.96 m disc width (DW). Live
young in the wild have been observed at around 1 m DW. A
wild birth has not been observed.
Large energy investment that the parent manta put in
the offspring.
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29. Manta Lifecycle
Pregnancy last around
12.5 months
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30. Manta Lifecycle
Heavily pregnant females are frequently seen at cleaning
stations nearby large sheltered lagoons
e.g. Rasfari
Juveniles are frequently observed in sheltered lagoons used
by safari and fishing boats for anchorage so it is likely
that birth occurs in the lagoons.
This subject is a topic of current research
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31. Diurnal Activity
From dawn and throughout daylight hours mantas may be
observed at cleaning stations and feeding areas at shallow
reef areas. They are also observed hovering in current in
channels and locations with strong water flow.
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32. Diurnal Activity
From dawn and throughout daylight hours mantas may be
observed at cleaning stations and feeding areas at shallow reef
areas. They are also observed hovering in current in channels
and locations with strong water flow.
After dusk mantas rays are commonly observed still feeding at
inshore areas and can be attracted to feed in shallow lagoons.
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33. Diurnal Activity
From dawn and throughout daylight hours mantas may be observed at
cleaning stations and feeding areas at shallow reef areas. They are also
observed hovering in current in channels and locations with strong water
flow.
After dusk mantas rays are commonly observed still feeding at inshore areas
and can be attracted to feed in shallow lagoons.
At night they travel offshore to feed in deep water (50-200
m) as zooplankton rises.
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34. Diurnal Activity
This pattern has been shown from independent study in
Okinawa prefecture (Japan), Komodo (Indonesia) and various
Hawaiian islands and suggested by initial study in the Maldives
(Yano et al. 2000; Clark 2008 ; Dewar et al. 2008). Similar behaviour has also be
shown by MB (Rubin et al. 2008).
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35. Distribution
Red: MB circumtropical plus temperate
Blue: MA Indo-Pacific tropical
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36. Distribution
Red: MB circumtropical plus temperate
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37. Distribution
Blue: MA Indo-Pacific tropical
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38. Distribution
MB has been reported from offshore islands (Revillagigedos/Mexico,
Galapagos/Ecuador, French Polynesia, Okinawa prefecture Southern
Japan, Maldives, and off most continental coastlines.
In areas where it is sighted regularly it is only reported seasonally, in
association with local increases in plankton productivity.
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39. Distribution
MA has been reported from Maldives, Hawaii, Okinawa
prefecture islands, throughout Indonesia, Malaysia and French
Polynesia.
It is reported from continental coastlines including E. Africa and
Australia in the Indo-Pacific but is absent from the western
Atlantic and very rarely reported from W. Africa.
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40. Distribution
MA is reported year round at the majority of locations
where sighted and at most locations the local
populations are considered resident.
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41. Thank you for your attention
contact details: amkw9@sky.com
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