Mangrove Ray
Urogymnus granulatus
Mangrove rays are a physically large species of the Dasyatidae family of rays. They are a lightly studied member of the Dasyatidae family of rays, which include approximately seventy species, including the southern stingray and blue spotted stingray. Distinctive in their coloring, they feature a series of white spots on a dark body and a totally white tail below the area of the stinger which sets them apart from many rays. Unlike some other species of rays, they are generally solitary. Their name comes from using mangroves to provide a protective habitat for the juvenile rays during the development stage.
SPECIES IN DETAIL
Mangrove Ray
Urogymnus granulatus
CONSERVATION STATUS: Endangered
CLIMATE CHANGE: Vulnerable
At the Aquarium
They may be viewed in the Tropical Blue corner in the Coral Reef exhibit.
Geographic Distribution
They inhabit the Indo-Pacific region from Australia to Micronesia to the Red Sea.
Habitat
Adult mangrove rays are typically found on flat sandy or rocky bottoms in depths from 0 to 85 meters (0—279 feet). Juveniles reside in brackish estuaries or mangroves which provide food and protection from predators.
Physical Characteristics
Adult mangrove rays are oval shaped with the horizontal portion between the pectoral fins being longer than the area from the head to the beginning of the tail. Like many marine animals they are darker on top and lighter on the bottom to provide camouflage. They have a series of white spots along the top of their body with the lower section of the tail, below the stinger, turning to all white.
Size
Adults can reach 1.41 meters (4 feet, 7 inches) wide and 3.5 meters (11 feet, 6 inches) long including the tail. Their estimated life expectancy is 20—25 years.
Diet
Like other members of the species, they are bottom feeders. Using specialized senses of smell and an electrosensory system located near and around their mouth they can detect electric currents generated by their food source. Their primary diet is crustaceans, worms and small fish. Their mouth consists of flat rows of teeth that can be used to crush prey much like a vice. They use their large pectoral fins to stir up bottom sediment and locate food.
Reproduction
This species of rays maintains the eggs within their body prior to live birth (aplacentral viviparous reproduction). The juveniles are 14—28 centimeters (5-11 inches) in length at birth. They may have two to six young with a gestation period of approximately twelve months. Juveniles use mangroves as well as shallow estuaries for protection against predators during their early development.
Behavior
Mangrove rays frequent flat sandy or rocky bottoms which supports their feeding habits. The mangrove rays, unlike some other species, are solitary and rarely travel in schools. They can bury themselves in sandy bottoms during the day as a method of protection from predators. They generally feed at night as they do not use their eyes to discover food. Not aggressive by nature, their general defense method is to just swim away and may use their stinger for protection if they are attacked from above.
Adaptation
They possess a strong sense of smell along with the ability to sense movement around their body by use of their lateral line: a series of sensors exists along their body that can detect changes in water pressure or movement. In addition, a series of sensors that can detect electrical pulses (known as the ampullae of Lorenzini) located on the bottom of their body near the mouth allows them to detect food sources without the need to see them. They also have developed the ability to survive in various levels of salinity, expanding their potentially acceptable habitats.
Longevity
Studies on longevity of this species are inconclusive.
Conservation
Several issues contribute to the current vulnerable status for this species. Rays are a food source for some Asian cultures; without protection that does not currently exist, combined with a slow reproductive rate, their numbers can decline. Commercial fishing nets have posed a danger for the rays in their habitat. Climate change and its growing impact on the mangroves through warmer water, storms, and droughts will result in a cascading impact on juvenile rays who depend on these for protection and food during initial stages of growth.
Special Notes
Mangrove rays’ teeth are flat and in rows of 40—50 on both the upper and lower jaw. The teeth are ribbed similar to a vice and used for crushing foods such as shellfish and crustaceans. Like all rays they are cartilaginous with no bones except for vertebrates. Since the teeth are not connected to bones they regularly lose teeth as sharks do.
SPECIES IN DETAIL | Print full entry
Mangrove Ray
Urogymnus granulatus
CONSERVATION STATUS: Endangered
CLIMATE CHANGE: Vulnerable
They may be viewed in the Tropical Blue corner in the Coral Reef exhibit.
They inhabit the Indo-Pacific region from Australia to Micronesia to the Red Sea.
Adult mangrove rays are typically found on flat sandy or rocky bottoms in depths from 0 to 85 meters (0—279 feet). Juveniles reside in brackish estuaries or mangroves which provide food and protection from predators.
Adult mangrove rays are oval shaped with the horizontal portion between the pectoral fins being longer than the area from the head to the beginning of the tail. Like many marine animals they are darker on top and lighter on the bottom to provide camouflage. They have a series of white spots along the top of their body with the lower section of the tail, below the stinger, turning to all white.
Adults can reach 1.41 meters (4 feet, 7 inches) wide and 3.5 meters (11 feet, 6 inches) long including the tail. Their estimated life expectancy is 20—25 years.
Like other members of the species, they are bottom feeders. Using specialized senses of smell and an electrosensory system located near and around their mouth they can detect electric currents generated by their food source. Their primary diet is crustaceans, worms and small fish. Their mouth consists of flat rows of teeth that can be used to crush prey much like a vice. They use their large pectoral fins to stir up bottom sediment and locate food.
This species of rays maintains the eggs within their body prior to live birth (aplacentral viviparous reproduction). The juveniles are 14—28 centimeters (5-11 inches) in length at birth. They may have two to six young with a gestation period of approximately twelve months. Juveniles use mangroves as well as shallow estuaries for protection against predators during their early development.
Mangrove rays frequent flat sandy or rocky bottoms which supports their feeding habits. The mangrove rays, unlike some other species, are solitary and rarely travel in schools. They can bury themselves in sandy bottoms during the day as a method of protection from predators. They generally feed at night as they do not use their eyes to discover food. Not aggressive by nature, their general defense method is to just swim away and may use their stinger for protection if they are attacked from above.
They possess a strong sense of smell along with the ability to sense movement around their body by use of their lateral line: a series of sensors exists along their body that can detect changes in water pressure or movement. In addition, a series of sensors that can detect electrical pulses (known as the ampullae of Lorenzini) located on the bottom of their body near the mouth allows them to detect food sources without the need to see them. They also have developed the ability to survive in various levels of salinity, expanding their potentially acceptable habitats.
Studies on longevity of this species are inconclusive.
Several issues contribute to the current vulnerable status for this species. Rays are a food source for some Asian cultures; without protection that does not currently exist, combined with a slow reproductive rate, their numbers can decline. Commercial fishing nets have posed a danger for the rays in their habitat. Climate change and its growing impact on the mangroves through warmer water, storms, and droughts will result in a cascading impact on juvenile rays who depend on these for protection and food during initial stages of growth.
Mangrove rays’ teeth are flat and in rows of 40—50 on both the upper and lower jaw. The teeth are ribbed similar to a vice and used for crushing foods such as shellfish and crustaceans. Like all rays they are cartilaginous with no bones except for vertebrates. Since the teeth are not connected to bones they regularly lose teeth as sharks do.