Mistaken Identities: Stingrays vs. Skates

With their flat, kite-shaped bodies and wing-like pectoral fins, it's no wonder stingrays and skates are so easily confused with each other. Although these cartilaginous fishes—also known as elasmobranchs—share many visual similarities, there are also distinct differences between them, too.

Other Differences

Stinging spines vs. thorns, viviparous vs. oviparous—there are more differences between stingrays and skates than meets the eye.

Stinging Spines vs. Thorny Projections

If you take a look at a stingray's tail, you'll find their namesake stinging spines, or barbs, which they use as protection. These sharp, serrated spines deliver venom into predators—or into the feet of humans that accidentally step on a buried stingray, which can be extremely painful, but rarely fatal. Stingrays typically aren't aggressive but will protect themselves when threatened by raising their tails up, piercing the skin of their predators and injecting the venom.

Instead of stinging spines, skates' tails are lined with blunt, thorny projections, which also line skates' backs. These "thorns" aren't venomous like a stingray's spines, but they're also used for protection. A would-be predator, like a shark or grouper, that spots a skate may think twice about biting down on these thorn-like adornments.

Reproductive Strategy

The reproductive strategies of these two elasmobranchs are vastly different. Stingrays are viviparous, which means they give birth to fully formed young. Skates, however, are oviparous, which means they lay eggs.

If you've ever come across a rectangular, black, leathery pouch with horns extending from each corner while strolling the beach, you've found a skate egg case. These egg cases are sometimes referred to as mermaid's purses.

Size

Another clue that can help distinguish these two elasmobranchs is size. It's not a hard-and-fast rule, but generally, stingrays are larger than skates.

Teeth

Stingray's mouths are typically lined with flat, plate-like teeth that are used for crushing hard-shelled prey such as oysters and clams. Skates, on the other hand, have small, pointed teeth, which come in handy for capturing small fish, crustaceans and other prey.

Order

When it comes to their classification within the animal kingdom, both stingrays and skates belong to the class Chondrichthyes—but then they diverge. Stingrays are in the order Myliobatiformes; skates are in the order Rajiformes.

Exceptions

There are exceptions to the general rule of long-and-thin tails for stingrays and short-and-thick tails for skates. For example, typical freshwater stingrays have relatively short, stout tails that are similar to a skate's tail, and the butterfly ray—a species of marine stingray—has a thin, but exceptionally short, tail.

And although thorn-like spikes are typically a telltale sign of skates, the roughtail stingray also sports bony "thorns" on its disc and tail.

Aquarium Residents

Four species of stingrays and two species of skates can be found throughout the National Aquarium.

Roughtail Stingray

The roughtail stingray is the largest species of stingray at the National Aquarium; this species has been reported to grow as big as 7 feet across and 450 pounds. The roughtail stingray at the Aquarium can be found in Shark Alley.

White-Blotched River Stingray

The white-blotched river stingray's distinctive pattern of white dots on a black background helps it to blend into its riverbed habitat. This species can be found in the Aquarium's Amazon River Forest exhibit.

Reticulated Whiptail Ray

The reticulated whiptail ray, also known as an Australian whipray, has a tail that can reach three times the length of its body. This species can be found in Blacktip Reef.

Blotched Fantail Ray

The blotched fantail ray—another resident of Blacktip Reef—is listed as a vulnerable species on the IUCN Red List.

Clearnose Skate and Little Skate

There are two species of skate in the Aquarium: the clearnose skate, pictured above, in Atlantic Shelf, and little skates in the touchpool area of Living Seashore.