Round Stingray

Fascinating facts about the Round Stingray

• A 19th-century soldier’s son, who was stung while wading in San Diego Bay, gave the round stingray its scientific name halleri – a reminder that even a harmless-looking ray can pack a painful sting.
• Most round stingrays stay in water shallower than 15 m, but they have been found as deep as 91 m; they only tolerate temperatures above 10 °C (50 °F), with adults handling temperature swings better than juveniles.
• Their infamous tail spine isn’t permanent – each year a new secondary spine sprouts in July, peaks in September-October, and the old primary spine is shed and replaced by December.
• Females give birth to 1–6 pups after a three-month gestation, usually 2–3; the newborns are only 6–8 cm wide, and the rays grow about 3 cm per year until they’re roughly 31 months old, when growth slows.
• Hundreds of Southern California beachgoers are pricked by hidden round stingrays, especially at Seal Beach’s “Ray Bay,” where the shallow nursery grounds turn a casual stroll into a painful surprise.

At a glance

About the Round Stingray

The round stingray (Urobatis halleri) glides over soft sand and mud in the warm, shallow waters of the eastern North Pacific, its nearly circular pectoral disc a muted brown or grayish-brown canvas dotted with pale yellow spots. At up to 31 cm across in females, its short, stout tail ends in a long, serrated spine that it sheds and replaces each year, sprouting secondary spines from July to October before the primary spine is renewed by December. Its underside is a stark white to yellowish hue, and the male’s central teeth stand erect and curve inward, a subtle clue to its sex. In the sun-lit shallows of southern California and the Baja Peninsula, these rays dig expansive pits with their discs and mouths, unearthing polychaete worms, tiny crabs, and later bivalve molluscs, while the freshly exposed prey becomes a buffet for smaller fish, linking the stingray’s foraging to the broader benthic community. Seasonally, round stingrays shuffle between habitats: juveniles and males linger in waters less than 14 m deep, while adult females retreat to deeper zones, especially in winter when cooler, more stable temperatures prevail. Their daily activity peaks in the warm months, and they congregate near the warm effluent of coastal electric generators, a behavior that mirrors their natural estuarine preferences. A surprising facet of their biology is the female’s ability to emit a localized positive electric field from near the spiracles, a subtle lure that draws curious males to bite, a prerequisite for successful copulation. After gestating for three months, females give birth to 1–6 pups that measure 6–8 cm, and the cycle of shallow nursery grounds and deeper adult refuges repeats, underscoring the species’ finely tuned life-history rhythm.

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