Gray Smooth-hound

Fascinating facts about the Gray Smooth-hound

• A 2021 genetic study found that two gray smooth-hound mothers produced litters where every pup traced back to a single father, hinting at genetic monogamy in a group that usually mates with many males. If true, this would set the species apart from its smooth-hound cousins and could reshape how we think about shark mating strategies.
• Gray smooth-hounds can give birth to as many as 17 pups after a gestation of 9–12 months, and larger females have proportionally larger litters.
• Juvenile gray smooth-hounds often hide among eelgrass edges in restored tidal basins, where they become seasonally abundant in the summer.
• Despite living mostly in waters shallower than 80 m, these sharks have been recorded at depths of 265 m in the Gulf of California.
• Only three gray smooth-hounds have ever been documented as true albinos, including a pregnant female in 1971 that carried five completely white pups with pink eyes, a rarity that underscores how unusual albinism is among sharks.

At a glance

About the Gray Smooth-hound

The gray smooth-hound (Mustelus californicus) glides along the warm continental shelves of the eastern Pacific, a sleek, spotless shark whose brown-to-dark-gray back contrasts with a stark white belly. Its narrow head and long, blunt snout give it a distinctive silhouette, while the dorsal fin sits nearer the pelvic fin than the pectoral, a subtle clue that separates it from the brown smooth-hound. Adults range from 0.5 to 1.6 m, with females growing larger than males, and newborns emerge at about 20–30 cm after a viviparous gestation supported by a yolk-sac placenta. These sharks favor shallow, muddy estuaries and bays, often less than 12 m deep in California, but up to 80 m along the Gulf of California, where they hunt benthic crustaceans, especially red and Pacific rock crabs, and supplement their diet with herring, toadfish, and occasional innkeeper worms. Their movements are dictated by temperature and oxygen, shuttling between warm mid-basin waters by day and cooler, prey-rich edges at night, a behavior that likely aids thermoregulation. A rare quirk sets this species apart: three documented cases of true albinism, including a pregnant female in Elkhorn Slough that bore five albino pups, highlight the genetic mysteries still lurking beneath their muted coloration.

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