Shark Babies and Motherhood
- Sharks4Kids
- 1 day ago
- 2 min read
Author: Adina Hoffman
Scientists recognize three main reproductive strategies in sharks: laying eggs (oviparity), retaining eggs until they hatch inside the mother (ovoviviparity or aplacental viviparity), and giving birth to live young nourished by a placenta (viviparity).
About 70% of shark species give birth to live young, while roughly 30% lay eggs. Among the live-bearing species, many embryos first develop inside eggs that remain within the mother's body until hatching. Some species, like nurse sharks, have babies, or pups, that will eat their brothers and sisters who have not yet hatched.
Sharks can also lay eggs outside their bodies, like birds. These eggs have tough, leathery “shells,” or cases, and are attached to seaweed or rocky seabeds, where the young hatch on their own. Horn, Swell, Bamboo, Catsharks, and Zebra sharks all lay egg cases, with each species having a unique shape for its egg case. Because of their unique shapes, these shark egg cases are nicknamed mermaid purses. Some shark eggs glow under ultraviolet light because of compounds in their egg cases. Talk about a fashion statement.
Photo of two shark egg cases ("mermaid purses") by Michelle Trigg
Sharks can also give birth to live young nourished by a placenta, like people, with a miniature shark emerging from the mother. Bull, Lemon, Blue, Hammerhead, and Blacktip reef sharks all give birth to live pups.
These shark mothers often travel to shark nurseries, which are warmer, shallower, and more shaded areas where they give birth. These areas have abundant food resources and provide shade and protection from predators, allowing the babies to hide. Lemon, Blacktip, Bull, and Bonnethead sharks all use nurseries.
These shark babies need to protect themselves from other sharks, including those of their own species and sometimes even their mothers. Unlike most mammals, shark mothers provide little or no parental care after birth. Shortly after giving birth, the mothers leave the nursery. However, not all sharks use nursery habitats; some pups are born directly into the open ocean. Shark pups are fully independent from the moment they are born or hatch, with no parental care.
Different sharks produce different numbers of pups; sand tigers have only 2 pups, while blue sharks can have over 100, and in a female whale shark, over 300 pups were found. The pups also vary in size; dwarf lanternshark pups are the smallest, about 6 cm (2. 2.4 in), while whale shark pups are the largest, at around 55–64 cm (22–25 in).
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