Species Spotlight: Zebra Shark
Zebra sharks (Stegostoma tigrinum) are a familiar sight for aquarium-goers. They have a charismatic appearance: thick bodies, rounded fins, and a long, slinky caudal fin. The sharks are covered in spots, giving them a unique and recognizable appearance. With their small eyes and mouths, zebra sharks aren’t exactly the most sharky-looking shark.
But, there’s a lot more to this species than their cute, non-intimidating appearance suggests. At night, they stalk through the dark oceans, dragging hidden prey loose from crevices in the coral reefs. For small, reef-dwelling organisms, zebra sharks are a ferocious, terrifying spectre of the night.
How can some shark species breathe without swimming? What is parthenogenesis, and how can female zebra sharks reproduce without males? How are aquariums and zoos facilitating conservation efforts for this endangered species? Let’s dive in and cover some of the fascinating traits of this common aquarium resident!
Acrylic marker illustration of a zebra shark (S. tigrinum) by me. ©LivInSeas, 2026
Appearance:
Adult zebra sharks are covered in distinct spots–not quite a feature which evokes “zebra.” In some regions, they are also referred to as “leopard sharks,” referencing the shark’s adult pattern. However, this name may cause some confusion, as is also used for the north American houndshark, Triakis semifasciata. The common name “zebra” references the sharks’ juvenile form which features distinctive, white stripes.Â
Typically, adults of the species range between seven to nine feet long (2.13 – 2.74 meters). The largest recorded individual was 3.54 meters in length (~11.6 feet).
The sharks have rounded, tan-colored bodies and a very long, blunt caudal fin. They also have whiskery feelers on their snouts called “barbells,” which help them find prey in crevices. Five, raised ridges run down the shark’s body. Zebra sharks have broad, flattened pectoral fins and rounded dorsal and anal fins.
A juvenile zebra shark, displaying the distinctive striped pattern that gave the species its name. Gp258, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons.
Range & Habitat:
Zebra sharks are found in the tropical Indo-Pacific, occurring around east Africa, Asia, and Oceania. They typically occur in shallow waters between 5 to 30 meters (16.4 – 49.2 feet) but can reach a maximum depth of 62 meters (203.4 feet). Zebra sharks live in coral reef ecosystems, particularly regions with sandy seafloor substrate.
Biology:
At night, the zebra shark stalks the reef, searching for prey sheltering in crevices and holes. Zebra sharks dine on mollusks, benthic crustaceans, and small fish, slurping them out of the reefs. During the day, these nocturnal sharks rest on the seafloor.Â
Certain shark species, including the zebra sharks, can breathe without actively swimming. Most fish breathe this way, suctioning water into their mouths, then pumping it out over their gills. This method of respiration is referred to as “buccal pumping”. This allows zebra sharks to rest lazily on the seafloor during the day before their nightly hunts.
Reproduction:
Zebra shark are not only capable of standard sexual reproduction. Females of the species also undergo parthenogenesis, a form of asexual reproduction.Â
Parthenogenesis has been observed in aquarium settings without male zebra sharks present. It has also been documented even in the presence of males, detailed in the paper, “Artificial Insemination and Parthenogenesis in the Zebra Shark Stegostoma tigrinum.”
Within this experiment, staff and scientists at the Aquarium of the Pacific in Long Beach, California tested the effectiveness of artificial insemination, following procedures outlined by the aquarium’s veterinarian and lead author of the paper, Dr. Lance Adams. One female shark, named Fern, participated in the experiment. Fern was housed in the Shark Lagoon exhibit seven months before the experiment began, separate from the aquarium’s other zebra sharks. Two more females, Yin and Yang, and one male, Carlbe, lived in the Tropical Reef exhibit for the duration of the study.
Surprising Findings:
While the study’s intent was to determine the effectiveness of artificial insemination (AI), the experiment yielded fascinating results. All female sharks produced offspring during the course of the study. However, not only did all three female sharks produce offspring which resulted from parthenogenesis, but Yin and Yang (housed with the male, Carlbe) only produced offspring via parthenogenesis.
The sharks produced 12 offspring total during the duration of the experiment: 2 sexually-produced (via AI) and 8 parthenogenetic offspring. The exact statuses of 2 offspring were unknown, but they were presumed to have resulted from parthenogenesis as the eggs were laid a significant period after AI occurred. All offspring hatched between 2012 and 2015.
A “transitional zebra shark” (between juvenile and adult morph) at the Aquarium of the Pacific in Long Beach, California. Coughdrop12, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons.
However, Dr. Adams and colleagues published a follow-up titled, “Costs of parthenogenesis on growth and longevity in ex situ zebra sharks Stegostoma tigrinum.”Â
While parthenogenic and sexually-produced offspring appeared the same upon hatching, parthenotes displayed stunted or impaired growth within the first year of life. Half of the parthenotes died within the first year of life. The two longest-surviving parthenotes survived for ~5.5 and ~6.5 years respectively, dying of organ issues. Additionally, many of the parthenotes exhibited physical and behavioral abnormalities.
One of the sexually-produced offspring died at approximately 2 years and 4 months of age. The other was still alive at the time of publication (2023).
Parthenogenesis results in extreme inbreeding, which increases the likelihood of deleterious genes being expressed. However, the study noted observations of a parthenote from a different species of shark (whitespotted bamboo shark – Chiloscyllium plagiosum) surviving to adulthood and reproducing.Â
Parthenogenesis in an Intersex Individual:
A different study, “First case of parthenogenesis in an intersexual zebra shark (Stegostoma tigrinum) having incomplete claspers”, was published by lead authors Kazuyuki Momota and Itsuki Kiyatake and colleagues. The paper details the hatching of one parthenogenic offspring laid by an intersex individual housed at the Osaka Aquarium NIFREL. The intersex individual had small, under-developed claspers (an external, male feature of elasmobranchs), and tubular structures in the ovaries which resembled internal structures within the testis. Unfortunately, the parthenogenic offspring also did not survive long after hatching.
A zebra shark swims over a reef in the ocean near New South Wales, Australia. Image uploaded from iNaturalist, no rights reserved, CC0, via Wikimedia Commons.
Conservation Measures:
The zebra shark is classified as endangered by the IUCN Red List. They are regularly seen at fish markets throughout their range. Due to the narrow habitat range of the species, along with the tendency to form aggregations, they are particularly vulnerable to habitat loss and over-exploitation.
The IUCN predicts that zebra shark populations will reduce by over 50% within three generations. They may become locally extinct soon in several regions throughout Indonesia.Â
In the wild:
In Australian waters, populations of zebra shark benefit directly from marine protected areas. These include the Great Barrier Reef Marine Park and Moreton Bay Marine Park in Queensland.Â
Read more about how marine protected areas benefit people and nature alike here!
Additionally, several countries have implemented specific fisheries management procedures to protect sharks. In 2021, Papua New Guinea implemented a targeted plan for managing and conserving shark populations in their national waters. Following increased bans and regulations to shark-targeted fishing in the early 2010’s, they further tightened regulations and protective efforts. These include heightened monitoring and data collection and implementing measures to mitigate shark bycatch in non-directed fisheries (i.e. the tuna fishery).Â
The collective ReShark aims to help conserve wild shark populations through rewilding efforts. Their Stegostoma tigrinum Augmentation and Recovery Project (StAR Project) launched in 2020 and is the world’s first conservation translocation program for elasmobranch species. Through the StAR project, juveniles hatched from captive breeding programs are released into their natural habitats to support wild populations.
Zoo & Aquaria Conservation Programs:
Zoos and aquariums directly support conservation plans like StAR and the Association of Zoos and Aquariums’ (AZA) Saving Animals From Extinction (SAFE) Program.
The SAFE plan for sharks and rays focuses on research and data sharing, direct conservation action, influencing policy, and expanding communications and messaging. One of the aims of the SAFE plan is to support breeding of target elasmobranch species (including zebra sharks) in captivity. Across participating aquariums, the AZA aims to manage a genetically-diverse, sustainable, and healthy population of zebra sharks in captivity.
These closely-monitored populations can then contribute to the StAR project. Animals selected for breeding for this project are carefully screened to ensure healthy, genetically-sound offspring will be released into the wild.
This effort is already well underway. Two sharks participating in the StAR Project, Peanut (female) and Butter (male), produced viable eggs in the Point Defiance Zoo & Aquarium in Tahoma, Washington. Once the eggs were confirmed to be viable and not resulting from parthenogenesis, they were sent to a shark nursery in Indonesia. After hatching, the pups will grow in sea pens until they’re ready to be tagged and released into a marine sanctuary.
To date, more than 60 juvenile zebra sharks have been released into the Raja Ampat marine sanctuary in Indonesia!
