How Indianapolis Zoo Aquarists Figured Out How Dogsharks Do It
There’s a famous line from the movie Jaws where oceanographer Matt Hooper is describing the shark to the town mayor as a kind of miracle of evolution, a perfect eating machine. Says Hooper, “All this machine does is swim and eat and make little sharks, and that's all.” And for a great white shark, and all the rest of the other 350 plus species of sharks, even the part about making little sharks is pretty mechanical in nature. Whether the shark species deposits egg cases onto the ocean floor or gives live birth to shark pups, the little sharks are always perfect small replicates of the adults and completely on their own from the word go. Doting parents, sharks aren’t.
That doesn’t mean, however, that the process is necessarily simple or even well understood. Surprisingly little is known about shark reproduction of any kind, and until the last few years, virtually nothing was known about the reproduction of dogsharks (also called smooth dogfish), a relatively small and unassuming shark that is easy to ignore since, unlike the star of Jaws, it poses no danger to humans. Those qualities make the dogshark the perfect candidate for shark encounter exhibits in zoos and aquariums, and when the Indianapolis Zoo opened its Oceans exhibit in 2007, it wasn’t surprising that visitors gravitated immediately to an opportunity to touch a real live shark – even such a harmless variety as our dogsharks.
Fortunately, these sharks are not endangered and are relatively common in Atlantic waters from Brazil to Cape Cod. They have little or no commercial value, and hence have escaped the fate of so many other shark species that are over fished for food. Voracious little eaters of squid and small crustaceans, the dogshark’s biggest threat is getting caught up in fishermen’s nets by mistake.
It’s not unexpected that not much research has been done with these sharks, which as a group are notoriously difficult to study in the wild. The anatomy of the dogshark is well known, but how they live is a mystery. Although reproduction (dogsharks are one of the sharks that give birth to live young) had occurred before in other aquaria, what had never been done with dogsharks in human care was successfully raising baby dogsharks to adulthood, or even to adolescence.
From the beginning, the Indianapolis Zoo aquarists took on the task of learning more about dogsharks than how many gills they have (five) and how long they grow (five feet). They studied and observed the behavior of the sharks, noting their curious habit of raising their heads out of the water and sometimes spinning around in circles. They discovered what the sharks liked to eat and what they food items they snubbed. They tested water quality and salinity, water levels and temperatures, and the sharks’ interactions with other members of the school and with the humans who cared for them and those who just got a thrill out of being able to touch them.
For nearly four years, the aquarists watched and learned more information about this species than had previously been discovered – and the staff encountered the same disappointments as had others when their baby sharks did not survive long. Then in 2010, it all came together. One of the females gave birth to a litter of shark pups that were strong – very strong. The aquarists were determined this time, and after months and months of shark TLC, Zoo staff were able to celebrate a history-making milestone – baby dogsharks that had reached their first birthdays. The expectation is that these “yearlings” will soon be able to graduate from the behind-the-scenes shark nursery to the big pool on the public side, where zoogoers will be fascinated once again watching young sharks learn to be adults. As more sharks mate and more pups are born, the Zoo will continue its work uncovering some of the real mysteries of the natural world.
Connections to the Indianapolis Prize
The Indianapolis Zoo is proud to support Dr. Carl Safina, founder of the Blue Ocean Institute, twice nominated for the Indianapolis Prize and a finalist for the Prize in 2010. Dr. Safina’s work and passion are dedicated to the conservation and the health of the world’s oceans, especially getting the message out about the effects of pollution and global warming.
Read more about the Indianapolis Prize.
Learn more about the Indianapolis Zoo’s Oceans exhibit.