The news is full of stories about wild animals that are apparently invading our cities. A group of tourists had their Florida golf vacation delayed by an enormous alligator walking on the 7th hole. A fox was spotted waiting in line for an ATM outside a London bank. A mountain lion tried to move into a basement in California. What’s going on?
Human settlements are expanding into areas that were once wilderness. As this continues, it’s going to get more and more likely that we will see animals other than pigeons and squirrels downtown. Dr Neil Hammerschlag and his team are studying how coastal development in Florida is affecting animals that few city dwellers think of as neighbours: large sharks!
‘To study or dive with sharks, we usually have to travel long distances to the relatively remote or pristine places where healthy shark populations occur,’ says Dr Hammerschlag. ‘However, when Dr Austin Gallagher and I were talking this over, we realised that we were probably missing an important aspect of shark biology and ecology. The trials and tribulations of sharks having to make it in human-dominated areas have to date been overlooked, yet this is becoming the new normal.’
Many shark species use shallow coastal waters, including bays and the rivers that feed into them, as nursery areas or feeding grounds. Miami is full of these waterways: man-made canals crisscross South Florida and the Miami River flows through downtown into Biscayne Bay. Coastal South Florida is an ideal place to study how urbanisation and development affect sharks, Dr Hammerschlag points out. ‘Austin and I were flying over Miami on our way to a conference and we remarked about how human-dominated the landscape is. We could not make out any area from our bird’s-eye view that did not show signs of human influence,’ he adds.
Even though some sharks use the highly urbanised waterways around Miami, according to Dr Hammerschlag these channels aren’t an ideal habitat. He continues, ‘Human-dominated and highly disturbed areas tend to have poor water quality, are highly polluted and carry lots of boat traffic, which is not exactly great habitat for animals. We don’t necessarily expect to find the density and diversity of sharks that would be in healthy, productive waters.’ Although many species of fish eaten by sharks can be found in Miami waterways, they often occur in smaller numbers than in a pristine habitat.
Have you ever imagined a shark swimming through downtown? Biologists have found at least five species of sharks in Miami’s waterways. Neil hopes to learn how they use this space and how well they are coping with their urban lifestyles.