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Golfers have had to deal with alligators before, but sharks in the water will make any golfer want to take the drop.

In the 1990s, a group of juvenile bull sharks were left stranded in a golf course pond in Australia, where they thrived for decades. Now scientists are trying to understand why.

A new paper has now been published in the journal Marine and Fishery Sciences and tries to chronicle the history of this unique population.

Bull sharks (Carcharhinus leucas) are unusual in that they can live in freshwater environments and are found in rivers around the world. Although their freshwater holidays are usually temporary, bull sharks have occasionally been trapped in freshwater environments for long periods — where they apparently thrive.

The golf course sharks were likely washed inland during periods of flooding as the golf club is directly adjacent to the Logan and Albert rivers in Brisbane. Summer storms occasionally result in rainfall that breaches the banks of these rivers, inundating the surrounding floodplain. Given that the course is less than 6.2 miles (10 kilometres) inland from the coast, it is well within the freshwater zone inhabited by bull sharks.

The golf course pond was the remnant of a sand mining operation, and during a period in the early nineties, three floods breached the rivers’ banks and swept inland, bringing the sharks with them.

When the floodwaters receded, the sharks were stranded.

While the pond — which is around 2,300 feet (700 metres) long and 1,250 feet (380m) deep — is relatively small and shallow, no formal population counts were ever established. The sharks were, however, frequently visible, often coming near the shore.

Their presence was welcomed by the golf course management, and the species became a mascot for the establishment.

The sharks were likely juveniles when they found themselves stranded, but eventually grew up to 9.8 feet (3 metres) long, according to observational reports. Their feeding habits were not studied, but it is likely that other species that were also introduced to the pond during flooding events provided ample food.

According to Michael Heithaus, a shark biologist at Florida International University who was not involved in the study, sharks can do well in these circumstances.

“If sharks can get the food they need, being in these low-salinity environments can be super beneficial because there are fewer predators.”

The sharks were last seen in 2015, although it is believed that another flood in 2013 may have allowed some of the sharks to escape back into the adjacent riverways. The paper’s authors however think others may have simply died and sank. Only one carcass was ever recovered by golf course staff.

While the pond appears to be devoid of sharks now, this strange episode shows the adaptability of these predators and their tolerance of freshwater environments.

This should give credence to your irrational fear of sharks when skinny dipping in your pool at night (Come on, admit that it’s crossed your mind).

[source:livescience]