Climate change has been on everyone’s tongue lately, with many wondering how this phenomenon is changing our animals. Australian scientists have discovered one way it is altering the behavior of one of our oceanic predators: sharks. According to the study published in the Symmetry magazine, our warming oceans are causing the Port Jackson shark (Heterodontus portusjacksoni) to change its swimming patterns and essentially becoming “right-handed.”
But how does one figure this out? Researchers Catarina Vila Pouca, Connor Gervais, Joshua Reed, and Culum Brown incubated 24 Port Jackson shark egg cases from the waters of eastern Australia and incubated. Half of these eggs were placed in water that was heated to current temperature averages (about 20.6 Celsius or 69.08 Fahrenheit) and the rest were in heated tanks to simulate the project temperature changes at the end of the century (about 23.6 Celsius or 74.48 Fahrenheit). Five of the sharks in the higher temperature tank were dead by the first month, and the survivors were placed in a long tank with a Y-shaped partition with food on either end. The sharks would be rewarded with a tasty treat at either end, it was just up to the animal to figure out what direction to swim: left or right.
The scientists noticed that the sharks exposed to higher temperatures began preferring swimming to the right, in a movement known as “lateralization.” Lateralization is the tendency of one or the other half of the brain to automatically control certain behaviors. It is one of the fundamental patterns of the organization of the brain not only of the animals but humans.
“Sharks incubated at high temperature showed stronger absolute laterality and were significantly tilted to the right in relation to sharks raised at the current temperature,” the scientists said in their published piece. The sharks of the control group showed no inclination either on the left or on the right. This experiment has allowed these marine scientists to concluded that climate change is generating a much greater and faster effect on the brains of maritime species.
“Since laterality is an expression of functional asymmetries of the brain, changes in the strength and direction of lateralization suggest that rapid warming of the climate could affect brain development and function,” they continued.
The team of researchers from Macquarie University in Sydney believe that sharks born in warmer waters may be forced to develop faster, leading to smaller brains than those that develop under current conditions. With less mental energy to spare, sharks may go on “auto-pilot” certain behaviors, such as always turning to the right.
Studies looking at how climate change is affecting biodiversity have increased, as have methods to assess species’ vulnerability to climatic changes. Assessing chondrichthyan (shark, skate, ray, and chimaera) vulnerability to climate change is difficult due to their environment (i.e. the ocean) and how varied their lifestyles are. In 2010, an Integrated Risk Assessment for Climate Change (IRACC) was developed and implemented by scientists from James Cook University to assess the vulnerability of sharks and rays on Australia’s Great Barrier Reef (GBR) to climate change. The assessment found that freshwater/estuarine and reef-associated sharks and rays in this region are most vulnerable to climate change. The study also highlights the need for better understanding of the biology and ecology of the chondrichthyans that call the GBR home.
Climate change represents a serious threat to not only marine ecosystems but the animals inhabiting them… including our top predators we cannot live without.