First Great White Shark Palaeo-Nursery
Rebecca Gibson shares how the discovery of the first fossil great white shark nursery is providing vital information about how the endangered species has evolved, and how conservationists could use it to protect great whites more effectively in the future.
No matter how much you know about wildlife, great white sharks are instantly recognisable. While a certain Hollywood blockbuster has given the species an unfairly warped reputation as a thoughtless killer, the great white is a hugely successful animal that has been an apex predator in our oceans for millions of years. They are highly migratory and are found in a broad range of environments from shallow to deep water and at temperatures anywhere between 5-25°C. The great white shark’s presence at the top of the food chain is vital for the stability of marine ecosystems, but increased fishing has now made the species vulnerable to extinction.
Nurseries are a key component for the survival of many shark species, including great whites. To avoid predation, young great white sharks spend the first part of their lives in designated breeding areas. These nurseries are usually defined as having an abundance of food and a safe place to shelter until the young sharks grow large enough to defend themselves. Nurseries are considered essential because they help to maintain stable and sustainable populations and minimise predation by limiting access to larger sharks. As a result, researchers are always hoping to find nurseries in an attempt to alleviate the current population drops in shark numbers. However, fossil nurseries are a little trickier to identify than their modern equivalents.
In a ground breaking new study, published last week in peer-reviewed journal Scientific Reports, co-author Jaime Villafaña from the University of Vienna explains that despite “the rich fossil record of the modern great white shark (Carcharodon carcharias), its use of nursery areas in the fossil record has never been assessed before. Our knowledge about current breeding grounds of the great white shark is still very limited [and] palaeo-nurseries are completely unknown.”
However, the first great white palaeo-nursery has now been found. Villafaña and his team found fossil great white teeth on several sites off the coast of Peru and Chile. They used the fossil teeth, which dated back approximately five to two million years, to determine the sharks’ body size and saw that it varied greatly across the study area. Coquimbo in northern Chile had the highest percentage of young sharks with no sexually mature adults present there at all. This strongly suggests that Coquimbo used to be a nursery area for great white sharks. The fact that these nurseries have been used for millions of years underlines just how important they are for breeding success.
This study marks the discovery of the first nursery area for great white sharks in the entire fossil record, which is extremely significant for the conservation of the species. The fossils originate from a time that was much warmer than today – it has been suggested that these conditions represent the most accurate forecast of what the modern environment could be like in years to come as a result of global warming. This means scientists are able to anticipate expected trends and focus marine conservation efforts more accurately in their attempts to curb the decline of the great white shark.
"If we understand the past,” palaeobiologist Jürgen Kriwet explains, “It will enable us to take appropriate protective measures today to ensure the survival of this top predator, which is of utmost importance for ecosystems. Our results indicate that rising sea surface temperatures will change the distribution of fish in temperate zones and shift these important breeding grounds in the future. Studies of past and present nursery grounds are essential to protect such ecological key species."
To find out more about great whites and many other species across the world, check out the Shark Trust. As well as news, blogs and merchandise, the website includes key information about sharks and what’s being done to protect them.
For more from Rebecca, visit her website.