Animal movement are anything but random; they’re governed by a myriad of factors, both internal and external. But understanding the movements of animals in their natural habitats is akin to deciphering a complex puzzle. One whose pieces are missing or somewhere in the box and the instructions are in a foreign language that Google Translate doesn’t have on their list.
How do monarch butterflies navigate thousands of miles during migration, returning to the same overwintering sites each year?
How do salmon find their way back to the exact stream where they were born after years of oceanic travel, often spanning thousands of miles?
How do African elephants know the location of distant water sources during their migrations across vast savannas?
The questions are endless.
We do know that predator movements are influenced by a myriad of factors, including energy requirements, reproductive status, environmental conditions, prey availability, competition, and predation risk. For great white sharks (Carcharodon carcharias), these factors play a crucial role in shaping their movements across vast oceanic environments, with a particular focus on aggregations around pinniped colonies. These aggregations serve as hotspots for feeding opportunities, especially for larger individuals that are capable of capturing that sort of prey. Not all sharks are created equal in their culinary prowess, with juveniles honing their skills on smaller prey before graduating to seal feasts in adulthood. But it isn’t known why individuals choose specific aggregation areas or how movements vary by size, sex, or environmental conditions. The answers… well, they’re coming. And a groundbreaking study led by Dr. Oliver Jewell of Murdoch University, Western Australia, has recently found one of those missing puzzle pieces, with their study exploring how internal and external factors influence the movements of white sharks off the coast of Central California. “We tagged 22 sharks in the three years of my PhD fieldwork, and found their movements were shaped by the habitats they were swimming within, meaning the sharks behaved differently in different areas regardless of their size or sex,” Jewell said in a Facebook post.
The sharks showcased distinct movement signatures, shaped predominantly by their location and demographic attributes. Juvenile sharks at Aptos charted erratic trajectories, while their counterparts at Año Nuevo and the Farallon Islands opted for deeper dives and more purposeful paths. Nighttime movements differed significantly from daytime activities, with sharks displaying lower activity levels and straighter swimming trajectories during the night.
Understanding the nuances of predator movements holds profound implications for conservation and management efforts. Says Jewell, “The results are important because they suggest the same shark will likely behave differently from one area to the next.” By unraveling the factors driving movement patterns, researchers can better predict and mitigate human-wildlife conflicts, preserve critical habitats, and inform the design of marine protected areas. As our understanding of white shark movements continues to evolve, so too will our ability to safeguard these predators and the delicate marine ecosystems they inhabit.
