Juvenile great white sharks prefer shallow coastal waters

Remember the social media sensation that wasn’t the catchy “Baby Shark” tune, but actual footage of a newborn great white shark spotted by a drone? That glimpse into the lives of these majestic creatures was just the beginning of an exciting scientific discovery.

Marine scientists at California State University have recently demonstrated that juvenile great white sharks predominantly inhabit warm, shallow waters close to the shore, specifically within one kilometer.

This study significantly advances our knowledge of the habitat preferences of juvenile great white sharks. Understanding these preferences is crucial for shark conservation and public safety, especially as ocean temperatures continue to rise.

“Animals respond behaviorally to environmental conditions over a range of spatio-temporal scales, often in ways that shape their habitat use and movement patterns,” wrote the study authors.

“While seasonal environmental changes across a species’ entire range may dictate long-term migration patterns, many aquatic animals likely make movement decisions based on micro-scale differences in conditions which may vary based on ontogenetic stage.”

Unique opportunity to study juvenile white sharks

In a region off Padaro Beach near Santa Barbara, baby great white sharks, known as “pups,” are found congregating in areas dubbed nurseries. These young sharks receive no care after birth and are left to thrive in the shallows unaccompanied by adult sharks.

According to Dr. Christopher Lowe, this site provided a unique opportunity to study a large group of juveniles in their near-shore environment.

“This is one of the largest and most detailed studies of its kind,,” said Dr. Lowe. “The dense congregation of juveniles around Padaro Beach allowed us to observe how environmental conditions affect their movement patterns.”

Technology meets marine biology

From 2020 to 2021, Dr. Lowe’s team equipped 22 juvenile white sharks (JWS), aged one to six, with sensor-transmitters. These devices tracked water pressure, temperature, and the sharks’ locations using acoustic ‘pings’ to coastal receivers. Data collection paused in winter when the sharks migrated to deeper waters.

Additionally, an autonomous vehicle mapped the local water column’s temperature, and artificial intelligence helped create a 3D model showing the juvenile white sharks’ preferred temperatures and depths – enhancing our understanding of their behaviors in different conditions.

Daily rhythms of juvenile white sharks

The juvenile white sharks displayed distinct behavioral patterns. They dove deepest around dawn and dusk, likely for feeding, and stayed closer to the surface in the warmer afternoon sun, possibly to elevate their body temperatures.

Emily Spurgeon, a research technician on Dr. Lowe’s team and the study’s first author, explained: “We found that juveniles adjust their vertical position to maintain a temperature range between 16 and 22 °C. Optimally, they stay between 20 and 22 °C to maximize growth efficiency within the nursery.”

The study revealed that juveniles occupy much shallower waters than adult great whites, who are seldom seen in nursery areas. The three-dimensional temperature variations significantly influence the juveniles’ horizontal distribution. They move to deeper areas when seafloor temperatures rise and come closer together towards the surface as deeper waters cool.

Exploring other factors in shark nursery behavior

While it’s clear that temperature is a crucial factor attracting juvenile white sharks to these nursery areas, it’s not the only consideration. “There are many locations along the California coast with similar environmental conditions, so temperature isn’t the entire story,” said Spurgeon.

“While we do not know where JWS are predominantly foraging, it is likely that they are using particular areas within the aggregation site to increase their foraging success,” noted the researchers.

“Tradeoffs must occur throughout JWS developmental period as individuals attempt to find and select areas with adequate environmental conditions to maintain efficient physiological performance, but also try to find sufficient food sources and avoid intra-specific conflicts.”

“They may therefore choose a micro-habitat that is a high prey resource environment to maximize their growth by speeding up their metabolic rate in warmer water.”

Broader study implications

Upcoming research will explore potential individual behaviors and relationships, such as whether some juveniles move among different nurseries together. As these studies progress, they not only help in shaping effective conservation strategies but also minimize human-shark interactions.

“The results of this study may be used to inform and improve habitat suitability models and species distribution models within a specific location and help predict potential locations of new aggregation sites as well as advise beach public safety officials,” wrote the researchers.

“Knowledge on how JWS respond to the environment is vital for management and future space use predictive models to understand how these patterns will transform as micro-habitat thermal patterns are altered due to climate change.”

The study is published in the journal Frontiers in Marine Science.

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