Baylor College marine biologist Sarah Kienle, Ph.D., has at all times been fascinated by leopard seals. These prehistoric, reptilian-looking seals are sometimes portrayed as scary villains in motion pictures akin to “Joyful Ft” and “Eight Under,” however little is understood about their primary biology. The mixture of the acute local weather in Antarctica, the species’ solitary habits and their deadly popularity makes leopard seals some of the troublesome high predators to check on Earth.
In a first-of-its-kind examine funded by the Nationwide Science Basis awarded to professor Daniel Costa (lead PI; UCSC), affiliate professor Stephen Trumble, Ph.D. (Baylor), professor Shane Kanatous, Ph.D. (Colorado State College), wildlife biologist Mike Goebel, Ph.D. (NOAA), and professor Daniel Crocker, Ph.D. (Sonoma State College), the PIs and Kienle (a graduate pupil and postdoctoral researcher on the time) set out with one shared objective: to be taught extra about leopard seals. Over the course of two years, the analysis group studied 22 leopard seals off the Western Antarctic Peninsula, an space quickly warming and altering. They weighed and measured every seal and adopted every seal’s actions and dive patterns utilizing satellite tv for pc/GPS tags.
Within the examine printed in Frontiers of Marine Science — “Plasticity within the morphometrics and actions of an Antarctic apex predator, the leopard seal” — Kienle (first writer) and the crew documented the versatile behaviors and traits which will provide leopard seals the resilience wanted to outlive the acute local weather and environmental disturbances occurring round Antarctica.
This examine drastically will increase our understanding of leopard seals’ life historical past, spatial patterns and diving habits,” Kienle mentioned. “We present that these leopard seals have excessive variability (or, flexibility) in these totally different traits. Throughout the animal kingdom, variability is significant for animals adapting and responding to adjustments of their atmosphere, so we’re excited to see excessive variability on this Antarctic predator.”
Among the many analysis crew’s discoveries detailed within the journal article:
Grownup feminine leopard seals are a lot bigger than grownup males; in reality, females are 1.5 occasions bigger and longer.
- The crew measured one of many largest leopard seals ever, an grownup feminine they nicknamed “Bigonia,” who weighed 540 kg (1,190 lbs.).
- Feminine-biased sexual dimorphism (the place females are bigger) is uncommon amongst marine mammals, a various group that features polar bears, whales, dolphins, seals and sea lions, however leopard seals are essentially the most excessive instance of female-biased dimorphism among the many 130+ species of marine mammals.
- Why females are bigger than males just isn’t recognized, though Kienle defined different research present that bigger females are higher at defending feeding areas, in addition to stealing prey from smaller seals. Bigger females additionally eat larger, energy-rich prey, together with fur seals and penguins, whereas males and smaller females usually eat smaller prey like krill and fish. This means that the bigger physique measurement in grownup females is useful and provides a selective benefit that Kienle and crew will proceed to discover.
From the motion knowledge, feminine leopard seals spent extra time “hauled out” — or popping out of the water to relaxation on ice or land — than males.
- Two grownup feminine leopard seals on this examine spent two weeks straight hauled-out on ice in the midst of the ocean, not consuming and never getting within the water. Kienle and colleagues recommend that this two-week haul-out interval is when feminine leopard seals give delivery and nurse their pup.
- On the finish of the 2 weeks, females return to water and start diving for meals once more, and, on the similar time, they possible wean their pup. It is a quick interval to spend with their pups as a result of the leopard seal is doing all of those actually energetically demanding issues with none meals.
Female and male leopard seals swim quick and lengthy distances in each coastal and open-ocean habitats.
- One seal solely traveled 46 km from the place the crew labored with the seal, staying in and round islands off the Antarctic Peninsula.
- One other seal, nevertheless, traveled 1,700 km throughout that very same interval away from the tagging location, swimming to an island greater than a thousand kilometers away.
Leopard seals of each sexes are quick, shallow divers — diving to a median of 30 meters and taking three-minute-long dives.
- Different seals can dive hundreds of meters deep and maintain their breath for greater than 40 minutes. Nonetheless, the analysis crew recorded the longest and deepest dive ever recorded for leopard seals made by a male nicknamed “Deadpool,” who dove to 1,256 meters for 25 minutes.
“It is attention-grabbing to see such variation [in movements and dive behavior] in a comparatively small variety of animals. To me, because of this leopard seals are extremely versatile of their motion patterns, and that is a very good factor when it comes to adapting to adjustments in your atmosphere,” Kienle mentioned.
What’s subsequent for this crew of leopard seal biologists? Kienle mentioned the crew continues to investigate extra knowledge from these similar 22 leopard seals for publication. Kienle additionally is happy to match how the leopard seals from this examine examine to different populations of leopard seals throughout the Southern Ocean.
“I’ve so many extra questions, and I am excited to proceed studying about leopard seals for years to come back. There’s a lot extra to find about this unbelievable Antarctic predator,” mentioned Kienle, who leads the Comparative Ecophysiology of Animals Lab at Baylor that focuses on understanding how totally different animals work within the context of their atmosphere.
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