Sometimes, you just really want to go some place special to eat, even if there are plenty of options nearby.

But that's easy for humans to say. We can easily get in a car or hop on a bus to head to that out-of-the-way destination. Fiordland penguins (Eudyptes pachyrhynchus) don't have those convenient transportation options. Instead, they'll swim 4,350 miles (7,000 kilometers) round-trip over eight weeks just to eat, despite having easy access to the same food near their breeding sites on the southwestern coast of New Zealand. To top it off, the penguins make this journey right before an energy-intensive molting process.

Thanks to new research, we might have an answer for this seemingly inexplicable behavior.

The opposite of fast food

The fiordland penguin, sometimes referred to by its Maori name of tawaki, lives and breeds on the mainland of New Zealand, but not a lot is known about the species. The extent of our knowledge of them is their basic habitat. They are only found on the rocky and inaccessible southwestern coast of New Zealand's South Island, which is their favored nesting area. Few studies have been conducted regarding this crested penguin. The most comprehensive research dates back to 1974.

Thomas Mattern from the University of Otago in New Zealand and other researchers formed The Tawaki Project, a research initiative intended to better understand the birds' feeding habits and how their choice of habitat affects their population. The project has put out field reports since 2014, and a recently published study in PLOS One sought to explain the birds' odd marathon swimming habit.

Around mid-November every year, fiordland penguins take to the sea to eat until about mid-January, trying to fatten themselves up after using a great deal of energy during the late summer and early fall for breeding and raising chicks. They spend these months eating because their molting process, which runs from the end of January and into February, is a so-called catastrophic one. The name doesn't signify that the birds are in great peril; it means that instead of losing and regrowing a few feathers at a time, they lose and regrow all of them over the course of three weeks. During this time, they cannot eat or swim, and so they must rely on stored body fat to survive.

You would think the birds would conserve as much energy as possible before this process begins. The food the birds eat, including squid, krill and fish, is readily available around their breeding sites. Instead, Mattern and his team found that fiordland penguins will travel nearly 1,864 miles (4,000 kilometers) south — almost halfway to Antarctica — to eat. They will often swim up to 50 miles (80 kilometers) a day, the maximum distance the birds are probably physically capable of handling.

"The conditions closer to the New Zealand mainland are pretty good," Mattern told Gizmodo. "There are no obvious reasons why tawaki would have to travel as far as they did — there is no logical explanation for it."

The study's sample size was small; only 17 adult penguins — 10 males, 7 females — were tracked between November 2016 and March 2017, and a few of them lost their receivers over the course of the study, leaving the researchers with complete data from five penguins. Another 48 penguins have since been tagged with trackers an in effort to trace their movements over the course a year and see if they match up to the study's findings.

Mattern's theory for the species' behavior is that it's a genetic component the penguins haven't evolved out of yet. Some ancestor penguin lived and evolved further to the south than where the species currently lives, and the fiordland penguins are genetically wired to believe that the area they migrate to every year is the best spot for dining before their molting process begins. In essence, it's instinct.

Fiordland penguins swim marathons for food
Not much is known about the elusive fiordland penguin, but we do know that they swim far out of their way to feed before molting.