Don’t worry, they’ll don their tuxedos later.

Biologists got their first chance to weigh some of the New England Aquarium’s newest additions Thursday: four 2-week-old African penguins still covered in fluffy brown down.

The chicks weigh between a half-pound and 3 pounds and “look terrific,’’ said Tony LaCasse, an aquarium spokesman.

“The thing about birds is that growth happens extremely quickly. The third chick, the one that weighs 3 pounds, gained 18 percent of its weight in the last two days,’’ LaCasse said.

In the wild, the chicks stay with their parents for about 80 days, growing to the size of adults. At the aquarium, they are separated shortly from their parents before the end of that period and hand-fed by aquarium biologists instead, LaCasse said.

“Chicks are completely self-absorbed in terms of food — a lot like human adolescents. By the end of it, the parents are completely exhausted, so when we step in, it’s a huge relief for them,’’ LaCasse said.

The aquarium is home to about 40 African penguins, though that number varies as animals are rotated out to maintain genetic diversity, ­he said.

“We’ve helped to start penguin colonies at facilities across the country,’’ LaCasse said.

Breeding programs such as the one at the aquarium are a way to counteract the damage that humans have done to wild bird populations through climate change and overfishing, LaCasse said.

“African penguins are classified as endangered,’’ he said. “The real tragedy is that as recently as 2000, populations were fairly stable. Since then, though, there’s been a real crash as birds aren’t able to find the food that they once had. Less food means higher chick mortality and a declining population.’’

In addition to the four chicks in the limelight Thursday, the aquarium has two more African penguin eggs expected to hatch in about a month.

Add in the two rockhopper and two little blue penguins that hatched earlier this year, and that would bring the total to 10, which LaCasse called “a very good year.’’

“The number of hatchings in a year vary, and we’ve had similar numbers before, but our penguin biologists are very good. We’re really looking forward to getting [the chicks] on display,’’ he said.

If everything goes according to plan, the chicks are expected to be on exhibit by September.

Andrew Grant can be reached at andrew.grant@globe.com.