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All in the Family

From dolphins bonding over basketball to the avian species who've literally got each other's backs, for some Aquarium animals, every day is National Siblings Day.

As anyone with a brother or sister can attest, there are many benefits—and occasionally, some challenges—to life surrounded by siblings. While few species in the animal kingdom establish direct, long-term family bonds quite like human beings, different animal species do display some very relatable behaviors between biological siblings and parents, while others form sibling-like bonds just as people might with close companions of similar age. Since it's National Siblings Day, let's take a look at some of the brother/sister-style shenanigans that take place between Aquarium animals.

A pair of smooth-fronted dwarf caimans face the camera, one in the foreground and one in the background, in the Amazon River Forest exhibit
Smooth-fronted dwarf caimans use vocal signals to communicate with their families before they hatch.

Mom. Mom. Mommy? Mom. MA!

Some species of the order Crocodilia—like the freshwater crocodiles and smooth-fronted dwarf caimans at the National Aquarium—vocalize to their mother from inside their shells when they are ready to hatch. Their mother, on guard nearby awaiting their arrival, will respond to the call of her hatchlings and dig them up from their nest, which is a mound of vegetation and mud collected and built by mom to protect her eggs from predators.

Once they have hatched, caimans and some other crocodilians stick close to their mom for 18 months or longer. That may not seem like very long, but it's a substantial amount of time in the animal world. Large groups of newly hatched siblings may join together in a group known as a creche. With all those babies, even crocodilian moms need a break, so they have been known to swap babysitting responsibilities, watching each other's creche to allow each other time to find food.

Giant South American river turtle hatchlings like these two born at the Aquarium in 2020 communicate with each other from inside their shells.

Ready? Set. Go!

Similar to their distant crocodilian cousins, there is evidence to suggest that, in some species, turtle hatchlings communicate with each other from inside their eggshells before they hatch, coordinating the timing of their emergence, and that these vocal cues continue after hatching between siblings and their parents. These behaviors have been seen in giant South American river turtles like those in the Aquarium's Amazon River Forest. Also, recent research suggests that baby snapping turtles—like those recently hatched right outside of the Aquarium and spotted on our Inner Harbor floating wetland—communicate with each other before hatching. What's more, scientists have noted that baby snapping turtles that "talked" to each other emerged from the nest with higher weights, indicating a coordinated emergence.

An adult silver arowana with its mouth open in Amazon River Forest exhibit
Silver arowanas like this one in the Aquarium's Amazon River Forest exhibit use an adaptation known as mouthbrooding to protect their young.

Carry Me, Dad!

In some species of fish, like the silver arowana that live in Amazon River Forest, fertilized eggs are brooded in the mouth of the male fishes, developing over the course of about two months until the tiny fish—known as fry—hatch. Even after hatching, the larvae stay put in dad's mouth as they grow into the juvenile stage, occasionally venturing out to feed, but returning until they are about six weeks old and ready to survive on their own. During this extended incubation, dad will move around with his brood, but he cannot really bite down or swallow without harming the hatchlings. This behavior—known as mouthbrooding—is thought to have evolved as an adaptation to increase survivorship by reducing predation of both eggs and fry.

Dolphins Beau and Foster (in the background with a volleyball) in profile at pool edge with their heads above water
Pair-bonded Atlantic bottlenose dolphins Beau and Foster (background) spend most of their time together in our Dolphin Discovery exhibit.

Oh, Brother!

Like elephants and many other species, Atlantic bottlenose dolphins form pair bonds not necessarily in mating pairs, but by gender. Here at the Aquarium, Beau and Foster—the two male dolphins in the six-dolphin pod in our Dolphin Discovery exhibit—are not actually brothers, but they sure do seem like it! These two spend most of their time together, playing and egging each other on just like siblings. Like all BFFs—and many teenage boys—Beau, age 15, and Foster, age 13, have similar interests, generally selecting basketballs and volleyballs during their enrichment time. And, just as you might expect from human brothers, "older brother" Beau is the dominant personality of the pair. His caretakers describe him as watchful, thoughtful, creative and smart. He is the largest dolphin at the Aquarium, and while he can be cautious or slow to warm to new faces, he excels at independent thought.

"Little brother" Foster, however, is curious, active and high energy. He plays enthusiastically and is always on the go. When it's time to learn, he thrives on repetition to hold onto what he's taught. At about 100 pounds smaller than his buddy Beau, he is also notable for superficial "tooth rake" markings on his smooth body that are typically seen here at the Aquarium and among dolphins in nature on the less-dominant dolphin in any bonded pair. Could these markings be evidence of a "noogie"-style big brother behavior in dolphins? Either way, the bond shared by these two mimics the lifestyles of dolphins in the ocean—as well as human brothers everywhere—and denotes a lifelong relationship.

Yellow-headed Amazon parrots Coco and Uncoco on a Tree Limb in Upland Tropical Rain Forest
Yellow-headed Amazon parrots pair bond in nature and here at the Aquarium to help preen and protect each other.

Birds of a Feather

Beau and Foster are not the only Aquarium animals that have chosen their family. Many avian species exhibit pair bonds whether they are actually related or not, and these connections seem to provide not only companionship, but also mutually beneficial perks from grooming to protection.

Yellow-rumped caciques are a striking, slim black bird with bright yellow rump and wing patches. They are native to Central and South America, and like the pair that resides in the Upland Tropical Rainforest exhibit, they frequently bond in same-sex pairs to help each other out. At the Aquarium, Athena and Artemis, sisters by birth, display their kinship by communicating through songs specific not to their general species but to their specific colony—like a special secret language. In nature, a colony would teach new hatchlings their song while intruders would be identified by their inability to replicate a related colony's song. Pairs and colonies also assist each other in building adjacent nests that look like hanging baskets. The next time you're in Upland Tropical Rainforest, check for Athena and Artemis in their nests in the large ficus tree overlooking the deck.

Various parrot species also form lifelong bonds. Yellow-headed Amazon parrots Uncoco—who has lived at the Aquarium since it opened in 1981—and her buddy Coco (who arrived later) take care of each other by preening hard-to-reach areas of their bodies. In nature, bonded pairs serve as "lookouts" for each other while preening or bathing, offering protection from potential predators. Macaws—like scarlet macaw Billy and blue-and-gold macaw Charlie in Upland Tropical Rain Forest—also pair bond for life, assisting each other with preening and nesting together at night.

Two girl scouts watch and point as blue-and-gold macaw Charlie is preened by scarlet macaw Billy in the Upland Tropical Rainforest exhibit
See if you can spot animal pairs like macaws Charlie and Billy the next time you visit the Aquarium.

So, the next time you visit, see if you can spot these and other animals with a sibling-like affinity for each other and notice how they care for, protect and play with each other in some of the same ways that you interact with your family—genetic and chosen! And if you happen to spy Beau teasing Foster, or Coco and Uncoco helping to ruffle each other's feathers, what can we say? Siblings are just like that sometimes.

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