It’s a tough world out there for a newborn animal. You can’t forage for your own food, carnivores lurk around every corner, and everyone seems to be several times your size. Thankfully for the youngsters, animal mothers pull off incredible feats — from thousand-mile journeys to complex construction projects — to nourish and protect their babies.
This Mother’s Day, as we give thanks for all the caregivers in our lives, we’re featuring a few of nature’s most awe-inspiring moms and the intriguing ways they bring their young into the world.
Sensory sea turtles
When it comes to parenting, sea turtles definitely go the distance. Multiple species, including the strong-jawed loggerhead (Caretta caretta) and the plant-munching green turtle (Chelonia mydas), return from massive migrations to lay their eggs very close to the beaches where they themselves hatched. And it’s not just sea turtles who head back to their birthplaces to have their young; this process, known as natal homing, has been observed in a bevy of animals, including salmon, sparrows and sharks.
For sea turtles like loggerheads, the trek is a colossal one. Hatchlings scurry across the sand, dodging hungry herons and ghost crabs, and set out for the relative safety of the open ocean to mature. Once they’re big enough to fend for themselves, they find their way to rich feeding grounds along the coast. Eventually, the turtles will migrate again to lay eggs very near their own sandy birthplaces. All told, the journey can span up to 30 years and thousands of miles.
Exactly how loggerheads and other sea turtles find their way home, despite the distance and the decades, has long intrigued scientists. They’re known to navigate dizzying ocean expanses largely by sensing Earth’s magnetic field, which varies depending on geographic location. Recent research has suggested that sea turtles use this magnetic map, coupled with other local cues, to steer themselves back to their birthplaces. They’re looking for the precise magnetic fingerprint of their beloved beach — so, for sea turtles, there’s really no place like home.
As if giving birth weren’t enough of an undertaking already, porcupines seem like they might have an extra thorny challenge on their hands. Thankfully, species like the prehensile-tailed porcupine (Coendou prehensilis) are born with small, soft quills. Only once they’re exposed to air do the quills harden, eventually growing into long black-and-white spines tipped with barbs. A threatened porcupine’s quills will stand on end, making the animal look bigger — and if the situation goes south for the porcupine, it has an arsenal at its disposal.
Prehensile-tailed porcupines have other tricks up their sleeves, too. Babies, known (adorably) as porcupettes, quickly become expert climbers as they explore the treetops with their mothers. Their long tails are incredibly dexterous, looping around tree limbs and giving them free reign among the branches. These agile animals show off their talents at Smithsonian’s National Zoo, which welcomed a new porcupette in January.
They say to “fake it till you make it,” and some birds really seem to have taken that advice to heart. Take the common cuckoo (Cuculus canorus), which will sneak one of its eggs into the nest of another species in hopes of passing it off as one of that bird’s own. When the cuckoo nestling hatches, it will toss the other eggs to the ground, reserving all the host mother’s attention and food for itself.
That’s set off what biologists call a “coevolutionary arms race.” Natural selection favors the host birds that can spot the cuckoo egg threatening their brood, as well as the cuckoos that can outsmart them — producing a sort of evolutionary one-upmanship. As host birds like the reed warbler evolved to better identify and reject cuckoo eggs, scientists believe, the common cuckoo evolved a trick of its own: females lay eggs that look incredibly similar to those of their hosts. Not to be outdone, host birds have evolved strategies to get around that, too. One type of fairywren teaches its young a warbled “password” before they’ve even hatched; the nestlings that use it get more food.
Cuckoos may be most notorious for this sneaky behavior, but other species, including certain ducks and catfish, do it too. The larvae of one species of butterfly trick unsuspecting ants into caring for them by secreting chemicals that closely mimic those of ant larvae. But, hey, they also say imitation is the sincerest form of flattery.
Newborn animals can look pretty precocious when compared to human babies — horses spring to their feet soon after they’re born, cuckoo hatchlings engage in egg-related sabotage before they even open their eyes. But a tiny marsupial would give them all a run for their money, finding its way from the mother’s uterus to her pouch when it’s hardly more than an embryo.
Mammals like humans are known as eutherians, a group that has long gestation periods and whose young are nourished until birth by an organ called the placenta, which is attached to the wall of the uterus. In marsupials — including kangaroos, wallabies, koalas and more — birth looks a little different. A developing marsupial uses its forelimbs to climb out of the uterus before its legs have formed. It makes its way into a specialized pouch on the outside of the mother’s body, where it will nurse and continue developing until it can move around on its own.
Those of us with a soft spot for the platypus (Ornithorhynchus anatinus) tend to love it partly because it’s one of only a few mammals that lay eggs. (The other four are all species of echidna, sometimes called “spiny anteaters.”) But platypus parenting has other quirks, too. Following a graceful courtship stage, during which the female leads the male in a dance-like swim, the female turns her attention to crafting a complex burrow that will keep her eggs healthy until they hatch.
Platypuses can be tough to study closely in the wild, so much of what scientists know about platypus burrowing comes from research on animals in captivity. Platypus mothers appear to be talented tunnelers, spending several hours before they lay their eggs digging meters-long burrows along riverbanks. The burrows can be complex, complete with branching passageways, dead ends and a special chamber just for nesting.
In that chamber, research suggests, a platypus mother is creating a perfect enclosed microclimate that keeps her eggs from drying out or getting too cold while she forages for food. She’ll bring in wet leaves and grasses from outside the burrow, then plug the entrance with soil, forming a warm, humid incubator for her eggs. The blocked entrance is also thought to provide protection from predators and, potentially, from flooding. When it comes to motherhood, it seems, platypuses really dig deep.
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