Oh, Snap!

African dwarf crocs are a big deal

BY Peggy Scott

Photography by Ken Bohn

Despite barely tipping the scale at less than six ounces, the African dwarf crocodile hatchlings at the San Diego Zoo are still making quite the splash. The 14 baby reptiles are the first of their species ever hatched in the 101-year history of the Zoo. And whether you call them dwarf, broad-nosed, or bony, these crocodiles rock. Just ask Lawrie Arends, a reptile keeper at the Zoo and croc fan extraordinaire. “These hatchings are exciting,” Lawrie says. “Dwarf crocs, and crocodiles in general, are such interesting and misunderstood animals—people need to know the truth about them.” Lawrie took over primary care of the Zoo’s adult African dwarf crocodiles in 2016. Yendi, an 11-year-old female, and Kumba, a 50-year-old male, have been here since 2007 and 2013, respectively. And now Lawrie has 14 additional reptilian responsibilities!

The African dwarf crocodile is also known as the broad-snouted crocodile and the bony crocodile.

(Pre)Historic Occasion

Crocodiles have existed for hundreds of millions of years. The African dwarf crocodile Osteolaemus tetraspis, one of the smallest surviving crocodile species, tops out at around 70 pounds and a length of 5 feet. (The other end of the spectrum finds the saltwater crocodile at 20 feet long and over 2,000 pounds.) This species was discovered in 1861, and the Zoo has kept African dwarf crocodiles, off and on, since the 1980s. Yet the pitter-patter of extra-tiny crocodilian feet is a new sound around here.

In preparation for her family, Yendi spent two months nesting—literally. She built a mound nest from soil, leaves, and other materials supplied by her keepers. “Then she laid her eggs, covered them up, and took her place as guard,” Lawrie says. “If she wasn’t on it, she was nearby, watching us like a hawk.” As interesting as it was to watch Yendi nest, the actual hatching process is a sight to behold—and something to be heard! “When it’s time to break out of their shell, the babies call to each other from inside the egg, making little puppy-like whimper noises that basically mean ‘let’s go guys, all together!’” Lawrie says, adding that Mom is right there to help any late bloomers. “If an egg doesn’t hatch, the mother will take it in her mouth and gently crack the shell, piercing the inner membrane without crushing the baby. It’s amazing!” A mother crocodile then carries her youngster to the water’s edge to join the rest of her brood.

Crocodile hatchlings use their teeth to break out of their shells.
In order to help her offspring escape its egg, a mother crocodile will use her teeth to bite the egg just enough to pierce the shell.

Because this was such an important clutch of eggs, keepers removed them from Yendi’s enclosure to check them out. Once it was determined which eggs were fertile, keepers incubated the little treasures at a carefully selected temperature. “If the temperature is high, the offspring develop as female,” Lawrie explains. “At a medium temperature, you get a mix of males and females. Lower temperatures produce males, and the lowest temperatures result in all females. A few degrees can make all the difference.” This clutch aimed for a mix; it will be a few months before keepers can verify the outcome.

And Kumba? His job is complete, Lawrie notes, since male crocodiles do not play a role in the raising of young.

Like other members of the crocodile family, dwarf crocs are well suited to live and feed in the water. They have a transparent third eyelid that can be closed to protect their eyes when under the water; as well as a flap of skin that closes to cover their windpipe—keeping water out of their lungs.

Life’s a Beach

Native to central and western Africa, dwarf crocodiles make their homes in tropical lowlands such as swamps, mild-current areas of rain forest rivers, riverbanks, savanna pools, or, as Lawrie says, “Anywhere there’s equatorial forest.” African dwarf crocs dig burrows along the water’s edge and come out at night. Their coloring—a black back and sides with yellowish patchy underbelly—helps them blend in with their surroundings. The belly and underside of the crocodile’s neck have bony deposits that form hard plates called osteoderms, and its neck, back, and tail are heavily armored. Lawrie notes that environment may affect the appearance of one population of African dwarf crocodiles. “There are some that live in caves, and they are slightly orange in color,” she says. “They eat bats and cave crickets, and researchers aren’t sure if the color comes from the guano that drops on them, or maybe from the animals not being exposed to the sun’s UV rays. It’s still being studied.”

The dwarf crocodile’s blunt snout sits above a mouth that holds sharp conical, rootless teeth inserted into deep sockets.

Their short, blunt snout houses 30 to 32 razor-sharp teeth. New teeth grow continuously, pushing the older teeth up and out of the jaw. Those teeth, coupled with jaw strength, allow the African dwarf crocodile to chomp down whole smaller prey like fish and amphibians, or tear off large pieces of a bigger meal, such as carrion. Here at the Zoo, Yendi and Kumba are fed fish, small rodents, special crocodile biscuits, earthworms, and crayfish; while the “croc-lets” dine on crickets, worms, and small fish.

Although they are found mostly in water, dwarf crocodiles can run (gallop) fairly quickly on dry ground.

Immersive Learning

Growing up in Australia, Lawrie saw her first saltwater crocodile at about age four, and was instantly smitten. “I have been fascinated with them ever since,” she says, adding that she studied the creatures extensively during her academic career, and attended an intensive, eight-day crocodilian biology and professional management program in St. Augustine, Florida that’s known as “croc school.” “I saw every single species of crocodile, from all over the world, all in one place,” Lawrie says. The experience seems to have cemented her role as a crocodile crusader. “People think crocodiles are not intelligent, and that all they do is sleep and eat people. It’s more complicated—and much more interesting than that.” As a smaller species living in a range with larger animals (like larger crocs), dwarf crocodiles survive by laying low during the day and keeping their activities nocturnal.

Lawrie points out that Yendi and Kumba do more than just sunbathe in their exhibit at Africa Rocks. “They can identify colors and they know their names,” she says. “We have done some husbandry training with them, which helped us discover that Yendi was pregnant. She responded to a target and came up on land, where we could see she was gravid.”

A dwarf crocodile’s eyes and nostrils are situated on top of the snout to enable breathing when crocodile is submerged.

A Shortened Future?

While Yendi and Kumba go about their life in Africa Rocks, and their babies grow up—some behind the scenes and some on exhibit on the Zoo’s Reptile Walk—African dwarf crocodiles in the wild may not be so lucky. “They’re currently listed as Vulnerable, but a big percentage of the population is lost to the bushmeat trade,” Lawrie says. “Logging clears habitat, which also threatens them, and climate change is affecting their population balance, as it is with so many animals. But these smart crocodiles have managed to live alongside bigger species and make it work. They have survived to outlive dinosaurs. Wouldn’t it be terrible if people turned out to be their downfall?” It’s hoped that with efforts such as those from San Diego Zoo Global, a new plan to save these prehistoric wonders can be hatched.