Blue and Crabby: Whooping Crane Winter Diet

    How would you like to eat the same thing every day for 5 or 6 months every year of your life? That's what whooping cranes do on their wintering grounds, in Texas and florida. Cranes can eat crabs, clams, eels, shrimp, crayfish, acorns, snails, mice, voles, grasshoppers, minnows, dead fish, marsh onions and snakes. But their clear favorite is blue crabs. An adult crane can eat up to 80 blue crabs in a day!

    Blue crab
    Photo Chesapeake Bay Program

    The Most Important Crane Food in Winter
    The breeding success of Whooping cranes each spring is closely related to the population of blue crabs on the wintering grounds. Even if there are plenty of other food sources, the cranes must have a large supply of blue crabs to build up their body resources. Without a lot of blue crabs to eat in winter, they have a poor chance of raising babies come spring.

    Crab Nutrition
    What's so great about blue crabs? One large blue crab has about 85 grams (g) of meat. This provides 87 calories, with 17 g of protein, 1.5 g of fat, and 0 g of carbohydrate. But it isn't just the protein and calories in blue crabs that is important for cranes. Each crab is also rich in calcium (necessary for strong bones and also for forming egg shells). It has iron, magnesium, phosphorus, zinc, copper, other minerals, and lots of vitamins. And this is just the actual meat in the crab. Cranes pick off the biggest claw and some of the hard parts of the shell on the largest crabs, but they swallow smaller crabs whole. They eat most of the shell even on large crabs. The shell is extremely rich in calcium and other minerals. A crane would have to eat a LOT of acorns or worms to get the nourishing vitamins, minerals, and calories of just one blue crab!

    Harder Than It Looks
    Whooping crane family foraging.

    Photo Laura Erickson

    Just because blue crabs are important in the crane winter diet doesn't mean that they're easy to eat.

    Biologist Tom Stehn tells us that the parents have to teach the baby cranes how to eat crabs: "Whooper chicks are fed most of the winter at Aransas by their parents, with feeding tapering off as the young get older and spring approaches. With vegetable matter such as wolfberries or acorns, the young cranes quickly feed on their own. When an adult catches a blue crab, Junior runs over and begs for an easy meal. Small crabs are swallowed whole. With a big crab, the adult usually carries it to the edge of a pond and pulverizes it on the muddy marsh soil rather than in the open water ponds. Once the crab is stunned and on marsh soil, Junior is usually pecking at the crab and trying to eat underfoot of the adult crane. The crab legs are pulled off and often swallowed whole. When crabs get inactive from cold temperatures (below 18 degrees C), adults stand in one spot and probe the mud until they hit a crab. I assume the youngsters also do this.

    "George Archibald (ICF) has suggested that the beaks of 6-month old cranes are still growing and may not be strong enough to be smashing crabs, but Felipe Chavez has observed young whoopers catching crabs. Dr. Chavez writes, 'The cranes I observed catching crabs generally took the crab to the edge, an open spot to tear them up. Occasionally, particularly with larger crabs, the crane would break off one of the claws before it took the crab to the edge of the pond. A free claw is dangerous, it appears. I saw crabs cling to the cranes beak after the crane had let go of it. Once on the edge, the second remaining claw was generally broken off first. Then the crane generally flipped the crab over and proceeded to peck it repeatedly. I am not sure if it was trying to kill it, or break it up regardless of whether it was alive or not. I'm not sure whether cranes kill the crab first then tear it up or tear and kill along the way. This generally left only the carapace of larger crabs, since the undersides, inside, and all extremities were consumed except for very large claws.'"

    Introducing Crabs to the Ultralight-led Chicks in Florida
    Without experienced crane parents to teach them, each new group of young cranes fledged in the north and coming to the wintering grounds will need to learn how to eat blue crabs. (Ask your parent how easy it was for you to learn to eat with a spoon, and you'll realize that cranes aren't the only ones with eating challenges!)

    Try This! Demonstration or Skit

  • Imagine you are a human inside white costume with a crane puppet on your arm. Like a crane parent, you must teach a young whooping crane to eat blue crabs. How would you do it? In teams, plan out your strategies. Then each team demonstrates for the class. After all teams have presented, compare your plans with Tom Stehn's suggestions.