Did you hear about the cannibal who was late for dinner? He got the cold shoulder.
Some humans might find cannibal humor in bad taste, but for some animals, it’s no joke. Here are a few creatures for whom “I’d like to have you over for dinner” is a terrifying invite. (See “Surprise! Male Spiders Eat Females, Too.”)
Sand Tiger Shark
They say the earlier you learn something, the better it will stick. Well, no wonder sharks are such world-class killers: They start before they’re born.
The first to break out of its egg capsule will start feasting on its siblings. When this baby shark finishes off its brothers and sisters, it will start on unfertilized eggs that have entered the womb. The protein-rich diet works: At already about three feet (a meter) at birth, the newborn sand tiger shark is unlikely to become prey.
They’re the cutest infanticidal cannibalistic serial murderers you ever did see.
Not all prairie dogs merit such dastardly designations, but we know some do, thanks to the tenacious research of John Hoogland, behavioral ecologist at the University of Maryland Center for Environmental Science. After some major detective work discovered cannibalism among black tailed prairie dogs. (See video of Hoogland on NatGeo Wild: “Prairie Dog Alarms.”)
“We noticed that almost all the females were mating, but very few were weaning babies,” said Hoogland, who began researching the rodents in 1974.
The team also noticed females going into the burrows of their closest female relatives, and “when they come up, they frequently had some blood on their faces.” Mothers in those burrows stopped showing any signs of maternal behavior.
Eventually, after much effort, “we found decapitated babies that had mostly been cannibalized down there,” Hoogland said. “Now we had the smoking gun.”
Another species, the Utah prairie dog, also eats its young but the behavior is rare or non-existent in other species.
“My guiding hypothesis,” he said, “is that competition is so extreme that sometimes natural selection favors prairie dogs to kill the offspring of close relatives because doing that raises the chances that their own babies make it.
“In that sense,” Hoogland says, “it really is a dog-eat-dog world.”
Dog-eat-dog, yes … but frog-eat-frog?
Well, sort of. The tadpoles of cane toads, which are native to South America, like to dine on cane toad eggs, which they sniff out in the water. They’re specifically attracted to an egg-protecting toxin called bufadienolides. The nutritious caviar helps them develop and cuts down on future competition, according to a 2011 study from the University of Sydney and James Cook University.
But it’s not just the kids: A 2008 study found that cane toads waggle the middle toe of their hind foot in a luring display to attract prey, including young toads. In that study the researchers dissected 28 juvenile cane toads and found that 64 percent of their 149 prey items were other cane toads.
Alas, like so many of us, the cane toad may be undone by its own appetites. They’re an invasive species in Australia, and many people are working to eradicate them. (See a picture of a monster cane toad caught in Australia.)
A 2009 study of Mexican lance-headed rattlesnakes showed that 68 percent of new mothers ate all or part of their non-surviving offspring, probably to recover the nutrients needed to reproduce again.
A wonderfully descriptive New York Times story from 1901 describes an outsize female cobra at the Bronx Zoo who snacked with such gusto on black snakes provided to her that “already her appetite has made black snakes scarce in the park.” (Watch video: “Cannibalistic Snakes.”)
Snakes will even bite themselves on occasion. Check out this video of a copperhead that chomps down on its own tail … after its head has been cut off.
Australian Redback Spider
“Love bites,” “hungry for love,” “I could eat you up”—human sexual desire is rife with food metaphors.
In the micro-world, they’re not metaphors.
Some insects and arachnids practice sexual cannibalism, wherein the female eats the male after mating. Australian redback spiders get both acrobatic and deliciously spiteful about it.
The male redback will sacrifice itself to the female by somersaulting onto her mouthparts during sex and can transfer sperm while being consumed.
Maydianne Andrade of the University of Toronto Scarborough reported in a 2003 study that males that are cannibalized (which happens 65 percent of the time) mate far longer and produce twice the number of offspring than those that are not.
So, ready for that afternoon snack?