“Cannibalism” sparks a visceral reaction in us, calling back images of barbarity and desperation. For many creatures in the animal kingdom, however, eating one’s own is surprisingly common and often a strategic behavior.
Sometimes, eating one’s own kin is spurred on by a simple, yet essential, race for survival, while other times, it’s a macabre practice that some animals engage in after mating.
Here are three animals—tiger sharks, green and golden bell frogs and cane toads—whose cannibalistic tendencies serve a vital purpose.
Sand Tiger Sharks—Birth Is A Battle To Be Won
Sand tiger sharks (Carcharias taurus), have an unusual reproductive strategy that begins with a cannibalistic showdown in the womb. Female sand tiger sharks often mate with multiple males, resulting in embryos from different fathers.
As soon as the largest embryo in each of the mother’s two uteri reaches a certain size, it begins to feast on its smaller siblings in a process known as “embryonic cannibalism.” While the mother might carry embryos fertilized by multiple fathers, this gruesome competition ensures that only one father’s offspring typically makes it to birth.
Scientists used DNA profiling to investigate this phenomenon, examining the genetic relationships between mothers and their hatchlings. The results revealed that while 60% of the females mated with multiple males, only 40% of litters contained offspring from different fathers, according to a June 2013 paper published in Biology Letters.
In the majority of cases, the surviving hatchlings were full siblings, meaning they shared the same father. The rest? They were likely consumed before they had a chance to grow.
Green And Golden Bell Frogs—The Power Dynamics Of Cannibalism After Sex
Some creatures engage in what is known as “sexual cannibalism,” consuming their mates during or after copulation. While it seems bizarre, there’s a good reason to engage in such behavior: Females who practice sexual cannibalism have a greater chance of producing larger children.
Female green and golden bell frogs (Litoria aurea), which are native to eastern Australia and now found in various Pacific islands, such as New Zealand, have recently been observed preying on adult males during the breeding season, and this is described in a June 2024 study in Ecology and Evolution.
While Litoria aurea tadpoles frequently feed on each other, what made this study particularly interesting is that it had encountered a unique case of adult-on-adult cannibalism in these usually docile frogs. Even stranger was the case where a male was devoured for performing a poorly executed mating ritual.
When it comes to sexual cannibalism in these frogs, the act becomes a bid for reproductive dominance. The female—by consuming the male—gains essential nutrients for reproduction, asserting her reproductive superiority over other females and enhancing the survival of her offspring.
A Cane Toad Diet That Checks Their Numbers
In environments where an animal’s population exceeds the available resources, cannibalism also serves as a natural form of population control, helping reduce numbers to a sustainable level. The cane toad is a perfect example of this phenomenon.
Native to Central and South America, cane toads (Rhinella marina) can have disastrous ecological consequences when they’re introduced to other regions. This is mainly due to their unchecked breeding and lack of natural predators. This means they can quickly overpopulate an area and become pests. But, thankfully, they have evolved a behavior that keeps their numbers in check.
Adult cane toads prey on their tadpoles when they detect a toxin released by the tadpoles to protect themselves from predators, according to a March 2022 study in Ecology and Evolution.
This cannibalistic behavior helps to regulate the population density, ensuring that the limited resources available in their environment are sufficient for the survival of the rest. While this behavior is uncommon in their natural habitat, it is thought to have evolved as a natural form of population control in places with too many mouths to feed.
Cannibalism provides a unique window into animals’ lives and survival strategies. While it may seem drastic, the cannibalistic practices adopted by these animals demonstrate their remarkable resilience and ability to thrive even in challenging conditions.
While cannibalism can be an exercise in survival for many in the animal kingdom, not everyone will find animals killing their own acceptable. Discover the strength of your bond with the natural world through this quick test: Connectedness To Nature Scale