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In the wild, survival can be a brutal challenge, sometimes forcing animals to take extreme measures. While cannibalism and infanticide are common among various species, the most disturbing cases involve baby animals killing their own siblings shortly after birth. Here, we explore ten species where the young start their lives as cold-hearted fratricides.
10. Golden eagle
As with many large raptors, Golden Eagles rarely breed, usually laying just two eggs in each nest. Often, one of the eggs hatches a few days earlier than the other, giving the firstborn chick a head start in receiving food. As a result, the first chick grows bigger and stronger, typically dominating in food disputes. In times of food scarcity, the younger chick can become weak and may die from malnutrition. Worse still, when resources are extremely limited, the firstborn will often kill and consume its sibling, with the parents taking no action to prevent the fratricide.
This provides a substantial meal for the more dominant chick while also lightening the burden for the adult eagles, as feeding one chick is always less demanding than feeding two. Research suggests that up to 80% of second-born Golden Eagle chicks meet their end in this way. While fratricide has been observed in other raptors, such as the Bald Eagle, it occurs far less frequently compared to Golden Eagles.
9. Spotted hyena
Unlike many large predatory mammals like big cats, which are born defenseless with their eyes closed and toothless, African spotted hyenas enter the world wide-eyed, alert, and equipped with sharp teeth. From a young age, they engage in fierce battles for dominance, with the larger cubs aggressively biting their weaker siblings. While adult hyenas may intervene to separate them, the cubs' fighting continues as soon as they're left alone in their communal burrows. These brutal conflicts can persist for weeks.
Hyena cubs have even been observed digging small tunnels within the burrows to continue their fights out of reach of their mother. Some of the weaker cubs succumb to their injuries, but more often, their fate is even more tragic: after enduring relentless bullying from their stronger siblings, they become so timid that they won’t even leave the burrow when their mother returns to feed them. Ultimately, these cubs die of starvation inside the burrow.
Beyond serving as a tactic for the dominant cubs (the future leaders of the hyena clan) to remove potential rivals, fratricide also acts as a natural method of population control. Hyenas are the most abundant large predators in Africa, and besides lions, who occasionally kill some, they have no other natural predators.
8. Praying mantis
These predatory insects are notorious for their disturbing mating behavior; the female often devours the male after or even during copulation, typically starting by severing the unfortunate male’s head. But cannibalism isn’t reserved for adults alone. After a female mantis lays her eggs in a specialized case attached to a stem, leaf, or branch, all 100 to 200 baby mantises hatch at once. Their first meal is often one of their siblings, especially when there is a lack of other small insects in the vicinity.
The mantis isn’t the only fratricidal invertebrate; baby spiders and scorpions have also been known to occasionally consume each other. In the case of spiders, the mother may even join in, feasting on her own offspring, particularly if she has been fasting while guarding her eggs.
7. Snowy Egret
Snowy egrets are admired for their graceful appearance and flight, rarely seen as ruthless creatures. Yet, they are among the most prone to fratricidal behavior. Typically, a female snowy egret lays three eggs, with a distinct difference between the first two and the third. The first two eggs receive a high dose of hormones during development, while the third only receives half the amount, resulting in less aggressive behavior.
In times of food scarcity, the older egret chicks often bully their younger sibling, which, being more passive, struggles to defend itself and is eventually killed—either by being pecked with the sharp bills of its siblings or thrown from the nest. This leaves more food for the surviving chicks.
It might seem strange that Snowy Egrets lay three eggs when only two chicks are expected to survive, but there’s a reason for this. If something happens to the first two eggs or the firstborn chicks during the early days, the third chick serves as a backup. As harsh as it seems, the third Snowy Egret chick is essentially just a spare.
6. Tiger Salamander
Like most amphibians, Tiger Salamanders begin their lives as aquatic larvae or 'tadpoles.' However, they stand out because their eggs can develop into two distinct types of tadpoles: the 'normal morph' and the 'cannibal morph.' The cannibal morph has a larger head, bigger mouth, more developed teeth, and is bigger than its normal siblings. This morph typically emerges when the pond dries up or when food becomes scarce. These larger tadpoles consume smaller ones, growing faster and undergoing metamorphosis earlier, allowing the species to survive under harsh conditions.
What's remarkable about these cannibalistic Tiger Salamanders is their ability to recognize their siblings and typically avoid consuming them. Instead, they target unrelated tadpoles born in the same pond. They can even identify their first cousins and steer clear of eating them! However, when food becomes critically scarce, they won’t hesitate to devour a few of their own, earning them a place on this list.
5. Common Cuckoo
Common Cuckoos are undoubtedly the most notorious fratricides in the Animal Kingdom. However, they don’t typically kill their actual siblings but rather their foster siblings. The adult female Cuckoo resembles Sparrowhawks, small yet fierce raptors that prey on smaller birds. This resemblance helps her scare other birds away from their nests. Once the nest is abandoned, the female Cuckoo swiftly consumes one of the eggs and replaces it with her own, before flying off.
When the host birds return, they notice nothing amiss and continue to care for their brood. But the baby Cuckoo hatches first and, still blind and featherless, immediately begins pushing the other eggs or chicks out of the nest to their death. This violent behavior is not intentional, but is driven by the Cuckoo’s sensitivity to contact with other objects in the nest. If two Cuckoo chicks share a nest, one will eventually eliminate the other, though this is a rare occurrence.
In the end, the foster parents, unable to stop the 'crime,' have no choice but to feed the lone remaining chick—the Cuckoo. The baby Cuckoo’s begging calls mimic those of a full brood, tricking the adult birds into thinking they are feeding many chicks. The parents continue to bring food for the impostor, which grows quickly to an enormous size compared to the foster parents. They keep feeding the Cuckoo until it is ready to leave, and if it’s a female, to mate and repeat the cycle.
4. Great spotted cuckoo
If you think the Common Cuckoo is bad, you might want to brace yourself for its slightly larger relative, the Great Spotted Cuckoo, which inhabits parts of Europe and Asia. The female Great Spotted Cuckoo often lays one (sometimes two) eggs in a magpie’s nest. Unlike the Common Cuckoo, the baby Spotted Cuckoos don’t toss the other eggs and chicks out, but they tend to develop more quickly than their unfortunate foster siblings. They also have large, brightly colored mouths that are irresistible to the adult magpies. As a result, the magpies end up feeding the Spotted Cuckoos more frequently than their own young. Eventually, the fast-growing Cuckoo chicks leave the nest, but continue demanding food from the magpies, leading to the starvation of the magpie chicks, who are abandoned in their own home.
Why do magpies tolerate the Great Spotted Cuckoo’s eggs instead of discarding them? Scientists were shocked to find that adult Great Spotted Cuckoos will mercilessly destroy all eggs or chicks in any magpie nest where the Cuckoo egg is rejected. In essence, the magpies are forced to raise the Cuckoo chicks as their own or face the horrific fate of losing all their offspring. Though cruel, this behavior serves as a natural way to control the magpie population, as magpies themselves often raid the nests of other birds and, if left unchecked, can wreak havoc on other species.
3. Sand tiger shark
Known in Australia as Grey Nurse Sharks, these fierce-looking (but usually harmless to humans) predators top the list for a very good reason. Female Sand Tiger Sharks possess two wombs, each producing numerous eggs. These eggs hatch while still inside the womb, and the embryos develop sharp teeth. Soon, they start attacking and devouring their siblings and any unfertilized eggs, leaving only one embryo alive in each womb. Consequently, the mother gives birth to only two pups – the last survivor from each womb – and due to their nourishment in the womb, they are already quite large, measuring about one meter at birth!
The Sand Tiger Shark is unique in this list, being the only fratricidal species that starts killing its siblings before birth. When it is born, it is already a seasoned predator. This brutal survival tactic, known as intrauterine cannibalism, was first discovered in 1948 when a scientist, examining the womb of a Sand Tiger Shark, was bitten by one of the embryos. While other shark species, including the Great White Shark and Basking Shark (which feeds on plankton as an adult), have been reported to engage in intrauterine cannibalism, they typically consume only unfertilized eggs. The Sand Tiger Shark, however, is the only one known to cannibalize other embryos.
2. Copidomopsis floridanum
Copidomopsis floridanum is a parasitoid wasp, one of the most extreme examples of fratricide in the animal kingdom. The adult wasp begins by finding a caterpillar and stinging it, causing the insect to become completely paralyzed. It then injects two eggs into the caterpillar's body, one male and one female. However, instead of producing a single brother and sister, the eggs clone themselves through a process known as polyembryony. Soon, the caterpillar, still alive but completely impotent, serves as the nursery for approximately 200 male larvae and over 1,200 female larvae.
Among these females, around fifty grow larger than their siblings, developing massive jaws but no sexual organs. It was once believed that these 'monster larvae' were intended to guard their smaller, fertile siblings, protecting them from any other wasps that might attempt to inject their brood into the already occupied caterpillar.
However, it is now understood that this is not the case. These larvae actually hunt down and devour as many of their brothers as possible. The reason for this behavior is that the male larvae fertilize the females while still inside the caterpillar, with just one or two males being enough to fertilize all the females. By eliminating the excess males, the cannibalistic larvae ensure there is more food (the caterpillar's body) for their fertile sisters, thereby increasing their chances of survival. The cannibalistic larvae serve no other purpose since they are sterile and will never reproduce themselves.
1. Queen Honey Bee
As is widely known, Honey Bees live in colonies with one Queen, a few Drones (male bees whose sole role is to fertilize the Queen), and Workers, which are sterile females. The Workers handle all the laborious tasks within the colony, from gathering food to producing honey, wax, and a special substance called Royal Jelly, which is secreted by a specific gland in the Worker’s head.
Royal Jelly is an exceptionally nourishing food that is provided to both the Queen and all developing larvae in the colony. As the Queen grows older and her reproductive abilities decline, the Workers select several larvae, move them to special cells separate from the others, and begin feeding them large quantities of Royal Jelly. This nourishment causes the larvae to mature into fertile Queen Bees. Once they reach a specific age, the future Queens pupate, wrapping themselves in cocoons and undergoing metamorphosis into adult bees.
However, only one Queen can exist in the colony at a time. So, the first Queen Bee to be born immediately seeks out the other Queens and kills them by stinging them to death before they can emerge. If two or more Queens emerge simultaneously, they engage in a brutal fight until one defeats the others. When this happens, the Worker bees will kill the old, original Queen, and the young, new Queen takes her place. Life for a bee is not as sweet as it seems. All the bees in a colony are siblings, born from the same Queen, which is why they rank #3 on this list.
