Really Weird Animal Behavior

Flatworms engage in a battle like no other to secure a mate. All flatworms are hermaphrodites meaning they have both male and female sexual organs. All flatworms therefore can inseminate and be inseminated. Some species of flatworms have two penises and one or more genital pores needed for receiving unique two tailed sperm which is delivered during copulation.

When certain species of marine flatworms meet, they engage in what is known as penis fencing to determine who will be the mom and who will be the dad. Both worms try to pierce the skin of the other using one of their two penises. This battle can last for hours and even harm the worms in the process. The first worm to pierce the other becomes the male and the one pierced becomes the female. Both worms would prefer to be the male as the one that assumes the female role has the more difficult and energy expending task of raising the young and caring for the developing eggs.

Flatworms lack a body cavity with organs and body systems, instead they have specialized cells that perform various functions. They get their oxygen by absorbing it through diffusion. They can dehydrate quickly and therefore are often found in moist environments. Many species of flatworms are parasites, including the tapeworm, which can be ingested by consuming undercooked meats.

Starfish are well known for their powers of regeneration. An arm can break off as a defensive tactic and grow into a complete new animal. In some species, an arm will pull off purposefully to grow a new animal, serving as a form of asexual reproduction.

This behavior is certainly fascinating, yet even more fascinating is the many different ways different species of starfish feed. Most starfish are carnivores and feed on sponges, mollusks, bryozoans and ascidians. In species that eat mollusks,the starfish will slowly creep over its hapless victim, say an innocent clam. Its hundreds of tiny tube feet then create a suction cup vice like grip which opens the clam and exposes the soft muscular foot inside. Having no mouth parts to help it eat, it uses its stomach. The starfish expels its stomach into the prey, thus covering the exposed mollusk with its digestive organs. Digestive juices are then excreted and the tissues of the prey are dissolved and literally eaten alive. The digested food together with the stomach is then sucked back in to the starfish.

The crown of thorns starfish is one of the largest and most unique starfish species. It can have between 10 - 25 huge arms that all contain venomous spines. Feeding on coral polyps, this menace has destroyed many coral reefs worldwide as its natural predator, the giant triton, has been hunted nearly to extinction for it beautiful shell. The crown of thorns has interesting feeding behavior that scientists can't clearly explain. At the same time every evening they congregate together, hundreds of them arrive right on time at the designated meeting spot and then on cue of some mysterious signal, they spread out in a massive feeding frenzy, desecrating hundreds of coral colonies in a night.

The rumor you have heard that cockroaches can live without their head for weeks is actually true. Also true is that the head alone can survive without the body. Just how exactly does it do this?

Cockroaches do not have blood and blood pressure like humans do. Should a human or other mammal become decapitated, blood loss and a drop in blood pressure create a situation in which you would bleed to death, not to mention be unable to receive the oxygen and vital nutrients the organs need to survive. Not so with the roach. After their head is cut off, their open circulatory system (with much less pressure and no huge network of blood vessels) allows their neck to simply seal off by clotting.

In addition, roaches breathe through spiracles, or tiny holes. Their brain does not control this breathing and their blood does not carry oxygen throughout the body. The spiracles pipe air directly to the tissues. So while all breathing would cease in a human or mammal, breathing does not cease without the head of a roach.

Finally, since cockroaches are cold blooded animals, they can survive with very little food. The headless roach can go for weeks as long as it conserves energy and does not get eaten. Of course, eventually it will end up dieing of starvation or perhaps a mold or bacterial infection.

Having clumps of nerves called ganglia distributed within each body segment allows the headless roach to move, stand, and react to touch all without needing a brain.

And, as mentioned earlier, it is not just the body that can survive decapitation; the head can too, but only for several hours. In laboratory experiments, when a roach head was given nutrients and refrigerated it lasted even longer. The head cannot survive as long as the body can because the brain needs the sensory input from the body.

Spiders from the family Uloboridae have lost their fangs, evolving instead different ways of killing and consuming their prey.


After a hapless moth, beetle or other insect is unlucky enough to get caught, a small uloborid spider will weave more than 140 meters of silk to surround and engulf its innocent victim. It binds the silk around its prey so tightly that this vice like compression causes the legs and exoskeleton crush, its limbs buckle, and its compound eyes implode.