Animal Tails – as Tools
In our last issue, we looked at a few unique functions of animal tails (Animal Tails: Locomotion). In fact, more tactical uses of tails have been developed over the long evolutionary process. To many animals, their tails are valuable tools for foraging, and for luring and even killing their prey!
Alluring Bait
In the Middle East, the Spider-tailed Horned Viper (Pseudocerastes urarachnoides) has a specialised tail that is used as bait. The snake is camouflaged, brown as the soil, with its tail having a fish bone shape. When still, it can hardly be spotted, except that it sways its tail to imitate a lively spider, attracting birds to prey on it. Yet once a bird comes close, it will become prey of the snake instead. Interestingly, researchers have found that the tactic is more effective in deceiving migratory birds, while resident birds are now more alert to the trickery.
Shock Wave Gun
Thresher shark (Alopias sp.) has an elongated tail, almost as long as its body. The seemingly disproportionate tail is in fact an essential foraging tool. Biologists have spent a long time recording the hunting behaviour of the shark. The shark is good at controlling its tail and will strike at high speed from the front or the side of a large fish school. The shock wave generated will hit a certain amount of the fish, allowing the thresher shark to readily feed on the stunned fish. A study showed that the success rate of the shock wave attack can be as high as 65%, which is very effective!
Venom Syringe
The scorpion’s stinger is frightening, and its tail makes the stinger most deadly. Engineering researchers have used high-speed video cameras to capture the attack action of scorpions. Slow motion analysis demonstrates that the segmented tail can to sting repeatedly and rapidly in various locations. Venom is only injected when the most vulnerable location is found, in order to paralyse the prey without wasting much of the precious venom.
Ovipositor
The female giant ichneumonid wasp (Megarhyssa sp.) has an extremely long “tail” attached to the abdomen. It is in fact an ovipositor. Upon successful mating, the female wasp will search for the ideal borer host - the favourite target is the larvae of longhorn beetles hiding in tree trunks. With its long, needle-like “tail”, the wasp deposits its eggs through a crevice with a longhorn beetle inside. When its eggs hatch, the larvae will not only occupy the borer’s hole but also feed on the larvae of the host!