Onager (weapon) Onager (weapon) The onager (British /ˈɒnədʒə/, /ˈɒnəɡə/, U.S. /ˈɑnədʒər/) was an imperial-era Roman torsion powered siege engine; in other words, a small catapult. The onager was first mentioned in 353 AD by Ammianus Marcellinus, who described onagers as the same as a scorpion. According to two authors of the later Roman Empire who wrote on military affairs, the onager derived its name from the kicking action of the machine that threw stones into the air, as did the hooves of the wild ass, the onager, which was native to the eastern part of the empire. The onager consisted of a
Animal communication individual. The altered signal provides information that can indicate food, predators or conspecifics. Because the sender and receiver are the same animal, selection pressure maximizes signal efficacy, i.e. the degree to which an emitted signal is correctly identified by a receiver despite propagation distortion and noise. There are two types of autocommunication. The first is active electrolocation found in the electric fish Gymnotiformes (knifefishes) and Mormyridae (elephantfish) and also in the platypus ("Ornithorhynchus anatinus"). The second type of autocommunication is echolocation, found in bats and toothed whales. There are many functions of animal communication. However, some have been studied in