for the squids to escape predators. The ability to hear is particularly relevant for avoiding mammalian predators of the suborder Odontoceti (particularly dolphins), who use echolocation to find prey. Mating behaviour Bigfin reef squids exhibit two most common social body patterning and posturing behaviours related to mating. The first is dubbed "accentuated gonads", in which they will sometimes increase the visibility of their gonads while reducing the rest of their body colouration. This makes their reproductive organs appear bright white through the transparent mantle. It may indicate the reproductive condition of the signalling squid. Another common behaviour, primarily seen in males, is dubbed "spread arms", in which the squid will slightly tilt its body forward, head down and arms spread widely and raised above. The mantle is darkened. This behaviour is exhibited mostly when the squids are chasing or following another individual. It is thought to be a signal of reproductive arousal or aggression, similar to the "zebra display" behaviour of Sepioteuthis sepioidea, the "intense zebra display" behaviour of Sepia officinalis, and the "lateral display" of Loligo plei. Females will also sometimes use this display to rebuff courting males. There are three known courtship behaviours in bigfin reef squids, dubbed "male-upturned" mating, "male-parallel" mating, and "head-to-head" mating. Actual insertion in each position lasts for only a few seconds. "Male-upturned" mating involves rapid back and forth swimming by the courting male beside a slower-swimming female. The male will then flip over so that he is swimming upside down and quickly lunge forward towards the female. He will quickly eject several spermatophores from his funnel into his hectocotylus and attempt to deposit them on the female's mouth funnel, then jet away from the female. "Head-to-head" mating is regarded as a variation of this tactic. "Male-parallel" mating involves the male and female swimming side by side. The male will then raise one or two of his arm pair I upwards and swing them back and forth. He moves below the female and clasps the female's neck with his arms. In contrast to the previous behaviours, in this position the male actually inserts his hectocotylus into the mantle cavity of the female, attaching the spermatophores right at the opening of the oviduct rather than at the mouth. Possibly for this reason, it is usually more successful in fertilizing the female than other mating behaviours. In addition to the above, males will often engage in