Negative feedback from maternal signals reduces false alarms by collectively signalling offspring

Abstract

Within animal groups, individuals can learn of a predator's approach by attending to the behaviour of others. This use of social information increases an individual's perceptual range, but can also lead to the propagation of false alarms. Error copying is especially likely in species that signal collectively, because the coordination required for collective displays relies heavily on social information. Recent evidence suggests that collective behaviour in animals is, in part, regulated by negative feedback. Negative feedback may reduce false alarms by collectively signalling animals, but this possibility has not yet been tested. We tested the hypothesis that negative feedback increases the accuracy of collective signalling by reducing the production of false alarms. In the treehopper Umbonia crassicornis, clustered offspring produce collective signals during predator attacks, advertising the predator's location to the defending mother. Mothers signal after evicting the predator, and we show that this maternal communication reduces false alarms by offspring. We suggest that maternal signals elevate offspring signalling thresholds. This is, to our knowledge, the first study to show that negative feedback can reduce false alarms by collectively behaving groups.

Sound recordings of Apis cerana japonica colonies over 24 h reveal unique daily hissing patterns

“…Frequent occurrence of loud hissing sounds in a colony can have a function of threating potential (daytime) predators approaching the colony. Furthermore, among some group-living birds and insects, such as the pied babbler (Bell et al 2009), greylag geese (Kahlert 2006), or treehopper (Hamel and Cocroft 2012), it is known that false alarms are common, often occurring more frequently than the correct detections (Cresswell et al 2000;Beauchamp 2010). Since hissing is the simultaneous wing movement of multiple honey bees, if the first group of individuals detected a non-threatening stimulus and mistakenly hissed, neighboring bees may imitate their movement, resulting in a false alarm through the colony.…”

Motor and mechanical bases of the courtship call of the male treehopper,Umbonia crassicornis

“…In addition, we did not find any sexual dimorphism in the muscular arrangement or cuticular structure (C.I.M., personal observation). Female treehoppers generate a tonal signal during courtship, and also generate clicks while brooding eggs or nymphs (Cocroft, 1999a,b;Cocroft and McNett, 2006;Hamel and Cocroft, 2012), so the lack of sexual dimorphism is not surprising. The position and orientation of the I a dvm1 muscles do bear a resemblance to the tymbal muscle of the cicada, but whether this is a homolog and whether its action on the I a apod could be considered a tymbal-like action need to be further studied.…”

“…Plantdwelling insects are often able to create a range of differing vibrational disturbances in the stems depending on their intended purpose. Changes in the characteristics of the signal serve as cues to defend their territory from approaching predators, to develop mutualistic relationships and to inform other group members about available resources (Cocroft, 1999a(Cocroft, ,b, 2001Hamel and Cocroft, 2012). Because low-frequency vibrations can be transmitted up to several meters through the plant stem, this can be an effective mechanism for small insects to use for relatively long-range communications (Michelsen et al, 1982;Bennet-Clark, 1998a;Čokl and Virant-Doberlet, 2003).…”

“…The treehopper Umbonia crassicornis (Amyot & Serville 1843) uses vibrations to locate mates and to signal danger (Hamel and Cocroft, 2012;Cocroft, 1999a,b). To locate mates, male U. crassicornis use a 'call-fly strategy', in which they fly to a tree and, upon landing on a branch, generate a vibrational calling signal.…”

Honeybees tune excitatory and inhibitory recruitment signalling to resource value and predation risk

“…The pharaoh ant uses a 'no-entry' odour signal to indicate that a food odour trail is no longer rewarding (Robinson, Jackson, Holcombe, & Ratnieks, 2005). A treehopper mother can reduce false alarms by producing a vibrational signal that inhibits the alarm signal vibrations produced by her offspring (Hamel & Cocroft, 2012). Honeybees possess a powerful excitatory signal, recruitment dancing, which can rapidly increase the number of workers visiting a resource (von Frisch, 1967).…”