Modeling and Analysis of the Effects of Startle Reaction on Group Coordination

Startle reaction is an alarm behavior observed in animal groups during anti-predatory response or fear-inducing stimulation. This behavior is characterized by spontaneous change in heading direction and increasing speed that can drastically affect group coordination. In this work, we leverage a mathematical model of fish social behavior to recreate startle reaction. Specifically, we model startle reaction through a biased jump diffusion process, where the jumps process captures sudden and fast changes of heading direction observed during this escaping behavior. Then, using extensive numerical simulations, we test their effects on group of fish including an informed individual prescribing the direction of motion and several followers by systematically varying the frequency and intensity of the sudden and fast turns introduced in the heading direction of a single individual. We demonstrate the emergence of novel form of leadership and phase transition between complete ordered states and disorganized states. In addition, we evidence that at specific range of frequencies and amplitudes, the initiation of this behavior might be utilized to divert group followers from their reference trajectory while keeping them in a synchronized state with the startling individual. Our findings offer a new paradigm to recreate the emergence of leadership applicable to divert or contain multi-vehicle systems.

Subterranean Termite Social Alarm and Hygienic Responses to Fungal Pathogens

In social insects, alerting nestmates to the presence of a pathogen should be critical for limiting its spread and initiating social mechanisms of defense. Here we show that subterranean termites use elevated vibratory alarm behavior to help prevent fatal fungal infections. The elevated alarm leads to elevated social hygiene. This requires that termites coalesce so that they can groom each other’s cuticular surfaces of contaminating conidial spores. Groups of 12 Reticulitermes flavipes workers varied in their response when immersed in conidia solutions of nine different strains of Metarhizium. Pathogen alarm displays of short 2–7-second bursts of rapid longitudinal oscillatory movement (LOM), observed over 12 min following a fungal challenge, were positively correlated with the time that workers spent aggregated together grooming each other. The frequency of these LOMs was inversely correlated with fatal fungal infections. The variation in fatalities appeared to be largely attributable to a differential response to Metarhizium brunneum and Metarhizium robertsii in the time spent in aggregations and the frequency of allogrooming. Isolated workers challenged with conidia did not display LOMs, which suggests that the alarm is a conditional social response. LOMs appear to help signal the presence of fungal pathogens whose virulence depends on the level of this emergency alert.

Multimodal alarm behavior in urban and rural gray squirrels studied by means of observation and a mechanical robot

Urbanization of animal habitats has the potential to affect the natural communication systems of any species able to survive in the changed environment. Urban animals such as squirrels use multiple signal channels to communicate, but it is unknown how urbanization has affected these behaviors. Multimodal communication, involving more than one sensory modality, can be studied by use of biomimetic mechanical animal models that are designed to simulate the multimodal signals and be presented to animal subjects in the field. In this way the responses to the various signal components can be compared and contrasted to determine whether the multimodal signal is made up of redundant or nonredundant components. In this study, we presented wild gray squirrels in relatively urban and relatively rural habitats in Western Massachusetts with a biomimetic squirrel model that produced tail flags and alarm barks in a variety of combinations. We found that the squirrels responded to each unimodal component on its own, the bark and tail flag, but they responded most to the complete multimodal signal, containing both the acoustic and the moving visual components, providing evidence that in this context the signal components are redundant and that their combination elicits multimodal enhancement. We expanded on the results of Partan et al. (2009) by providing data on signaling behavior in the presence and absence of conspecifics, suggesting that alarm signaling is more likely if conspecifics are present. We found that the squirrels were more active in the urban habitats and that they responded more to tail flagging in the urban habitats as compared to the rural ones, suggesting the interesting possibility of a multimodal shift from reliance on audio to visual signals in noisier more crowded urban habitats.

Interference of β-eudesmol in nestmate recognition in Atta sexdens rubropilosa (Hymenoptera: Formicidae)

Leaf-cutter ant species (Atta spp.) are key pests of cultivated crops in the Neotropics, and recent studies have demonstrated that workers of Atta spp., particularly of Atta sexdens rubropilosa, exhibit aggressive behavior among nestmates when in contact with the sesquiterpene β-eudesmol, found in leaves of Eucalyptus maculata. However, the underlying mechanism sparking this behavior pattern has yet to be investigated. This work aimed to elucidate the mechanism by which this substance elicits aggression in workers of A. sexdens rubropilosa. The results, thus obtained, showed that β-eudesmol is able to modify the chemical composition of the workers cuticle, impairing nestmate recognition, triggering alarm behavior and leading to nestmate aggression.

Loss of adenosine-induced negative inotropic effect in hyperexcited rabbit hearts: relationship to PKC

Adenosine produced a negative inotropic effect in hearts isolated from calm rabbits but not from those exhibiting alarm behavior during handling. This study was conducted to determine whether protein kinase C (PKC) activation is responsible for the loss of adenosine-induced negative inotropism in the hearts of hyperexcited rabbits. Adenosine (10 microM) decreased myocardial contractility (dP/dtmax) in the hearts of calm, but not hyperexcited, rabbits but decreased heart rate (HR) and coronary perfusion pressure (PP) in the hearts of both calm and hyperexcited animals. During infusion of calphostin C (200 nM), a PKC inhibitor, adenosine also decreased dP/dtmax in the hearts of hyperexcited rabbits. Calphostin C did not alter the actions of adenosine in the hearts of calm rabbits. Agents that stimulate PKC directly [phorbol 12,13-dibutyrate (PDBu), 1 nM] or indirectly [norepinephrine (NE), 3 nM; angiotensin II (ANG II), 5 nM] abolished the adenosine-induced decrease in dP/dtmax but not HR or PP in the hearts of calm rabbits. During calphostin C, infusion of PDBu, NE, and ANG II failed to prevent the adenosine-induced decrease in dP/dtmax. These data suggest that the lack of a negative inotropic effect of adenosine in hyperexcited rabbits is due to an increase in PKC activity.

Adnexal Glands Chemistry of Messor ebeninus Forel (Formicidae: Myrmicinae)

Anabasine is the major volatile product in the poison gland exudate of Messor ebeninus, acting as a defensive compound. Exudates of the poison gland also contain minor, yet unidentified, components that are possibly responsible for the alarm behavior that is also elicited by the venom. Dufour’s gland secretion is characterized by aliphatic hydrocarbons of which 1-pentadecene predominates. Upon exposure to Dufour’s gland secretion the ants recruited to the emitting source, but did not exhibit any aggressive behavior. The possible concordant effects of both adnexal glands secretions is discussed.