Comparative study of predator avoidance behaviour of pheasants (Phasianus colchicus) of different genetic origin

Effects of age and disturbance on fear in pheasants kept in a rearing facility

The survival of captive-reared pheasants in the wild depends primarily on their ability to avoid predators, therefore, pheasants need to maintain their innate anti-predatory behaviour. The aim of this study was to assess the effects of age and disturbance on tonic immobility (TI) in pheasants (Phasianus colchicus) kept in a commercial rearing facility. TI tests were performed in pheasants aged 8, 10, 12, 14 and 16 weeks. Randomly selected pheasants of the same age were tested either immediately after capture (group C) or after exposure to various stimuli/disturbance (group D). No significant differences in the number of attempts to induce TI were found between the observed groups of pheasants (the vast majority of pheasants remained immobile on the first attempt). The effect of age was found only in group D, where birds aged 14 and 16 weeks showed a reduction in the duration of TI compared to younger birds. In group C, the duration of TI in pheasants of different ages did not differ. The results document a change in the duration of TI in response to an intense stimulus depending on the age of captive-reared pheasants. Knowledge of changes in anti-predatory behaviour depending on age and habituation to the environment and new stimuli is essential when determining the optimal age for pheasants to be released into the wild considering its impact on the subsequent survival of the released birds. Birds released at an older age and thus accustomed to repeated disturbances during captive rearing may have impaired defence behaviour.

"I just became like a log of wood … I was paralyzed all over my body": women's lived experiences of tonic immobility following rape

Tonic immobility is considered the last involuntary self-protecting act/mechanism experienced by victims of rape when they are under attack. It is associated with trauma related mental health risks post-rape. Despite this, tonic immobility has not received priority as an area of research on Nigerian female victims of rape. As a result, little has been known about this phenomenon by nurses and other professionals who are involved in the care and management of rape survivors in Nigeria. The limited knowledge about tonic immobility as a phenomenon might have resulted in mismanagement and secondary victimization of rape victims experiencing manifestations suggestive of tonic immobility during or after rape. This study was a qualitative narrative inquiry that explored, analysed, and interpreted the lived experiences suggestive of tonic immobility, and the meaning attached to such experiences by victims. A sample of fourteen Nigerian women who self-identified as rape victims was utilized. Individual semi-structured, in-depth interviews were conducted to generate data. Thematic data analysis revealed four overarching themes: namely (i) Tonic immobility as an Altered Physical State, (ii) Tonic Immobility as Mental Paralysis, (iii) Painful Loss of Self-defence, and (iv) Constant Self-blame. The findings provided an insight into the traumatic experience of raped women and the psychological implication of tonic immobility as extreme defence mechanism. This study will prove invaluable to nurses and other professionals/stakeholders involved in the care and management of rape victims; to help them develop and use appropriate strategies for management and prevention of secondary victimisation.

Immobility reactions under threat: A contribution to human defensive cascade and PTSD

Violence exacts a burden on public health. Gun violence is a major trigger for motor defensive reactions in humans and post-traumatic stress disorder (PTSD) is its main psychiatric sequela. However, studies of the human defensive cascade, especially the motor reactions, are at an early stage. This review focuses on studies that employ stabilometry, a methodology that assesses whole body motor reactions, to address defensive behaviors to violence-related threats. Special attention is given to three reactions: "attentive immobility", "immobility under attack" and "tonic immobility", with emphasis on the latter - a peritraumatic reaction which has been strongly associated with the severity of PTSD. These reactions are characterized by reduced body sway and bradycardia, except tonic immobility that presents robust tachycardia. The advances made by investigations into the immobility reactions of the human defensive cascade contribute to helping to bridge the gap between human and non-human species. Furthermore, progresses in basic research to objectively monitor motor defensive reactions under threat can help to develop a dimensional, trans-diagnostic approach to PTSD.

Peritraumatic tonic immobility is associated with PTSD symptom severity in Brazilian police officers: a prospective study

OBJECTIVE

Peritraumatic reactions feature prominently among the main predictors for development of posttraumatic stress disorder (PTSD). Peritraumatic tonic immobility (PTI), a less investigated but equally important type of peritraumatic response, has been recently attracting the attention of researchers and clinicians for its close association with traumatic reactions and PTSD. Our objective was to investigate the role of PTI, peritraumatic panic, and dissociation as predictors of PTSD symptoms in a cohort of police recruits (n=132).

METHODS

Participants were asked to complete the following questionnaires during academy training and after the first year of work: Posttraumatic Stress Disorder Checklist - Civilian Version (PCL-C), Physical Reactions Subscale (PRS), Peritraumatic Dissociative Experiences Questionnaire (PDEQ), Tonic Immobility Scale (TIS), and Critical Incident History Questionnaire.

RESULTS

Employing a zero-inflated negative binomial regression model, we found that each additional point in the TIS was associated with a 9% increment in PCL-C mean scores (RM = 1.09), whereas for PRS, the increment was 7% (RM = 1.07). As the severity of peritraumatic dissociation increased one point in the PDEQ, the chance of having at least one symptom in the PCL-C increased 22% (OR = 1.22).

CONCLUSIONS

Our findings highlight the need to expand investigation on the incidence and impact of PTI on the mental health of police officers.

Is there tonic immobility in humans? Biological evidence from victims of traumatic stress

Tonic immobility, characterized by profound motor inhibition, is elicited under inescapable threat in many species. To fully support the existence of tonic immobility in humans, our aim was to elicit this reaction in a laboratory setting and measure it objectively. To mimic exposure to life-threatening events in the lab, trauma-exposed participants with PTSD (n=18) and without PTSD (n=15) listened to the script of their autobiographical trauma. Posturography and electrocardiography were employed. Reports of script-induced immobility were associated with restricted area of body sway and were correlated with accelerated heart rate and diminished heart rate variability, implying that tonic immobility is preserved in humans as an involuntary defensive strategy. Immobility reports seemed more evident in PTSD, suggesting that, in some patients, tonic immobility may be elicited during re-experiencing episodes in daily life. This study provided a measure of tonic immobility, a peritraumatic reaction for which cumulative clinical evidence had linked to the severity of PTSD.