Conspecific Threat Research Articles

Alarm cues and alarmed conspecifics: neural activity during social learning from different cues in Trinidadian guppies.

Learning to respond appropriately to novel dangers is often essential to survival and success, but carries risks. Learning about novel threats from others (social learning) can reduce these risks. Many species, including the Trinidadian guppy (Poecilia reticulata), respond defensively to both conspecific chemical alarm cues and conspecific anti-predator behaviours, and in other fish such social information can lead to a learned aversion to novel threats. However, relatively little is known about the neural substrates underlying social learning and the degree to which different forms of learning share similar neural mechanisms. Here, we explored the neural substrates mediating social learning of novel threats from two different conspecific cues (i.e. social cue-based threat learning). We first demonstrated that guppies rapidly learn about threats paired with either alarm cues or with conspecific threat responses (demonstration). Then, focusing on acquisition rather than recall, we discovered that phospho-S6 expression, a marker of neural activity, was elevated in guppies during learning from alarm cues in the putative homologue of the mammalian lateral septum and the preoptic area. Surprisingly, these changes in neural activity were not observed in fish learning from conspecific demonstration. Together, these results implicate forebrain areas in social learning about threat but raise the possibility that circuits contribute to such learning in a stimulus-specific manner.

Temporal patterns in the social network of core units in Rwenzori Angolan colobus monkeys: Effects of food availability and interunit dispersal.

Multi‐level societies are complex, nested social systems where basic social groups (i.e., core units) associate in a hierarchical manner, allowing animals to adjust their group sizes in response to variables such as food availability, predation, or conspecific threat. These pressures fluctuate over time and examining the extent to which this variation affects the clustering of core units into different tiers may be instrumental in understanding the evolution of multi‐level societies.The goal of our study was to determine the degree of temporal variability in interunit associations in a multi‐level society of Rwenzori Angolan colobus monkey (Colobus angolensis ruwenzorii), and to determine the social and ecological factors that underlie association patterns. The C. a. ruwenzorii multi‐level society consists of at least three tiers, with core units clustering into clans that share a home range in a band tier.We performed social network analyses on 21 months of association data from 13 core units (totaling 139 identifiable individuals) at Lake Nabugabo, Uganda. We described the patterns of variation in core‐unit associations over time and investigated how changes in rainfall, food availability, and interunit dispersals were correlated with these associations over the short‐term (month to month) and long‐term (year to year).Although clans were relatively stable, larger‐scale changes in association patterns included the formation of an all‐male unit and the transfer of one core unit between clans (within the band tier). Seasonally, core units associated significantly more when fruit, their preferred food source, was abundant (i.e., social networks were denser and more clustered) and there was no direct effect of rainfall seasonality or young leaf availability. Male dispersals also occurred more during periods of high fruit availability, suggesting that greater band cohesion allowed males to prospect and transfer between core units. Once males transferred, their previous and new units associated significantly more with one another than with other core units for 1–2 months postdispersal. The dispersal of five males from one core unit to another in a different clan co‐occurred with this core unit switching its clan affiliation.By examining temporal shifts in social network structure among core units, this study shows the interconnected roles that food availability and dispersal have in shaping the C. a. ruwenzorii multi‐level social system. Our findings highlight how ecological conditions can drive association patterns, impact interunit relationships, and influence social organization.

Testing conditions in shock-based contextual fear conditioning influence both the behavioral responses and the activation of circuits potentially involved in contextual avoidance

Previous studies from our group have shown that risk assessment behaviors are the primary contextual fear responses to predatory and social threats, whereas freezing is the main contextual fear response to physically harmful events. To test contextual fear responses to a predator or aggressive conspecific threat, we developed a model that involves placing the animal in an apparatus where it can avoid the threat-associated environment. Conversely, in studies that use shock-based fear conditioning, the animals are usually confined inside the conditioning chamber during the contextual fear test. In the present study, we tested shock-based contextual fear responses using two different behavioral testing conditions: confining the animal in the conditioning chamber or placing the animal in an apparatus with free access to the conditioning compartment. Our results showed that during the contextual fear test, the animals confined to the shock chamber exhibited significantly more freezing. In contrast, the animals that could avoid the conditioning compartment displayed almost no freezing and exhibited risk assessment responses (i.e., crouch-sniff and stretch postures) and burying behavior. In addition, the animals that were able to avoid the shock chamber had increased Fos expression in the juxtadorsomedial lateral hypothalamic area, the dorsomedial part of the dorsal premammillary nucleus and the lateral and dorsomedial parts of the periaqueductal gray, which are elements of a septo/hippocampal–hypothalamic–brainstem circuit that is putatively involved in mediating contextual avoidance. Overall, the present findings show that testing conditions significantly influence both behavioral responses and the activation of circuits involved in contextual avoidance.

What lies beneath the face of aggression?

Recent evidence indicates that a sexually dimorphic feature of humans, the facial width-to-height ratio (FWHR), is positively correlated with reactive aggression, particularly in men. Also, predictions about the aggressive tendencies of others faithfully map onto FWHR in the absence of explicit awareness of this metric. Here, we provide the first evidence that amygdala reactivity to social signals of interpersonal challenge may underlie the link between aggression and the FWHR. Specifically, amygdala reactivity to angry faces was positively correlated with aggression, but only among men with relatively large FWHRs. The patterns of association were specific to angry facial expressions and unique to men. These links may reflect the common influence of pubertal testosterone on craniofacial growth and development of neural circuitry underlying aggression. Amygdala reactivity may also represent a plausible pathway through which FWHR may have evolved to represent an honest indicator of conspecific threat, namely by reflecting the responsiveness of neural circuitry mediating aggressive behavior.

Cost-free vigilance during feeding in folivorous primates? Examining the effect of predation risk, scramble competition, and infanticide threat on vigilance in ursine colobus monkeys (Colobus vellerosus)

Vigilance often decreases with increasing group size, due to lower predation risk or greater scramble competition for food. A group size effect on vigilance is seldom seen in primates, perhaps because scanning and feeding often occur simultaneously or because the distinction between routine and induced vigilance has not been investigated. We analyzed feeding and resting observations separately while distinguishing between routine and induced scans in four groups of wild ursine colobus monkeys (Colobus vellerosus) experiencing scramble competition for food and infanticide risk. We used linear mixed-effect models to test the effect of group size, age–sex class, number of neighbors, number of adult male neighbors, and height in the canopy on scanning rates (vigilance) with and without evident conspecific threat. Food type was also examined in the feeding models. Perceived predation risk affected vigilance more than scramble competition for food and infanticide risk. Routine and induced vigilance were greatest at lower canopy heights during feeding and resting and increased when individuals had fewer neighbors while resting. A group size effect was found on induced vigilance while resting, but scanning increased with group size, which probably indicates visual monitoring of conspecifics. Scanning rates decreased while feeding on foods that required extensive manipulation. This supports the idea that vigilance is relatively cost free for upright feeders when eating food that requires little manipulation, a common feature of folivore diets. In the presence of threatening conspecific males, close proximity to resident males decreased individual vigilance, demonstrating the defensive role of these males in the group.

Vigilance in ursine black and white colobus monkeys (Colobus vellerosus): an examination of the effects of conspecific threat and predation

Vigilance is thought to have evolved as an antipredator defense but, in primates, conspecific threat often better explains this behavior. We examined vigilance in one group of Colobus vellerosus inhabiting the Boabeng-Fiema Monkey Sanctuary in Ghana. We aimed to (1) describe factors affecting vigilance in this population, and (2) examine the importance of predation avoidance and conspecific threat in explaining vigilance patterns. Because of a male takeover preceding the study, our focal group (B2) consisted of six adult males and three adult females. We collected 490 10-min focal samples (82 hr) from all adults in the group (N=9) from July to November, 2001. To avoid predators, individuals should be more vigilant (i) with fewer neighbors, and (ii) in areas of the canopy with higher predation risks. Conspecific threats can be divided into extra- and intra-group threats. Extra-group threats should lead to higher vigilance levels (iii) during intergroup encounters, and (iv) in areas where the home range overlaps with other groups of colobus. Intra-group threats should lead to greater vigilance (v) in the presence of neighbors and (vi) while feeding or occupying food patches (if resources are limiting). Our results best support the hypothesis that vigilance functions primarily to detect extra-group, conspecific threats. Individuals were most vigilant during intergroup encounters and in areas of range overlap, and monthly vigilance rates were associated with monthly encounter rates. Individuals tended to scan less in proximity to familiar vs. unfamiliar group mates, suggesting that relationship quality may affect colobus vigilance. Finally, predation pressures or anthropogenic disturbances might have influenced vigilance, as individuals were more vigilant low in the canopy. However, this last result could also be due to the lower visibility because of dense foliage or to the fact that the monkeys have access to fewer escape routes when ranging lower in the canopy.

Conspecific Influences on Vigilance Behavior in Wild Chimpanzees

Diurnal primates rely on visual monitoring behavior to collect various kinds of ecological and social information. Vigilance behavior is monitoring specifically to detect external threats. Previous studies of vigilance behavior were focused mainly on the influence of predation threats, whereas the influences of conspecific factors, such as intragroup threats, have been relatively unstudied. Individual vigilance is predicted to be inversely related to the group size or the number of individuals nearby if the main target of the vigilance is a predation threat and positively related if the main target of the vigilance is a conspecific threat. I studied wild chimpanzees (Pan troglodytes schweinfurthii) in Mahale Mountains National Park, Tanzania, and measured the vigilance duration when they are resting on the ground via 2-min focal observation. In both males and females, vigilance duration increased as the number of individuals nearby increased. This result agrees with the idea that the chimpanzees are vigilant toward other group members. In addition, maternal vigilance monitors and protects the safety of dependent offspring as the duration of maternal vigilance was longer when a dependent infant was separated from its mother than when the offspring was in contact with its mother. The results indicate that the vigilance behavior in wild chimpanzees was affected by conspecific factors.

Effects of d-amphetamine on defensive behaviors related to fear and anxiety

In rodents, the administration of amphetamine has been associated with increased locomotor activity and stereotypy, and an emerging body of evidence suggests that it also enhances anxiety-like behavior in a number of animal models. Ethoexperimental analyses have outlined an array of defensive behaviors to threat that are responsive to anxiolytic, panicolytic-like and panicogenic agents, suggesting that the characterization of amphetamine effects on defense may provide further insights into the emotionality consequences of this drug. In Experiment 1, intraperitoneal administration of amphetamine (1 and 5 mg/kg, i.p.) on defensive behavior elicited by a predatory threat stimulus was assessed via time sampling analysis. Amphetamine dose-dependently suppressed freezing while potentiating locomotor activity. In Experiment 2, amphetamine was administered intravenously and animals were tested in a Rat Runway Test (RRT), designed to individually elicit a variety of defensive behaviors to a conspecific threat. All three doses of amphetamine (1, 2 and 5 mg/kg) produced robust changes in defensive responding by increasing directional flight behavior, jump escapes and upright/orientations. The results are in agreement with those of another psychostimulant, cocaine, and support a previously hypothesized link between flight and panic.

Males as infant protectors in Hanuman langurs ( Presbytis entellus ) living in multimale groups - defence pattern, paternity and sexual behaviour

Hypotheses about the evolution of gregariousness and social organisation in primates are based on ecological explanations as well as on social factors such as conspecific threat (especially infanticide by males). The social explanation fits well with the conditions found in strepsirrhine primates and furthermore explains why infanticide in anthropoid primates living in one-male groups mainly occurs when the resident male (protector) is replaced. However, whether it likewise fits to the conditions in multimale groups will depend on the role of resident males as infant protectors, which has rarely been examined. We investigated long-term data of wild Hanuman langurs (Presbytis entellus) inhabiting a forest near the village of Ramnagar (southern Nepal). Twenty-two eye-witnessed attacks on infants by males were analysed in connection with male residency, paternity (DNA analyses) and sexual behaviour. Adult males played a major role in infant defence (65%). Only the genetic father or males who had been residents when the infant was conceived were observed to protect infants. Males who immigrated after a female had conceived may later attack her infant and were never observed to defend it. lt seems that the males took only copulations with potentially fertile females but not with pregnant females as clues for paternity. In the light of these results it seems likely that the risk of infanticide is an important determinant in female-male associations even in anthropoid primate multimale groups.

Conspecific threat, predation avoidance, and resource defense: implications for grouping in langurs

Data on langur (Presbytis entellus) populations were gathered from the literature to test the importance of three selective pressures in determining group size and composition: predation pressure, intergroup resource defense, and conspecific threat. There were no detectable difference in the size of groups in populations facing nearly intact predator communities compared to those populations where predators were severely reduced in number or absent, although there was a trend for the number of adult males per group to increase in areas with nearly intact predator communities. Using population density as an indirect measure of the frequency of intrusions into a group’s home range and thereby as an index of the demographic pressure favoring resource defense, we predicted that higher densities would result in larger defensive coalitions and higher numbers of females per group. This prediction was not upheld. Our third selective pressure, conspecific threat, encompasses those selective forces resulting from physical attack on females, infants, and juveniles. Our index of conspecific threat uses the number of non-group males divided by the number of bisexual groups, because in langurs, the major source of conspecific threat derives from non-group males who, following group take-over, kill infants, wound females, and expel juveniles from groups. This index of conspecific threat was strongly related to the mean number of resident females, was weakly related to the mean group size, but was not related to the number of males in the group. In addition, as predicted, populations with a high index of conspecific threat had higher levels of juvenile expulsion. These analyses were corroborated by a simulation model which used a computer-generated series of null populations to calculate expected slopes of immatures regressed on adult females. These randomly generated populations, matched to means and ranges of real populations, allowed us to determine if deviations of the observed slopes from the expected null slopes could be explained by variation in predation pressure, population density, or conspecific threat. We found no evidence that predation pressure was associated with decreases in immature survival in smaller groups, as would be predicted by the predation-avoidance hypothesis. We found no evidence that immature survival was compromised by small group size in high-density populations, as would be predicted by the resource-defense hypothesis. However, as the index of conspecific threat increased, groups with larger numbers of females were more successful than groups with fewer females in reducing mortality or expulsion of immatures. Overall, conspecific threat received the strongest support as a selective pressure influencing langur group size and composition, suggesting that this selective pressure should be evaluated more widely as a factor influencing composition of animal groups.

Ontogeny of Stress-Induced Ultrasonic Vocalization and Pituitary-Adrenal Hormone Secretion in Preweanling Norway Rats

Adult organisms rapidly exhibit protective behavioral responses when threatened. In addition, physiological systems are activated reflexively to facilitate survival. How these defensive systems are integrated in order to produce appropriate responding demands a developmental psychobiological analysis. This paper summarizes studies examining in the Norway rat the concurrent ontogeny of 30-50 kHz ultrasonic vocalizations and pituitary-adrenal hormone responses induced by stressors presented during the preweaning period. Postnatal Day 7 male rats exposed to social isolation emit significantly more ultrasounds than Day 14 pups, and by 21 days of age social isolation is no longer effective in eliciting ultrasonic vocalizations. This age-dependent attenuation in occurrence of ultrasounds is accompanied by an increased responsiveness of the pituitary- adrenal system. Studies incorporating the use of psychophysical, that is, electric foot shock, and psychological, that is, conspecific threat, stressors indicate further that exposure to such stimuli significantly reduces in Day 14 rats the emission of ultrasonic vocalization but may potentiate their occurrence in Day 7 pups. Application of foot shock reliably induces ultrasonic emission in normally silent Day 21 pups as in adult rats. The hormonal response to these stressors is similar to that found in pups exposed to social isolation; pituitary adrenocorticotropin and adrenal corticosterone secretion increases significantly in Day 14 pups and a further notable increased secretion occurs in Day 21 males and reflects the intensity of the stressor. The increased secretion of pituitary-adrenal hormones coupled with the modulatory capacity to reduce ultrasonic vocalizations by 14 days of age suggest that systems have developed to provide increased behavioral and physiological flexibility during confrontations with varied threats.

Individual differences in temporal lobe sensory processing of threatening stimuli in the cat

In Experiment I, neurosensory responses from three limbic areas in the cat brain were recorded when cats of differing defensive temperamental traits were exposed to species characteristic threat. The cats investigated were more or less defensive in response to rats and conspecific threat howls. The behavioral disposition of these cats was stable over retest periods of more than one year. It was found that during visual inspection of rats, more defensive cats displayed greater neural activity in the amygdala and the ventromedial hypothalamus than less defensive cats, who showed no change over baseline. Neurosensory response of the amygdala to conspecific threat howls was also found to be greater in more defensive cats. In contrast, there was no neural response to threat howls in the hypothalamus. Neurosensory response to mice was different from the response to rats and threat howls. Visual inspection of the mouse was associated with a decrease in activity in the amygdalas of more difensive cats. Finally, response of the ventral hippocampus was unspecific, appearing to signal only a change in the stimulus environment. The increase in hypothalamic neural activity in response to rats in more defensive cats appeared to be driven by a potentiated output from the amygdala, since the ratio of hypothalamic to amygdala neurosensory response to rats was greater than one in more defensive cats, but equal to one in less defensive cats. Output of the amygdala was directly investigated using evoked potential techniques in Experiment II. Potentials evoked in the hypothalamus by amygdala stimulation were larger in more defensive cats. Size of the hypothalamic potential was highly correlated with the ratio of hypothalamic to amygdala neurosensory response (ratio response) to rats. Removing the effects of size of the hypothalamic evoked potential from the ratio response by analysis of covariance eliminated the difference between more and less defensive cats in ratio response to rats. The significance of these findings for the physiological bases of defensive response to threat and of temperamental traits are discussed.

Partial kindling of the ventral hippocampus: Identification of changes in limbic physiology which accompany changes in feline aggression and defense

This study examined the interictal consequences of partial kindling of the ventral perforant path on attack and defensive behavior in the domestic cat. Partial kindling produced a lasting increase in defense response of cats to both rats and conspecific threat howls. In addition, there was a lasting suppression of approach-attack behaviors directed toward rats. The suppression of some components of approach-attack were shown to be independent of the increases in defensive response. The effects of partial kindling of the ventral perforant path on spread of seizure activity into the amygdala, and on the output of the amygdala to both the ventromedial hypothalamus (VMH) and bed nucleus of the stria terminalis (BNST) were also examined. In addition, the effects of repeated hippocampal seizures on recurrent inhibition in the trisynaptic circuit (areas CA1 and CA3) were investigated. Growth of seizure activity in the amygdala and VMH as partial kindling progressed was essential for behavioral change. In addition, interical long-term potentiation of potentials evoked in the VMH and in the BNST by pulsed stimulation of the amygdala followed partial kindling or afterdischarge threshold determination in the ventral perforant path. A lasting interictal increase in inhibition in area CA3 and a lasting interictal failure of inhibition in area CA1 of the ventral hippocampus also followed partial kindling. These changes in limbic physiology were related to the behavioral changes produced by partial kindling. The analysis revealed the importance of the amygdalo-VMH pathway in increased defensive response to rats. The amygdalo-BNST pathway is not important in mediating defensive response to prey, but it is implicated in suppression of some types of predatory aggression. Finally, changes in neural inhibition in the ventral hippocampus in areas CA1 and CA3 are associated with changes in both defensiveness and predatory aggression.

Acute and lasting effects of FG-7142 on defensive and approach-attack behavior in cats—implications for models of anxiety which use response suppression

The effect of the anxiogenic β-carboline, FG-7142, on defense and approach-attack behavior in the cat was investigated. FG-7142 (10 mg/kg) enhanced defensive responses to rats and mice when tested 10 and 20 min after injection. At the same time, FG-7142 suppressed approach and attack responses to prey. Behavioral effects of FG-7142 were blocked by the specific benzodiazepine receptor blocker RO-15-1788 (10 mg/kg). One or two administrations of FG-7142 were sufficient to produce a lasting (up to 105 days) enhancement of defensive response to rats but not to mice. Defensive response to conspecific threat vocalizations was also lastingly increased. Two injections of FG-7142 produced a lasting suppression of approach-attack on rats only, whereas one injection of FG-7142 did not. The lasting suppression of some measures of approach-attack was found to be independent of the fear-enhancing properties of FG-7142. Tests of the effects of RO-15-1788 on the lasting after-effects of FG-7142 revealed at least two mechanisms which mediate the lasting changes in behavior, one which is dependent upon the benzodiazepine receptor and one which is not. The implications of these findings for rodent models of anxiety which use response suppression to assess fearful 'anxiogenic' effects of drugs are discussed.

Specificity of the cardiac response to conspecific vocalization in chimpanzees.

Heart rate measures were used to examine the functional response of young chimpanzees and orangutans to acoustic stimuli, including white noise and chimpanzee vocalizations (threat, stress, and alarm). The initial response of the animals to all stimuli was characterized by a prominent cardiac deceleration and an increase in heart period variability. The deceleratory responses persisted with repeated presentations of the noise, stress, and alarm stimuli. In contrast, the response of chimpanzees to the conspecific threat stimulus reverted over trials to a notable cardiac acceleration. This acceleratory response was not attributable to potential patterns of evoked somatic responses. The features of the cardiac response, together with the results of frequency-domain analyses of heart period variability, suggest that this acceleratory response was consistent with the evocation of an aversive or a defensive reaction characterized by sympathetic activation. This pattern of cardiac response appeared early in ontogeny (within 48 hr postnatally) and was not manifest in orangutans. Taken together, the results suggest the existence of specialized perceptual processing mechanisms for vocal stimuli in the chimpanzee. Further examination of these mechanisms may contribute to our understanding of central perceptual processes and the evolution of vocal communication.

Defensive behaviors of laboratory and wild Rattus norvegicus..

Analysis of the defensive behaviors of wild rats to an inescapable approaching threat stimulus (the experimenter) indicated a pattern of freezing to distant stimuli, giving way to vocalization, jumps, and jump-attacks at shorter defensive distances. Comparisons of the defensive reactions of wild-trapped and laboratory-bred wild rats to a variety of threatening stimuli, in escapable as well as inescapable situations, indicated that the two wild strains were similar and consistently more defensive than laboratory rats to both human and conspecific threat stimuli. These results thus suggest that the defensive behaviors of rats have been substantially reduced during the process of domestication, with relatively little of this reduction being attributable to housing in standard laboratory conditions.

Epileptiform effects of met-enkephalin, β-endorphin and morphine: Kindling of generalized seizures and potentiation of epileptiform effects by handling

Repeated spaced injection of small amounts of β-endorphin or Met-enkephalin into the hippocampus or posterior amygdala of the rat led to the development of kindled generalized convulsions. Similar injection of morphine into the hippocampus or anterior amygdala resulted in epileptiform spiking followed by tolerance. The epileptiform spiking and convulsive behavior varied in a dose-related manner. Naloxone blocked or greatly attenuated the electrographic seizure and convulsive behavior. Prior kindling with β-endorphin or Met-enkephalin significantly facilitated electrical kindling of the amygdala. Handling or conspecific threat potentiated the epileptiform spiking and convulsive behavior in some cases. The results indicate that the epileptogenic response to intracerebrally applied opioid peptides is site-specific within the rat brain, and they support the idea that endogenous opioid mechanisms may play a role in convulsive seizures. They also suggest a possible opiate-based mechanism for the stress-induced exacerbation of seizures.

Intracerebral beta-endorphin, met-enkephalin and morphine: kindling of seizures and handling-induced potentiation of epileptiform effects.

The effects of repeated infusion of small, initially subconvulsive amounts of beta-endorphin, met-enkephalin or morphine sulfate into the amygdala and hippocampus were investigated. beta-endorphin and met-enkephalin evoked epileptiform spiking when infused into the posterior amygdala or ventral hippocampus. Morphine evoked epileptiform spiking when infused into the anterior amygdala. Naloxone blocked or terminated the spiking. Repetition of the infusions led to the gradual development of bilateral generalized convulsions by beta-endorphin and met-enkephalin and to the development of tolerance to morphine. An unexpected observation was that handling, immobilization or conspecific threat potentiated the epileptiform effects of beta-endorphin and morphine in many cases. These results suggest that endogenous opiate mechanisms might play a role in convulsive seizures and that stressful stimuli can exacerbate opiate seizures.

Partial kindling and emotional bias in the cat: lasting aftereffects of partial kindling of the ventral hippocampus: I. Behavioral changes

Repeated electrical evocation of afterdischarges in the perforant-path ventral hippocampal system of the cat produces lasting changes in species characteristic behavioral responses to environmental threat. After 7 to 12 afterdischarges, cats showed greatly enhanced defensive (withdrawal) responses to rats, and mildly enhanced defensive responses toward mice. Measures of predatory attack which negatively correlate with withdrawal from rats were also changed in a direction consistent with the increase in withdrawal tendency. There was little effect of afterdischarges on the same parameters of attack on mice. Thus the stimulation seemed to attenuate predatory aggression by increasing defensive sensitivity to the threat posed by prey self-defense, and not by reducing predatory motivation per se. The change in defensiveness was not restricted to the predatory test situation, however. Tests of defensive response to conspecific threat vocalizations revealed an increased defensive responding to this stimulus as well. On the other hand, there was no change in social responsiveness shown toward a highly familiar human. Given the sudden onset (1 hr to 24 hr after the last afterdischarge), the long-lasting nature of the change (30-60 days) which persisted in the absence of seizures, and the generality of expression of the behavioral change, it was concluded that the afterdischarges produced an interictally maintained alteration in a defensive personality characteristic of the cats.

The expression of an early developmentally emergent defensive bias in the adult domestic cat (Felis catus) in non-predatory situations

Previous research has revealed that in some cats, predisposition to respond defensively towards rats emerges early in life, between 30 and 50 days of age, and persists into adulthood. The present study examined the generality of this defensive bias toward prey. Cats whose developmental history and defensive biases toward prey were known were exposed to 3 testing situations representing threats of differing degree: (1) a novel room; (2) a familiar human in a relatively novel environment; (3) recorded conspecific threat vocalizations. Measures of unwillingness to explore novel environments olfactorily, to purr during human social contact and readiness to adopt defensive immobility patterns of behavior in response to conspecific threat all correlated with defensive response to rats, and were found to distinguish between predatorily aggressive and non-aggressive (defensive) cats. It was concluded that there appears to be a defensive cat “personality” which emerges within the first 30–50 days of life.