Risk-taking in free-living spotted hyenas is associated with anthropogenic disturbance,predicts survivorship,and is consistent across experimental contexts

Anthropogenic disturbance can have important influences on the fitness and behaviors of wild animals, including their boldness when exposed to risky conditions. We presented spotted hyenas (Crocuta crocuta) from two populations, each exposed to a different level of human activity, with a life-size model hyena representing an intruder from another clan. The high-disturbance population lived adjacent to human settlements, and the low-disturbance population inhabited a relatively undisturbed part of the same national park in Kenya. The mock intruder was presented to individual hyenas to assess their reactions to an alien hyena, and to determine whether their reactions varied with their exposure to anthropogenic activity. We found that human disturbance was indeed associated with hyena risk-taking behavior in response to the model intruder. Hyenas tested in the low-disturbance area exhibited more risk-taking behaviors by approaching the mock intruder more closely, and spending more time near it, than did their counterparts living in high-disturbance areas. Hyenas that spent less time in close proximity to the model had greater survivorship than those that spent more time in close proximity to it, regardless of disturbance level. Furthermore, the individual differences in risk-taking measured here were consistent with those obtained previously from the same animals using a different set of experimental manipulations. However, the experimentally induced behaviors were not consistent with naturally occurring risk-taking behaviors in proximity to lions; this suggests that risk-taking behaviors are consistent within individuals across experimental contexts, but that exposure to lions elicits different responses. Although our results are consistent with those from earlier tests of anthropogenic disturbance and boldness in spotted hyenas and other predators, they differ from results obtained from birds and small mammals, which are generally found to be bolder in areas characterized by human disturbance.     

Ritualized behavior in a territorial limpet

The territorial system of the owl limpet Lottia gigantea Sowerby was found to have ritualized characteristics resulting in much less aggressive physical contact between interacting individuals than has been previously implied. Many limpets showed a marked evasion behavior in response to limpet contact while intruding on another limpet's territory. In addition, a resident limpet when performing an aggressive pushing response, usually only pursued an intruder it had repelled for a short distance rather than to the edge of the resident's territory as previously reported. These behaviors strongly suggest a ritualized territorial system. The push-and-pursue territorial behavior that was previously reported for L. gigantea, is the rare exception to the rule; contact between limpets usually results in the intruder retreating, either immediately or subsequent to the thrusts of the resident, the latter only rarely pursuing.     

Manifestation of active and passive defensive behavior in juvenile rats

The dynamics of freezing and flight reactions in juvenile rats was investigated. The rats were tested on the 20th, 25th, 35th, and 40th postnatal days. A sound of 6-sec duration (bell) was used as a threatening stimulus. The following parameters were recorded: number of rearing reactions and defecations within 5 min prior to stimulation, reactions to the bell, latent periods and durations of freezing reactions, freezing posture rigidity, and time of recovery of movements after freezing. It was shown that the intensity of freezing reduced in the period from the 20th to 35th postnatal day. The flight reactions were highest on the 25th and 40th days. Correlations between freezing indices and numbers of rearing and defecation reactions were different in rats of all age groups. The results suggest that the structure of defensive behavior changes with maturation of principal defensive reactions in rats within the first 40 postnatal days.     

Facilitation of hypothalamic-pituitary-adrenal responses to novel stress following repeated social stress using the resident/intruder paradigm

Our goal in these studies was to characterize some specific aspects of hypothalamic-pituitary-adrenal (HPA) activity in rats exposed to repeated social stress. We used a modification of the resident/intruder paradigm in which male intruder rats were subjected to defeat and then separated from the resident by an enclosure for a total of 30 min on Day 1. On Days 2-7, intruder rats were exposed to different resident rats every day through a wire mesh enclosure for 30 min in order to minimize injurious physical contact between the two rats. The intruder rats gained significantly less weight than controls over the 7-day period of stress though basal corticosterone levels and adrenal and thymus weights were not significantly different between the two groups. On Day 8, repeatedly stressed rats exhibited facilitation of HPA responses to novel restraint compared to controls but no differences in negative feedback sensitivity to dexamethasone (0.05 or 0.2 mg/kg) were observed. Thus, the HPA axis of socially stressed rats remains responsive to a stimulus that has never been encountered. Using this type of repeated presentation to an aggressive resident allows us to examine the neuroendocrine and behavioral consequences, and their underlying neural mechanisms, of exposure to a stressor that is social in nature and naturalistic for rodents.     

Spatial aspects of nest defence by pumpkinseed sunfish (Lepomis gibbosus): Stimulus features and an application of catastrophe theory

Using fixed stimulus dummies as territory intruders, we studied the spatial distributions of the aggressive responses made by nesting male pumpkinseed sunfish. Results replicated over three field seasons indicate that males defend two territory boundaries concurrently, depending on whether an intruder is approaching (“the defence perimeter’) or withdrawing (‘the attack perimeter’). This finding supports Zeeman's (1976) ‘cusp catastrophe model’ of nest defence. In addition, the defence perimeter remains constant over the breeding cycle while the attack perimeter varies. We discuss the ecological costs and benefits of this variation and present a motivational interpretation of the cusp catastrophe model. By varying the speed at which dummies intruded into nests, we determined that males react with a fixed latency to intruders at a fixed distance from the nest. Finally, the spatial distributions of male defence responses were partially determined by the location of the nest rim, but were unaffected by dummy size (contrary to Zeeman's model) or posture.     

Additional Information on the Relationship between Intra-specific Aggression and Anti-predator Behaviour in the Three-spined Stickleback,Gasterosteus aculeatus

18 non-breeding three-spined sticklebacks from a heavily predated site a further 24 fish from a predator-free site were screened for their responses to a realistic model pike. The behaviour of the same fish when confronted with a territorial intruder during the breeding season was also recorded, the two tests being carried out in random sequence and with an interval of at least 6 weeks. Multivariate analyses identified major behavioural dimensions in the pike test and in the intruder test, summarized by the labels ‘boldness’ and ‘aggression’ respectively. Sticklebacks from the heavily predated site were both less bold and less aggressive than those from the unpredated site. Levels of aggression for individuals within each population were positively correlated with their boldness scores, but only for the period when the subjects were recovering from a simulated predatory attack.     

Neuron activity in the motor cortex of a cat with inhibition of a conditioned postural change reflex

A study was made of the neuron spike reactions in the primary motor cortex of the cat in the projection zone of the contralateral forelimb with external and internal inhibition of the conditioned reflex for posture change that consisted of shifting the body weight to the forelimb being studied. Spike responses of the neurons to extraneous stimuli and the conditioned signal were determined to a significant degree by the condition of the animal and its habituation to the signal used. In trained animals, the duration of responses to extraneous stimulation was shorter than in the nontrained. With external and internal inhibition, we observed simultaneous disappearance of conditioned reflex movements and the trace spike discharges connected with them. Frequently extraneous stimulations could suppress trace discharges even when learned movement was present. Extraneous stimulations of a different modality inhibited the reflex to different degrees. The change in neuron spike reaction connected with a conditioned reflex change in posture was similar to well-learned local reflex phenomena.A. A. Bogomol'ets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 17, No. 4, pp. 489–500, July–August, 1985.     

Dynamic risk assessment: does a nearby breeding nest predator affect nest defence of its potential victim?

There is growing evidence that birds are able to discriminate different types of nest intruders and adjust their nest defence behaviour according to intruder dangerousness and distance from the nest (the dynamic risk assessment hypothesis). Here, we tested whether birds’ decisions about nest defence may additionally be affected by an increasing familiarity with a particular nest predator. We tested nest defence responses of great reed warblers Acrocephalus arundinaceus to a nest predator, the little bittern Ixobrychus minutus. Great reed warbler nests located close (≤7 m) to synchronously breeding little bitterns were “neighbour”, other nests were “solitary”. Great reed warbler specific aggression towards a little bittern dummy was much lower (~5-times) at neighbour than solitary nests. In contrast, generalised responses to a control innocuous intruder (the turtle dove, Streptopelia turtur) were statistically identical at neighbour and solitary nests. These patterns are in line with dynamic risk assessment hypothesis. We hypothesise that decreased great reed warbler aggression at neighbour nests also represents a specific behavioural adaptation to nesting in association with the little bittern. Little bitterns breeding closer to great reed warblers showed decreased risks of failure due to predation. However, further research is needed to experimentally test the causal links behind these patterns.     

How does a parent respond when its mate emphasizes the wrong role? A test using a monogamous fish

The convict cichlid fish, Archocentrus nigrofasciatus, is biparental: the male spends the majority of his time defending the territory and the female spends much of her time close to the offspring. Under natural conditions, this separation into sex-typical roles is somewhat blurred as males do spend some time with the offspring and females do attack intruders. Here we tested whether an individual selects a parental role based on the location (i.e. parental role) of its mate. For example, do females emphasize offspring care because the male is away from the offspring? Will males be more likely to care for the offspring when the female is away from the offspring? We manipulated the location of one parent by placing it in a transparent plastic box, either near the offspring or at the far end of the tank near a clear plastic compartment that held a conspecific male intruder. We tested both male and female parent under the following four conditions: boxed mate near offspring with no intruder present, boxed mate near offspring with intruder present, boxed mate near intruder compartment with no intruder present, and boxed mate near intruder compartment with intruder present. We found that both parents spent more time with the offspring and less time attacking the intruder when the mate was positioned near the offspring and more time away from the offspring and more time attacking the intruder when the mate was near the intruder. Males were more affected by the location of their mates than were females and we concluded that males were attracted both to their mates' location and their offspring while females were mostly attracted to their offspring. Overall, the location of the mate had little effect on the types of aggressive activities used against the intruder. We did find that males increased their aggression towards boxed females when they were positioned far from the offspring, whereas the aggressive behaviour of females towards boxed males when they were positioned near the offspring was ambiguous. We suggest that males in particular enforce the separation of sex-specific parental roles via this aggression.     

Sickness and Aggressive Behavior in Dominant and Subordinate Mice*

Sick animals show a set of organized behavioral changes (sickness behavior), which is the result of a motivational re‐organization of the behavior as a whole. Sickness behavior display can be influenced by the social context. In this work, we sought to investigate the regulation of sickness behavior within a pair of mice in the presence of an intruder mouse. Dominant and subordinate mice were treated with the bacterial endotoxin lipopolysaccharide (LPS) and were challenged with the presence of an intruder mouse. LPS effects depended on ranking and social context. Even though dominant mice displayed more agonistic interaction towards the intruder, subordinate mice displayed agonistic behavior towards the intruder when their dominant companion was treated with LPS. The results show that, not only sickness behavior is differentially expressed among different social ranks, but also that sickness behavior is related to different reactions among surrounding animals. These data are relevant for a biological approach to the relation between sickness behavior and social behavior.     

Genetic influences on behavioral inhibition and anxiety in juvenile rhesus macaques

In humans and other animals, behavioral responses to threatening stimuli are an important component of temperament. Among children, extreme behavioral inhibition elicited by novel situations or strangers predicts the subsequent development of anxiety disorders and depression. Genetic differences among children are known to affect risk of developing behavioral inhibition and anxiety, but a more detailed understanding of genetic influences on susceptibility is needed. Nonhuman primates provide valuable models for studying the mechanisms underlying human behavior. Individual differences in threat-induced behavioral inhibition (freezing behavior) in young rhesus monkeys are stable over time and reflect individual levels of anxiety. This study used the well-established human intruder paradigm to elicit threat-induced freezing behavior and other behavioral responses in 285 young pedigreed rhesus monkeys. We examined the overall influence of quantitative genetic variation and tested the specific effect of the serotonin transporter promoter repeat polymorphism. Quantitative genetic analyses indicated that the residual heritability of freezing duration (behavioral inhibition) is h ² = 0.384 ( P  = 0.012) and of 'orienting to the intruder' (vigilance) is h ² = 0.908 ( P  = 0.00001). Duration of locomotion and hostility and frequency of cooing were not significantly heritable. The serotonin transporter polymorphism showed no significant effect on either freezing or orienting to the intruder. Our results suggest that this species could be used for detailed studies of genetic mechanisms influencing extreme behavioral inhibition, including the identification of specific genes that are involved in predisposing individuals to such behavior.     

Response of Wolves to Experimental Disturbance at Homesites

ABSTRACT Events during the denning period (parturition to first autumn) often determine the reproductive success of wolves (Canis lupus). Consequently, there is concern about the potential adverse effects of human-caused disturbance at wolf den and rendezvous sites (homesites), but relatively little information on this subject is available. We conducted standardized experimental disturbance treatments at 12 unique wolf homesites in the Northwest Territories, Canada, during summers 2002 and 2003. The treatment consisted of an intruder approaching a homesite once per day for 3 consecutive days and recording behavioral responses, response distance, and response intensity of wolves. We counted pups and estimated their ages prior to the initial treatment at each site. Adult wolves moved pups at 3 of 6 treated homesites in each year. The amount and type of known human activity within a pack's home range did not influence whether adults moved pups in response to the treatment. The response intensity of wolves to the treatment was inversely related to the amount of human activity near a homesite. There was no relationship between the distance at which wolves responded to the intruder and the amount or type of human activity. There was a positive relationship between increasing age of pups and their relocation in response to the treatment. Reproductive success was not influenced by the treatment or by the amount and type of human activity. Treated sites were used by wolves the following year in the same proportion as untreated sites. It appears that pups are most vulnerable early in the year when less mobile; therefore, managers should consider age of pups before human activity at or near wolf homesites occurs.     

A factor analysis of fearfulness in potential guide dogs

The correlations between measurements of a variety of responses, including approach, avoidance, nature of contact with the stimulus, tail position and posture, to a large number of stimuli were analysed. In general, the measurements were correlated, indicating a general trait of fearfulness, but some of the correlations were very low. Factor analysis showed that measurements were more likely to be highly correlated if they were based on similar responses, or used similar stimuli, or were made close together in time. In most cases, it was avoidance responses which were most highly correlated with fearfulness as assessed by guide dog trainers. Adult fearfulness could be predicted to some degree from fearfulness at 3 months of age, but the accuracy of the prediction improved with age.     

The Return of the Intruder: Immediate and Later Effects of Different Approach Distances in a Territorial Songbird

Male songbirds often maintain territories throughout the breeding season, and one of the main functions of song is to deter invaders. Therefore, the distance of an unknown singing rival should play a crucial role within territorial singing interactions of males. This distance is expected to be assessed as more threatening the closer the rival approaches. Here, we tested this assumption by conducting nocturnal playbacks from two different distances in territorial Common nightingales (Luscinia megarhynchos). Immediate vocal responses of birds were examined by analysing changes in song structure as well as temporal response features. The next morning, follow‐up playbacks from an intermediate distance allowed us to investigate longer‐lasting effects of nocturnal playbacks. We found that the distance of a simulated rival had an effect on both immediate and later vocal responses of territorial male nightingales with different song parameters being affected during nocturnal and diurnal singing. This indicates that birds perceive intruder distances and adjust their response behaviour both immediately and in later interactions.     

Paracrystalline arrays of membrane-to-membrane cross bridges associated with the inner surface of plasma membrane

In cultured cells of the rat kangaroo PtK2 line, veils of the cell surface were observed which consisted of only plasma membrane and paracrystalline arrays of membrane-associated particles sandwiched in between. These membrane-to-membrane cross-bridging 9-to 11-nm wide particles were somewhat coumellar-shaped and were arranged on a hexagonal lattice with an interparticle distance of 16nm. At higher magnification, they revealed an unstained core, thus suggesting a ringlike substructure. Similar arrays of paracrystal-containing veils, which were rather variable in size and frequency, were also observed in other cultured cells. It is hypothesized that these paracrystals represent protein macromolecular complexes associated with the inner plasma membrane surface which crystallize when plasma membranes come into close intracellular contact and other components of the subsurface network are removed.     

Agonistic interactions between nymphs of Lycorma delicatula (Hemiptera: Fulgoridae)

The nymphs of Lycorma delicatula typically aggregate on tree branches for feeding. We studied agonistic interactions between nymphs in the field and investigated the effects of prior residence and body size on contest outcome. Resident nymphs maintained positions on tree branches and engaged in feeding, whereas intruding nymphs moved along tree branches. When an intruder approached, the resident typically raised its front legs as a threat posture. The intruder would either move away or palpate the resident, and the resident often lowered its body when palpated. The intruder would then attempt to shake the resident back and forth, with the number of attempts varying from one to several. The resident either maintained its position or fled. After a contest, the winner was determined to be the one occupying the contested position on the branch. The resident nymphs won 84.2% of the agonistic encounters, and the nymphs with larger body size won 63.2% of the agonistic encounters. Logistic regression analysis revealed that prior residence was a significant factor for the contest outcome, but body size was not. We discuss the hypotheses for the dominance of the residents in agonistic interactions between nymphs of L. delicatula.     

Variation in and Meaning of Alarm Calls in a Social Desert Rodent Rhombomys opimus

The great gerbil (Rhombomys opimus), a social rodent that lives in family groups, emits three different alarm vocalizations in the presence of predators: a rhythmic call; a faster more intense call; and a single whistle. We tested the hypothesis that the alarm calls communicate risk of predation. We quantified the relationship between predator distance and type of alarm call via human approaches to gerbils. We also tested responses of focal adults in family groups to playback broadcasts of the different calls and controls of bird song and tape noise. Results showed that alarm calls were related to distance from a predator. Gerbils gave the rhythmic call when the predator was farthest away, the more intense call as the predator moved closer; and a short whistle when startled by a close approach of the predator. Gerbils stopped feeding and stood vigilant in a frozen alert posture in response to playbacks of all three alarm calls. They decreased non‐vigilant behavior to the alarm vocalizations more than to the controls and decreased non‐vigilant behavior significantly more in response to the intense alarm and whistle compared with the rhythmic alarm. We conclude that one function of gerbil alarm calls is to communicate response urgency to family members. The rhythmic alarm communicates danger at a distance, whereas the intense alarm and whistle signal the close approach of a predator.     

Chinchilla (Chinchilla lanigera) behavioral responses to a visual signal preceding handling

Zoos use ambassador animals in educational programs featuring close contact with humans. Chinchillas (Chinchilla lanigera) at the Saint Louis Zoo are retrieved for programs by a keeper wearing brown handling gloves, but green cleaning gloves are worn during normal husbandry when physical contact with the animal is only incidental. The chinchillas’ primary keeper anecdotally reported more reactivity and movement from chinchillas when approached with handling gloves. Animals’ behavioral reactions to the presence of humans often include locomotion and vigilance, but these responses may be attenuated by predictability. To investigate these behaviors, handling trials involving brief contact attempts with both cleaning and handling gloves were filmed. Results indicated that chinchillas responded to disturbances by moving, jumping, and adopting more alert body postures. Surprisingly, movement was recorded in longer durations when the keeper attempted to touch the animals with cleaning gloves. This higher arousal may indicate that the animal was not expecting to be handled, yet an attempt to do so was being made. This reaction provides evidence that potentially aversive events should be reliably and consistently signaled.     

Thigh-calf contact parameters for six high knee flexion postures: Onset,maximum angle,total force,contact area,and center of force

In high knee flexion, contact between the posterior thigh and calf is expected to decrease forces on tibiofemoral contact surfaces, therefore, thigh-calf contact needs to be thoroughly characterized to model its effect. This study measured knee angles and intersegmental contact parameters in fifty-eight young healthy participants for six common high flexion postures using motion tracking and a pressure sensor attached to the right thigh. Additionally, we introduced and assessed the reliability of a method for reducing noise in pressure sensor output. Five repetitions of two squatting, two kneeling, and two unilateral kneeling movements were completed. Interactions of posture by sex occurred for thigh-calf and heel-gluteal center of force, and thigh-calf contact area. Center of force in thigh-calf regions was farther from the knee joint center in females, compared to males, during unilateral kneeling (82 and 67 mm respectively) with an inverted relationship in the heel-gluteal region (331 and 345 mm respectively), although caution is advised when generalizing these findings from a young, relatively fit sample to a population level. Contact area was larger in females when compared to males (mean of 155.61 and 137.33 cm² across postures). A posture main effect was observed in contact force and sex main effects were present in onset and max angle. Males had earlier onset (121.0°) and lower max angle (147.4°) with onset and max angles having a range between movements of 8° and 3° respectively. There was a substantial total force difference of 139 N between the largest and smallest activity means. Force parameters measured in this study suggest that knee joint contact models need to incorporate activity-specific parameters when estimating loading.     

Nest defense of the red-backed shrike Lanius collurio against five corvid species

We compared the antipredation behavior of the red-backed shrike against five European corvids including the jay, nutcracker, rook, crow, and raven. These species differ in body size and in the proportion of eggs and nestlings in their diets. The jay and nutcracker are the smallest, the rook and crow are middle-sized, and the raven being the largest corvid of all. The jay, crow, and raven are habitual nest predators, whereas the nutcracker and rook are not. The harmless pigeon was presented as a control. We analyzed (1) the number of attacks executed by shrikes against intruder presented close to shrike nests and (2) the distance between the intruder and the shrikes during the trial. The small corvids (the jay and nutcracker) were attacked significantly more intensively than the other, larger, corvids (the rook, crow, and raven) and pigeon control. All three large corvids were attacked as exceptionally as the pigeon. Shrikes approached closer to the small corvids and the pigeon than to the large corvids. These results imply that shrike antipredation strategy is adjusted to intruder size, but not to the level of intruder nest plundering specialization. Shrikes weigh up their ability to chase a given intruder away and avoid pointless aggression against large, undefeatable, intruders. This suggests that shrikes are able to asses not only the dangerousness of the intruder but also the potential advantageousness, or otherwise, of active defense.