Predatory attack by rats: Its relationship to feeding and type of prey.

Investigated mouse killing behavior in 5 experiments with male Long-Evans rats (N = 233). Hunger potentiated mouse killing by naive Ss, but not by Ss familiarized with mice before and during food deprivation. Once Ss had been made hungry, mouse killing was unaffected by increasing or decreasing severity of food deprivation or by time of testing with respect to a regular feeding hour. Ss fed either dead mice, powdered chow, or hard pellets while on cyclic food deprivation were about equally likely to kill, showing that hunger does not indirectly potentiate killing by increasing practice of responses like pouncing and biting. Whether hungry or not, killers were likely to eat their prey, whereas nonkillers were unlikely to eat the same prey. Ss killed 12-14 day-old rat pups as often as they killed mice, but killed weanling rat pups less often. Findings question several common notions regarding predatory aggression. (26 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Killing of conspecific and mouse young by male rats.

Conducted 6 experiments, using approximately 375 male Long-Evans rats. The probability that male rats would kill and eat rat pups was inversely related both to age of the pup and to the amount of prior exposure to pups. Also studied were (a) the effects of hunger and subsequent food satiation on killing of neonatal rat pups, (b) the generalization of experience in killing neonatal rat pups to the killing of weanling rats and of mice, (c) the effect of nonkilling experiences with either neonatal rat pups or with weanling rats in reducing the probability of killing neonatal rat pups, and (d) the effects of these variables when mouse pups were the stimuli. The data suggest that (a) neonatal pups, conspecific or not, were killed because they were perceived as food and not because they triggered aggressive response systems, (b) older pups did trigger aggressive response systems, and (c) species-specific characteristics of rat pups triggered maternal response systems in the male rat with a subsequent decrease in the incidence of rat pup killing. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of prior prey-eating experiences in the initiation of predation by rats.

Studied mouse killing by more than 400 male and female Sprague-Dawley rats in 6 experiments after Ss had been maintained on various flesh diets. Ss maintained on dead mice killed live mice more often than did Ss on Purina Chow, under both ad-lib feeding and food deprivation conditions. The effect was not dependent on these eating experiences taking place early in life, but there was suggestive evidence that the more there were of such feedings, the higher were the probabilities of subsequent killing. Ss maintained on flesh diets other than dead mice did not kill more than did Purina-maintained controls. Consequently, neither a chemical mechanism that would prime brain centers for predatory attack nor response-learning (e.g., biting hard) processes easily account for the phenomenon. Rather, stimulus generalization, the transfer of biting a dead mouse to biting a live mouse, is the simplest explanation. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Predation: Separation of aggressive and hunger motivation by conditioned aversion.

Reports results of 2 experiments with a total of 50 male Long-Evans rats. In Exp I, Ss were given LiCl 15 min after ingesting mice or saccharin for either 1 day or 4 days. Intake of both substances dropped in the 1-trial groups but not in the 4-trial groups. In Exp II, Ss that received LiCl after killing mice they were not permitted to eat showed no changes in mouse killing. Ss permitted to feed on mice they had killed continued to kill but ate less after a single LiCl trial. Feeding and killing appear to be separable by this technique. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mouse killing induced by para-chlorophenylalanine injections or septal lesions but not olfactory bulb lesions is similar to that of food-deprived spontaneous killers.

Compared mouse killing induced by septal lesions, olfactory bulb lesions, or parachlorophenylalanine (PCPA) injections in 21 rats with the behavior of 14 sated or 10 food-deprived spontaneous mouse-killing rats to evaluate whether the experimentally induced killing corresponded to killing that occurred spontaneously. On the 1st mouse kill, the intensity of the initial reaction to the mouse, the site of the initial attack, and the time required to kill by all groups were similar except that bulbectomized Ss required longer to kill. Following the kill, only Ss with septal lesions and bulbectomized Ss bit the mouse significantly more than spontaneous killers. With the 2nd mouse kill, there was an increase in the intensity of the response to the mouse and a decrease in attack latency by all groups except the bulbectomized Ss and the nondeprived spontaneous killers. When presented with a freshly killed mouse, Ss with septal lesions attacked with the greatest intensity, but PCPA-injected Ss and food-deprived spontaneous killers also attacked more intensely than nondeprived killers. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The ontogeny of a natural food aversion in domestic rats (Rattus norvegicus) and house mice (Mus musculus).

During a 1-hr feeding test, 34 hungry male Long-Evans rats that had been reared individually from weaning with a Swiss Webster house mouse were less likely to feed on the intact carcass of a freshly sacrificed mouse than were 39 rats that had been reared individually with another rat. Likewise, 42 hungry mice that had been reared individually with a rat were less likely to feed on a dead rat than were 29 mice that had been reared individually with another mouse. Regardless of the social conditions during rearing, hungry mice were more likely to feed on a dead mouse than were hungry rats to feed on a dead rat. Findings suggest that the tendency by rats to reject conspecific flesh stems, at least in part, from prior experience with conspecifics and with their own bodies. The experiential factors mediating the tendency by mice to reject conspecific flesh remain unclear. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfactory bulbectomy and mucosal damage: Effects on copulation, irritability, and interspecific aggression in male rats.

Assigned 77 male hooded rats to groups receiving bilateral olfactory bulb ablations or nasal mucosal damage with zinc sulphate and to control groups. Bilateral olfactory bulbectomy resulted in markedly impaired copulation, irritability, and an increase in the number of Ss which would kill mice. Damage to the nasal mucosa did not change copulatory effectiveness or mouse killing, and resulted in transient mild irritability. Change in irritability was significantly correlated with mouse killing in both groups. It is concluded that the effects of bulbectomy are not due to an olfactory deficit, but rather to the olfactory deficit combined with the central nervous ablation, and that the bulbectomy-induced mouse killing and irritability may be the result of altering a common motivational mechanism. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Suppression of mouse killing and apomorphine-induced social aggression in rats by local anesthesia of the mystacial vibrissae.

Local anesthesia of the facial epidermis can effect a substantial decrease in shock-elicited fighting of paired rats. The present experiments constitute methodological extensions to mouse killing and spontaneous drug-induced social aggression. In Exp I 28 known mouse-killing male Long-Evans hooded rats were given bilateral lidocaine or placebo injections administered under ether anesthesia. Attack and kill latencies were significantly longer under lidocaine than under placebo; all Ss killed under placebo, whereas a third of all Ss failed to kill on the initial lidocaine test. On subsequent lidocaine testing, latencies decreased and nonkilling Ss killed. In Exp II intense apomorphine-induced conspecific fighting of 48 Ss preselected for aggressiveness was markedly reduced following lidocaine anesthesia. Comparative results of both experiments are interpreted in reference to theoretical assertions regarding the import of sensory information in stimulus-bound attack and the typology of central aggression systems. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of target movement on mouse-killing attack by rats.

Tested 2 groups of 30 naive Long-Evans hooded rats for their reaction to motionless anesthetized mice and to active normal mice. Group 1 was tested 1st with normal mice, and Group 2 was tested 1st with anesthetized mice. More Ss in both groups killed anesthetized than normal mice, and more Ss in Group 2 than in Group 1 killed both types of mice. Normal mice were attacked faster and attacks on anesthetized mice were not stereotyped unless experience in attacking normal mice preceded. Probability of killing normal mice was increased following experience with anesthetized mice, and probability of killing anesthetized mice was decreased following experience with normal mice. (22 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of preadolescent experiential factors on the development of sexual behavior in albino rats.

Weaned 48 male Charles River rat pups at 14 days of age and then maintained them in groups or isolation within either restricted or play-enriched environments. At approximately 120 days of age, Ss were given 4 mating tests, 7 days apart. Isolation resulted in a marked reduction of Ss exhibiting appropriate sexual behavior. Play-enriched environments significantly decreased aberrant sexual behaviors such as climbing but also tended to reduce rather than enhance the level of sexual responding, as had been predicted. It is suggested that social grooming is likely to be a more critical factor than play in the development of normal sexual behavior in rat pups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Some determinants of a natural food aversion in Norway rats.

Adult male Long-Evans rats were permitted to feed on the carcasses of adult male rodents, freshly sacrificed by CO? asphyxiation. In a 2-choice preference test (Exp I), hungry Ss were offered 1 conspecific and 1 house mouse, the pair of carcasses being either intact or skinned. 18 Ss offered intact carcasses fed on the mouse or on neither carcass, but 18 Ss offered skinned carcasses fed indiscriminately, usually on both carcasses. In Exp II, 10 hungry Ss that earlier had observed a cagemate feeding on intact conspecific carcasses fed more readily on a similar carcass during a single-choice test than did 8 controls. In Exp II, 20 food-deprived Ss (96 hrs) fed more readily and consumed more tissue from an intact conspecific carcass than did 20 nondeprived Ss. It is concluded that the aversion to feeding on the intact carcass of a freshly sacrificed adult conspecific is deprivation dependent and is mediated by chemoreceptive stimuli from the skin and/or fur. The aversion is diminished by social facilitation. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acute hunger of rat pups elicits increased kyphotic nursing and shorter intervals between nursing bouts: Implications for changes in nursing with time postpartum.

Earlier findings, based on limited behavioral observations, indicate that nursing behavior in rats declines dramatically in duration over time postpartum--despite increasing ingestion of milk by rat pups to meet their growth and metabolic needs--although hungry pups elicit more nursing than do well-nourished pups. The authors compared the nursing pattern in detail for 6 hr on Days 7 and 14 and induced hunger in pups acutely with mammary-duct-ligated dams unable to provide milk. Compared with Day 7, on Day 14, supine nursing and the interval between nursing bouts increased, whereas hovering over pups and kyphotic nursing decreased. When pups were increasingly hungry, these age-related changes were counteracted. Thus, the ingestive motivation of pups largely regulates the nursing pattern over time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Short-term early exposure to pups alters infanticide in adulthood in male but not in female wild house mice (Mus domesticus).

Male and female wild house mice (Mus domesticus) were allowed to remain in the cage of their parents until 30–35 days of age. When a second litter was delivered, the first litter was exposed to the younger pups for 2–20 days. In adulthood the male and female mice that had been exposed to pups as juveniles and an additional group that had cohabitated with their parents for the same length of time but were not exposed to pups were tested for infanticidal behavior. The frequency of infanticide by the adult female mice was not significantly different (55% vs. 70%, respectively). In contrast, the adult males that were exposed to pups as juveniles were significantly less likely to kill young in adulthood when compared with males that were not similarly exposed (35% vs. 80%, respectively). These data further demonstrate the strong influence of experience on the expression of infanticide by male mice and its relative unimportance to the expression of female infanticide. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pup and object carrying by maternally and nonmaternally behaving female albino rats (Rattus norvegicus).

Pups and toys (rubber dropper-bulbs) were presented to 48 nulliparous and 10 lactating female albino Sprague-Dawley rats either together (choice test) or in separate tests. Regardless of their reproductive state, Ss fell into 3 categories according to their behavior: (a) Postpartum Ss as well as virgins that behaved maternally picked up pups much faster than toys, carried more pups than toys, gathered young into the nest, but scattered toys outside the nest site. (b) Virgins that carried young spontaneously but did not show any other elements of maternal behavior picked up pups and toys after equal latencies, carried pups and toys in equal numbers, and scattered both the pups and the toys about the floor of the cage. (c) Virgins that ignored pups did not carry young, but they did show high levels of toy carrying and dispersed the toys about the cage. It is proposed that the term retrieving should be limited, by its definition, to those cases in which the objects are carried to a specific location. Thus, pup retrieval was seen exclusively in Ss that showed maternal behavior (i.e., crouching, pup licking), because only these Ss carried pups consistently to the nest. On the other hand, pup carrying shown by nonmaternally behaving Ss and toy carrying shown by all Ss are both cases of scattered, nondirected object carrying, rather than retrieving. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Retention of maternal behavior in nulliparous and primiparous rats: Effects of duration of previous maternal experience.

Lactating primiparous and nonlactating pup-induced maternal nulliparous female CD rats were given 1, 4, or 9 days of maternal experience with rat pups before they were isolated from the young. 25 days later, Ss were reexposed to 3–8 day old foster pups, and latencies to show maternal behavior in the home cage and a T-maze test were scored. In the home cage, the latencies of all nulliparous groups were shorter upon reinduction. Comparisons of primiparous and nulliparous groups revealed that primiparous females (1, 4, and 9 days combined) carried a pup, crouched, retrieved, and grouped the pups and built a good nest faster than did nulliparous females (combined groups). The number of behavioral differences between specific primiparous and nulliparous groups decreased as the length of prior maternal experience increased. In the T-maze, latencies to retrieve a pup were shorter in primiparous females. Results indicate that the processes underlying establishment of the long-term retention of short-latency maternal behavior in these groups may be comparable. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The ontogeny of feeding in rats: I. Ingestive and behavioral responses to oral infusions.

Reports on 3 experiments with Charles River rat pups. When milk infusions were made through oral cannulas in the front of their mouths, 1–20 day old Ss actively ingested the diet, and their intake was related to the length of deprivation. Ss decreased their ingestive responding after they had consumed large volumes of milk. In addition, 1-, 3-, and 6-day-old Ss, when 24-hr deprived, exhibited an intense behavioral activation in response to milk infusion. The behavioral activation appeared to be stimulated primarily by taste and the opportunity to swallow. Milk infusions did not produce activation in older Ss; their behavior was more exclusively ingestive and food directed. Results demonstrate that (a) from birth, rat pups are capable of an active form of ingestion, independent of normal suckling from the mother; (b) such ingestion is controlled by physiological factors; (c) food has arousing properties in young animals; and (d) as pups grow older, their ingestive responding is refined from a generalized and nondirected activation to specific and directed feeding responses. (57 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfactory stimulation induces filial preferences for huddling in rat pups.

Rat pups of all ages huddle with conspecifics, but the sensory control of contact behavior changes ontogenetically. Thermal cues control huddling until about Day 15, at which time species' odors become the dominant stimulus. The present 2 experiments with 150 Sprague-Dawley rat pups indicate that the filial response to conspecifics is dependent on olfactory experience. A synthetic chemical scent was added to the smells of the dam from Day 1 to Day 20 postpartum. Standardized videographic tests were used to assess the development of huddling preference. Preferences for nest-typical smells emerged by Day 15 in Ss from both scented and nonscented litters. Ss from scented nests preferred to huddle with a scented stimulus rat, whereas control Ss preferred a nonadulterated rat stimulus. Additional testing indicated that the affirmative preferences were specific to rearing odor and were not based on decreased aversion to test scents or on disrupted olfactory discrimination. The ontogeny of species-typical contact behavior is discussed in terms of the induction of a perceptual preference that is based on early odor stimulation. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prepartum changes in maternal responsiveness and nest defense in Rattus norvegicus..

Examined 297 female rats for changes in maternal responsiveness during late pregnancy by exposing Ss to foster pups in tests lasting 15–30 min under conditions favoring the rapid initiation of maternal behavior. Ss were divided into 17 groups according to state of pregnancy (nonpregnant, Day 17, Day 20, Day 21, or Day 22); type of nest; and parity. Nulliparous Ss were compared with primiparous and with experienced breeders. Nest defense was observed by introducing unfamiliar males (2-min tests) on Day 22. Results are presented for 3 periods: Days 17–20, when maternal responsiveness was lower than in the nonpregnant condition; Day 21, when maternal responsiveness returned to or rose above nonpregnant levels; and on Day 22 (the 3.5 hrs prior to delivery), during which 90% of Ss almost immediately retrieved, gathered, and tended foster pups and during which 92% attacked the unfamiliar intruders. (Attacks were rare earlier.) Maternally experienced Ss were more responsive to pups than nulliparous Ss when nonpregnant and throughout late pregnancy, but both groups were equally likely to show prepartum aggression. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Strain and sex differences in mouse killing by rats.

Tendency to exhibit muricide was examined in 481 adult rats of 15 inbred strains. Marked strain differences were observed; frequency of mouse killing ranged from 0 to 91% among the males and from 0 to 68% among the females. Whether males and females differed in their propensity to kill mice also appeared to be strain-dependent. Overall, there was a significant correlation between the frequency of mouse killing by males of each strain and that of females. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behaviorally functional opioid systems in infant rats: I. Evidence for olfactory and gustatory classical conditioning.

Conducted 2 series of experiments to characterize the behavioral function of opioid systems in neonatal rats. In the 1st series, the reinforcing properties of exogenous opioids were investigated in 112 5-day-old pups. Ss' ability to associate the novel taste of saccharin, received while suckling, with intraperitoneal morphine injections was assessed. Results show that Ss that received 0.5 ml of saccharin prior to morphine administration ingested considerably more saccharin on Day 10 than did control rats. The 2nd set of experiments was conducted to determine whether 144 rat pups could associate a novel odor with morphine administration. Five days after conditioning, that stimulus was highly preferred by morphine-treated Ss compared with saline control Ss. Thus positive associations were formed with either a novel taste stimulus experienced while suckling or with an odor experienced during social isolation. Conditioning was cue specific and was retained for at least 5 days. The formation of these associations was blocked with opioid antagonists given prior to conditioning. Data suggest behaviorally functional opioid receptors and raise the possibility of a functional role of the endogenous opioids in motivational processes in infant rats. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)