Bitter avoidance in guinea pigs (Cavia porcellus) and mice (Mus musculus and Peromyscus leucopus)

Rejection of bitter substances is common in many species and may function to protect an animal from ingestion of bitter-tasting toxins. Since many plants are bitter, it has been proposed that high tolerance for bitterness would be adaptive for herbivores. Earlier studies conducted on herbivorous guinea pigs (Cavia porcellus) have been used to support this proposal. We tested guinea pigs with bitter plant secondary metabolites (salicin, caffeine, quinine hydrochloride) and bitter protein hydrolysates (two types of hydrolyzed casein, hydrolyzed soy) in a series of two-choice preference tests. For comparison, we tested two nonherbivorous mouse species (Mus musculus and Peromyscus leucopus). Guinea pigs did show weaker avoidance of quinine hydrochloride than did the mice, confirming predictions generated from earlier work. However, guinea pigs had similar responses to caffeine as did Peromyscus. Both of these species showed weaker avoidance responses than Mus to 10 mM caffeine. For salicin, guinea pigs were the only species to avoid it at 10 mM and their preference scores at this concentration were significantly lower than for the two mice species. Guinea pigs avoided all of the protein hydrolysates more strongly than the other species. Responses to the protein hydrolysates did not reflect the patterns observed with the simple bitter compounds, suggesting that other properties of these complex stimuli may be responsible for guinea pig avoidance of them. Our results suggest caution in accepting, without further empirical support, the premise that guinea pigs (and herbivores in general) have a generalized reduced bitter sensitivity.     

Social preferences of developing guinea pigs (Cavia porcellus) from the preweaning to the periadolescent periods

Preference tests in a novel environment (Experiment 1) and unobtrusive observations in a specialized living environment (Experiment 2) examined the attractiveness of various classes of conspecifics for maturing guinea pigs (Cavia porcellus). It was found that (a). the young continued to remain near the mother well beyond weaning; (b). there was increased time spent with unrelated adult females, but not males, after weaning; (c). male and female offspring behaved similarly; and (d). littermates spent considerable time with each other. These results provide no evidence that guinea pigs approaching sexual maturity begin to associate preferentially with novel animals or potential breeding partners. Choices were largely predictable from earlier findings of the ability of various classes of conspecifics to reduce hypothalamic-pituitary-adrenal activity of the young.     

Development and control of licking in the guinea pig (Cavia porcellus)

Guinea pigs were taught to lick an electronic lickometer by successive approximations brought about by a gradually receding lickerandum-liquid feeder mounted in their home cage. All Ss learned to lick and obtain their total liquid intake by tongue licking. An optimum deprivation schedule was determined, and the response was brought under schedule control comparable to that of the rat.     

Light-dark variation and changes across the lactational period in the behaviors of undisturbed mother and infant guinea pigs (Cavia porcellus)

Lactating guinea pigs (Cavia porcellus) and their litters were observed by videophotography across the light/dark cycle at 1, 11, 21, and 31 days postpartum. The highest level of behavioral activity was seen in the dark, particularly in the hour after light offset. This circadian pattern was evident from Day 1 in mothers and from Day 11 in pups. Contact between mothers and pups was inversely related to activity, occurring more frequently during light. Maternal grooming of pups occurred on Day 1 and then declined: self-grooming by pups increased across days. Intake of solid food and water by pups occurred on Day 1 and increased thereafter. A nearly complete transition from nursing to independent ingestion was observed between 21-31 days of age. Overall, we document several ontogenetic changes in young guinea pigs and demonstrate that under laboratory conditions mother and infant guinea pigs exhibit a nocturnal activity pattern.     

Family first! Influence of parental investment in Guinea pigs (Cavia porcellus) prosocial choices

Animal Cognition - Literature often assumed that prosocial behaviours (behaviours that benefit others with or without a cost for the actor) would have evolved many species to improve the...     

Rehousing periadolescent male guinea pigs (Cavia porcellus) apart from their mothers for 24 hours increases maternally directed sexual behavior and plasma testosterone

Periadolescent male guinea pigs (Cavia porcellus) housed continuously with their mother displayed little or no sexual behavior when they were tested with her in a novel environment. However, if males were rehoused without their mother for 24 hr before testing, they frequently directed courtship and sexual behavior toward her. This effect occurred whether the mother was isolated or not during the rehousing period. In addition, rehousing without the mother produced a significant rise in the plasma testosterone levels of the males. It appears that continuous housing with the mother inhibits sexual and courtship behavior directed toward her, as well as gonadal activity, in periadolescent male guinea pigs. These effects may serve to prevent inbreeding.     

Effects of olfactory bulbectomy on social behavior of male guinea pigs (Cavia procellus)

Effects of olfactory bulbectomy on social behavior in male guinea pigs were studied. Both brief-exposure pairing techniques and a group-living observation period were employed to test for disruption. During short-term testing sessions bulbectomized animals courted females less than but mounted them as frequently as control subjects. While the groups did not differ in fighting behavior during short-term tests, control subjects scent-marked more frequently. Subsequently, animals were observed as same-treatment pairs living continuously with females, and behavior was sampled over a 3-wk period. Under these conditions bulbectomized males, unlike controls, failed to form dominance orders, exhibited virtually no intermale aggressive activity, had markedly depressed sexual activity, and scent-marked rarely. It is concluded that olfactory bulbectomy profoundly alters the behavior of male domestic guinea pigs and that hose alterations are most evident when experimental subjects are observed in a species-typical group-living environment.     

Motivated behaviors elicited from hypothalamus, midbrain, and pons of the guinea pig (Cavia porcellus).

Eating, drinking, biting attack, male mating behavior, and gnawing were elicited by electrical stimulation through electrodes located predominantly in a region extending from the preoptic area through the lateral hypothalamus into the ventral midbrain. Escape and digging were elicited from a parallel but more medial region that overlapped the lateral zone only in the preoptic-anterior hypothalamic area. Several differentiable vocalizations were produced from sites distributed through most, although not all, areas explored. Sites yielding painlike responses were located principally in the vicinity of the presumed pain pathway traced after anterolateral cordotomy in other species. Reward was obtained from widespread sites that were generally congruent with catecholaminergic systems as described in the rat. Although there was considerable overlap of the effective zones for many responses, their underlying mechanisms were differentiated anatomically by localized differences in their distribution or functionally by the elicitation of pure responses from some electrodes. Response mechanisms localized in the brain stem of the guinea pig generally resembled those in the rat, although there were differences in details, especially in the posterior midbrain and pons.     

Social organization predicts nature of infant-adult interactions in two species of wild guinea pigs (Cavia aperea and Galea monasteriensis)

The authors compared interactions of infants with mothers and unfamiliar females in a novel environment in 2 caviomorph rodent species: the harem-living Cavia aperea, the probable progenitor of the domestic guinea pig; and the pair-living Galea monasteriensis. In C. aperea, interactions with mothers and unfamiliar females were largely similar; in G. monasteriensis, interactions with the mother, but not unfamiliar female, were characterized by physical closeness and sociopositive behavior. In G. monasteriensis, plasma cortisol levels were lower when with the mother than when with the unfamiliar female. Results are consistent with the species' social organizations and suggest that behavioral interactions of pups with mothers and other females in domestic guinea pigs reflect primarily the social organization of the progenitor species rather than domestication.     

Cortisol and behavioral responses to separation in mother and infant guinea pigs

In Experiment 1, lactating guinea pigs 3 days postpartum exhibited an elevation of plasma levels of cortisol when their litters were taken from the home cage and placed out of auditory range for 30 min. If pups were left within auditory range during the period of separation, or if the litter was disturbed but not removed, no increase in plasma cortisol levels was observed. In Experiment 2, 11/12- and 18/19-day-old guinea pig pups placed alone in a novel environment for 30 min displayed levels of plasma cortisol and vocalizations that were greater than those of pups tested in the same environment but with their mother. Pups tested with littermates but not with their mother exhibited plasma cortisol levels that were as great as those of pups tested alone. Pups tested with littermates vocalized much less than pups tested alone but more than pups tested with their mother. These results indicate that brief mother-infant separation can activate the pituitary-adrenal system in mother as well as infant guinea pigs and they provide further evidence for the existence of a reciprocal mother-infant attachment in this species.     

Offence and defence in fights between young pigs (Sus scrofa)

Fights were observed between young, unacquainted, domestic pigs. These fights were described in terms of the frequency of bites and the time spent in each of five spatial configurations of the animals. Depending on the rate that bites were given or received, each spatial configuration was characterized as resulting from offence or defence by one of the pigs. Bites were mainly directed at the head and ears, and defensive moves placed these areas out of reach. The most effective offensive move was an attack from the side. Pigs that lost fights tended to turn away from such attacks: winners were as likely to turn towards the attacker. Whether turning away is submission or simply defence is not clear. Factor analysis showed that fights could be described on three dimensions: offence by the loser along with mutual offence and mutual defence: offence by the winner and defence by the loser: and defence by the winner. Long fights involved much offence by the loser and defence by the winner: short fights involved much defence by the loser. When the pigs met again after 24 h, the fights were shorter and involved less offence and more defence by the loser. The transitions between the configurations reflect a balance of offence and defence by the pig responsible making for the transition. This balance is, in turn, affected by attacks from the opponent, fatigue, and the pig's assessment of its relative fighting ability. Retaliation against attacks is partly responsible for the persistence of fighting.     

Short-term effects of residence on the testosterone responses to fighting in alpha male guinea pigs

The short-term effects on testosterone (T) levels of (a) taking blood samples, (h) fighting in one's own home cage, and (c) fighting in another male's home cage were examined in eight alpha male guinea pigs, each living together with two females and two subordinate males in their home cages for 4 months. Every male was given two 5-minute agonistic encounters, one in his home cage and one in another male's home cage. After the encounter, intruder males were returned to their home cages. Three blood samples were taken 10 minutes before and 5 and 45 minutes after the agonistic encounters (sampling times were designated as 0, 20, and 60 minutes, respectively). One week before the agonistic encounters were conducted, blood samples were taken from each male on the same time schedule (0, 20, and 60 minutes). The main findings were as follows: (1) the animals showed an increase in T-levels after an agonistic encounter in their home cages and a decline in T-levels after an agonistic encounter in the home cages of other alpha males' irrespective of being the winner or the loser and the degree of escalation during the encounter; (2) the smaller the differences in T-titers between both opponents 10 minutes before the encounter, the more escalated the agonistic encounter.     

Association between dyads and correct responses on the Paced Auditory Serial Addition Task (PASAT)

The sensitivity of the Paced Auditory Serial Addition Task (PASAT) to working memory deficits may be enhanced by examining "dyads" (i.e., correct responses immediately preceded by a correct response) as a complement to the traditional total correct summary score. In a sample of 397 mostly African American (79%) healthy adults, total dyad and total correct scores were highly correlated (r = .96, p < .001); however, the magnitude of this association diminished in faster stimulus presentation trials, particularly among participants with impaired working memory abilities.     

Directional responses to sounds in young gerbils (Meriones unguiculatus)

Three experiments were conducted to determine the ability of infant gerbils to approach an auditory stimulus. In the first experiment, gerbil pups, 16-23 days of age, were tested in a circular apparatus with a central start area and a movable sound source located at one of eight positions around the perimeter. Stimuli included high- and low-intensity presentations of a tape-recorded gerbil social call, a broad-band white noise stimulus, and a no-stimulus control condition. The subjects showed a strong tendency to approach the low-intensity social call and a less pronounced tendency to approach the white noise. In the second experiment, gerbil pups were tested in the same apparatus with or without ear blocks to determine the role of binaural cues in directional approach responding. The tendency to approach a low-intensity vocalization was disrupted by obstruction of one ear but not by blocking both ears. Thus, binaural balance was shown to be important for early sound localization. In the third experiment, the tendency to approach a social call was compared at different ages, 12-15, 16-19, 20-23, and 24-27 days after birth. Approach responses were first seen at 16-19 days. The responses continued during the 20-23-day period but began to wane at 24-27 days of age.     

Heart-rate responses of infant rats and guinea pigs to stimulus onset and offset: tests of the generality of a bidirectional effect

To test the generality, across modality and across species, of a bidirectional effect of photic stimulation in infant rats found in previous experiments, two experiments examined the effects on heart rate (HR) of onset and offset of auditory stimulation in rats and of photic stimulation in guinea pigs. Experiment 1 demonstrated a unidirectional, decelerative response in rats 17 and 21 days of age to the onset and offset of a 1-kHz tone, at both low (80 dB) and high (100 dB) intensity levels and at 14 days to the onset of the high-intensity tone. Experiment 2 demonstrated that infant guinea pigs, which unlike infant rats are precocial and not nocturnal, responded to the offset but not to the onset of light, and that this response was decelerative. These results indicated a lack of generality of the bidirectional HR effect, and were discussed in terms of the orienting/defensive reflex distinction.     

Auditory evoked brain responses: Comparison of ON and OFF responses at long and short durations

Average evoked brain responses (EBRs) to three durations of one kilohertz pure-tone stimuli were computed from human scalp recordings. Stimuli of 25, 75, and 2,000 msec duration were each presented binaurally at each of eight equally spaced intensity levels, ranging from 58 to 86 dB SPL. EBRs computed immediately following presentation, and immediately following removal of the 2,000-msec-duration stimulus result in ON and OFF responses, respectively. EBRs computed immediately following presentation of the 25- and 75-msec-duration stimuli appear to be the result of the sum of separate responses to stimulus onset and offset. Computer-dissected ON and OFF EBRs to short-duration stimuli are very similar in waveform and amplitude to the responses evoked by the onset and offset, respectively, of the 2,000-msec duration stimulus. Dissected ON and OFF responses demonstrate linear amplitude-intensity functions in amplitude ranges similar to respective ON and OFF responses to 2,000-msec stimulation. The data suggest that ON and OFF responses are mediated by independent physiological mechanisms.     

Auditory food cue conditioning: Effects of spatial contiguity and taste quality

The effects of spatial location of an auditory stimulus and quality of a potentiating taste on the aversive conditioning of an auditory food cue were investigated. In Experiment 1 rats ate salty food activating a tone from a speaker either in (spatially contiguous with) or displaced from the food and were then made ill. It was found that spatial contiguity during conditioning resulted in avoidance of food with a contiguous or a displaced tone in testing, and spatial displacement during conditioning resulted in avoidance of food only if the tone was also displaced in testing. Experiment 2 was identical, except rats ate salty, bitter, or sweet food with a displaced tone during conditioning and testing. The salty and bitter food groups demonstrated an avoidance of noisy food relative to the sweet food group. These results indicate that spatial contiguity interacts with taste quality in the conditioning of nongustatory food cues.