Proximity patterns of female western lowland gorillas (Gorilla gorilla gorilla) during the six months after parturition.

Studies of wild mountain gorillas have demonstrated strong preferences among new mothers for the silverback. Protection against infanticide has been theorized to be the primary cause for this attraction. We examined social partner preferences in captive western lowland mothers during the 6 mo after parturition and found that juveniles and females were the primary members of the new mothers' social network. Mothers spent significantly more time in close proximity with both of these subgroups than with the silverback. Proximity patterns changed over time: new mothers spent more time near females in the month after parturition than in the month prior to parturition, and spatial proximity increased again in months 2-6 postparturition. These findings differ from those reported for wild mountain gorillas, which may reflect the lack of infanticide risk in captivity. Given current hypotheses that infanticide may be a limited in western lowland gorillas, the social partner preferences observed here may be indicative of patterns in wild populations.

A preliminary behavioral comparison of two captive all-male gorilla groups.

Gorillas live in polygamous harem groups, generally composed of one male, several adult females, and their offspring. With an equal numbers of male and female gorillas born in captivity, however, housing gorillas in social breeding units inevitably means that some males will not have access to female social partners. Thus, the future of the captive gorilla population depends on the collective ability of zoos to house equal numbers of males and females. This study examined the behavioral profiles of two all-male groups of captive lowland gorillas (Gorilla gorilla gorilla) to provide information on this type of housing situation. One group consisted of three subadult individuals, while the other consisted of two subadults and a silverback. Data were collected during two 6-month intervals, for a total of 284 hr. The behavioral profiles of the animals were stable over the course of the study but proximity patterns changed. Differences in feeding, solitary play, and object-directed behavior were found between groups, while no significant differences were observed in affiliative or agonistic social behavior. At both institutions, group cohesion appeared to be high, particularly between subadults; these individuals spent approximately 10% of their time engaging in social behavior and 25-50% of their time in close proximity (within 5 m). However, the Zoo Atlanta males spent significantly more time within 1 m and 5 m of each other than the Santa Barbara males, which may reflect a higher level of cohesiveness among members of the Zoo Atlanta group. The behavioral profiles of the animals in this study were similar to those found in bachelor groups of wild mountain gorillas. One notable exception was the absence of homosexual behavior between the silverback and subadults in Santa Barbara and the low frequency of this behavior between subadults in both groups. Although more longitudinal data are needed, these data suggest that all-male groups can be a feasible housing strategy for males at certain periods of their life span. Zoo Biol 20:27-40, 2001. Copyright 2001 Wiley-Liss, Inc.

Separation and depression in infant gorillas.

Three 27-month-old infant gorillas living with their mothers and a silverbacked male were separated to a cage for 24 weeks. The infants initially showed threat responses and increased locomotion, characteristic of the protest stage of anaclitic depression in children. Within several days, these were replaced by dorso-ventral contact among the infants as well as self-holding and fetal positioning. Additionally, social and solitary play and object examination occurred at lower levels through separation than in the pre-separation condition. These changes were characteristic of the despair stage of separation. There was a substantial recovery of many infant nonsocial and social behaviors in the later months of the separation. Upon reunion, the infants did not immediately engage in attachment behaviors with their mothers, and spent more time in contact with each other than with their mothers for the first several days, indicating detachment. Following this, there was an increase in mother-infant attachment behaviors.

Infectious complications in liver transplantation.

Thirty-five patients received 42 liver homografts between February 1984 and August 1985. One or more infections developed in 23 patients (66%) some time after transplantation. An average of 2.5 infections per infected patient occurred. Of 37 bacterial infections, two thirds were either bacteremias or localized intra-abdominal infections. The median onset was 29 days after operation. Thirteen viral infections were identified, with a median onset of 18 days after operation. Nine fungal infections, six disseminated and three localized, were identified, with a median onset of nine days after operation. Infection was the primary cause of death in five (14%) of 35 patients. Fatal infections were evenly distributed among bacterial (two), fungal (three), and viral (two) pathogens. Despite advances in surgical techniques and the use of cyclosporine, infection after orthotopic liver transplantation is a serious problem. Certain patients can be identified as high risks for infection and require an aggressive diagnostic workup followed by early institution of antimicrobial therapy.

Activity rhythms in the Mongolian gerbil under natural light conditions.

Male and female Mongolian gerbils (Meriones unguiculatus) were maintained from birth under natural light conditions. They were observed in adulthood over 24-hour periods for the occurrence of locomotion, digging, scrabbling, sleeping, grooming, eating and drinking. The animals exhibited a crepuscular activity rhythm in all behaviors except drinking. Peak activity levels occurred at approximately 6-8 a.m. and 6-8 p.m., the hours of day which encompassed dawn and dusk. There were no sex differences in the rhythmic cycling of activity. Results are discussed in relation to basal metabolic rate of the animals, nutritional requirements and ambient temperature conditions.

Control role of an adult male in a captive group of lowland gorillas.

An adult male gorilla was removed from the social group in which it had resided for 27 months. There was an immediate increase in aggressive behaviors among the remaining adult females, as well as an intensification of mother-infant social behaviors. The return of the male resulted in an immediate rise in male aggression and a decline in female aggression, with a gradual return to baseline levels in most behaviors. The control role of the male in the group through aggressive behaviors is suggested.

Development of infant independence in a captive group of lowland gorillas.

In March 1976, 3 lowlands gorillas (Gorilla gorilla gorilla) were born to primiparous females living with an adult male in a large compound at the field station of the Yerkes Regional Primate Research Center of Emory University. Observations of parent and infant behavior began at the birth of the infants, using several methods of data collection. This report focuses on the development of independence in these infants over the 1st 1 1/2 years of life. As expected, measures of mother-infant contact and proximity decreased with age. Several measures suggested that infant independence developed as an interactive process between mothers and infants, with primary responsibility changing over the months of study. Maternal behaviors that served to maintain mother-infant contact were found to decrease with age, with an eventual shift to infant responsibility for contact maintenance. Additionally, the adult male appeared to influence developing independence as reflected in the maternal protectiveness evoked by his behavior.