PubMed Health⌕ Search

Biomedical subjects

Melissa S Gerald

Publications and source records attributed to Melissa S Gerald.

10 recordsLinked to original sources
PubMed2006

Effects of parity and age on female attraction to faces of infants and neonates in rhesus macaques.

This study investigated the effects of parity and age on female rhesus macaque attention toward infants, and assessed whether the faces of neonates are more attractive than those of older infants. Six nulliparous and six multiparous females were shown digitized images of neonates' and 5- to 6-month-old infants' faces. Attention and preferences for images were measured by gaze duration and other picture-directed behaviors, including lip smacking, approaches, and presentations. As predicted, nulliparous females displayed significantly longer gaze durations for images than did multiparous females. There were no significant differences in gaze duration for faces of neonates and those of infants, but images of infants were approached more frequently than images of neonates. This difference is tentatively explained on the basis of differences in female familiarity with neonates' and infants' faces and differences in opportunities for allomothering with neonates and infants.

Age Factors↗
PubMed2006

An experimental examination of female responses to infant face coloration in rhesus macaques.

In many primates, infants possess distinctive coloration that changes as a function of age. This colour is thought to serve the purpose of eliciting caretaking behaviour from the mother as well as other conspecifics. The present study investigated the responses of adult female rhesus macaques (Macaca mulatta) to pictures of infant faces in relation to infant age and facial coloration. Study animals were shown digitized images of neonates and 5-6-month-old infants displaying either unaltered facial colour, pink neonatal colour, or novel (green) facial colour. While infant and neonate faces of all colours elicited the attention of adult females, pink neonatal facial coloration did not appear to be especially attractive to subjects in contrast with the findings from an earlier study [Higley, J.D., Hopkins, W.D., Hirsch, R.M. Marra, L.M. Suomi S.J., 1987. Preferences of female rhesus monkeys (Macaca mulatta) for infantile coloration. Dev. Psychobiol. 20, 7-18]. The results suggest that infant facial colour is not particularly important in mediating infant attractiveness to rhesus macaque females as previously suggested or that other infantile facial characteristics might be more important than colour in eliciting caretaking behaviours amongst females.

Animals↗
PubMed2006

Tetanus antibody titers and duration of immunity to clinical tetanus infections in free-ranging rhesus monkeys (Macaca mulatta).

Prior to 1985 tetanus was a major cause of mortality in the free-ranging colony of rhesus monkeys on Cayo Santiago, accounting for almost a quarter of annual deaths. In 1985 and 1986 all animals (except infants) received primary and booster doses, respectively, of tetanus toxoid. In subsequent years primary immunizations were given to all yearlings, and boosters were administered to all 2-year-old animals during the annual capture of the colony. The main objectives of the tetanus immunization program were to reduce the pain and suffering caused by tetanus infections and to decrease mortality in the colony. Other objectives were to evaluate the efficacy of the two-dose tetanus toxoid immunization protocol and to determine whether additional boosters might be required to provide adequate long-term protection against tetanus infections. The immediate effect of the mass immunization program was the elimination of clinical tetanus infections in the population and a 42.2% reduction in the overall mortality rate. Since the immunization program began, no cases of tetanus have been observed in the colony, except in two unimmunized infants, and it has not been necessary to give tertiary injections of tetanus toxoid to maintain protection against infection. A sample collected in 2004 of the original cohort of monkeys immunized in 1985 and 1986 showed that 93.3% (14/15) had protective tetanus antibody titers (>0.01 IU/ml) at the ages of 20-23 years, which is close to the life expectancy of the Cayo Santiago rhesus macaques. Two intramuscular doses of tetanus toxoid provided long-term, if not lifelong, protection against tetanus for rhesus monkeys living in a tropical clime where tetanus is enzootic and the risk of infection is great.

Animals↗
PubMed2006

Selective attention toward female secondary sexual color in male rhesus macaques.

Pink-to-red anogenital and facial sexual skin occurs in females of many primate species. Since female sexual skin color varies with reproductive state, it has long been assumed that color acts to stimulate male sexual interest. Although there is supportive evidence for this as regards anogenital skin, it is unclear whether this is also the case for facial sexual skin. In this study we experimentally manipulated digital facial and hindquarter images of female rhesus macaques (Macaca mulatta) for color within the natural range of variation. The images were presented to adult male conspecifics to assess whether the males exhibited visual preferences for red vs. non-red female coloration, and whether preferences varied with anatomical region. The males displayed significantly longer gaze durations in response to reddened versions of female hindquarters, but not to reddened versions of faces. This suggests that female facial coloration may serve an alternative purpose to that of attracting males, and that the signal function of sexual skin and the intended recipients may vary across anatomical regions.

Animal Communication↗
PubMed2004

Body composition, age and fertility among free-ranging female rhesus macaques (Macaca mulatta).

The relationship of morphometric measures and birth status among 93 females on Cayo Santiago trapped during the 2001 and 2002 seasons was assessed. The proportion of females giving birth differed between the two seasons (0.58 vs. 0.38; P = 0.006) with a prominent decline among older females. Most morphometric measures increased from adolescent to adult groups, but bicep circumference showed a significant decrease among adults. When controlled for age differences, females with infants during the 2002 season exhibited greater bicep circumference, but no difference in abdominal fat than those without. Members of the socially dominant group did not have a higher rate of birth in either 2001 or 2002, despite being significantly longer and weighing more than those of the subordinate group. Abdominal skinfold and bicep circumference were significant predictors of birth status during the 2002 season, controlling for age group, social group membership, and parity in the previous year. Bicep circumference was also a significant predictor of birth status for the 2001 birth season. These findings suggest that individual variation in body composition among females of Cayo Santiago is associated with differences in fertility.

Age Factors↗
PubMed2002

Relationship between platelet-activating factor concentration in rhesus monkey (Macaca mulatta) spermatozoa and sperm motility.

Platelet-activating factor (PAF) is a potent signaling phospholipid that has been implicated in a number of biological activities. PAF concentration in primate spermatozoa has a positive correlation with fertility. While PAF is present in rhesus spermatozoa, there are no relational reports on its concentration and the cell's motility. The study objective was to determine if PAF concentration in rhesus spermatozoa was correlated with motility indices (percent motility and forward progression). Semen was collected from sexually mature males and cell counts, and percent motilities and forward progressions were recorded prior to PAF measurement by radioimmunoassay. Spermatozoa-derived PAF concentration ranged from a low of 0.9 picomoles/10(6) cells to a high of 13.0 picomoles/10(6) cells. The overall mean (+/-SEM) PAF concentration was 4.6 (+/-1.6) picomoles/10(6) spermatozoa. Regression analysis revealed a positive and significant relationship between PAF concentration in the spermatozoa and percent motility (R2 = 0.914; P < 0.01) as well as forward progression (R2 = 0.849; P < 0.05). A receiver-operator characteristic curve and the calculation of the probability that a positive forward progression will be predicted indicated a cutoff limit of 1.5 picomoles/10(6) cells for PAF concentration in rhesus sperm. Rhesus monkey spermatozoa motility was significantly greater (P < 0.01) in the high-PAF (> or =2 picomoles/10(6) cells) group (31.0 +/- 7.6) than in the low-PAF (<2 picomoles/10(6) cells) group (6.8 +/- 2.1). Rhesus monkey spermatozoa forward progression was significantly greater (P < 0.05) in the high-PAF (> or =2 picomoles/10(6) cells) group (3.0 +/- 1.0) than in the low-PAF (<2 picomoles/10(6) cells) group (0.7 +/- 0.3). The data demonstrate that PAF concentration in rhesus spermatozoa has a significant relationship with percent motility and the cell's forward progression. Determining PAF concentration in spermatozoa may be a significant predictor of fertility in the primate. Additional studies will elucidate the role of PAF in spermatozoa function and the significance PAF plays in primate fertility.

Animals↗
PubMed2002

The finding of an inverse relationship between social dominance and feeding priority among pairs of unfamiliar adult male vervet monkeys (Cercopithecus aethiops sabaeus).

Dominance is often presumed to confer priority of access to resources. This study evaluated the relationship between two assessments of dominance: (1) social dominance, based on agonistic interactions and (2) feeding priority among pairs of unfamiliar adult vervet monkeys (Cercopithecus aethiops sabaeus) differing in scrotal colour, but matched for height, weight and testicular volume, during paired introduction experiments. Results of this investigation showed that neither size differences nor scrotal colour were predictive of feeding priority, and social dominance was inversely related to feeding priority. This finding demonstrates that different assessments of dominance can yield different outcomes even within the same primate taxon. I propose that male dominance rank may best predict access to resources when there is direct contest competition over a resource, which is not immediately exhaustible, whereas highly impulsive low ranking males may gain a competitive edge in scramble competitions for ephemeral and small resources.

Aggression↗
PubMed2002

Evolutionary underpinnings of excessive alcohol consumption.

Given our close phylogenetic relatedness, non-human primates, in principle, could serve as an ideal model for alcoholism. Indeed, many studies in both humans and rhesus macaques show relationships between excessive alcohol consumption, aggression and serotonergic function, as measured by concentrations of the principal metabolite of serotonin, 5-hydroxyindoleacetic acid (5-HIAA) in the cerebrospinal fluid (CSF). An important behavioral predictor of excessive alcohol consumption in both humans and rhesus monkeys is the propensity toward impulsivity. Integrating behavioral and neuroendocrine data from captive and semi-free-ranging rhesus macaques, we posit that benefits derived from impulsive and aggressive behaviors in some contexts might contribute indirectly to the maintenance of traits involved in alcoholism and excessive alcohol intake.

Alcoholism↗
PubMed2002

Variation in reproductive outcomes for captive male rhesus macaques (macaca mulatta) differing in CSF 5-hydroxyindoleacetic acid concentrations.

In rhesus macaque males, lower than average cerebrospinal fluid (CSF) concentrations of the principle metabolite of serotonin, 5-hydroxyindoleacetic acid (5-HIAA), have been linked to impulsivity, involvement in escalated aggression, failure to elicit consort relationships, production of fewer sperm plugs, and a relatively early age of mortality. Given these potential fitness costs, we performed two studies aimed at elucidating the effects of CSF 5-HIAA on reproduction. Study 1 retrospectively evaluated over a four-year period, the relative reproductive outcome for pairs of adult male rhesus macaques (n = 15) who lived in social groups and who differed in concentrations of CSF 5-HIAA. Study 2 examined the relationship between CSF 5-HIAA and sperm motility and density (n = 12), as a potential mechanism for maintaining variability in CSF 5-HIAA. For Study 1, an average measure from two CSF 5-HIAA samples was calculated for the two males who were present during the time when conception most likely took place (offspring birth date -165 +/- 14 days). Within-pair comparisons of CSF 5-HIAA concentrations between the sire and the non-successful male were drawn for each of the 72 offspring in the study. We found that while sires were typically the male with relatively higher CSF 5-HIAA within the pair, there were no absolute differences in CSF 5-HIAA between males who sired at least one offspring (sires) and those who failed to reproduce (non-sires). Furthermore, while absolute age was not predictive of reproductive outcome, sires with relatively high CSF 5-HIAA also tended to be also relatively older than their competitors. By contrast, for the males with relatively low CSF 5-HIAA who reproduced, sires were relatively younger than the non-sires. These differences in reproductive outcome for males differing in CSF 5-HIAA could not be explained by variability in sperm quantity or quality as we did not find evidence of a relationship between CSF 5-HIAA and either sperm measure. The results of this study suggest that as serotonergic function affects many aspects of behavior and survivorship, it might also be associated with reproductive outcome and different life-history strategies for males differing in concentrations of CSF 5-HIAA.

Animals↗