A Free Choice Task Evaluating Chimpanzees’ Preference for Photographic Images of Sex Swellings: Effects of Color, Size, and Symmetry

Exaggerated sex swellings characterized by increased size of skin surrounding the anogenital region occur in female chimpanzees in response to ovarian hormone fluctuations and are associated with increased likelihood of ovulation and female receptivity. The swellings generate heightened sexual interest from males and evoke increased male competitive behavior. To determine potential attractiveness of specific visual characteristics of these signals to males, a free choice task using push-button methodology that allowed subjects to choose one stimulus in a pair by pressing a button corresponding to the stimulus choice was developed. Initially, preferences for specific food items were first determined based on animals’ selection of actual items, followed by selection of same items from photographs and subsequently selection of preferred food utilizing push-button responses to photographs. We found that when allowed to choose between photographs of sex swellings, novel objects, and other body parts, male chimpanzees preferred images of both sex swellings and other body parts over images of objects, and showed a significant preference for sex swellings over other body parts. However, chimpanzees showed no preference in sex swelling color or symmetry. Only one subject displayed a preference for normal sized swellings rather than enlarged swellings. Overall these results suggest that when considered individually, visual characteristics alone are not sufficient to provoke preference responding

A Free Choice Task Evaluating Chimpanzees’ Preference for Photographic Images of Sex Swellings: Effects of Color, Size, and Symmetry

Exaggerated sex swellings characterized by increased size of skin surrounding the anogenital region occur in female chimpanzees in response to ovarian hormone fluctuations and are associated with increased likelihood of ovulation and female receptivity. The swellings generate heightened sexual interest from males and evoke increased male competitive behavior. To determine potential attractiveness of specific visual characteristics of these signals to males, a free choice task using push-button methodology that allowed subjects to choose one stimulus in a pair by pressing a button corresponding to the stimulus choice was developed. Initially, preferences for specific food items were first determined based on animals’ selection of actual items, followed by selection of same items from photographs and subsequently selection of preferred food utilizing push-button responses to photographs. We found that when allowed to choose between photographs of sex swellings, novel objects, and other body parts, male chimpanzees preferred images of both sex swellings and other body parts over images of objects, and showed a significant preference for sex swellings over other body parts. However, chimpanzees showed no preference in sex swelling color or symmetry. Only one subject displayed a preference for normal sized swellings rather than enlarged swellings. Overall these results suggest that when considered individually, visual characteristics alone are not sufficient to provoke preference responding

Characterization of Cerebrospinal Fluid Monoamine Metabolites in Peripubertal Chimpanzees (\u3ci\u3ePan troglodytes\u3c/i\u3e)

Background Assessment of cerebrospinal (CSF) monoamine metabolites 5-hydroxyindoeacetic acid (5-HIAA) and homovanillic acid (HVA), and the serotonin precursor tryptophan (TRP), in chimpanzees may help in understanding the neurobiology underlying aggressive, impulsive behavior in humans and non-human primates. Methods Two CSF samples were obtained from 11 peripubertal chimpanzees 8 months apart and were assayed for monoamine metabolite and TRP concentrations. Results Substantial inter-individual stability was observed for 5-HIAA (n = 11; r = 0.83, P \u3c 0.001) and HVA (r = 0.91, P \u3c 0.001). Females had significantly higher concentrations of 5-HIAA compared to males (F(1,8) = 7.31; P \u3c 0.05). Levels of 5-HIAA (r = -0.62, P \u3c 0.05), HVA (r = -0.86, P \u3c 0.001) and TRP levels (r = -0.67; P \u3c 0.05) decreased with age. Conclusion Close parallels were observed between chimpanzees and humans with respect to absolute levels, sex effects, ontogeny, and 5-HIAA-HVA correlations, supporting the potential utility of the measures in understanding relationships between monoamine functioning and behavior in chimpanzees and humans

Influence of Estradiol on Cortisol Secretion in Ovariectomized Cynomolgus Macaques (\u3ci\u3eMacaca fascicularis\u3c/i\u3e)

In an investigation of cortisol secretion in fully mature, ovariectomized cynomolgus monkeys (Macaca fascicularis), we compared monkeys that were given either placebo (OVX, n = 26) or 17β estradiol (E2 ) (EST, n = 26) in a daily oral dose. Serum cortisol concentrations were measured prior to the experimental manipulation and 3, 6, 9, and 12 months following initiation of treatment. Pretreatment cortisol values did not differ between groups. Assessment of the treatment period values revealed that cortisol concentrations were significantly higher (≈10%) in the EST than in the OVX monkeys. Cortisol also varied significantly across periods of sampling. This time‐dependent variation was attributable to elevations in months 6 and 9 (when daylight was generally long), relative to months 3 and 12 (when daylight was relatively short). The modest stimulatory effect of estrogen on corticosteroid production observed in this study is consistent with what has been seen in women, and contrasts with the more robust effects observed in New World monkeys. The possible relationship between season and cortisol secretion observed here has not been previously described in monkeys