Christian Welker

Rearing without Paternal Help in the Bolivian Owl Monkey Aotus azarae boliviensis: A Case Study1

It is well established that in owl monkeys, Aotus, the father participates in infant care [1–12]. Generally, all group members participate in infant care, but the adult male owl monkey is the primary infant caregiver [1–3, 6–12]. In contrast to other Neotropical primates living in small family groups, titi monkeys (Callicebus) and callitrichids, where the father starts to transport the infant(s) regularly from the first day of life [7, 13–15], as a rule the newborn owl monkey is carried nearly exclusively by its own mother [1–3, 6, 7, 9] in a distinctive ventrolateral position. This well-documented result does not exclude exceptions; either the father [8] or a sibling [9] may be the main carrier from the first day of life. Invariably from the third week of life, however, the father becomes the main caregiver, carrying the infant on the back in a longitudinal position. Considering this well-documented fact, true for different species of this genus, at least in captivity, it makes no sense to separate the father before birth with the consequence of a severe risk for the survival of the infant. Thus, the outcome of an unplanned case study is worth reporting: a very old wild-born male owl monkey died shortly (14 days) after the birth of its last (male) infant who had to be raised by his mother and one older (female) sibling (2.5 years old) without any paternal support. We compare the data with those gained from intact family groups of the same species, and under the same laboratory conditions, and discuss the results from an evolutionary perspective. Received: December 30, 1996 Accepted: February 7, 1997

Twinning in Tufted Capuchins (Cebus apella): Rate, Survivorship, and Weight Gain

We calculated the rate of twinning across four captive collections of tufted capuchins (Cebus apella) to be 2.4%. This rate contrast with previous reports that twinning in tufted capuchins is rare. Additionally, we present data on the survival and weight gain of twins in this species as compared to singletons. Twins face their greatest risk of mortality on or before the first day of life, when 45% will die compared to 16% of singletons. After the first day of life, twins and singletons demonstrate comparable survival rates. This, in conjunction with the finding that at no time during the first year of life do twins and singletons differ significantly in their weights, suggests that twinning is a viable reproductive form for these animals, especially in the captive setting where nutritional demands are met.

Ethologische Bedeutung des Harnwaschens von Galago crassicaudatus E. Geoffroy, 1812 (Lorisiformes: Galagidae)

The frequency of urine-washing depends on temperature, atmospheric moisture and substrate conditions. The function of this behaviour is an additional moistening of the volar surfaces. By this habit, the tactile integument of hands and feet will get their special capacity. No indications, however, could be found to verify the theory of olfactory marking of traces. The activity of the animals is given as well in each experiment.

Female dominance in African lorises (Otolemur garnettii)

African lorises show sexual size dimorphism and are supposed to be characterised by male dominance [1]. They have been regarded as an outgroup for comparison with Malagasy prosimians, a grouping in which female dominance has been repeatedly reported [2, 3]. Males are assumed to be dominant because measures of body weight in captive populations reveal that males are larger than females. In contrast to most polygynous haplorhine primates, in which male dominance is correlated with larger male body size [4], many polygynous lemurs lack significant sexual dimorphism [5] and instead are characterised by female dominance [3, 6]. Female dominance has been inferred from the outcome of agonistic interactions [7], that is females were able to elicit submissive behaviour patterns from males. Here, we report from observations of captive Garnett’s greater bushbabies (Otolemur garnettii), which indicate female dominance and lack of sexual size dimorphism. Observing male/female pairs allowed us to study dominance relationships between the sexes that would be otherwise hard to investigate in a nocturnal and normally solitarily foraging species.

Aufzucht des Halbaffen Galago crassicaudatus E. Geoffroy, 1812 (Lorisiformes: Galagidae) im Familienverband

A female thick-tailed Galago has given birth to two male offsprings within 1 year and has reared both successfully, while the adult male, respectively the first youngster were present. This work outlines some of the social behaviour of the family group. Weight data of five male infants are given.