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In the cooperative breeding common marmoset monkey, Callithrix jacchus, fathers share the care responsibility and energetic load with their mate from the time their infants are born. However, not all fathers show the same level of participation in direct infant care. Here we present the first results demonstrating that fathering style can improve both survival and growth trajectory of a male's offspring during the first 30 weeks of life and that these infant outcomes are consistent within a father throughout successive births. Twenty-four marmoset fathers were tested for their responsiveness to an infant distress call when their infants were approximately two weeks old. These fathers were categorized as either responsive (RS) or nonresponsive (NRS) based on their response to the calls. Survival past 1 month was then determined and bi-monthly weights of current infants through 30 weeks of age were taken. Infant survival to the first month was significantly higher with RS fathers than with NRS fathers during this critical time period. Infants from RS fathers also had a higher growth trajectory with significant differences in body weight in the 28th and 30th week after birth. Only the RS fathers showed a significant increase in serum testosterone in response to infant cries suggesting a physiological role of testosterone in the motivation to search for the infant. Furthermore, all offspring born to RS fathers from subsequent births also showed a significantly higher survival rate and higher growth trajectory than for offspring of NRS fathers. These results suggest that fathering style is a consistent trait and responsive fathers improve infant survival rate and growth during the first 30 weeks. Such fathering style traits may be passed on to the male offspring due to environmental or genetic factors.

Rhesus macaques represent an important species for translational and pre-clinical research studies across a multitude of disease and injury models, including aging. Ketamine anesthesia is used in humans and non-human primates but may be associated with adverse effects, including neuromuscular reactions. The effects of aging on ketamine adverse effects is not well characterized. Urodynamic recordings and electromyography (EMG) studies were performed in aged (>20 years old) and adult (3.9-14.9 years old) female rhesus macaques under an equal and light plane of sedation by constant rate infusion (CRI) of ketamine. A total of 4 of 41 adult subjects (9.7%) showed clinical signs of ketamine-induced abnormal neuromuscular reactivity, whereas a larger portion of 14 of 26 aged subjects showed similar ketamine-induced neuromuscular reactivity (53.8%; P< 0.001). The ketamine CRI rate was 19.8±0.9 mg/kg/h in adults and lower in aged subjects at 16.5±1.4 mg/kg/h (P

A smaller length ratio for the second relative to the fourth finger (2D:4D) is repeatedly associated with fetal male-typical testosterone (T) and is implicated as a biomarker for a variety of traits and susceptibility to a number of diseases, but no experimental human studies have been performed. The present study utilizes the rhesus monkey, a close relative of humans, and employs discrete gestational exposure of female monkeys to fetal male-typical T levels for 15-35 days during early-to-mid (40-76 days; n = 7) or late (94-139 days; n = 7) gestation (term: 165 days) by daily subcutaneous injection of their dams with 10 mg T propionate. Such gestational exposures are known to enhance male-typical behavior. In this study, compared to control females (n = 19), only early-to-mid gestation T exposure virilizes female external genitalia while increasing 2D:4D ratio in the right hand (RH) by male-like elongation of RH2D. RH2D length and 2D:4D positively correlate with androgen-dependent anogenital distance (AG), and RH2D and AG positively correlate with duration of early-to-mid gestation T exposure. Male monkeys (n = 9) exhibit a sexually dimorphic 2D:4D in the right foot, but this trait is not emulated by early-to-mid or late gestation T exposed females. X-ray determined phalanx measurements indicate elongated finger and toe phalanx length in males, but no other phalanx-related differences. Discrete T exposure during early-to-mid gestation in female rhesus monkeys thus appears to increase RH2D:4D through right-side biased, non-skeletal tissue growth. As variation in timing and duration of gestational T exposure alter male-like dimensions of RH2D independently of RH4D, postnatal RH2D:4D provides a complex biomarker for fetal T exposure.