The costs of infant carrying in captive cotton‐top tamarins

Abstract

Marmosets and tamarins have a communal rearing system in which all group members help to care for the twin infants characteristic of this family of primates. Helpers are likely to incur time and energy costs by contributing to infant care. Predictions that cotton-top tamarin (Saguinus oedipus) helpers would change their behavior when carrying infants because of reduced mobility and/or a need for increased vigilance were tested in a captive colony. Tamarins carrying an infant spent significantly less time feeding, foraging, moving, or engaging in social activities such as grooming than they did when not carrying. Frequencies of scratching, autogrooming, and scent marking were significantly reduced in carriers, suggesting that their mobility was reduced. However, carriers were significantly less likely to be vigilant (measured by direction of gaze) than when not carrying. Further observations showed that carriers spent more time in concealed areas than they did when not carrying and were probably therefore adopting a cryptic strategy to reduce predation risks to themselves and to infants. These results demonstrate that tamarin helpers pay costs by carrying infants. Some possible compensating benefits are indicated.

Opportunistic mothers: female marmosets (Callithrix kuhlii) reduce their investment in offspring when they have to, and when they can

“…In Study 1, female marmosets faced with the impending demands of nursing and carrying newly conceived litters during early infant care significantly reduced their investment in their current litters-perhaps shifting investment away from their current litters to ensure sufficient resources for upcoming litters. Although studies have indicated that callitrichid caregivers sometimes reduce the energetic burden of infant care by spending less time foraging and traveling while transporting infants (e.g., saddle-back tamarins: Goldizen, 1987; cotton-top tamarins: Price, 1992c; see review in Tardif, 1994), and that some may be physically limited in their ability to travel while carrying infants (common marmosets: Schradin and Anzenberger, 2001), our results are consistent with recent reports that energetically challenged callitrichid females may actually provide less care to their offspring than females that are in better condition and/or have access to higher quality resources. Tardif et al (2001) reported that, among common marmosets, smaller females engaged in fewer nursing bouts than larger females, and Bales et al (2002) found that females with the lowest body weights also exhibited the lowest levels of carrying effort.…”

“…Carrying callitrichid infants comes at a 21% increase in the caloric cost (per minute) of traveling (Tardif, 1996). Infant transport is also associated with other costs, such as decreased foraging and feeding time (e.g., saddle-back tamarins: Goldizen, 1987;cotton-top tamarins: Price, 1992c; also see review in Tardif, 1994) and increased risk of predation (cotton-top tamarins: Price, 1992c; see review in Tardif, 1994). Conception APCID was operationally defined as conception four weeks following birth, and later, as maternal caregiving effort is not expected to be as intensive during this time period.…”

“…No distinction was made as to whether females and males carried one versus two infants, because infants born into large social groups are not generally carried by the same individual (cotton-top tamarins: Price, 1992c), and because there is evidence that there are few additional energetic costs associated with carrying more than one infant at a time (e.g., Saddleback tamarins, S.fuscicollis: Goldizen, 1987;cotton-top tamarins: Price, 1992c). We should note, however, that Schradin and Anzenberger (2001) reported a negative correlation between carrying weight and the distance marmosets could leap, such that an animal carrying two infants might have greater difficulty foraging and avoiding predators than an animal carrying one infant.…”

“…These energetic demands have often been cited as factors necessitating some form of assistance for callitrichid females (e.g., Leutenegger, 1980;Garber, et al, 1984;Goldizen, 1987;Dunbar, 1988;Wright, 1990;Price 1992c), and, indeed, cooperative rearing of offspring is a hallmark of callitrichid reproduction (see review in Tardif, 1996). In every species studied to date, females share the responsibility of infant care with members of their family or social group (e.g., Cleveland and Snowdon, 1984;Goldizen, 1987).…”

Elevated urinary testosterone excretion and decreased maternal caregiving effort in marmosets when conception occurs during the period of infant dependence

“…Mothers were determined to be carrying infants when one or more infants were observed clinging to the body or pelage of a parent or alloparent. We did not distinguish between the carrying of one versus two infants, because infants born into large social groups are not generally carried by the same individual (cotton-top tamarin: Price, 1990Price, , 1992a, and there is evidence that there are few additional costs associated with carrying more than one infant at a time (e.g., saddle-back tamarin: Goldizen, 1987; cotton-top tamarin: Price, 1992b).…”