On the quantification of suckling intensity in primates

Abstract

The inhibitory effect that suckling has on the reproductive function of primate mothers varies as a function of the intensity with which they are suckled. Here we present an easily computed index of one parameter of suckling intensity, namely the temporal patterning of suckling bouts. High intensity suckling is characterized by frequent nursing bouts demarcated by short interbout intervals. Therefore, our suckling index is based on the brevity of observed interbout intervals, more specifically the proportion of such intervals that fail to exceed a criterion length. The index is an appropriate means of making interspecific comparisons of the development of infant suckling and is well suited for application to field data that include interbout intervals that were not observed in their entirety. To demonstrate its utility, we apply the index to field data collected on the suckling behavior of free-ranging rhesus monkey (Macaca mulatta) infants in India. In this context, we demonstrate that, in rhesus, between-infant differences in suckling intensity manifest themselves early in the postpartum period and contribute to between-female differences in the timing of first mating postpartum.

Richer milk for sons but more milk for daughters: Sex‐biased investment during lactation varies with maternal life history in rhesus macaques

“…Daughter-biased nursing behavior has generally been restricted to low-ranking mothers as a tactic to keep daughters, more often the target of social aggression, in close proximity to the mother (Gomendio, 1990(Gomendio, , 1996. There are potential consequences; increased suckling has been associated with suppression of ovulation and increased interbirth intervals, especially for young mothers (Gomendio, 1989(Gomendio, , 1991Johnson et al, 1998;Ö rdög et al, 1998;Pope et al, 1986;Wilson, 1992;Wilson et al, 1988). However, milk production is not associated with social rank in rhesus macaques at the CNPRC (Hinde et al, 2009) and subsequent reproduction was not associated with infant sex.…”

Postpartum recuperation in primiparous rhesus macaques and development of their infants

“…Measuring actual milk yield in animals have proven to be difficult and has demonstrated conflicting results [Cameron, 1998]. When possible, the coupled use of isotopic methods [Auchtung et al, 2002;Caire et al, 2002;Reik et al, 2007] and behavioral measures such as the duration of sucking bout rate or sucking index [Berman et al, 1993;Gomendio, 1989;Johnson et al, 1998] could provide a more accurate estimation to the influence of lactation on maternal postpartum recuperation and infant development.…”

A novel fecal stable isotope approach to determine the timing of age‐related feeding transitions in wild infant chimpanzees

“…The completion of weaning is also difficult to record because infants may appear weaned from daytime observations but may continue to nurse at night when observations are not normally conducted (Nicolson, ; Reitsema, ). In addition, a weaned individual that continues to latch to the mother's nipple for comfort (i.e., “comfort nursing”) rather than nutrition may be classified inaccurately as a nursing infant from observations alone (Johnson, Malik, & Berman, ; Martin, ).…”