Growth, weaning and maternal investment from a comparative perspective

Abstract

The process of weaning is related to a critical or threshold body weight attained by offspring among large‐bodied mammals; the anthropoid primates, ungulates and pinnipeds. While weaning weight was allometrically related to maternal weight in interspecific comparisons, it was isometrically related to neonatal weight. When a neonate had grown to four times its birth weight, it was weaned. Differences between taxonomic groups were found only among the fasting phocids, where weanlings attained a lower, but proportional, weight. The duration of lactation was only weakly allometrically related to maternal or neonatal weight, and varied between individuals intraspecifically as a function of maternal condition. The time to weaning appears to be ecologically sensitive rather than to reflect interspecific life‐history variation, in that, irrespective of the time to weaning, similar proportional weights appear to be attained. Interspecific similarities in threshold weaning weights are suggested to result from constraints on maternal abilities to meet energetic requirements of offspring through lactation after infants attain a threshold weight.

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

“…If females reduce their investment in current offspring in favor of future reproductive attempts when resources are low and/or body condition is challenged (Clutton-Brock, 1991;Lee et al, 1991), then we predicted that marmoset females would invest less in their current litters when they conceived during the period of critical infant dependence (DPCID) than when they conceived after the period of critical infant dependence (APCID). More specifically, we expected that conception DPCID, the time of maximal maternal involvement in infant care, represents a cue for upcoming energetic demands, as well as an opportunity for females to make a behavioral trade-off between investment in current versus future offspring.…”

“…Moreover, contradictory to what one might expect, some females might even spend more time carrying infants as group size increases and more alloparents are present (e.g., Wied's black tufted-ear marmosets and Geoffroy's marmosets, C. geoffroyi: Santos et al, 1997). We predicted that, if females do, in fact, reduce investment in current offspring in favor of future reproductive attempts when resources allow them to do so (Lee et al, 1991), then marmoset females would invest less in their current litters when experienced alloparents were present.…”

“…When their physical condition is poor and when they have difficulty meeting their own subsistence needs, females may sacrifice their current offspring's fitness, and possibly survival, in favor of maternal survival and the possibility of producing offspring in the future (Clutton-Brock, 1991;Hrdy, 1999). There is also good reason to believe that females in the best physical condition, and those with abundant resources, might also reduce their overall investment in offspring relative to females in lesser condition and/or with fewer resources available to them (Lee et al, 1991;Fairbanks and McGuire, 1995;Hrdy, 1999). Without jeopardizing offspring survival, these females can improve their own physical condition and prepare for future breeding attempts by providing offspring with the necessary resources in less time and with less effort than other mothers.…”

A whole genome scan to detect quantitative trait loci for gestation length and sow maternal ability related traits in a White Duroc × Erhualian F2 resource population

“…The selection for increased litter size brings problems with increasing piglet mortality and decreasing piglet growth (Johnson et al, 1999). Sows are required for good maternal ability to take care of their litters, because maternal effects are more important than any other single factor in determining early offspring growth and survival (Lee et al, 1991).…”

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

“…When they have difficulty meeting their own subsistence needs, and when their physical condition is poor, females may invest less in their current offspring's fitness in lieu of maintaining or improving maternal condition and the possibility of producing future offspring (e.g., CluttonBrock, 1991;Hrdy, 1999;Lee et al, 1991). It appears, therefore, that the quality and quantity of care that mothers provide to any given offspring is the result of complex trade-offs between their ability to invest in current offspring and the probability of producing offspring in the future (Trivers, 1974).…”