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Maternal Effort (maternal + effort)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Maternal Effort is State Dependent: Energetic Limitation or Regulation?

ETHOLOGY, Issue 4 2008
Anke Rehling
Many small altricial rodents have a postpartum oestrus and are often simultaneously pregnant and lactating. Negative influences of concurrent pregnancy and lactation on both lactational performance and the litter in utero are commonly observed and have been interpreted as resulting from high simultaneous energetic demands of gestation and lactation. We studied these effects in the precocial guinea-pig (Cavia aperea f. porcellus) that, like many altricial rodents, has a postpartum oestrus, but in which the peaks of energy expenditure on lactation and gestation are widely separated. This life history allowed to investigate whether physiological regulation other than by energetic limitations may be responsible for allocation conflicts arising when lactation and gestation overlap. By comparing simultaneously pregnant and lactating females with lactating non-pregnant females, we show that females in the former group nurse less and wean earlier than females of the latter group. In a comparison of litter size, litter mass, and pup mortality of females that had not been lactating during pregnancy with females that had been simultaneously pregnant and lactating, we show that the latter do not reduce investment in the following litter. In our study, energetic constraints on ad libitum fed females are unlikely and we therefore suggest that the results must be explained by regulatory constraints on lactational effort. We point out that this explanation has not been excluded for the effects observed in altricial small mammals. [source]

Maternal effort and joey growth in koalas (Phascolarctos cinereus)

JOURNAL OF ZOOLOGY, Issue 4 2006
J. R. Tobey
Abstract The extent to which sex-biased maternal investment characterizes mammals is controversial, with less information available for evaluating patterns of maternal effort in marsupials than in placentals. Koalas Phascolarctos cinereus are size-dimorphic animals with a lengthy period of dependency and they reside in mating systems that might favour sex-biased maternal investment. We examined 18 years of data recorded from koalas living at the San Diego Zoo in order to examine how joey development and maternal condition might be connected. Koalas are pregnant for only 1 month, but joey emergence from the pouch does not occur until 32 weeks of age. Neither maternal condition nor age affected sex ratio at joey emergence, and both sexes had the same survivorship prospects. Koala dams transport and nurse joeys for close to 1 year, at which time the two sexes are size dimorphic. Given the poor-quality diet of koalas, combined with maternal transport of infants who are at least 25% of maternal mass, we suggest that infant rearing poses high energetic costs on koala females. We suggest that ecological and energetic constraints have moulded koala maternal strategies such that females maximize allocation of resources to offspring, regardless of sex, in order to increase prospects for joey survivorship. [source]

Lactating Females Do Not Discriminate Between Their Own Young and Unrelated Pups in the Communally Breeding Rodent, Octodon degus

ETHOLOGY, Issue 9 2006
Luis A. Ebensperger
Females in numerous rodent species engage in communal nesting and breeding, in which they share one or more nests to rear their young. A potential cost of communal nesting and breeding is that mothers divert resources to unrelated offspring. One way mothers could avoid this cost is to recognize and favour their own young over unrelated offspring when allocating maternal effort. We assessed whether female degus (Octodon degus), a communally nesting and breeding caviomorph rodent, discriminate between their own and unrelated offspring during lactation. Female degus previously have been shown to distinguish between their own and unrelated pups when exposed to odours from both. We measured pup discrimination based on differences in the retrieval behaviour of females that were in early or intermediate lactation directed towards their own and unrelated offspring; offspring presented were of similar or different age. Before any event of pup retrieval, lactating females spent similar amounts of time and interacted to a similar extent with their own and unrelated pups. During pup retrieval, all lactating females transported both pups to the nest. Neither relatedness to pups, nor pup-age differences, influenced the order in which pups were retrieved to the nest. Dams waited similar amounts of time before retrieving the first pup when the first transported young was their own or unrelated. Likewise, females waited similar amounts of time before retrieving the second pup when the pup transported first was their own or unrelated. The time between first and second pup transport events was longer when dams were in early when compared with intermediate lactation, but only when pups were of similar age. All experimental subjects nursed unrelated pups after they were retrieved. Collectively, our results do not support the hypothesis that communally breeding female degus use their recognition ability to discriminate against unrelated offspring in favour of their own young. [source]