Environmental factors affecting the length of gestation in mammals

Racey, P. A.

doi:10.1007/978-1-349-03964-7_14

Cited by 120 publications

(160 citation statements)

References 64 publications

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“…Jamaican fruit bat, Fleming, 1971; pipistrelle bat Pipistrellus pipistrellus, Racey & Swift, 1981; Schreibers' long-®ngered bat Miniopterus schreibersii, Kimura, Takeda & Uchida, 1987;Crichton, Seamark & Krutzsch, 1989). The 5-month gestation in greater spearnosed bats (James, 1977) is normal for a large (80 g), non-hibernating bat (Racey, 1973(Racey, , 1982 and does not suggest a post-conception delay in reproduction. None the less, brief delays may be dif®cult to detect, and it is possible that females postpone parturition or reduce gestation by a few days to co-ordinate birth with their group-mates (Berger, 1992).…”

Section: Discussionmentioning

confidence: 99%

Birth synchrony in greater spear‐nosed bats (Phyllostomus hastatus)

Porter

Wilkinson

2001

Journal of Zoology

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For many animals, strategies for optimally timing reproduction involve monitoring not only the physical environment, but also the social context. To explore the potential for social factors to modulate reproductive seasonality, the in¯uence of social and environmental cues on birth timing was examined in greater spear-nosed bats Phyllostomus hastatus. Births were observed or dated from pup growth curves in three caves on Trinidad, West Indies, over 4 years. Nearly 40% of the variability in birth dates could be explained by environmental factors because birth dates differed signi®cantly between years and showed consistent differences between locations that receive differing rainfall amounts. Nevertheless, the timing of births within caves and in captivity indicated that social cues also affect the timing and synchrony of births within female social groups. Within each cave, social groups differed signi®cantly in mean birth dates. Two groups of greater spear-nosed bats brought into captivity and maintained without seasonal cues initially exhibited less birth synchrony than wild groups, but birth synchrony did not decline over 3 subsequent years. Further evidence for the in¯uence of social cues on reproductive timing came from four females that were transferred between the captive groups and then gave birth in synchrony with their new group and out of schedule with their original group. Social cues in¯uencing reproductive timing are unlikely to be volatile chemicals or other passively transferred cues, given that frequent prolonged physical contact did not increase birth synchrony between adjacent wild groups. Cues are more probably transferred actively between female group members, perhaps by grooming, or through mating with one attendant male.

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Section: Discussionmentioning

confidence: 99%

Birth synchrony in greater spear‐nosed bats (Phyllostomus hastatus)

Porter

Wilkinson

2001

Journal of Zoology

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“…Therefore, the retarded embryonic development of the long-fingered bat is a direct and passive response to the cold and depressed metabolism as indicated by Kimura & Uchida (1983), and seems to differ essentially from that of the above 2 non-hibernating species. On the other hand, in the pipistrelle bat, delayed development can take place experimentally under cold conditions after fetuses have reached a palpable size (Racey, 1973); under natural conditions also, the gestation period is extended in cold weather, and the duration of the low progesterone period that occurs between the apparent initial rise and fall in early pregnancy and the later high levels just before parturition is lengthened (Racey & Swift, 1981), and this prolonged period of low progesterone seems to coincide with the period of cold weather. This phenomenon in the pipistrelle bat may be analogous to the low progesterone period that appears to occur in response to the cold during delayed development in the Japanese long-fingered bat.…”

Section: Discussionmentioning

confidence: 99%

Changes in progesterone concentrations in the Japanese long-fingered bat, Miniopterus schreibersii fuliginosus

Kimura¹,

Takeda²,

Uchida³

1987

Reproduction

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Summary. In the Japanese long-fingered bat, when compared with the baseline values during non-pregnancy in the autumn, plasma progesterone concentrations were not significantly elevated during the delayed implantation stage that begins before the bats enter hibernation. However, progesterone concentrations were significantly lower during the delayed development stage that occurs during hibernation and rose significantly during the rapid embryogenesis that occurs after arousal from hibernation in the spring. Changes in the corpus luteum volume corresponded closely with those of plasma progesterone values. Maintenance of gravid females at 25\s=deg\Cfor 2 weeks in winter resulted in significant increases in the plasma progesterone concentration and the corpus luteum volume.

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“…In some white rats, for example, there was little or no difference in food consumption between pregnant and non-reproductive females (Slonaker, 1925;Wang, 1925); however, activity (=wheel running) was 57-96% lower in the pregnant individuals. Thus, at least some species may shift allocation of energy from activity to gestation by reducing the frequency and/or duration of certain behaviors (Racey, 1981(Racey, , 1982; without integration of behavioral and energetic data, this tactic can result in an underestimation of the total energy allocated to gestation. A combination of caloric consumption, respirometry, and time budgets of behavior, before and during gestation (reproduction) is a requisite for assessment of the allocation of energy to maintenance, "the work of growth" (Brody, 1945), and net production during gestation.…”

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confidence: 99%

“…Fat storage may be of importance to bats, however, because of their unavoidably high activity levels and obvious flight costs. For example, in some species {e.g., big brown bat, Eptesicus fuscus) the fraction of body fat increases by as much as 68% in one week during mid-pregnancy (Stack, 1985) and if storage is unavailable foetal growth rates and pregnancy rates often decline (Racey, 1973;Kurta, 1986). Although the causal mechanisms of these results are not known, it appears from more extensive data on other species that smaller mammals may be more "hard-wired" to gestation length itself rather than storage.…”

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confidence: 99%

“…Although the causal mechanisms of these results are not known, it appears from more extensive data on other species that smaller mammals may be more "hard-wired" to gestation length itself rather than storage. After controlling for body size, birth weight, litter size, and body temperature (Racey, 1981), increases in ingestion rates correlate most closely with gestation length {e.g., Millar, 1977Millar, , 1978McClure, 1987).…”

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confidence: 99%

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Energy Allocation in Mammalian Reproduction

Gittleman

Thompson

1988

Am Zool

739

523

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SYNOPSIS. On behavioral, hormonal, and physiological grounds, mammalian reproduction can be compartmentalized into the following continuous sequence of events: mating (courtship, estrous), gestation, parturition, lactation, post-lactational parental care, and maternal recovery. We point out that comparing the relative allocation of energy for these events across mammals is difficult because of life history variability (e.g., litter size, birth weight), allometry, phylogeny, and individual variation. We review the empirical and theoretical literature on each of these events with respect to: different methodologies in measuring energy use; broad patterns of energy consumption across diverse mammalian taxa; and, identification of particular reproductive characteristics {e.g., birthing, parental care) which may be costly but have yet to receive energetic measurements. Although most studies have considered gestation and lactation the critical reproductive events for energy expenditure, variation in these events is substantial and almost certainly is a function of relative allocation of time to gestation vs. lactation as well as the presumed energetic costs of mating, birthing and parental care. In addition, repeated observations show that behavioral compensation is an extremely important strategy for minimizing energy requirements during reproduction. From this review, we argue that more complete analyses will come from (1) incorporating energetic measurements in studies of mammalian behavior and (2) including mechanisms of behavioral compensation into physiological studies.

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Environmental factors affecting the length of gestation in mammals

Cited by 120 publications

References 64 publications

Birth synchrony in greater spear‐nosed bats (Phyllostomus hastatus)

Birth synchrony in greater spear‐nosed bats (Phyllostomus hastatus)

Changes in progesterone concentrations in the Japanese long-fingered bat, Miniopterus schreibersii fuliginosus

Energy Allocation in Mammalian Reproduction

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