Responses of phenology, synchrony and fecundity of breeding by African ungulates to interannual variation in rainfall
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Joseph O. Ogutu, Hans-Peter Piepho, Holly T. Dublin. (20/3/2014). Responses of phenology, synchrony and fecundity of breeding by African ungulates to interannual variation in rainfall. Wildlife Research, 40(8), pp. 698-717.
Abstract
Context: The timing and synchrony of births are important components of fitness
among ungulates living in seasonal environments.
Aims: We investigated the effects of rainfall variation on interannual variation in the
timing, synchrony and prolificacy of births for six African ungulate species inhabiting an
equatorial savanna with bimodal rainfall.
Methods: We analyse how seasonally and aseasonally breeding African savanna
ungulates maintain reproductive success despite rainfall constraints, and adjust the
phenology, synchrony and fecundity of their breeding to track interannual variation in
rainfall. We use data on six ungulate species inhabiting the Masai Mara National
Reserve (Mara) of Kenya to test five hypotheses concerning the influences of
seasonality in resources, gestation length and the hider–follower strategy on the
timing, synchrony and prolificacy of calving.
Key results: Births were more synchronised for topi, warthog and zebra than for
hartebeest, impala, and giraffe. Births occurred in most months, but tended to peak
during the early rains when forage quality peaks for all species. The rainfall
component exerting the strongest influence on timing of births varied with species.
Gestation length, the hider–follower dichotomy, and hence predation, had apparently
weak influences on birth synchrony. In drought years with nutritionally deficient
forage, births were delayed, less synchronised and fewer. This portrayed protracted
calving seasons, suppression of early conceptions, and delayed onset of births, calf
losses, reproductive pauses or failures. However, in rainy years with sufficient forage,
births peaked early, or were not delayed, and the synchronicity of calving increased
for all species. This suggested early breeding by primiparous females; or higher
fertility early in the mating period. The prolificity of calving increased with rainfall for
topi and warthog but decreased for the remaining species.
Conclusions: Marked interannual variability in rainfall, plant phenology and forage
sufficiency in tropical savannas impose strong constraints on ungulates, favouring
flexible timing of births over strictly seasonal reproduction characteristic of temperate
latitudes with predictable seasonal resource cues.
Implications: Despite high flexibility in their timing of births, widening rainfall
variability expected to result from global warming could lower reproductive success of
tropical ungulates by lowering their fecundity and survival prospects of their calves if
droughts became more frequent and severe.
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Ogutu, Joseph O. https://orcid.org/0000-0002-7379-0387