Interannual Variation in Timing and Synchrony of Parturition in Dall's Sheep

Rachlow, Janet L.; Bowyer, R. Terry

doi:10.2307/1382131

Cited by 98 publications

(113 citation statements)

References 20 publications

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“…Our findings contrast with those of research conducted in northern temperate regions on Dall sheep (Ovisdalli, Rachlow and Bowyer 1991), moose (Alces alces, Bowyer et al 1998;Garel et al 2009), roe deer (Capreolus capreolus, Linnell and Andersen 1998) and reindeer (Rangifer tarandus, Post et al 2003), suggesting that synchronisation of the mother and newborn requirements with high nutritional conditions after parturition (Dauphiné and McClure 1974;Bunnell 1982;Thompson and Turner 1982;Rutberg 1987;Risenhoover and Bailey 1988;Bowyer 1991;Keech et al 2000;Côté and Festa-Bianchet 2001) is the overriding factor in the timing of births.…”

Section: Monthly Rainfall Influence On Fecundity and Recruitment Ratescontrasting

confidence: 99%

Reproductive seasonality in African ungulates in relation to rainfall

2014

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Context. Reproductive seasonality in ungulates has important fitness consequences but its relationship to resource seasonality is not yet fully understood, especially for ungulates inhabiting equatorial environments.Aims. We test hypotheses concerning synchronisation of conception or parturition peaks among African ungulates with seasonal peaks in forage quality and quantity, indexed by rainfall.Methods. We relate monthly apparent fecundity and juvenile recruitment rates to monthly rainfall for six ungulate species inhabiting the Masai Mara National Reserve (Mara) of Kenya, using cross-correlation analysis and distributed lag non-linear models. We compare the phenology and synchrony of breeding among the Mara ungulates with those for other parts of equatorial East Africa, with bimodal rainfall and less seasonal forage variation, and for subtropical southern Africa, with unimodal rainfall distribution and greater seasonal forage variation.Key results. Births were more synchronised for topi, warthog and zebra than for hartebeest, impala and giraffe in the Mara, and for impala and hartebeest in southern than in eastern Africa. This pattern is likely to reflect regional differences in climate and plant phenology, hider-follower dichotomy and grazing versus browsing. All six species except the browsing giraffe apparently time the conception to occur in one wet season and births to occur just before the onset or during the next wet season, so as to maximise high-quality forage intake during conception and parturition. Fecundity and recruitment rates among the African ungulates peak at intermediate levels of rainfall and are reduced at low or excessive levels of rainfall. Fecundity rate is most strongly positively correlated with rainfall pre-conception, during conception and during early gestation, followed by rainfall at about the time of parturition for all the grazers. For giraffe, fecundity rate is most strongly correlated with rainfall during the gestation period.Conclusions. Rainfall seasonality strongly influences reproductive seasonality and juvenile recruitment among African ungulates. The interaction of the rainfall influence with life-history traits and other factors leads to wide interspecific and regional variation.Implications. Global climate change, especially widening annual rainfall variation expected to result from global warming, could reduce the predictability of the timing of peak forage availability and quality based on meteorological cues, the length of time with adequate nutrition or both, and hence reduce reproductive success among tropical ungulates.

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Section: Monthly Rainfall Influence On Fecundity and Recruitment Ratescontrasting

confidence: 99%

Reproductive seasonality in African ungulates in relation to rainfall

2014

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“…We considered using an index of trophic mismatch defined as the percentage of forage species emergent on the date at which 5% of births have occurred, which would quantify the temporal state of the forage resource at the onset of the season of caribou births. However, in some years, our observations of plant phenology were sparse at the beginning of the growing season, and we were concerned about the bias inherent to nonlinear-based estimation of values at the tails of a distribution of observed values (Rachlow & Bowyer 1991). Nonetheless, the index of trophic mismatch we used, that was based on the state of plant phenology on the date of 50% caribou births, correlated closely with the index of trophic mismatch we did not use, that was based on the state of plant phenology on the date of 5% caribou births (rZ0.93).…”

Section: Study Site and Methodsmentioning

confidence: 99%

Climate change reduces reproductive success of an Arctic herbivore through trophic mismatch

Post

Forchhammer

2007

Phil. Trans. R. Soc. B

533

518

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In highly seasonal environments, offspring production by vertebrates is timed to coincide with the annual peak of resource availability. For herbivores, this resource peak is represented by the annual onset and progression of the plant growth season. As plant phenology advances in response to climatic warming, there is potential for development of a mismatch between the peak of resource demands by reproducing herbivores and the peak of resource availability. For migratory herbivores, such as caribou, development of a trophic mismatch is particularly likely because the timing of their seasonal migration to summer ranges, where calves are born, is cued by changes in day length, while onset of the plantgrowing season on the same ranges is cued by local temperatures. Using data collected since 1993 on timing of calving by caribou and timing of plant growth in West Greenland, we document the consequences for reproductive success of a developing trophic mismatch between caribou and their forage plants. As mean spring temperatures at our study site have risen by more than 48C, caribou have not kept pace with advancement of the plant-growing season on their calving range. As a consequence, offspring mortality has risen and offspring production has dropped fourfold.

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“…Temperature is one of the most critical factors influencing phenology in plants (Rachlow and Bowyer 1991). Therefore, we calculated an index to growth and senescence of plants based on mean daily temperatures (Chapin 1983).…”

Section: Plant Phenologymentioning

confidence: 99%

“…In some instances, timing of parturition by large herbivores may respond rapidly to effects of climatic warming on plant phenology (Rachlow andBowyer 1991, Loe et al 2005). Timing of migration and parturition by caribou in West Greenland, however, has failed to keep pace with the advancement of the plant-growing season; consequently, recruitment of young has declined fourfold during a single decade .…”

Section: Climatementioning

confidence: 99%

Timing of seasonal migration in mule deer: effects of climate, plant phenology, and life-history characteristics

et al. 2011

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Abstract. Phenological events of plants and animals are sensitive to climatic processes. Migration is a life-history event exhibited by most large herbivores living in seasonal environments, and is thought to occur in response to dynamics of forage and weather. Decisions regarding when to migrate, however, may be affected by differences in life-history characteristics of individuals. Long-term and intensive study of a population of mule deer (Odocoileus hemionus) in the Sierra Nevada, California, USA, allowed us to document patterns of migration during 11 years that encompassed a wide array of environmental conditions. We used two new techniques to properly account for interval-censored data and disentangle effects of broad-scale climate, local weather patterns, and plant phenology on seasonal patterns of migration, while incorporating effects of individual life-history characteristics. Timing of autumn migration varied substantially among individual deer, but was associated with the severity of winter weather, and in particular, snow depth and cold temperatures. Migratory responses to winter weather, however, were affected by age, nutritional condition, and summer residency of individual females. Old females and those in good nutritional condition risked encountering severe weather by delaying autumn migration, and were thus risk-prone with respect to the potential loss of foraging opportunities in deep snow compared with young females and those in poor nutritional condition. Females that summered on the west side of the crest of the Sierra Nevada delayed autumn migration relative to east-side females, which supports the influence of the local environment on timing of migration. In contrast, timing of spring migration was unrelated to individual life-history characteristics, was nearly twice as synchronous as autumn migration, differed among years, was related to the southern oscillation index, and was influenced by absolute snow depth and advancing phenology of plants. Plasticity in timing of migration in response to climatic conditions and plant phenology may be an adaptive behavioral strategy, which should reduce the detrimental effects of trophic mismatches between resources and other life-history events of large herbivores. Failure to consider effects of nutrition and other life-history traits may cloud interpretation of phenological patterns of mammals and conceal relationships associated with climate change.

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Interannual Variation in Timing and Synchrony of Parturition in Dall's Sheep

Cited by 98 publications

References 20 publications

Reproductive seasonality in African ungulates in relation to rainfall

Reproductive seasonality in African ungulates in relation to rainfall

Climate change reduces reproductive success of an Arctic herbivore through trophic mismatch

Timing of seasonal migration in mule deer: effects of climate, plant phenology, and life-history characteristics

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