Heat stress reduces growth rate of red deer calf: Climate warming implications

but it is unlike to apply to a wide range of physical environments. The use of multivariate anal- ysis overcomes these problems, as it enables identifying the contribution of each variable while taking into account the effects of all other variables on the responses of interest [61]. We applied a multivariate approach, in which all physical environment variables that constituted our thermal stress indices were fitted into the model. This analysis indicated that the contribu- tion of the different variables was not the same on calf growth than on mother weight. Indeed, some variables did not even have any significant contribution, which suggests they were obso- lete as constituents of our heat stress indices. Our analysis revealed that daily means of air tem- perature and wind speed had a negative effect on calf growth, while the effect of humidity was positive. Air temperature and wind speed effects were as predicted, as these variables are posi- tively correlated with convection heat exchange. The positive effect of humidity on calf growth was unexpected, contrasting with heat stress chart predictions [62]. However, mean humidity Fig 6. Predicted mother weight (kg) against daily mean air temperature (˚C) and percentage of air humidity and the additive effect of bearing a male or a female through lactation from model in Table 6. Dashed line: ± standard error. Response variable has been centred by subtraction of the mean value. https://doi.org/10.1371/journal.pone.0233809.g006 PLOS ONE Heat stress and calf growth in red deer

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