Indirect calorimetry measurements were made continuously over a 2-year period in 10 adult female roe deer (Capreolus capreolus) maintained in outdoor enclosures on ad libitum feeding. Results from adult nonpregnant does revealed no endogenous seasonal rhythm in resting metabolic rate (RMR), in contrast to most cervid species. Throughout the 2 years of our study, RMR (overall mean 4695 ± 65 kJ∙d−1) fluctuated in parallel with variations in body mass. The mass-specific RMR ranged from 221.2 ± 4.8 to 230.7 ± 4.0 kJ∙kg−1∙d−1 (466.0 ± 10.8 to 495.5 ± 9.7 kJ∙kg−0.75∙d−1). Results from pregnant females (five in the first year, four in the second) showed that their energy expenditure increased by 15% during the last 2 months of gestation, in step with the increase in body mass. A 27% increase in RMR was recorded in lactating females during the first month post partum. These results show that in a small-bodied cervid such as the roe deer, reproduction costs are no higher than in other wild herbivores.

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We measured energy expenditure by means of indirect calorimetry in European roe deer (Capreolus capreolus) fawns at frequent intervals from birth to 45 days of age. Mean resting metabolic rate (RMR) and body mass (BM) did not differ significantly between males (N = 9) and females (N = 14). RMR significantly increased with the fawn age following the equation RMR (kJ·d-1) = 956 + 31.4 age (days). Growth in BM was linear: BM (kg) = 1.565 + 0.135 age (days). Mass-specific RMR decreased from a peak value of ca. 500 kJ·kg-1·d-1 in the first week to 290.4 ± 10.0 kJ·kg-1·d-1 in the sixth week. Concomitant metabolic trials performed with 14 lactating females and their 19 fawns indicated that metabolic weaning began in the third week, when the fawn's energy expenditure became markedly higher than could be compensated for by the mother's milk. Comparison of the energy expenditure of singletons and twins showed that female roe deer are energetically well adapted to nurse two fawns.

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Among cervids, maternal investment, estimated as the amount of resources and care allocated to the offspring, was expected to be related to species body size. Therefore, maternal investment in a herd of captive Chinese water deer Hydropotes inermis, a relatively small species of cervid, was investigated over 3 years. Except during the lactation period, reproductive females spent about 2-fold more time resting than feeding. During lactation, the amount of time spent feeding increased highly (25.3 min/h during lactation vs 17.3 min/h during the gestation period). Females spent less than 30% of time in communal behaviours with offspring. They did not reject alien fawns during this care period. Frequency and duration of suckling events decreased exponentially from the second week onwards. More than 10% of suckling bouts were non-filial. Prenatal investment leads to a mean litter mass (about 12% of maternal mass) higher than in most cervid species. Postnatal investment in fawns represents a daily mass gain of ca. 85 g/d during the first 2 weeks, without any sexual difference. Female production, timing and synchrony of births and survival of fawns characterized reproductive success. Seventy percent of mature females gave birth, with a mean of 1.9 offspring per female. The sex ratio was even. Births were synchronous, 80% of births occurring in 25 days. In this herd, 0.74 fawn per female was successfully weaned and 0.56 fawn per female survived through their first year. Based on these results we conclude that reproductive strategy of Chinese water deer was efficient and characterized by mother-offspring relationships typical of hiders and high levels of pre- and postnatal investments. This strategy seems typical of small species of cervids without marked sexual dimorphism.