Energy requirements and metabolism of the Phillip's dikdik (Madoqua saltiana phillipsi)

Abstract

Basal metabolic rates in mammals are mainly determined by body mass, but also by ecological factors. Some mammalian species inhabiting hot, dry environments were found to have lower metabolic rates compared to temperate species. We studied energy metabolism in Phillip's dikdik (Madoqua saltiana phillipsi), a small antelope inhabiting xeric shrubland habitats in the Eastern 'horn' of Africa, and compared results to literature data. We measured body mass (BM) changes and digestibility in 12 adults kept on different food intake levels to determine, by extrapolation to zero BM change, maintenance energy requirements (MEm) for metabolizable energy (ME). The MEm averaged at 404 ± 20 kJ ME kg BM -0.75 d-1. In addition we conducted 24 h-chamber respirometry with seven fed (non-fasted) individuals. Their mean metabolic rate as calculated from oxygen consumption was 403 ± 51 kJ kg BM-0.75 d-1, corroborating the results of the feeding trials. Selecting the 20 lowest values of the respiration measurement period to estimate resting metabolic rate (RMR) resulted in a mean RMR of 244 ± 39 kJ kg BM-0.75 d-1, which was numerically (but not significantly) lower than the expected basal metabolic rate of 293 kJ kg BM-0.75 d-1. Therefore, resting metabolism was similar to the expected average basal metabolism of a mammal of this size, which suggests a comparatively low metabolic rate in dikdiks. Compared to literature data Phillip's dikdiks have a MEm similar to measurements reported for small domestic ruminants, but considerably lower than those reported for other wild ruminant species inhabiting temperate and cold climates.

Metabolic rates of three gazelle species (Nanger soemmerringii, Gazella gazella, Gazella spekei) adapted to arid habitats

“…This is in contrast to findings in another wild ruminant species of similar geographic distribution, the Phillip's dikdik, which was assessed at the same location, and with the same equipment and setup as used in the present study (Dittmann et al 2014a). Given the closely overlapping and ecologically similar habitats, it cannot be argued that dikdik are exposed to differences in climate that could explain this physiological difference from these gazelle species.…”

“…To our own experience, gazelles usually become calm when confined in dark, narrow spaces in a quiet environment, and this was our subjective impression in the animals of this experiment. Also, in a former study with Phillip's dikdiks, we followed the same procedures in animal handling and respiration measurements, which resulted in relatively lower values (also corroborated by measures on body mass changes in relation to digstible energy intake) (Dittmann et al 2014a), suggesting that the higher MR in the gazelles in the present study do not mirror handling stress. However, stress that was not represented by movement but nevertheless influenced the O 2 consumption, and species-specific responses to stressful situations, could not be excluded.…”

“…On the one hand, there may be a generally reduced metabolism even under conditions of unlimited resources, as one can assume for most animals in which metabolic measurements are performed, including the animals of the present study. Such a generally reduced metabolism was, for example, demonstrated in dikdik or (Dittmann et al 2014a) in camelids (Dittmann et al 2014b). On the other hand, another possible component of such an adaptation could be the flexibility to reduce the MR under conditions of resource limitation, as was demonstrated in many ruminants from seasonally variable habitats (e.g.…”

“…All individuals were adult, male and healthy according to the veterinarian in charge, and all procedures were approved by the internal ethics committee of AWWP. Generally, respiration measurements were identical in setup to those reported previously for Phillip's dikdik (Madoqua saltiana phillipsi) (Dittmann et al 2014a).…”

“…G. gazella occurs in southern Lebanon, Syria, Israel, on the Arabian peninsula and isolated regions of Iran, and is reported to be able to withstand severe, hot and dry climatic conditions; some populations allegedly occur in areas without surface water (Mendelssohn 1995). N. soemmerringii occurs in semiarid to arid areas from Eritrea to Somalia (Heckel et al 2008b ruminant species from the same geographic region, the Phillip's dikdik (Madoqua saltiana phillipsi) (Dittmann et al 2014a). Therefore, we predicted that the selected gazelle species would, in a similar manner, display lower MR than expected based on their body mass.…”