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The objective of this study was to evaluate the maternal costs of reproduction and pup development in the subterranean rodent Ctenomys talarum (Thomas 1898). Statistical differences were detected in whole-animal metabolic rates between nonreproductive and pregnant or lactating females. Whole-animal metabolic rates during pregnancy and lactation were 128% and 151% of the resting metabolic rate (RMR) observed in nonreproductive females. The total additional energy cost of reproduction (above the nonreproductive level) was similar for both the gestation and lactation periods. Mass-specific RMR revealed an upregulation of cell or tissue metabolism during lactation but not during gestation. The mass-specific metabolic rate of pups was 237% of the adults' metabolic rates. No differences were observed in body temperature among nonreproductive, pregnant, or lactating females. No differences were detected in body mass at birth among pups from litters with different numbers of nestlings. Pups increased their body temperature, reaching adult temperature at 30 d of age, when they were near weaning. Milk constituted the exclusive food for pups until they started eating solid food at 10 d old. Suckling time decreased with age of pups, and at the same time, mother chases directed toward their pups increased. These reproductive characteristics may contribute to successful existence in a subterranean habitat.

Subterranean burrows provide inhabitants with shelter, a relatively stable thermal environment, and potentially access to food resources. However, one cost of living in such burrows is the energetically expensive mode of locomotion. Soil hardness and the physiological capabilities of animals are likely important factors that affect the cost of burrow construction, and hence, distribution of burrows. We assessed the effect of soil hardness on the cost of digging by captive individual Ctenomys talarum Thomas, 1898 in soft soils. Digging metabolic rate (DMR) was higher in harder soil than in softer soil (408.30 ± 51.35 mL O2·h–1 vs. 267.59 ± 20.97 mL O2·h–1, respectively). In C. talarum, a higher soil hardness augments DMR by increasing, in terms of the cost of burrowing model, the costs of shearing and of pushing the removed soil. Additionally, these costs differ between C. talarum and other subterranean species (e.g., Thomomys bottae (Eydoux and Gervais, 1836)), depending on soil hardness and digging mode. Thus, the relationship between digging cost and soil hardness appears to be one of the most important factors that affect burrowing efficiency in subterranean rodents.