a b s t r a c tAnsell's mole-rats (Fukomys anselli) live in families of a breeding pair and several overlapping generations of their non-breeding offspring. Locomotor activity of 47 Ansell's mole-rats from six laboratory families was recorded for a week using radio frequency identification (RFID). This technique allowed monitoring each animal's activity without isolating them from other members of their family. Animals were active about 17% of the recording time, and older animals were significantly less active than younger ones. Females tended to be slightly more active than males. There was no significant difference in the amount of activity between breeding and non-breeding individuals. Consequently, the activity pattern does not seem to account for previously reported differences in longevity between breeding and non-breeding animals.

BackgroundReproduction is an energetically expensive process that supposedly impairs somatic integrity in the long term, because resources are limited and have to be allocated between reproduction and somatic maintenance, as predicted by the life history trade-off model. The consequence of reduced investment in somatic maintenance is a gradual deterioration of function, i.e. senescence. However, this classical trade-off model gets challenged by an increasing number of contradicting studies. Here we report about an animal model, which adds more complexity to the ongoing debate. Ansell’s mole-rats are long-lived social subterranean rodents with only the founder pair reproducing, while most of their offspring remain in the parental burrow system and do not breed. Despite of a clear reproductive trade-off, breeders live up to twice as long as non-breeders, a unique feature amongst mammals.MethodsWe investigated mass-specific resting metabolic rates (msRMR) of breeders and non-breeders to gain information about the physiological basis underlying the reproduction-associated longevity in Ansell’s mole-rats. We assessed the thermoneutral zone (TNZ) for breeders and non-breeders separately by means of indirect calorimetry. We applied generalized linear mixed-effects models for repeated measurements using the msRMR in the respective TNZs.ResultsTNZ differed between reproductive and non-reproductive Ansell’s mole-rats. Contrary to classical aging models, the shorter-lived non-breeders had significantly lower msRMR within the thermoneutral zone compared to breeders.ConclusionThis is the first study reporting a positive correlation between msRMR and lifespan based on reproductive status. Our finding contradicts common aging theories, but supports recently introduced models which do not necessarily link reproductive trade-offs to lifespan reduction.

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