Energetic expenditure during vocalization in pups of the subterranean rodent Ctenomys talarum

Nestlings reduce their predation risk by attending to predator-information encoded within conspecific alarm calls

Predation is one of the main threats to altricial nestlings, with predators often locating nests via eavesdropping on begging signals. Nestlings may be able to adjust their begging based on the current level of risk by monitoring both intra- and interspecific alarm calls near the nest. We show that noisy miner (Manorina melanocephala) nestlings can differentiate between terrestrial and aerial alarm calls of their own species, as they suppressed begging behaviour for longer in response to terrestrial rather than aerial alarm calls. This differential response is potentially due to greater danger that terrestrial calls encode. In contrast, nestlings ignored alarm calls of the sympatric grey butcherbird (Cracticus torquatus) and continued to beg but reduced begging intensity in response to the non-alarm calls of a sympatric eastern rosella (Platycercus eximius), suggesting nestlings were likely responding based upon similarity to a known signal as opposed to expressing a learnt behaviour. Results show that nestlings respond adaptively to two different intraspecific alarm signals but have not learnt to respond to the alarm calls of sympatric species. These suggest that nestlings are able to take advantage of the complex vocal repertoire that adults produce, although discernment is an issue when filtering out irrelevant stimuli.

Social modulation of the daily activity rhythm in a solitary subterranean rodent, the tuco-tuco (Ctenomys sp)

South American subterranean rodents are mainly described as solitary and mutual synchronization was never observed among individuals maintained together in laboratory. We report that a single birth event was capable of disrupting the robust nocturnal activity rhythm of singly housed tuco-tucos from north-west Argentina. "Around-the-clock activity" was displayed by 8 out of 13 animals whose cages were closer to the newborn pups. However, experimental exposure to a pup vocalization did not produce a similar effect on the rhythms of adult animals. Our results indicate an effect of social interaction in the expression of biological rhythms even in solitary animals.

Thermoregulatory development and behavior of Ctenomys talarum pups during brief repeated postnatal isolation

In altricial mammals, the role of the mother and siblings throughout pup's early ontogeny is critical to determine "normal" development in neonates. It has been reported that variations in parental investment during pups' development affect thermoregulatory capacity, growth patterns, brain development and behavior during lifetime, such as spatial learning and memory in adults. Ctenomys talarum (tuco-tuco) is a solitary subterranean rodent, who inhabits complex burrows and exhibits developed spatial orientation abilities. Tuco-tuco's pups display an altricial development, spending more than 80% of the time in contact with the mother. Throughout weaning period, pups display active exploratory behavior and improvements in their spatial capabilities. Then, we determined the effect of repeated brief postnatal isolations on the acquisition of physiological thermoregulation and the development of spatial learning capabilities in tuco-tuco's pups. As it occurs in wild animals, daily brief isolations (30min) did not affect the acquisition of adult's body temperature nor resting metabolic rate's development pattern. Moreover, behavioral response and adult spatial abilities of isolated pups were similar to that observed in non-isolated ones. Then, during periods of mother's absence, minor physiological and behavioral adjustments, such as shivering and postural changes, are required to keep C. talarum pups within allostasis.