Ontogeny of long-range vocalizations in a Neotropical fossorial rodent: the Anillaco Tuco-Tuco ( Ctenomys sp.)

AMAYA, JUAN PABLO; ARETA, JUAN IGNACIO

PeerJ

PeerJ

Lugar: London; Año: 2018 vol. 6

Tuco-tucos (Ctenomys spp.) are subterranean rodents that produce territorial, highintensity long-range vocalizations (LRVs) of broadband and low frequency that areessential for long-distance communication between individuals in different tunnelsystems. Despite their importance, the development of LRVs remains poorly understood.In adult Anillaco Tuco-Tucos (Ctenomys sp.) the LRV is composed by twotypes of syllables (series and individual notes) that are repeated a variable numberof times. We studied the development of the LRVs in eight juveniles of the AnillacoTuco-Tuco ranging from 14?28 to 104?118 days after birth. We (1) tested whether thesyllables followed any of three alternative developmental modes (retention of juvenilevocalizations, modification of juvenile precursors or de novo appearance in adults), (2)evaluated the development of structural and acoustic features of syllables, and (3) testedthe prediction that juveniles should produce a greater proportion of atypical series inprecursors of the LRV than adults, due to lack maturation and/or precise couplingof neuromuscular and anatomical structures. The LRV of the Anillaco Tuco-Tucoexhibited a mixed developmental mode: while series developed from juvenile precursorswhose acoustic features gradually approached those of adults, individual notes appearedlater in the ontogeny and de novo with acoustic features indistinguishable from thoseof adults. The number of series per vocalization increased through development andvaried from one to 25 in juvenile males and from one to six in juvenile females. Thestructure of the most common series type (triad) did not exhibit ontogenetic changesand was present as such at the onset of the emission of vocalizations. On the contrary,acoustic features of juvenile triad notes changed with age in both sexes (duration 90%increased through development, while bandwidth 90% and peak frequency decreased).Furthermore, juveniles emitted a higher proportion of atypical series than adults (7.4%vs. 0.3%), as expected in the development of any complex behavior that requires practiceto be mastered. The maturation of the LRV occurred well before the sexual maturation,presumably due to the protracted time needed to acquire or build a burrow system longbefore mating is possible. We propose that protracted vocal development is anothercomponent in the slow developmental strategy of Ctenomys and subterranean rodentsin general.