Dynamic spatial overlap in a solitary subterranean rodent: the Anillaco tuco-tuco (Ctenomys sp.)

Abstract

Despite striking diversity in mammalian social behavior, studies of social organization have often dichotomized species by identifying them as either solitary or social (i.e., group living). This tendency has been particularly pronounced for subterranean rodents, the majority of which have long been assumed to be solitary. As a result, variation in social organization has likely been underestimated for these animals, particularly for species in which patterns of space use suggest limited or temporally dynamic opportunities for interactions among conspecifics. Here, we characterize patterns of space use in a population of tuco-tucos (Ctenomys sp.) from Anillaco, La Rioja Province, Argentina. Although these animals have been the subject of extensive research regarding circadian patterns of activity, spatial and social relationships among free-living individuals have not been documented. Analyses of radiotelemetry data from 17 individuals monitored during the breeding season (December 2015) revealed that partial overlap of individual home ranges was common, occurring between male–female as well as female–female pairs of animals. Spatial relationships, however, were dynamic, with both home range sizes and overlap changing on a daily basis. Although members of the study population did not meet the criteria typically used to identify group living in subterranean species, they were not completely solitary. Instead, the animals displayed an intermediate form of social organization characterized by persistent partial overlap of the areas occupied by different adults. These data add to the growing comparative picture of social variation in Ctenomys and suggest that further studies of these animals should contribute to improved understanding of the factors underlying differences in mammalian social systems.

Telling the Seasons Underground: The Circadian Clock and Ambient Temperature Shape Light Exposure and Photoperiodism in a Subterranean Rodent

“…Nevertheless, the magnitude of the temperature effect was potentially lower than that encountered for some epigeous species (Long et al, 2005). This suggests that other factors, such as variable foraging demands and social interactions (Amaya et al, 2021), may also have an important role modulating timing of surface activity in tuco-tucos. Interestingly, while epigeous species retreat to shelters as a reaction to extreme surface temperatures (Chappell and Bartholomew, 1981;Long et al, 2005), subterranean tuco-tucos refrain from exiting to the surface if aboveground temperatures are too high in summer, being a subtly distinct behavioral response.…”

Review of three neglected species of Ctenomys (Rodentia: Ctenomyidae) from Argentina

“…In addition, its distribution has been recently extended to include populations from the localities of Anillaco and Pampa de la Viuda, in La Rioja province, Argentina (Tammone et al 2022). The populations from Anillaco (then treated as C. famosus) have been previously the subject of detailed studies of circadian rhythms, vocalization, and ecology, although they have been erroneously identified under the names of other species (see Valentinuzzi et al 2009;Fracchia et al 2011;Tomotani et al 2012Tomotani et al , 2016Tachinardi et al 2014;Amaya et al 2016Amaya et al , 2021Amaya and Areta 2018;Jannetti et al 2019).…”

Spatial and social organization of the burrowing rodent Clyomys laticeps (Thomas, 1909)

“…While taxa identified as subterranean perform almost all activities underground and only rarely emerge on the surface (Lacey et al 2000), taxa characterized as semifossorial use burrows for critical functions such as nesting and escape from predators but spend a considerable proportion of time above ground foraging and, in some cases, interacting with conspecifics (Kinlaw 1999;Ojeda et al 2013). Because these animals cannot be observed directly when underground, the social organizations and mating systems of burrowing rodents are often characterized based on analyses of spatial overlap among individuals (Lacey 2000;Steinwald et al 2013;Amaya et al 2021). For example, species in which adults display little or no overlap with conspecifics are typically described as solitary (Mares et al 1997;Cooper and Randall 2007;Amaya et al 2021), whereas those displaying extensive and persistent overlap (i.e., burrow sharing) are often identified as group living (Sobrero et al 2014;Lacey et al 2019;O'Brien et al 2020).…”