Sociality ofOctodontomys gliroidesand other octodontid rodents reflects the influence of phylogeny

Influence of climate change on the predicted distributions of the genus Tympanoctomys (Rodentia, Hystricomorpha, Octodontidae), and their conservation implications

Viscacha rats (genus Tympanoctomys Yepes, 1942) are ecologically, physiologically, and behaviorally unusual octodontid rodents endemic to the Monte and Patagonian desert biomes of Argentina. The geographic ranges of the different species of Tympanoctomys have been described in general terms but have not been associated with spatial and climate data. Within species, populations are patchily distributed and genetically distinct. We investigated the predicted distribution of Tympanoctomys and the influence of climate fluctuations on their geographic range in historical, current, and future, scenarios. Our objectives were to characterize the environmental niche of the genus, propose a paleoclimatic context for the oldest fossils, characterize the environmental niches for T. barrerae and T. kirchnerorum, and forecast potential future distributions for these taxa. Ecological niche models were constructed using occurrence records from 1941 to the present wherein we identified several precipitation and temperature variables as important predictors of the geographic distributions of the genus, and the species T. barrerae and T. kirchnerorum. Based on our models’ results, we hypothesize that the distribution of Tympanoctomys has contracted from historical to modern times. At the species level, T. kirchnerorum likely experienced the most dramatic change, suffering a large contraction of its historical distribution resulting in its limited present distribution. Given these findings, projected future climate fluctuations and global warming are expected to affect the distributions and persistence of these species.

Spatial relationships among free-living cururos (Spalacopus cyanus) demonstrate burrow sharing and communal nesting

Spatial relationships among conspecifics can provide insights into numerous aspects of social behavior. Spatial data may be particularly important for characterizing the behavior of difficult-to-study species such as subterranean rodents, direct observations of which are challenging. To characterize the social organization of the cururo (Spalacopus cyanus), a subterranean species in the rodent family Octodontidae, we used radiotelemetry to quantify spatial relationships within populations of this species located in Parque Nacional Bosque Fray Jorge and Santuario de la Naturaleza Yerba Loca, Chile. Specifically, we sought to determine if adults in this diurnal species share burrows and subterranean nests, the two criteria typically used to identify subterranean rodents as social. Analyses of radio fixes collected during February–March 2003 revealed that cururos at both Fray Jorge and Yerba Loca shared nighttime nest sites; cluster analyses of these data identified multiple spatially distinct subsets of adults in each population. Overlap of minimum convex polygons constructed from radio fixes collected during daylight hours suggested burrow sharing by animals in both populations. Cluster analyses of overlap values revealed the same spatially distinct groups of individuals identified from analyses of nest sharing; in addition, these analyses revealed one cluster of animals in each population that was not evident from analyses of nighttime data. Collectively, these results confirm that cururos are social, with adults in both study populations sharing burrow systems and communal nests. Our findings add to the growing understanding of social organization in octodontid rodents and reveal a new system for comparative studies of the ecology and evolution of behavioral variation in burrow-dwelling mammals.

On cognitive ecology and the environmental factors that promote Alzheimer disease: lessons from Octodon degus (Rodentia: Octodontidae)

Cognitive ecologist posits that the more efficiently an animal uses information from the biotic and abiotic environment, the more adaptive are its cognitive abilities. Nevertheless, this approach does not test for natural neurodegenerative processes under field or experimental conditions, which may recover animals information processing and decision making and may explain, mechanistically, maladaptive behaviors. Here, we call for integrative approaches to explain the relationship between ultimate and proximate mechanisms behind social behavior. We highlight the importance of using the endemic caviomorph rodent Octodon degus as a valuable natural model for mechanistic studies of social behavior and to explain how physical environments can shape social experiences that might influence impaired cognitive abilities and the onset and progression of neurodegenerative disorders such as Alzheimer disease. We consequently suggest neuroecological approaches to examine how key elements of the environment may affect neural and cognitive mechanisms associated with learning, memory processes and brain structures involved in social behavior. We propose the following three core objectives of a program comprising interdisciplinary research in O. degus, namely: (1) to determine whether diet types provided after weaning can lead to cognitive impairment associated with spatial memory, learning and predisposing to develop Alzheimer disease in younger ages; (2) to examine if early life social experience has long term effects on behavior and cognitive responses and risk for development Alzheimer disease in later life and (3) To determine if an increase of social interactions in adult degu reared in different degree of social stressful conditions alter their behavior and cognitive responses.