Ctenomys

The zooarchaeological study of small-vertebrate consumption requires a taphonomical approach to differentiate animal bones that were incidentally incorporated from those that were intentionally exploited in the past human subsistence. In order to make this distinction, the relationship between archaeological small-rodent burned bones and prehistoric human behavior was explored using an experimental cooking study as a modern analogue. During the cooking experiment the entire carcasses of three guinea pigs (Cavia porcellus) and two yellow-toothed cavies (Galea leucoblephara) were placed in the coals of an open fire that simulate a real campfire, rotating their positions until the meat was completely cooked. Subsequently, the intensity of burning damage and the loss of skeletal elements were analyzed at macroscopical levels. The data was used to identify cooking evidence in the Ctenomyidae and Caviidae rodent bones recovered from Quebrada del Real 1 (ca. 6000–300 BP, Córdoba, Argentina). Remarkable similarities between the archaeological and analogical records were found, including the distinctive burning pattern on the distal extremities of the unmeaty long bones (e.g, radii and tibiae), the high frequency of broken incisor teeth and the loss of autopodium elements. Based on these comparative results, it is suggested that the small-rodent assemblages of QR1 were primary accumulated by humans though butchery, cooking and consumption related activities. Extending this study to other archaeological sites in South America may help to identify the prehistoric bone collectors of these small-animals.► We conducted a cooking experiment exposing cavy rodent's carcasses directly on fire. ► Then, we examined the pattern of burning bone modification and elements loss. ► We compared the results with the small-rodent assemblage from Quebrada del Real 1. ► We conclude that archaeological rodent bones were primary accumulated by humans.

Diversas especies de roedores se encuentran con frecuencia en los sitios arqueológicos del norte de Tierra del Fuego. Sin embargo, discriminar las vías de incorporación en los contextos arqueofaunísticos y su potencialidad resulta una tarea ardua. La identifi-cación de aquellos restos que ingresaron por acción antrópica o por agentes naturales resulta necesaria para poder inferir el rol que tuvieron en la subsistencia humana. En este trabajo se estudian los restos de roedores del sitio arqueológico Las Vueltas 1 (Isla Grande de Tierra del Fuego, Argentina), donde representan el segundo taxón más abundante en la muestra. Se identificaron un total de 2191 elementos esqueletarios; 1488 corresponden al caviomorfo Ctenomys magellanicus y 703 a representantes de la familia Cricetidae, con al menos 4 especies. La interpretación tafonómica efectuada sugiere un origen múltiple; buena parte del material parece haber ingresado por la acción acumuladora de aves rapaces y cánidos y también por incorporación natural a través de muerte en madrigueras. No obstante y aunque en menor grado, hay evidencias de consumo y descarte antrópico en C. magellanicus.
Abstract
It is frequent to find the remains of several rodent species among the many archaeological sites of Northern Tierra del Fuego. However, the taphonomic interpretation of rodents is a complex issue, given that it is necessary to identify if these were incorporated into the archaeological assemblages through anthropic or natural action or agents. Yet, the identification of those assemblages that accumulated through human action or due to natural agents is an important issue given that only then can we infer the role that rodents had in human subsistence. In this article, we study

Ctenomys are mainly solitary subterranean rodents. Life underground has advantages (protection against predators, environmental control and reduced competition) but also implies disadvantages (digging costs, coping with hypercapnia, physiological and sensory changes, and communication problems) that can affect the social structure. Reproduction is a critical moment in the use of the signal repertoire, because individuals should locate in space, travel to, contact and copulate with a suitable partner. Energy expenditure involved in digging (connecting) tunnels makes difficult to attain a partner burrow system , but predation risk involved in moving above ground can counterbalance it and coupled with the spatial structure of the population, can determine the best communicative strategy to contact and locate a potential partner. Vocalisations allow to communicate over longer distances an with a reduced risk, while chemical signals, mostly aimed at vomerolfaction involve proximity or direct contact with the sample odour thus making information gathering more risky. As Ctenomys can use different signal types to gather different types of information leading to copulation, we propose that the use of these signals would be flexible, depending mostly on population spatial structure and type of predators living in the zone. This is because differences among species and/or populations in the use and characteristics of long-range vocalisations could be induced by environmental and/or social factors. This variation could be considered as a case of phenotypic plasticity, determining communication strategies variability in reproductive context, mostly dependent on long-range communication signals and the behaviour of males.

Ontogenetic allometries of craniomandibular and dental features linked to digging were analyzed in 5 species of the South American subterranean rodent Ctenomys (tuco-tucos). With the exception of upper incisor procumbency, variables showed high correlation with overall skull size. In particular, craniomandibular variables related to the production of bite forces at the incisors showed near-geometric similarity during postnatal growth and interspecific changes in early developmental stages resulting in different starting forms (lateral transposition). Such an interspecific pattern of change is similar to one previously reported to occur among living and extinct ctenomyid genera. These results suggest more evolutionary flexibility for changes in early ontogenetic stages and allow rejection of the hypothesis that interspecific shape differences in the skull of Ctenomys would be associated with differences in size alone.

South American subterranean rodents (Ctenomys aff. knighti), commonly known as tuco-tucos, display nocturnal, wheel-running behavior under light-dark (LD) conditions, and free-running periods >24 h in constant darkness (DD). However, several reports in the field suggested that a substantial amount of activity occurs during daylight hours, leading us to question whether circadian entrainment in the laboratory accurately reflects behavior in natural conditions. We compared circadian patterns of locomotor activity in DD of animals previously entrained to full laboratory LD cycles (LD12:12) with those of animals that were trapped directly from the field. In both cases, activity onsets in DD immediately reflected the previous dark onset or sundown. Furthermore, freerunning periods upon release into DD were close to 24 h indicating aftereffects of prior entrainment, similarly in both conditions. No difference was detected in the phase of activity measured with and without access to a running wheel. However, when individuals were observed continuously during daylight hours in a semi-natural enclosure, they emerged above-ground on a daily basis. These day-time activities consisted of foraging and burrow maintenance, suggesting that the designation of this species as nocturnal might be inaccurate in the field. Our study of a solitary subterranean species suggests that the circadian clock is entrained similarly under field and laboratory conditions and that day-time activity expressed only in the field is required for foraging and may not be time-dictated by the circadian pacemaker.

ABSTRACT Burrow construction in the subterranean Ctenomys talarum (Rodentia: Ctenomyidae) primarily occurs by scratch-digging. In this study, we compared the limbs of an ontogenetic series of C. talarum to identify variation in bony elements related to fossorial habits using a morphometrical and biomechanical approach.Diameters and functional lengths of long bones were
measured and 10 functional indices were constructed. We
found that limb proportions of C. talarum undergo significant changes throughout postnatal ontogeny, and no significant differences between sexes were observed. Five of six forelimb indices and two of four hindlimb indices showed differences between ages. According to discriminant analysis, the indices that contributed most to discrimination among age groups were robustness of the humerus and ulna, relative epicondylar width, crural and brachial indices, and index of fossorial ability (IFA).
Particularly, pups could be differentiated from juveniles and adults by more robust humeri and ulnae, wider epicondyles, longer middle limb elements, and a proportionally shorter olecranon. Greater robustness indicated a possible compensation for lower bone stiffness while wider epicondyles may be associated to improved effective forces in those muscles that originate onto them, compensating the lower muscular development. The gradual increase in the IFA suggested a gradual enhancement in the scratch-digging performance due to an improvement in the mechanical advantage of forearm extensors. Middle limb indices were higher in pups than in juveniles–adults, reflecting relatively more gracile limbs in their middle segments, which is in accordance with their incipient fossorial ability. In sum, our results show that in C. talarum some scratch-digging adaptations are already present during early postnatal ontogeny, which suggests that they are prenatally shaped, and other traits develop progressively. The role of early digging behavior as a factor influencing on morphology development is discussed.

Se describe y se discute la anatomía del cráneo, mandíbula, dentición y esqueleto poscraneano de Praectenomys Villarroel, 1975 sobre la base de comparaciones métricas y morfológicas con el resto de los representantes de la familia. Se concluye que Praectenomys es un ctenomino monoespecífico, con adaptaciones a la excavación en sus miembros anteriores y en el cráneo y de relaciones filogenéticas inciertas respecto del resto de los ctenominos.