Navigational experience affect cognition: Spatial learning capabilities in captive and wild-born tuco-tucos.

There is a growing recognition of the influence of both genetic and ecological context in shaping different cognitive traits. The hippocampal region is identified as a critical area for memory and learning in mammals, susceptible to modification by environmental influences. Although previous studies have identified the effects of various factors on cognitive parameters during early development, comparatively few research was conducted on wild species to analyze the role of natural environmental stimuli in the formation of spatial learning and memory abilities. Thus, to assess the importance of exposure to a complex and challenging environment during early development, we compared spatial learning performance of captive-born tuco-tucos with previous data obtained in our laboratory from wild-born adult tuco-tucos. The results showed that wild-born individuals learned faster, requiring less time to complete a labyrinth and making fewer errors than those who had no experience in their natural environment. These findings underscore the importance of considering ecological factors in understanding the evolution of brains and cognitive abilities.

Individual differences in behaviour are related to metabolism, stress response, testosterone, and immunity in the subterranean rodent Ctenomys talarum.

The growth of personality research has led to the integration of consistent variation of individual behaviour in multidimensional approaches including physiological variables, which are required to continue building a more comprehensive theory about coping strategies. In this study, we used wild-caught males of Ctenomys talarum (tuco-tucos), a solitary subterranean rodent, to assess the relationships among personality traits and several physiological variables, namely stress response, testosterone, immunity, and energy metabolism. Subjects (n = 21) were used in experimental tests assessing behaviour, energy metabolism, testosterone levels, inflammatory cell-mediated and humoral immunity, and stress response to a simulated predator attack. The structural equation model explained a moderate portion of the variance of personality behaviours related to activity (52%), boldness (35%), and socioaversion (30%). More active and bold individuals showed higher oxygen consumption. While those subjects had lower baseline cortisol levels, there was no relationship between cortisol levels of the stress-induced response. Cell-mediated immune response was related to activity levels. Finally, testosterone only affected boldness. Despite some of these relationships diverge in direction to predicted ones, overall they support the existence of coping styles in male C. talarum; and are discussed in the light of current hypotheses and particular behavioural and ecological traits of tuco-tucos.

Temporal Dissociation Between Activity and Body Temperature Rhythms of a Subterranean Rodent (Ctenomys famosus) in Field Enclosures.

Several wild rodents, such as the subterranean tuco-tucos (Ctenomys famosus), switch their time of activity from diurnal to nocturnal when they are transferred from field to the laboratory. Nevertheless, in most studies, different methods to measure activity in each of these conditions were used, which raised the question of whether the detected change in activity timing could be an artifact. Because locomotor activity and body temperature (Tb) rhythms in rodents are tightly synchronized and because abdominal Tb loggers can provide continuous measurements across field and laboratory, we monitored Tb as a proxy of activity in tuco-tucos transferred from a semi-field enclosure to constant lab conditions. In the first stage of this study ("Tb-only group," 2012-2016), we verified high incidence (55%, n = 20) of arrhythmicity, with no consistent diurnal Tb rhythms in tuco-tucos maintained under semi-field conditions. Because these results were discrepant from subsequent findings using miniature accelerometers (portable activity loggers), which showed diurnal activity patterns in natural conditions (n = 10, "Activity-only group," 2016-2017), we also investigated, in the present study, whether the tight association between activity and Tb would be sustained outside the lab. To verify this, we measured activity and Tb simultaneously across laboratory and semi-field deploying both accelerometers and Tb loggers to each animal. These measurements (n = 11, "Tb + activity group," 2019-2022) confirmed diurnality of locomotor activity and revealed an unexpected loosening of the temporal association between Tb and activity rhythms in the field enclosures, which is otherwise robustly tight in the laboratory.

Natural life cycle of Versteria cuja (Taeniidae) in Argentina and histopathology of metacestodiasis in intermediate hosts.

Using morphological and molecular studies, the life cycle of Versteria cuja (Cestoda: Taeniidae) was elucidated, involving subterranean rodents (Ctenomyidae) as intermediate hosts, and the lesser grison, Galictis cuja (Mustelidae), as definitive host. Metacestodes (cysticerci and polycephalic larvae) were found mainly in the liver but also in spleen, pancreas, lungs and small intestine of 2 species of tuco-tucos (Ctenomys spp.) from Chubut, Argentina. Identity of the metacestodes with the adult was based primarily on the number, size and shape of rostellar hooks: 40­48 hooks in 2 rows, particularly small (10­16 µm total length by 6­10 µm wide), composed of handle, blade and guard with characteristic shapes. Genetic analysis (cox1 gen mtDNA) performed on metacestodes from both intermediate hosts corroborated their conspecificity with adults of V. cuja from lesser grisons in the same locality. Histopathological study showed the hepatic parenchyma altered by the presence of cysts containing larvae, each surrounded by a capsule of connective tissue with inflammatory infiltrate, atrophied hepatocytes and an increase of bile ducts. In the lung, in addition to the cysts, dilated alveoli, oedema and hyperaemic blood vessels were observed. This is the first report of a natural life cycle of a Versteria species from South America. It shows strong similarities with that described for a North American zoonotic lineage of Versteria, confirming a close relationship between V. cuja and this North American lineage, as previously demonstrated by molecular studies. Consequently, the zoonotic potential of V. cuja should not be disregarded.

Daylength Shapes Entrainment Patterns to Artificial Photoperiods in a Subterranean Rodent.

Photoperiodism plays an important role in the synchronization of seasonal phenomena in various organisms. In mammals, photoperiod encoding is mediated by differential entrainment of the circadian system. The limits of daily light entrainment and photoperiodic time measurement can be verified in organisms that inhabit extreme photic environments, such as the subterranean. In this experimental study, we evaluated entrainment of circadian wheel-running rhythms in South American subterranean rodents, the Anillaco tuco-tucos (Ctenomys aff. knighti), exposed to different artificial photoperiods, from extremely long to extremely short photophases (LD 21:3, LD 18:6, LD 15:9, LD 9:15, LD 6:18 and LD 3:21). Artificial photoperiods synchronized their activity/rest rhythms and clear differences occurred in (a) phase angles of entrainment relative to the LD cycle and (b) duration of the daily activity phase α. These photoperiod-dependent patterns of entrainment were similar to those reported for epigeous species. Release into constant darkness conditions revealed aftereffects of entrainment to different photoperiods, observed in α but not in the free-running period τ. We also verified if animals coming from summer and winter natural photoperiods entrained equally to the artificial photoperiods by evaluating their phase angle of entrainment, α and τ aftereffects. To this end, experimental animals were divided into "Matching" and "Mismatching" groups, based on whether the experimental photoperiod (short-day [L < 12 h] or long-day [L > 12 h]) matched or not the natural photoperiod to which they had been previously exposed. No significant differences were found in the phase angle of entrainment, α and τ aftereffects in each artificial photoperiod. Our results indicate that the circadian clocks of tuco-tucos are capable of photoperiodic time measurement despite their natural subterranean habits and that the final entrainment patterns achieved by the circadian clock do not depend on the photoperiodic history.

Redefining the Distributional Boundaries and Phylogenetic Relationships for Ctenomids From Central Argentina.

With about 68 recognized living species, subterranean rodents of the genus Ctenomys are found in a multiplicity of habitats, from the dunes of the Atlantic coast to the Andes Mountains, including environments ranging from humid steppes of Pampas to the dry deserts of Chaco region. However, this genus needs an exhaustive reevaluation of its systematic and phylogenetic relationships regarding the different groups that compose it. This knowledge is essential to propose biodiversity conservation strategies both at species level and at higher hierarchical levels. In order to clarify the taxonomy and the recent evolutionary history from populations of Ctenomys in the Pampas region, Argentina, phylogenetic relationships among them were evaluated using mitochondrial DNA sequences: gene encoding cytochrome b protein (1,140 bp) and the non-coding D-loop region (434 bp). To infer the divergence times inside the Ctenomys clade, a Bayesian calibrate tree using fossil remains data from different families within Caviomorpha was performed at first. Secondly, that calibration data was used as priors in a new Bayesian phylogenetic inference within the genus Ctenomys. This phylogenetic tree emphasized on species currently distributed on the Pampas region, more precisely considering both the talarum and mendocinus groups. Bayesian inferences (BI) were integrated with the results of a Maximum Likelihood approach (ML). Based on these results, the distributional limits of the mendocinus and talarum groups appear to be related to the physiognomy of the Pampas region soils. On the other hand, the validity of C. pundti complex as a differentiated species of C. talarum is debated. According to previous evidence from morphological and chromosomal studies, these results show a very low divergence between those species that originally were classified within the talarum group. Mitochondrial DNA sequences from populations associated with these putative species have not recovered as reciprocal monophyletic groups in the phylogenetic analyses. In conclusion, C. talarum and C. pundti complex might be considered as the same biological species, or lineages going through a recent or incipient differentiation process. The results obtained in this study have important implications for conservation policies and practices, since both species are currently categorized as Vulnerable and Endangered, respectively.

A new species of Edrabius Fauvel (Coleoptera, Staphylinidae, Staphylininae) from Uruguay.

A new rove beetle species, Edrabius uruguayensis Martínez-Villar, González-Vainer Tomasco, sp. nov., associated with the subterranean rodent Ctenomys rionegrensis in Uruguay, is described and illustrated. Photographs, scanning electron micrographs and drawings of the diagnostic character states are provided. The new species is compared with other species of the genus. Nucleotide sequence of the cytochrome oxidase subunit I was reported for the first time for the genus and phylogenetic reconstruction confirms their close relationship with the other genus used from the tribe Amblyopinini (Heterothops).

Ecological specialization and niche overlap of subterranean rodents inferred from DNA metabarcoding diet analysis.

Knowledge of how animal species use food resources available in the environment can increase our understanding of many ecological processes. However, obtaining this information using traditional methods is difficult for species feeding on a large variety of food items in highly diverse environments. We amplified the DNA of plants for 306 scat and 40 soil samples, and applied an environmental DNA metabarcoding approach to investigate food preferences, degree of diet specialization and diet overlap of seven herbivore rodent species of the genus Ctenomys distributed in southern and midwestern Brazil. The metabarcoding approach revealed that these species consume more than 60% of the plant families recovered in soil samples, indicating generalist feeding habits of ctenomyids. The family Poaceae was the most common food resource retrieved in scats of all species as well in soil samples. Niche overlap analysis indicated high overlap in the plant families and molecular operational taxonomic units consumed, mainly among the southern species. Interspecific differences in diet composition were influenced, among other factors, by the availability of resources in the environment. In addition, our results provide support for the hypothesis that the allopatric distributions of ctenomyids allow them to exploit the same range of resources when available, possibly because of the absence of interspecific competition.

Influences of landscape characteristics and historical barriers on the population genetic structure in the endangered sand-dune subterranean rodent Ctenomys australis.

Understanding the processes and patterns of local adaptation and migration involves an exhaustive knowledge of how landscape features and population distances shape the genetic variation at the geographical level. Ctenomys australis is an endangered subterranean rodent characterized by having a restricted geographic range immerse in a highly fragmented sand dune landscape in the Southeast of Buenos Aires province, Argentina. We use 13 microsatellite loci in a total of 194 individuals from 13 sampling sites to assess the dispersal patterns and population structure in the complete geographic range of this endemic species. Our analyses show that populations are highly structured with low rates of gene flow among them. Genetic differentiation among sampling sites was consistent with an isolation by distance pattern, however, an important fraction of the population differentiation was explained by natural barriers such as rivers and streams. Although the individuals were sampled at locations distanced from each other, we also use some landscape genetics approaches to evaluate the effects of landscape configuration on the genetic connectivity among populations. These analyses showed that the sand dune habitat availability (the most suitable habitat for the occupation of the species), was one of the main factors that explained the differentiation patterns of the different sampling sites located on both sides of the Quequén Salado River. Finally, habitat availability was directly associated with the width of the sand dune landscape in the Southeast of Buenos Aires province, finding the greatest genetic differentiation among the populations of the Northeast, where this landscape is narrower.

Personality underground: evidence of behavioral types in the solitary subterranean rodent Ctenomys talarum.

BACKGROUND: Animal personalities have been studied in a wide variety of taxa, but among rodents, available studies are relatively scarce and have focused mainly on social species. In this study, we evaluated the existence of personality in the solitary subterranean rodent Ctenomys talarum. Specifically, we aimed to test individual differences in behavior that are stable over time and context in males of C. talarum captured in the wild. METHODS: Our experimental design included two series of three behavioral tests each, carried out with a 35 day time interval. Each series included an Open Field test, a Social Encounter test, and an Open Field test with a predator stimulus. RESULTS: Of the total recorded behaviors, 55.55% showed temporal consistency. Principal component analysis of consistent behaviors grouped them into four dimensions that explain inter individual behavioral variability, in order of importance: activity, socioaversion, boldness and exploration. Therefore, our results suggest that the concept of animal personality is applicable to C. talarum and the dimensions found are in accordance with the ecological and behavioral characteristics of this species.

Differential antipredatory responses in the tuco-tuco (Ctenomys talarum) in relation to endogenous and exogenous changes in glucocorticoids.

Glucocorticoids participate in the behavioral and physiological responses generated under stressful circumstances coming from different sources-physical and/or psychological. In mammals, the increases of these hormones are mediated by the activation of the hypothalamic-pituitary-adrenal axis. This response occurs after exposure to novel and unpredictable situations that lead to the loss of homeostasis, for example, a direct encounter with predators or their cues. However, the relationship between the physiological and behavioral responses is still a complex issue in vertebrates. We evaluate the effects of an experimental manipulation of glucocorticoid levels on the generation of the behavioral and physiological response to stress by predation in the subterranean rodent C. talarum. We found that when tuco-tucos encountered predator cues-fur odor, and largely, immobilization-they responded physiologically by secreting cortisol. This response was accompanied by an associated behavioral response. However, when the increase in plasma cortisol originated exogenously by the injection of cortisol, a behavioral response was not observed. Finally, inhibition of glucocorticoids' synthesis was effective in weakening the behavioral effects produced by immobilization. In conclusion, in tuco-tucos, predator cues act as stress factors that trigger differential increases in plasma cortisol and a behavioral response associated with the appearance of anxiety states.

A New Species of Ancylostoma (Nemata: Strongylida: Ancylostomatidae) from Two Species of Ctenomys in Lowland Bolivia.

From the small intestines of both Ctenomys boliviensis and Ctenomys steinbachi collected from August 1984 through June 1990 from the eastern lowlands of the Department of Santa Cruz, Bolivia a total of 36 specimens of Ancylostoma were recovered. Morphological investigation and comparisons with known species described and reported from mammals in the Neotropical Region show that this is an undescribed species, herein described as new. These nematans were collected from individuals of C. steinbachi collected from near a locality called Caranda (northwest of Santa Cruz de la Sierra) and from C. boliviensis from near Santa Rosa de la Roca (northeast of Santa Cruz de la Sierra) and from cajuchis collected from 3 km west of Estación El Pailón, 30 km east of Santa Cruz de la Sierra. The new species of Ancylostoma differs from all other species of Ancylostoma known from the Neotropical Region in the presence of paired sub-terminal papillae on the dorsal ray of males.

Day and night in the subterranean: measuring daily activity patterns of subterranean rodents (Ctenomys aff. knighti) using bio-logging.

While most studies of the impacts of climate change have investigated shifts in the spatial distribution of organisms, temporal shifts in the time of activity is another important adjustment made by animals in a changing world. Due to the importance of light and temperature cycles in shaping activity patterns, studies of activity patterns of organisms that inhabit extreme environments with respect to the 24-hour cyclicity of Earth have the potential to provide important insights into the interrelationships among abiotic variables, behaviour and physiology. Our previous laboratory studies with Argentinean tuco-tucos from the Monte desert (Ctenomys aff. knighti) show that these subterranean rodents display circadian activity/rest rhythms that can be synchronized by artificial light/dark cycles. Direct observations indicate that tuco-tucos emerge mainly for foraging and for removal of soil from their burrows. Here we used bio-logging devices for individual, long-term recording of daily activity/rest (accelerometry) and time on surface (light-loggers) of six tuco-tucos maintained in outdoor semi-natural enclosures. Environmental variables were measured simultaneously. Activity bouts were detected both during day and night but 77% of the highest values happened during the daytime and 47% of them coincided with time on surface. Statistical analyses indicate time of day and temperature as the main environmental factors modulating time on surface. In this context, the total duration that these subterranean animals spent on surface was high during the winter, averaging 3 h per day and time on surface occurred when underground temperature was lowest. Finally, transport of these animals to the indoor laboratory and subsequent assessment of their activity rhythms under constant darkness revealed a switch in the timing of activity. Plasticity of activity timing is not uncommon among desert rodents and may be adaptive in changing environments, such as the desert where this species lives.

Diet effect on osmoregulation in the subterranean rodent Ctenomys talarum.

Water conservation requires osmoregulatory skills, sometimes limited by the environment and/or physiological and behavioral characteristics acquired along the evolutionary history of the species. Fossoriality had probably emerged as a survival mechanism to face increasing aridity, as suggested for Ctenomys, a genus that radiated to different environments. Ctenomys talarum (tuco-tuco) is an herbivorous subterranean rodent that lives in coastal grasslands inside humid burrows that reduce evaporation. However, their osmoregulatory mechanisms may be challenged by atmospheric variations when foraging aboveground and by the annual variability in dietary water and salt content. Then, it is of great interest to identify how much of this flexibility of C .talarum is attributed to physiological regulation. We analyzed the effect of water and salt content of diet on urinary, plasmatic, fecal and respiratory parameters. Tuco-tucos were not able to maintain their body weight under the offered monodiet, especially under the low hydrated diet, which explains its generalist and opportunistic foraging behavior. C. talarum mainly obtained water through food, whereas water metabolic production was negligible. Evaporative water loss did not vary between diets, but individuals under water restriction showed decreased fecal water loss and urine volume, high urine concentration but stable plasmatic osmolality and ionic concentration values. Under salt stress, urinary parameters remained relatively stable and high plasmatic osmolality was detected. Despite C. talarum produced more diluted urine than rodents from xeric environments, it is able to concentrate it 4 times above than the required at field even under the lowest water availability. This may be a characteristic associated with the evolutionary history of the species, which evolved in an arid context.

Thermogenic capacity in subterranean Ctenomys: Species-specific role of thermogenic mechanisms.

One way to understand ecological patterns of species is to determine their physiological diversity on a large geographic and/or temporal scales, in a context of hierarchical biodiversity framework. In particular, macrophysiological studies analyze how environmental factors affect the physiology and therefore the distribution of species. Subterranean species are an excellent model for evaluating the large-scale effects of ambient temperature (Ta) conditions on thermal physiology and distribution, due to their extensive use of burrows that provide a relatively thermal stable environment. Species belonging to the genus Ctenomys are all subterranean and endemic of South America. Cold induced maximum metabolic rate (MMR), basal metabolic rate (BMR) and non shivering thermogenesis (NST) were analyzed, as well as the expression of uncoupled proteins (UCP) in brown adipose tissue (BAT). Biogeographical variables appear to have no effect MMR experimentally induced by cold condition within Ctenomys. Also, mechanisms of heat production are species-specific, varying from a combination of ST and NST to a complete use of shivering mechanisms. This pattern is correlated at tissue level, since species that use only ST show a smaller interscapular BAT patch, not detectable presence of UCP1 and low COX activity. Thus, other factors, including body mass, that constrain cold induced MMR could affect thermogenic variability among Ctenomys. In the evolutionary timescale, if low O2 levels of burrows impose a ceiling in cold induced MMR, and ST is enhanced due to species-specific life history traits, such as digging effort, then the observed differences among Ctenomys species might be explained.

Mandible strength and geometry in relation to bite force: a study in three caviomorph rodents.

The monophyletic group Caviomorpha constitutes the most diverse rodent clade in terms of locomotion, ecology and diet. Caviomorph species show considerable variation in cranio-mandibular morphology that has been linked to the differences in toughness of dietary items and other behaviors, such as chisel-tooth digging. This work assesses the structural strength of the mandible of three caviomorph species that show remarkable differences in ecology, behavior and bite force: Chinchilla lanigera (a surface-dwelling species), Octodon degus (a semi-fossorial species) and Ctenomys talarum (a subterranean species). Finite element (FE) models of the mandibles are used to predict the stresses they withstand during incisor biting; the results are related to in vivo bite forces and interspecific variations in the mandibular geometries. The study concludes that the mandible of C. talarum is better able to withstand strong incisor bites. Its powerful adducting musculature is consistent with the notorious lateral expansion of the angular process and the masseteric crest, and the enhanced cortical bone thickness. Although it has a relatively low bite force, the mandible of O. degus also shows a good performance for mid-to-strong incisor biting, in contrast to that of C. lanigera, which exhibits, from a mechanical point of view, the worst performance. The mandibles of C. talarum and O. degus appear to be better suited to withstand stronger reaction forces from incisor biting, which is consistent with their closer phylogenetic affinity and shared digging behaviors. The contrast between the low in vivo bite force of C. lanigera and the relatively high estimations that result from the models suggests that its adductor musculature could play significant roles in functions other than incisor biting.

Prenatal predatory stress in a wild species of subterranean rodent: Do ecological stressors always have a negative effect on the offspring?

In pregnant females, a failed predatory event not only induces individual responses but also represents a significant change in the developmental environment of the offspring, which may lead to modifications in their phenotype that may persist at different stages of life. We evaluate whether prenatal exposure to predatory cues affects anxiety behavior, behavioral response to predator cues, stress response to immobilization, and immune response to sheep red blood cells (SRBC) and phytohemagglutinin (PHA) in juveniles of the subterranean rodent Ctenomys talarum. We found that prenatal predator stress (PPS) (1) increased juvenile anxiety-like behaviors and the appearance of antipredator behaviors, (2) did not affect the response of offspring to predatory stressors, and (3) did not influence the physiological response of juveniles to stressors (immobilization) nor the immunological responses to SRBC and PHA challenges. This work shows the influence of PPS on the development of behavioral responses in the offspring, whom displayed a state of anxiety and behavioral changes associated with decreased locomotor activity and avoidance behaviors. Thus, these individuals prenatally exposed to predatory cues show behavioral adaptations that may contribute to avoid predators in the adult life.

Landscape genetics in the subterranean rodent Ctenomys "chasiquensis" associated with highly disturbed habitats from the southeastern Pampas region, Argentina.

Studies of genetic differentiation in fragmented environments help us to identify those landscape features that most affect gene flow and dispersal patterns. Particularly, the assessment of the relative significance of intrinsic biological and environmental factors affecting the genetic structure of populations becomes crucial. In this work, we assess the current dispersal patterns and population structure of Ctenomys "chasiquensis", a vulnerable and endemic subterranean rodent distributed on a small area in Central Argentina, using 9 polymorphic microsatellite loci. We use landscape genetics approaches to assess the relationship between genetic connectivity among populations and environmental attributes. Our analyses show that populations of C. "chasiquensis" are moderately to highly structured at a regional level. This pattern is most likely the outcome of substantial gene flow on the more homogeneous sand dune habitat of the Northwest of its distributional range, in conjunction with an important degree of isolation of eastern and southwestern populations, where the optimal habitat is surrounded by a highly fragmented landscape. Landscape genetics analysis suggests that habitat quality and longitude were the environmental factors most strongly associated with genetic differentiation/uniqueness of populations. In conclusion, our results indicate an important genetic structure in this species, even at a small spatial scale, suggesting that contemporary habitat fragmentation increases population differentiation.

The Interplay of Energy Balance and Daily Timing of Activity in a Subterranean Rodent: A Laboratory and Field Approach.

The tuco-tuco (Ctenomys aff. knighti) is among the rodent species known to be nocturnal under standard laboratory conditions and diurnal under natural conditions. The circadian thermoenergetics (CTE) hypothesis postulates that switches in activity timing are a response to energetic challenges; daytime activity reduces thermoregulatory costs by consolidating activity to the warmest part of the day. Studying wild animals under both captive and natural conditions can increase understanding of how temporal activity patterns are shaped by the environment and could serve as a test of the CTE hypothesis. We estimated the effects of activity timing on energy expenditure for the tuco-tuco by combining laboratory measurements of metabolic rate with environmental temperature records in both winter and summer. We showed that, in winter, there would be considerable energy savings if activity is allocated at least partially during daylight, lending support to the CTE hypothesis. In summer, the impact of activity timing on energy expenditure is small, suggesting that during this season other factors, such as predation risk, water balance, and social interaction, may have more important roles than energetics in the determination of activity time.

Female choice, male dominance and condition-related traits in the polygynous subterranean rodent Ctenomys talarum.

Ctenomys talarum is a solitary and highly territorial species in which dominant males aggressively deter other males and monopolize reproductive activity. Female preference for dominant males is not easy to assess due to coercive mating by males. Hence, we aimed to answer if behavioural dominance and several condition-related traits like testosterone and cortisol levels, endoparasite load, and hematocrit volume may affect female preference when they have the opportunity to exert it. We designed a laboratory experiment using wild-caught C. talarum and employed a combined approach involving behavioural observations and the measurements of parameters of physical condition. We staged dyadic encounters between males to determine dominance index and then analyzed female preference towards tethered males (n=15) or their odours (n=18). Male dominance did not affect female preferences when odours were presented. When two tethered males were offered, females preferred those with higher dominance index. Preference of females for dominant males would mainly represent indirect benefits. Females did not show preference for males in relation to any physiological trait evaluated. Dominance was found negatively related to cortisol levels, probably avoiding the glucocorticoids-related costs, and positively related to parasite diversity, since they could tolerate it without impairing their health.