Source Odor, Intensity, and Exposure Pattern Affect Antipredatory Responses in the Subterranean Rodent Ctenomys talarum

Abstract

Predation is a strong selective force, and prey species may show specific adaptations that allow recognition, avoidance, and defense against predators. Facing a situation of predatory risk, anxiety constitutes a reaction of adaptive value, allowing to evaluate the potential risk of this encounter as well as to generate a physiological and behavioral response. Previous studies in the subterranean rodent Ctenomys talarum revealed that exposure to predator odors (urine or fur) generates an anxiety state and induces behavioral changes. However, no differences between the responses generated by both odor sources were observed, although fur odors may indicate a higher level of predatory immanence. Therefore, the aim of this study was to evaluate the behavioral and physiological responses of C. talarum to different intensities of predator odors (urine and fur) and to the repeated exposition to the same odorous stimulus. When comparing the highest behavioral effects elicited by both predatory odors on C. talarum, our study supports the assumption that fur odors are more anxiogenic than urine, while the former provoked significant changes in the distance traveled, the number of arm entries and time in transparent arms in the elevated plus maze; cat urine only caused slight changes on those behavioral parameters. Furthermore, we also found that the intensity of natural predator odor presented to tuco‐tucos has a role on the appearance of defensive behaviors, although an amount‐dependent relationship between predator odor and anxiety levels was not observed. Finally, while individuals exposed for 1 day to fur odor displayed an evident anxiety state, those exposed repeatedly for 5 consecutive days did not differ with the control group in their behavioral response, indicating a clear habituation to the predatory cue. In our intensity and habituation experiments, we did not find differences in the measured physiological parameters among control individuals, exposed to different cues intensity (urine and fur odor) and exposed only once or for 5 days to fur odor. These results provide valuable evidence that the types of predatory odor, along with the frequency of exposition, are important determinants of the appearance, strength, and extinction of defensive behaviors in the subterranean rodent C. talarum.

Aggression, Boldness, and Exploration Personality Traits in the Subterranean Naked Mole-Rat (Heterocephalus glaber) Disperser Morphs

“…Some studies apply predator cues [ 45 ], novel arena emergence [ 46 ], or novel objects such as toys [ 47 ] to test for boldness. Given the poor vision in naked mole-rats [ 48 ] and the importance of olfaction in their recognition behavior [ 34 ], the current study applied both olfactory predator cues [ 49 ] by using fresh snakeskin [ 21 ], and tissue paper, a novel object. There was no difference between the snake-skin test and the tissue paper test, which suggests that there was no difference in how the animal perceived the two different stimuli.…”

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

“…This result opposes to previous findings which indicated that prenatally stressed rodents display greater HPA axis responsiveness to acute stress during juvenile and adult stages (Brunton, ). Although it is known that the influence of maternal stress on the offspring HPA axis can be highly dependent on the stage of gestation when the contact with the stressors occurred (Kapoor & Matthews, ), preceding studies on adult tuco‐tucos showed that physiological parameters did not vary after exposition to predator urine or fur odors presented at different intensities or frequencies (Brachetta et al, ). Therefore, it is more likely that this low HPA responsiveness is the result of a poor association between the physiological and behavioral responses to stress (predator cues exposures) in this species of subterranean rodent, than to an effect of the moment the stressor was applied.…”

“…In first instance, these results could be attributed to the action of the placental enzyme 11-beta hydroxysteroid dehydrogenase 2 (11HSD2), which protects the developing fetus from high maternal levels of GCs (Drake, Tang, & Nyirenda, 2007). However, in adult tuco-tucos exposed to diverse stress factors, variations in cortisol levels are not so severe, even when clear behavioral changes were observed (Brachetta et al, 2014(Brachetta et al, , 2015(Brachetta et al, , 2016.…”

“…Additionally, the exposure of adult tuco-tucos to predator odors (fur or urine) generates a state of anxiety and induces behavioral changes associated with decreased locomotor activity and avoidance of open spaces (Brachetta, Schleich, & Zenuto, 2015). Recently, we found that the intensity of predator odor presented to tuco-tucos has a role on the appearance of defensive behaviors, although an amount-dependent relationship between predator odor and anxiety levels was not observed (Brachetta, Schleich, & Zenuto, 2016). Moreover, cat fur odors are more anxiogenic than cat urine for this subterranean species; while the former provoked significant changes in the distance traveled, the number of arm entries and time in transparent arms in the elevated plus maze, urine only caused slight changes on those behavioral parameters (Brachetta et al, 2016).…”

Personality underground: evidence of behavioral types in the solitary subterranean rodentCtenomys talarum

“…Given that information, and considering that our study implies a 35 day trial-tests period, the habituation effect found was not expected. Moreover, the habituation effect on antipredatory behavior after 5 days of exposure to predator odor was detected in C. talarum (Brachetta, Schleich & Zenuto, 2016) while no longer periods were assessed.…”