Central Control of Scent Marking

Latrines are important sites for intraspecific olfactory communication in mammals, especially for solitary or widely distributed species. Communal latrines give visitors access to information about other visitors, notably conspecific chemical cues, even in their absence. Chemical communication has evolved to allow information transfer among individuals that, due to other ecological constraints, do not co-occur in time. Latrines can be difficult to find and monitor but provide useful information about the behavioral ecology of otters. The aim of this study was to describe the behaviors of Neotropical otters (Lontra longicaudis, Olfers, 1818) in two communal latrines using video-camera traps. A total of 1,651 one-minute footage of otters visiting the latrines were used to elaborate an ethogram that included individuals (1) passing by, (2) rubbing, (3) scent marking, (4) scratching, (5) in vigilance, (6) smelling, (7) defecating, (8) urinating, (9) digging, (10) self-grooming, and (11) interacting with others. These results suggest that latrines are not only used by Neotropical otters to deposit feces and urine but that they also play a role in intraspecific communication. We suggest that L. longicaudis latrines function as information centers where individuals can monitor the location and activities of potential sexual partners and/or competitors.

For canid species, scent marking plays a critical role in territoriality, social dynamics, and reproduction. However, due in part to human dependence on vision as our primary sensory modality, research on olfactory communication is hampered by a lack of tractable methods. In this study, we leverage a powerful biologging approach, using accelerometers in concert with GPS loggers to monitor and describe scent-marking events in time and space. We performed a validation experiment with domestic dogs, monitoring them by video concurrently with the novel biologging approach. We attached an accelerometer to the pelvis of 31 dogs (19 males and 12 females), detecting raised-leg and squat posture urinations by monitoring the change in device orientation. We then deployed this technique to describe the scent marking activity of 3 guardian dogs as they defend livestock from coyote depredation in California, providing an example use-case for the technique. During validation, the algorithm correctly classified 92% of accelerometer readings. High performance was partly due to the conspicuous signatures of archetypal raised-leg postures in the accelerometer data. Accuracy did not vary with the weight, age, and sex of the dogs, resulting in a method that is broadly applicable across canid species’ morphologies. We also used models trained on each individual to detect scent marking of others to emulate the use of captive surrogates for model training. We observed no relationship between the similarity in body weight between the dog pairs and the overall accuracy of predictions, although models performed best when trained and tested on the same individual. We discuss how existing methods in the field of movement ecology can be extended to use this exciting new data type. This paper represents an important first step in opening new avenues of research by leveraging the power of modern-technologies and machine-learning to this field.

We investigated the effect of sex, social status and life-stage on three behaviours (pasting, dry-pasting and pawing) associated with olfactory communication in the spotted hyena (Crocuta crocuta). Pasting is a behaviour used to place a fatty, anal scent gland secretion on vegetation. Dry-pasting behaviour resembles pasting except that scent is not deposited, but instead scent pasted on vegetation by other clan members is smeared on the ventral side of a dry-pasting animal. Pawing is vigorous scratching of the ground with one then the other front paw, which deposits scent from inter-digital glands at scratching sites. Our focus was olfactory communication within social groups termed clans. We obtained data from individually known members of three large clans in the Serengeti National Park, in northern Tanzania. Data were collected at clan communal dens, which are important social centres, and elsewhere in the clan territory. Adult female’s pasting and dry-pasting rates significantly declined with increasing age which indicated that younger adult females invested more than older females in depositing scent and anointing themselves with scent from other clan members. Females pawed the ground rarely. Pasting and dry-pasting rates of reproductively active males (mostly immigrant and a few natal males) above median social status were significantly higher than rates of those below median status at the clan communal den, but not elsewhere in the clan territory. This may result from a reduced opportunity for males below median status to scent mark at the clan den because of the presence of socially dominant males. Alternatively, a lower-ranking male (i.e. more recent immigrant) may gain fitness benefits from concealing its olfactory identity from den-bound juvenile females, because this would increase the number of females that would consider it a potential mate throughout its tenure in the clan. Males above median status pawed the ground at a higher rate both at the communal den and elsewhere in the territory than males below median status. We conclude that these sex differences reflect the importance of (1) olfactory communication and scent mixing between females during their initial years of social integration into the adult hierarchy; (2) male-male competition in terms of pawing throughout the territory and possibly pasting at the den; (3) social communication and scent mixing between males mostly away from the communal den.

Scent over‐marking occurs when an animal deposits its scent mark on top of the scent mark of a conspecific. Over‐marking may provide advantages in the transfer of information to the individual whose scent is on top but not to the individual whose scent is on the bottom. We tested the hypothesis that over‐marking is a competitive form of olfactory communication and that male prairie voles would over‐mark the scent marks of same‐sex conspecifics more than those of same‐sex siblings. Two age‐matched male voles (first male and second male) were placed successively into an arena in which they were allowed to explore freely and scent mark for 15 min at age 12, 20, 28, 36, 44, and 52 d. The first male was placed into a clean arena, whereas the second male was placed into an arena containing either the scent marks of an age‐matched male sibling or nonsibling. Age affected the total number of scent marks deposited by the voles; 12‐20‐d‐old voles deposited fewer scent marks, over‐marks and adjacent marks than did 28‐52‐d‐old voles. Sibship did not affect the total number of scent marks deposited by the first and second voles but did affect the number of over‐marks and adjacent marks deposited by the second vole. Siblings received significantly fewer over‐marks and adjacent marks than did nonsiblings; this effect was most dramatic after the voles reached 28 d of age, a time coincident with the onset of puberty. Males separated from siblings and housed singly at 44‐d‐old and tested at 52‐d‐old, deposited significantly more over‐marks and adjacent marks in arenas if the first vole was a nonsibling than if it was a sibling. This differential scent‐marking supports the hypothesis that over‐marking and adjacent marking are used as competitive forms of olfactory communication by male prairie voles.

Central oxytocin regulates social familiarity and scent marking behavior that involves amicable odor signals between male mice

The behaviour of marking trees by the brown bear occurs throughout the range of presence of the species. It has recently been recognised as a mean of intra-specific chemical communication, besides the likely function of ecto-parasite removal, and evidence from grizzlies showed that scent marking of trees is mainly performed by adult males during the breeding season. However, detailed studies on this behaviour in the Euroasian brown bear are lacking. We conducted a three year study on a wild bear population of 50 individuals in the Eastern Italian Alps, using camera traps. We aimed to assess the use of trees by bears’ age and sex classes, its temporal variation, and to determine key habitat and human disturbance drivers of the intensity of use of rub trees. Camera trapping yielded more than 500 videos of bears from more than 9000 camera trapping days, age and sex classes were identified in 59% of the videos. Results showed that rubbing was mainly performed by adult males, with females and sub-adults that only occasionally rubbed. Rubbing was performed more during the breeding season, confirming that the main function of this behaviour is associated to males' breeding strategy. Olfactory investigation was performed by bears of all ages and sexes, indicating the importance of scent marking at rub trees for intra-specific communication. We used the camera trapping event rate as a raw index of intensity of usage of rub trees and found it to be affected by aspect, type of roads and passage of motor vehicles at the sites, while the passage of people did not affect it. We also estimated bear occupancy and detectability and found that the latter was influenced by trail type and distance from roads and buildings. Our study provides a first contribution to the use of rub trees by brown bears in the Alps. Download the complete issue.

The study of vocal behavior can reveal important aspects of how and why a species communicates in relation to ecological and social challenges. We here focus on vocal communication in golden-backed uakaris (Cacajao melanocephalus), diurnal, pitheciine monkeys that exhibit fission-fusion social organization and typically inhabit dense forests that limit the potential for visual communication. Moreover, the species spends little time engaged in tactile or olfactory communication, e.g., social grooming and scent marking, respectively. Hence, vocalizations may be very important for the coordination of social organization in these monkeys. We 1) categorized golden-backed uakari vocalizations, 2) ascertained their behavioral context, and 3) investigated whether golden-backed uakari calls can encode information about the signaler. We observed the monkeys during 2 wet seasons in the flooded igapo forest of Jau National Park, Brazil. We showed that golden-backed uakaris have 9 call types in their vocal repertoire, all distinguishable by ear and from analysis of spectrograms. Some calls, e.g., play-specific calls, were used only in particular behavioral contexts, and by individuals of specific age, whereas others were emitted under a range of situations. The structure of the loud tcho call varied among individuals, and according to behavioral context, i.e., whether individuals were foraging/feeding, traveling, or performing agonistic interactions. This knowledge of the species’ vocal repertoire is valuable for surveying the monkeys acoustically in habitats where visual surveys are difficult.

Neural mechanisms of individual and sexual recognition in Syrian hamsters ( Mesocricetus auratus)

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Competitive countermarking occurs when animals compete to ensure that their scent marks are in the top-most position and more recently deposited than those of rivals. Because it takes a great deal of time and energy, and perhaps dominant or territorial status, to patrol the area and rapidly countermark rivals' marks, assessors may use the presence of countermarks as a reliable cue of the signaler's competitive ability. Selection on assessors, therefore, should favor the evolution of mechanisms to determine which scent is the countermark. Sexual selection theory predicts that females select high-quality males with whom to mate; therefore, females should mate preferentially with countermarking males. We examined the role of countermarking in intra-male competition and female mate choice in the pygmy loris. In experiment 1, we found that males deposit significantly more urine when countermarking other males' urine, but countermark female urine no more than control stimuli. In experiment 2, we exposed females to the urine of two males for several weeks. One male always deposited his urine first, whereas the second male always deposited his urine later and on top of the first male's urine. When reaching peak estrus, females were given a simultaneous choice test between the two males, and showed a significant preference for the countermarking male with regard to: (1) her location and orientation to the male, (2) her chemosensory interest in the male and his cage, and (3) her affiliative socio-sexual behaviors. These results are consistent with predictions from the competitive countermarking hypothesis, and demonstrate that chemosignals play a profound role in governing female reproductive behavior in the species.

Humans have caused widespread changes to environments worldwide. Such changes can impair animal communication by interfering with every stage of the communication process—from the way signals are produced and transmitted through the environment to how they are perceived and evaluated by receivers (Rosenthal and Stuart-Fox 2012). Critically, due to the pervasive nature of anthropogenic disturbance, few (if any) of the sensory modalities used by animals to communicate are likely to be immune. Changes that affect communication, in turn, can profoundly impact on animal reproduction and survival because of the vital role communication plays in mediating behaviors, such as foraging, predator avoidance, and mate selection (Candolin and Wong 2012). Not surprisingly, there has been considerable interest in trying to understand how human-induced environmental changes affect animal communication. Yet, despite this, much of our research attention remains focused narrowly on only a handful of taxa and sensory modalities. As a result, significant knowledge gaps remain. Radford et al. (2014) provides a timely reminder of why a more expansive approach is warranted.

To better understand the relation between form and function in the complex olfactory communication system of the ringtailed lemur (Lemur catta), we integrated observational, experimental, and chemical approaches applied to a population of semi free-ranging animals at the Duke Lemur Center in Durham, North Carolina. Our aim was to examine sex-role reversal in the expression and function of scent marking and unravel the contribution of multimodal components of information transfer, with the unifying framework for all three avenues of our research being that multiplicity of form implies multiplicity of function.

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