Cheetah behaviour at scent‐marking sites indicates differential use by sex and social rank

Mesocarnivores vary in their spatiotemporal avoidance strategies at communications hubs of an apex carnivore

Mesocarnivores face interspecific competition and risk intraguild predation when sharing resources with apex carnivores. Within a landscape, carnivores across trophic levels may use the same communication hubs, which provide a mix of risks (injury/death) and rewards (gaining information) for subordinate species. We predicted that mesocarnivores would employ different strategies to avoid apex carnivores at shared communication hubs, depending on their trophic position. To test our prediction, we examined how different subordinate carnivore species in the Santa Cruz Mountains of California, USA, manage spatial overlap with pumas (Puma concolor), both at communication hubs and across a landscape-level camera trap array. We estimated species-specific occurrence, visitation rates, temporal overlap, and Avoidance-Attraction Ratios from camera traps and tested for differences between the two types of sites. We found that mesocarnivores generally avoided pumas at communication hubs, and this became more pronounced when pumas scent-marked during their most recent visit. Coyotes (Canis latrans), the pumas' closest subordinate competitor in our system, exhibited the strongest avoidance at communication hubs. Gray foxes (Urocyon cinereoargenteus) avoided pumas the least, which may suggest possible benefits from pumas suppressing coyotes. Overall, mesocarnivores exhibited various spatiotemporal avoidance strategies at communication hubs rather than outright avoidance, likely because they benefit from information gained while 'eavesdropping' on puma activity. Variability in avoidance strategies may be due to differential predation risks, as apex carnivores often interact more aggressively with their closest competitors. Combined, our results show how apex carnivores trigger complex species interactions across the entire carnivore guild and how trophic position determines behavioral responses and subsequent space use of subordinate mesocarnivores across the landscape.

Sex-, age-, and time-specific visual communication in brown bears

Intraspecific communication in mammals is well-documented but generally restricted to chemical and acoustic signaling. However, other overlooked channels, such as visual signaling, may be used to communicate among conspecifics. Here, by using experimental manipulations together with camera traps on 13 brown bear (Ursus arctos) rubbing trees in the Cantabrian Mountains (northwestern Spain), we document detailed temporal patterns and behavioral aspects of a recently discovered novel communication channel for this species, visual signaling through the trunk debarking of focal trees. Video footage showed that visual marking is a sex-, age-, and time-specific means of communication in brown bears, being performed exclusively by adult males during the mating season (mainly April–June in the study area). Trunk debarking was always associated with chemical marking and was never an isolated behavior, suggesting that visual and chemical signals might be complementary. Visual and chemical marks may provide different information; for example, visual marks could be an indicator of individual size and, thus, the dominance status of adult males looking for mating opportunities. This is the first time that evidence is provided showing that visual signaling in a large carnivore is exclusive to a specific class of individuals (adult males) and linked to reproductive needs only. Bear visual signaling not only represents an advance in our comprehension of animal communication but may also serve to easily locate the mating areas of mammals, which are crucial for large carnivore species, such as the brown bear, that frequently need specific and urgent plans for conservation and management.

Characteristics of urine spraying and scraping the ground with hind paws as scent-marking of captive cheetahs (Acinonyx jubatus)

Olfactory communication is common in felids. We observed two scent-markings, urine spraying and scraping the ground with hind paws during excretion, of 25 captive cheetahs. We analyzed the association of sniffing with the timing of urine spraying and scraping, and differences in these behaviors based on sex, age, and captive environment to understand the olfactory communication among cheetahs. Both scent-markings were strongly associated with sniffing, especially scraping, and the presence or absence of scent was thought to be a trigger. Both behaviors were observed only in adults; scraping was observed only in males. To our knowledge, this study was first to confirm the discharge of secretions from the anal glands during scraping. The frequencies of both behaviors were significantly higher in males kept in shared enclosures containing other individuals than in males kept in monopolized enclosures, while there was no difference in the frequencies among females. Female cheetahs are solitary and have non-exclusive home range, whereas male cheetahs are either solitary or live in coalition groups and there are territorial and non-territorial males. Our results could be attributed to the differences in sociality between the sexes and effect of the living environment.

Cheetah marking sites are also used by other species for communication: evidence from photographic data in a comparative setup

Many mammalian species communicate via olfactory communication placed at particular locations. The majority of these studies focused on intraspecific communication. More recently, studies have also investigated interspecific communication and recorded prey animals sniffing olfactory cues left by predators and predators investigating or counter-marking cues left by other predator species. The purpose of exchanging olfactory cues within a species community is little understood. Using a comparative study design, we investigated the behaviour of a mammalian community at cheetah marking trees and paired control trees using camera traps on Namibian farmland. We tested the predictions derived from hypotheses regarding the reasons for visits to the marking trees. Cheetah marking trees and control trees were visited 1101 times by 29 mammalian species (excluding cheetahs), with more species recorded at the marking trees than control trees. Two competitively subordinate carnivore species made more visiting and sniffing events, respectively, at cheetah marking trees than control trees, possibly to assess the time since cheetahs were in the area. Two opportunistic scavenger species sniffed more frequently at the marking trees than control trees, perhaps to feed on undigested prey remains in scats. One common prey species of cheetahs had fewer visiting events at the marking trees than control trees, likely to reduce encounters with cheetahs. Further, one species that is rarely preyed by cheetahs marked cheetah marking trees at the same frequency as control trees, suggesting it uses conspicuous sites rather for intraspecific than interspecific communication. Thus, trees used by cheetahs for marking also play an important role in olfactory communication for a variety of mammalian species.

Sex differences in audience effects on anogenital scent marking in the red-fronted lemur

How the presence of conspecifics affects scent mark deposition remains an understudied aspect of olfactory communication, even though scent marking occurs in different social contexts. Sex differences in scent-marking behaviour are common, and sex-specific effects of the audience could therefore be expected. We investigated sex differences in intra-group audience effects on anogenital scent marking in four groups of wild red-fronted lemurs (Eulemur rufifrons) by performing focal scent-marking observations. We observed a total of 327 events divided into 223 anogenital scent-marking events and 104 pass-by events (i.e. passage without scent marking). Using a combination of generalised linear mixed models and exponential random graph models, we found that scent marking in red-fronted lemurs is associated with some behavioural flexibility linked to the composition of the audience at the time of scent deposition. In particular, our study revealed sex differences in the audience effects, with males being overall more sensitive to their audience than females. Moreover, we show that these audience effects were dependent on the relative degree of social integration of the focal individual compared to that of individuals in the audience (difference in Composite Sociality Index) as well as the strength of the dyadic affiliative relationship (rank of Dyadic Composite Sociality Index within the group). The audience effects also varied as a function of the audience radius considered. Hence, we showed that scent marking in red-fronted lemurs is associated with some behavioural flexibility linked to the composition of the audience, ascribing red-fronted lemurs’ social competence in this context.

Visual marking in mammals first proved by manipulations of brown bear tree debarking

The rather limited human ability to understand animal vision and visual signalling has frequently clouded our expectations concerning the visual abilities of other animals. But there are multiple reasons to suspect that visual signalling is more widely employed by animals than previously thought. Because visibility of visual marks depends on the background in which they are seen, species spending most of their time living in dark conditions (e.g., in forests and/or having crepuscular and nocturnal habits) may rely on bright signals to enhance visual display. Here, as a result of experimental manipulations, we present, for the first time ever, evidence supporting the use of a new channel of intraspecific communication by a mammal species, i.e., brown bear Ursus arctos adult males relying on visual marks during mating. Bear reactions to our manipulation suggest that visual signalling could represent a widely overlooked mechanism in mammal communication, which may be more broadly employed than was previously thought.