Mammals communicate through various means, including auditory, visually, or chemically (Macdonald, 1995; Eisenberg and Kleiman, 1972). The chemical mode of communication through odor is the most prominent in carnivores. The scent marks carrying the signals can retain in the environment long after their release and are, therefore, ideal for solitary, long-raging territorial species for intra- and interspecific communications (Johnston, 2005). The frequency of scent-marking often positively correlates with the individual’s fitness and increases with social status where dominant individuals have higher frequency of marking than the subordinate individual (Allen et al., 1999; Gosling and Roberts, 2001; Jordan et al., 2013). Sent marks deposited as semiochemicals can be carried through urine, feces, skin, and a range of secretions from different glands across the body (Bradbury and Vehrencamp, 2011; Apps, 2013) through various behaviors such as ground scratching, tree scratching, or rubbing of different body parts on the substrate (Asa et al., 1985; Harmsen et al., 2016; Barja et al., 2005; Bothma and le Richet, 1995), which convey different messages and are used for important functions such as defending territory (Gosling, 1982; Zub et al., 2003), mate selection (Meena, 2010; Allen et al., 2015a), intraspecific communication (Seidensticker et al., 1973; Allen et al., 2014, 2015b), interspecific interaction (Allen et al., 2017, 2015b; King et al., 2017; Li et al., 2013), and landmarks aiding in orientation (Barja et al., 2004; Gorman and Trowbridge, 1989).

In long-ranging and territorial felids, scent-marking is the prominent aspect for social organization and the primary form of communication (Smith et al., 1989; Allen et al., 2014, 2016) including lions (Panthera leo) and has been observed, as well described in detail (Andersen, 1998; Brahmachary and Singh, 2000; Schaller, 1972; Barja and de Miguel, 2010; Gilfillan, 2017). To maintain the social status, attract mates, and hold land tenure or prey rights, lions interact indirectly with conspecifics (Chakrabarti and Jhala, 2019). Major kinds of scent-marking behavior that have been observed in lions are spray marking, clawing, scrape marking, and chin rubbing (Schaller, 1972; Andersen, 1998; Jhala et al., 2009). In Asiatic lions, males are observed to mark more frequently than females and females were observed to mark and advertise their territories only during the estrous period (Jhala et al., 2009; Joslin, 1973), whereas in the Serengeti lions, both male and females are observed to show the similar extent of marking behavior (Schaller, 1972). However, clawing in particular has been observed in all age groups, and without any difference in both males and females (Schaller, 1972; Andersen, 1998). For lions, scratching is a common and natural action that they partake in for various purposes, viz, stretching and exercise, grooming, and shedding claws marking territory (Pageat and Gaultier, 2003; Stanton et al., 2015). Additionally, the foot pads include scent glands that serve as a territorial marking indication. Therefore, scratching serves as both a chemical and visual signal (Harmsen et al., 2016).

Asiatic lions (Panthera leo persica) are found in the Gir Forest and the surrounding landscape in the Saurashtra region of Gujarat, Western India. Within this population, prides predominantly consist of females and their dependent cubs, whereas males are either solitary or form coalitions, typically comprising an average of two adult males (Joslin, 1973; Meena, 2009; Chakrabarti and Jhala, 2017). Unlike African lions, female Asiatic lions do not exhibit estrous synchrony, resulting in fewer mating opportunities for males (Chakrabarti and Jhala, 2019). To prevent infanticide by males, lionesses engage in mating with multiple males, thereby creating paternity confusion among males (Chakrabarti and Jhala, 2019). Most studies on scent-marking in lions provide descriptive accounts of the form and function of scent-marking behaviors (Schaller, 1972), primarily focusing on the chemical communication aspect (Andersen, 1998; Andersen and Vulpius, 1999; Brahmachary and Singh, 2000; Pageat and Gaultier, 2003; Barja and de Miguel, 2010; Poddar-Sarkar et al., 2008). These studies have predominantly been conducted on captive lions, with limited research on free-ranging populations (Gilfillan, 2017). Notably, Joslin (1973) documented various advertisement behaviors in lions, including roaring, spraying, scraping, and defecation, in significant detail. However, these observations were largely anecdotal and lacked the quantitative rigor necessary for drawing robust conclusions. In Asiatic lions, the scent-marking behavior in wild populations remains poorly understood. Currently, there is limited information on the relative importance and ecological roles of different scent-marking behaviors in their natural habitat.

The selection of sites for scent-marking is not random; instead, it is influenced by specific habitat characteristics that enhance the likelihood of detection by conspecifics (Gosling and Roberts, 2001; Mohorović and Krofel, 2020; Ruiz-Olmo et al., 2013). For example, Allen et al. (2017) reported that Eurasian lynx (Lynx lynx) preferentially selected objects similar to their body size, positioned along straight road sections, while avoiding more commonly available object types. Similarly, neotropical felids such as jaguars (Panthera onca) and pumas (Puma concolor) chose sites predominantly covered with leaves, narrow paths, and clean, infrequently used areas for scraping (Palomares et al., 2018). Joslin (1973) observed that Asiatic lions frequently scraped on substrates like small bushes, grass tussocks, and dead teak (Tectona grandis) leaves. Vertical structures, such as trees, are particularly important for scent marking in some carnivores, as they increase the visibility and dispersion of scent marks due to their elevated position. This behavior has been documented in species such as leopards (Panthera pardus), cheetahs (Acinonyx jubatus), and giant pandas (Ailuropoda melanoleuca) (Alberts, 1992; Bothma and le Richet, 1995; Marnewick et al., 2006; Nie et al., 2012). Understanding the spatial and temporal patterns of scent-marking behavior in Asiatic lions is essential for identifying critical areas for their territorial and communication needs. Such insights can inform more effective conservation and management strategies for this endangered species, ensuring the preservation of their habitats and behaviors essential for their ecological success.

Motion-triggered cameras are widely utilized for documenting cryptic behaviors in elusive species that are challenging to observe through conventional field surveys (Caravaggi et al., 2017). In this study, we used infrared motion-detection cameras to record and analyze the activity and scent-marking behavior of Asiatic lions, enabling us to test various hypotheses. Our objectives were (1) to characterize scent-marking and associated behaviors across different age and sex classes and (2) to identify factors influencing site selection for these behaviors. We hypothesized that visitation rates at scent-marking sites would peak during nocturnal and crepuscular hours, aligning with periods of heightened lion activity, and would be higher during the mating season than at other times. Additionally, we expected adult males to exhibit greater involvement in scent-marking behaviors compared with females and predicted that scratching and spray marking would be the most frequent behaviors among adult males and females. Lastly, we hypothesized that lions would prefer trees with broader girths, located near forest tracks or trails in low-elevation areas, and favor tree species with hard bark capable of retaining scent marks for extended durations over those that diffuse scent more quickly.

Evaluating the spatial patterns and characteristics of scent-marking behavior is fundamental to understanding intra- and interspecific communication in carnivores (Mohorović and Krofel, 2020). Our study provides novel insights into the scent-marking behavior of free-ranging Asiatic lions, identifying key factors influencing marking site selection within the dry deciduous forests of western India. This represents the first quantitative study on scent-marking in free-ranging Asiatic lions, forming a foundation for future research on this critical aspect of their behavior.

The use of camera traps to monitor these elusive behaviors allowed us to quantify the proportional use of marking sites, a task that is otherwise challenging for free-ranging species. Our findings supported the hypothesis that lions are most active at scent-marking sites during crepuscular and nocturnal hours, exhibiting clear bimodal peaks at dawn and dusk. This aligns with Chaudhary et al. (2020), who documented similar activity patterns in lions within the Gir Wildlife Sanctuary. Telemetry studies (Jhala et al., 2009) have also shown that patrolling and territorial behaviors, such as scent-marking and vocalizations, predominantly occur during early morning and late evening hours. Furthermore, earlier observations by Joslin (1973) recorded that advertisement activities such as roaring, spraying, scraping, and defecation are mainly conducted at night, late evening, or early morning. These temporal patterns may help lions avoid heat stress during hot months, concentrating their scent-marking and territorial activities during cooler periods of the day. As hypothesized, our results also demonstrated that scent-marking site visitation peaked during winter, coinciding with the lions’ peak breeding period. While Asiatic lions breed year-round, mating activity tends to increase in winter (Jhala et al., 2009), potentially enhancing reproductive signaling and increasing mating success. The data indicated that the majority of these site were visited between January and June, aligning with previous studies showing a mating peak from January to May (Jhala et al., 2009). Although no statistically significant seasonal differences in temporal activity patterns were observed, which may be linked to the year-round breeding behavior of lions, the higher visitation rates during winter underscore the close link between scent-marking and reproductive behavior.

Contrary to our initial hypothesis, sniffing emerged as the most frequently observed behavior, followed by scratching and spraying. Sniffing appears to be more closely associated with exploratory territorial behavior rather than reproductive signaling and is often accompanied by other behaviors, such as the flehmen response. This pattern aligns with findings from olfactory investigations in solitary felids such as bobcats and clouded leopards (Allen et al., 2015b, 2016). While our focus on heavily marked trees may have resulted in an overestimation of scratching behavior, prior studies indicate that lions often prefer bushes for spray-marking and scraping on small or non-existent objects (Joslin, 1973). In captive lions, spray-marking and scrape/urination are the predominant scent-marking behaviors, whereas clawing and chin rubbing occur less frequently (Andersen, 1998). Similarly, telemetry studies have shown that spraying is the most common method of territorial advertisement, with scraping being a rarer event (Jhala et al., 2009). In contrast, Schaller (1972) observed that scrape/urination occurred three times more frequently than spray marking in African lions. In our study, scraping was recorded in only 0.02% of total observations, likely due to our focus on scratch-marked sites. Clawing and scratch marking are generally considered the most visually conspicuous scent-marking behaviors (Andersen, 1998; Allen et al., 2015b), whereas rubbing behaviors—such as chin, body, and neck rubbing—leave both olfactory and visual cues. In felids, rubbing behaviors have been linked to agonistic and sexual contexts (Reiger, 1979), but their specific role in communication remains unclear and requires further investigation. Additionally, tree climbing, which was predominantly observed in females, may serve as a playful activity and could also play a role in fostering social bonds within the pride. This aspect of social communication warrants further exploration to better understand its implications for lion behavior and interactions.

Adult male lions exhibited a higher frequency of scent-marking behaviors compared with females, a pattern consistent with findings in both captive and wild lions (Joslin, 1973; Andersen, 1998; Jhala et al., 2009). However, studies on Serengeti lions have reported a similar frequency of scent-marking behavior in both sexes (Schaller, 1972). Male lions are more invested in maintaining territorial boundaries, using scent marks to deter competitors. Similarly, in pumas, mature adult males are the primary visitors to scent-marking sites (Allen et al., 2014). Although the sex ratio in Gir Wildlife Sanctuary is more female-biased (Banerjee and Jhala, 2012; Ram et al., 2023b), males dominate scent-marking behaviors due to two key reasons. First, their wide-ranging movements (Ram et al., 2023c) necessitate frequent territorial maintenance to avoid competition from intruders. Second, the polyoestrous nature of female lions prompts males to repeatedly deposit scent marks to gain access to potential females. In contrast, females appear to visit scent-marking sites less frequently, possibly as a strategy to avoid aggressive encounters with males and mitigate the risk of infanticide. Both sexes, however, exhibit increased scent-marking activity during the winter months, coinciding with the peak breeding season (Jhala et al., 2009). Notably, African lions do not demonstrate a seasonal pattern in marking frequency (Schaller, 1972). Females in Gir showed higher sniffing and scratching activity than males during April and May, which may be linked to some females entering estrus following male-inflicted infanticide. Additionally, unlike African lions, Asiatic female lions do not exhibit estrus synchrony, further distinguishing their scent-marking and reproductive behaviors.

By examining the characteristics of trees frequently used for scent marking, we identified notable preferences influenced by ecological and behavioral factors shaping lion communication strategies. This study is the first to investigate the behavioral aspects associated with site selection for scent marking in free-ranging Asiatic lions. Previous studies have primarily focused on descriptive accounts or the chemical composition of scent marks in captivity (Brahmachary et al., 1999; Brahmachary and Singh, 2000; Barja and de Miguel, 2010). Carnivores are known to select marking sites that maximize the likelihood of scent detection and persistence while minimizing the energy required for marking large territories (Allen et al., 2017). Our findings supported the hypothesis that lions preferentially mark trees located near forest tracks or trails. Nearly all marked trees were within a 5-m radius of such paths, suggesting an energy-efficient strategy due to ease of access and a higher probability of conspecific detection of scent marks (Alberts, 1992; Fahrig and Rytwinski, 2009; Stępniak et al., 2020). Similar patterns of marking near roads, game trails, dried riverbeds, and intersections within territories have been observed in other carnivores, including tigers (Sunquist, 1981; Smith et al., 1989), brown bears (Clapham et al., 2013), giant pandas (Schaller et al., 1985), wolves (Peters and Mech, 1978), and foxes (Macdonald, 1979). It is also plausible that lions invest time in scent-marking at locations not visually detectable, which our study may not have captured due to reliance on camera traps at visible marking sites. Future studies could incorporate additional methodologies, such as tracking radio-collared individuals, to identify other potential scent-marking sites and further refine our understanding of scent-marking behavior in free-ranging Asiatic lions.

Moreover, as apex predators in the Gir forest, Asiatic lions are competitively superior to other carnivores, enabling them to select prime habitats for effective intraspecific communication without the fear of intruders or other carnivores. While other carnivores in the landscape might also utilize these areas for interspecific communication (Allen et al., 2017), this aspect requires further study. As per our hypothesis, Syzgium cumini had a higher average girth and had hard and rough bark, which increases the surface area for scent deposition and is also resistant to rainfall (Nie et al., 2012). Moreover, S. cumini has aromatic properties (Kavitha et al., 2012). Therefore, marking on these trees not only acts as an additional attractant for the intended receivers but also helps in the reduction of energetic expenditure (Gosling et al., 2000). Moreover, to make their marks more conspicuous, lions select trees in open dry scrub areas, which increases visibility. Moreover, to prevent scent marks from evaporation, trees are selected that are near the water body, which increases the success for the retention of the scent marks.

Scent-marking behavior in Asiatic lions appears to be more energy-intensive compared with African lions, as previous studies indicate that Asiatic lions allocate more time to marking and patrolling than to feeding or hunting (Jhala et al., 2009). Territorial males, in particular, dedicate a substantial proportion of their active time to patrolling and marking activities. For example, radio-collared males were reported to spend 63% of their active time patrolling, with scent-marking events lasting an average of 2.13 ± 0.9 (SD) hours (Jhala et al., 2009). Although females engage less frequently in scent-marking, their activities often overlap temporally with those of males, suggesting that female scent marking is closely tied to broader patterns of territorial defense and reproduction.

In conclusion, our study provides the first quantitative analysis of scent-marking behaviors in free-ranging Asiatic lions, shedding light on their communication strategies and territorial behaviors. The temporal, behavioral, and spatial patterns identified in this study offer valuable insights into the ecological and social factors that drive scent-marking behavior. By analyzing how these behaviors are linked to reproductive and territorial contexts, we gain a deeper understanding of how Asiatic lions manage their territories and communicate with conspecifics. Future research should focus on investigating individual variations in scent-marking behaviors by integrating GPS-collaring with camera trap monitoring. This combined approach will provide more detailed insights into spatial and temporal patterns of scent marking, allowing for a better understanding of how individual lions engage in this behavior. These efforts are crucial for advancing our knowledge of this endangered species’ behavioral ecology and informing conservation strategies.