Previous studies have posited the use of acoustics-based surveys to monitor population size and estimate their density. However, decreasing the bias in population estimations, such as by using Capture–Mark–Recapture, requires the identification of individuals using supervised classification methods, especially for sparsely populated species like the wolf which may otherwise be counted repeatedly. The cryptic behaviour of Indian wolf (Canis lupus pallipes) poses serious challenges to survey efforts, and thus, there is no reliable estimate of their population despite a prominent role in the ecosystem. Like other wolves, Indian wolves produce howls that can be detected over distances of more than 6 km, making them ideal candidates for acoustic surveys. Here, we explore the use of a supervised classifier to identify unknown individuals. We trained a supervised Agglomerative Nesting hierarchical clustering (AGNES) model using 49 howls from five Indian wolves and achieved 98% individual identification accuracy. We tested our model’s predictive power using 20 novel howls from a further four individuals (test dataset) and resulted in 75% accuracy in classifying howls to individuals. The model can reduce bias in population estimations using Capture-Mark-Recapture and track individual wolves non-invasively by their howls. This has potential for studies of wolves’ territory use, pack composition, and reproductive behaviour. Our method can potentially be adapted for other species with individually distinctive vocalisations, representing an advanced tool for individual-level monitoring.

Vocal communication in social animals plays a crucial role in mate choice, maintaining social structure, and foraging strategy. The Indian grey wolf, among the least studied subspecies, is a social carnivore that lives in groups called packs and has many types of vocal communication. In this study, we characterise harmonic vocalisation types of the Indian wolf using howl survey responses and opportunistic recordings from captive and nine packs (each pack contains 2–9 individuals) of free-ranging Indian wolves. Using principal component analysis, hierarchical clustering, and discriminant function analysis, we found four distinct vocalisations using 270 recorded vocalisations (Average Silhouette width Si = 0.598) which include howls and howl-barks (N = 238), whimper (N = 2), social squeak (N = 28), and whine (N = 2). Although having a smaller body size compared to other wolf subspecies, Indian wolf howls have an average mean fundamental frequency of 422 Hz (±126), which is similar to other wolf subspecies. The whimper showed the highest frequency modulation (37.296±4.601) and the highest mean fundamental frequency (1708±524 Hz) compared to other call types. Less information is available on the third vocalisation type, i.e. ‘Social squeak’ or ‘talking’ (Mean fundamental frequency = 461±83 Hz), which is highly variable (coefficient of frequency variation = 18.778±3.587). Lastly, we identified the whine, which had a mean fundamental frequency of 906Hz (±242) and is similar to the Italian wolf (979±109 Hz). Our study’s characterisation of the Indian wolf’s harmonic vocal repertoire provides a first step in understanding the function and contextual use of vocalisations in this social mammal.

Geographical isolation can often lead to speciation, and two disconnected populations of the same species living in drastically different bioclimatic regions provide an opportunity to understand the process of speciation. The Woolly wolf is found in the cold-arid, Trans-Himalayan landscape, while the Indian wolf inhabits the semi-arid grasslands of Central India. Both the lineages of wolves from India have generated scientific debate on their taxonomic status in recent years. In this study, we collected data and reviewed published literature to document the ecological and behavioral differences between the Woolly wolf and the Indian wolf. Most studies have used genetic data; hence we discuss variation in spatial ecology, habitat preferences, vocalization, diet diversity and cranial measurements of these two subspecies. The spatial ecology of two lineages was compared from the data on three Woolly and ten Indian wolves tagged with GPS collars. The telemetry data shows that there has been no difference in the day-night movement of Woolly wolves, whereas Indian wolves show significant high displacement during the night. The BBMM method indicated that Woolly wolf home ranges were three times larger than the Indian wolf. The Woolly wolf diet is comprised of 20 different types of food items, whereas the Indian wolf diet consists of 17 types. The Woolly and Indian wolf largely depend upon domestic prey base, i.e., 48.44 and 40.34%, respectively. We found no differences in the howling parameters of these subspecies. Moreover, the Woolly wolf skull was significantly longer and broader than the Indian wolf. Wolves of India are ancient and diverged from the main clade about 200,000–1,000,000 years ago. Their genetic and ecological evolution in different bioclimatic zones has resulted in considerable differences as distinct subspecies. The present study is a step in understanding ecological differences between two important, genetically unique subspecies of wolves.

38 Vocalisation plays a critical role in social animals for conveying information on 39 foraging, reproductive, and social behaviours [1][2][3][4][5][6][7]. Characterising the vocal repertoire 40 of a species provides a base for understanding the behavioural significance of different 41 vocalisations and studying how vocal communication varies across the populations, 3 42 subspecies, and taxa [8][9][10]. The wolf (Canis lupus) is a social mammal and uses a 43 variety of vocalisations for communication. Being present throughout Eurasia and North 44 America, the wolf is one of the most widely distributed land mammals and occupies a 45 wide range of different habitat types [11]. The Indian wolf is among the smallest [12] 46 and one of the most evolutionarily distinct wolf subspecies, having diverged around 47 270,000 and 400,000 years ago based on mitochondrial DNA [13][14][15]. Studying the 48 vocal repertoire of the Indian wolf can aid in future studies on the function of different 49 vocal signals in Indian wolves and, more broadly, the variation in vocalisation across 50 subspecies and taxa within the Canis clade.51 The best-known wolf vocalisation -the howl -is a long-range harmonic call used for 52 territorial advertising and social cohesion [1,[16][17][18]. Recent studies have shown 21 53 different howl types across various canid subspecies based on quantitative similarity in 54 modulation pattern [8]. Along with howl, wolves also communicate using 7 to 12 other 55 harmonic calls, which is a clear pitch sound wave that possesses multiple integral 56 frequencies [19][20][21]. Many of these other harmonic vocalizations are short-ranged, and 57 due to difficulties in recording these calls, remain less studied compared to the wolf 58 howl [22]. These short-ranged calls are important for communicating passive or 59 aggressive behaviour among social canids [22][23][24].60 The whimper, whine and yelp are various calls for communicating passive and friendly 61 behaviour among wolves [18,23], whereas noisy calls, which don't have a clear pitch or 62 distinct frequency band in their spectrograms, communicate different levels of 63 aggression [18,23]. The whimper and whine vocalization is similar to a crying sound 64 with the whimper having a comparatively shorter duration than whine [18,25]. The 65 whine vocalization is mostly used for submissive behaviour whereas the whimper is 4 66 primarily used for greeting [18]. Yelp is a short and sharp cry and is used in submissive 67 behaviour with body contacts [18,25]. To communicate different levels of aggression 68 behaviors, wolves use noisy calls which consist of the growl, woof, and bark. Growl is a 69 laryngeal sound to show dominance in any interaction, whereas the woof vocalization is 70 a non-vocal sound cue (without involvement of vocal cords) used by adults for their 71 pups [18,25,26]. The bark is a short low pitched sound with rapid frequency modulation 72 and is used during aggressive defence [19,26], such as defending pups or defending a 73 food resource. Wo...