Abstract
Phylogenetic conservatism or rapid anthropogenic habitat modifications could increase the incidences of interspecific associations of Hanuman and Nilgiri langurs (Family: Cercopithecidae, subfamily: Colobinae) in the southern Western Ghats. Opportunistic surveys were conducted at the Silent Valley National Park, Kerala and around Devimalai Ghats, Tamil Nadu for Tufted Grey-Nilgiri Langur association. Based on the observations from Researchers, field assistants, forest staff, and local people, the data in terms of the time of the sighting, number of individuals, phenotypes of individuals, and the time the interaction lasted, were recorded. The study reports data on a troop of Nilgiri Langurs (N=13) around O Valley tea estate at Devimalai Ghat, Gudalur, Tamil Nadu with some hybrid looking individuals and a Tufted female Grey Langur amongst them. A total of six and two uni-male troops of Nilgiri Langurs and grey langurs respectively with Tufted female Grey Langurs, and aberrant coat colored infants observed at the Neelikkal section of Silent Valley National Park are also reported. The study reasonably speculates that there could be more such locations in the southern western ghats and emphasizes the need for more systematic surveys to understand and explore the ecology, behavior, molecular, and other likely factors contributing to the conservation of vulnerable Nilgiri langur (Semnopithecus johnii) populations.
Highlights
Interspecific short-term associations among animal groups are known to naturally occur in the context of competition for food (Dickman 1992), mutual benefit (Oates & Whitesides 1990), and hybridization (Anderson 1948; Arnold 1997; Alberts & Altmann 2001; Arnold & Meyer 2006)
Biologists are aware of the purpose of the casual encounters of two different species, there seems to be a dearth of information in biological literature in the case of two species that exist as a single group going beyond the casual encounters
Three Nilgiri Langurs were observed foraging with a Tufted Grey Langur troop at a distance of about 50–75 m at Neelikkal for the whole of the study period, sexing and photographing these foraging Nilgiri Langur individuals was not possible due to limitations of visibility in the canopy
Summary
Interspecific short-term associations among animal groups are known to naturally occur in the context of competition for food (Dickman 1992), mutual benefit (Oates & Whitesides 1990), and hybridization (Anderson 1948; Arnold 1997; Alberts & Altmann 2001; Arnold & Meyer 2006) Such associations have generated varied interests among ecologists, behavioral biologists, and geneticists (Evans et al 2001; Hewitt 2001; Keller et al 2010; Cortes et al 2019); when two different species live together as a single cohesive unit, interspecific associations are difficult to explain. Such associations are known to vary in duration, frequency, range, and ecological and behavioral relations largely depending on the type of groups/species interacting (Cords 1990; Burton & Chan 1996; Porter 2001; Rehg 2006)
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