Demography and reproductive output in langurs of the Western Ghats, India

Abstract

Life history traits evolve such that the reproductive output of an organism is maximized. Demographic characteristics, a consequence of life history traits, indicate the reproductive output per individual in group-living species. Both phylogenetic and ecological factors influence demographic traits. In the forests of the Western Ghats, India, we studied the demography of three langur species: Semnopithecus johnii, a wet forest-dwelling species; Semnopithecus hypoleucos, largely a wet forest-dwelling species; and Semnopithecus priam, a primarily dry forest-dwelling species. S. hypoleucos and S. priam are genetically closer to each other than to S. johnii. We sampled a total of 193 groups of the three species of langurs. The group size was smaller in the two wet forest-dwelling species, S. johnii (median = 10) and S. hypoleucos (nine), than in the dry forest-dwelling species, S. priam (18). The number of adult females per group was higher in S. priam (seven) and S. johnii (six) than in S. hypoleucos (four). On the other hand, the adult female:immature ratio, indicating reproductive output and life history, was highest in S. johnii (1:0.33) followed by S. hypoleucos (1:1) and S. priam (1:1.09). Our results suggest that reproductive output is lowest in the arboreal wet forest species and increases as the species become somewhat dry deciduous forest dwellers, or almost facultative dry forest dwellers, and relatively more terrestrial. Some traits, such as group size, appear to be more sensitive to ecological factors, and some other traits such as age-sex ratios and reproductive output appear to be more conservative.

Behavioural Variability in Macaques and Langurs of the Western Ghats, India

“…By contrast, the present results of activity budgets are not conclusive on whether there is within-group scramble competition in Nilgiri langurs and black-footed grey langurs. It has been observed that black-footed grey langur group size varied between different forest types [Singh Erinjery/Kavana/Singh et al, 2016]. A good percentage of fruit in their diet also indicates that they might experience within-group scramble competition.…”

“…Although it has been found that Nilgiri langurs specialize on young leaves, no evidence suggests that there is within-group competition in the group. Previous studies have shown that Nilgiri langurs and blackfooted grey langurs inhabiting rain forests have small home ranges, small group sizes, and do not need to forage or travel long distances to acquire food [Sushma et al, 2014;Kavana et al, 2015;Singh et al, 2016]. This was probably because of their high degree of folivory which limits the time for other activities [Kavana et al, 2015;Singh et al, 2016].…”

“…Previous studies have shown that Nilgiri langurs and blackfooted grey langurs inhabiting rain forests have small home ranges, small group sizes, and do not need to forage or travel long distances to acquire food [Sushma et al, 2014;Kavana et al, 2015;Singh et al, 2016]. This was probably because of their high degree of folivory which limits the time for other activities [Kavana et al, 2015;Singh et al, 2016]. As in the case of macaques, future studies on these species should study whether larger groups travel longer distances to acquire specialized food.…”

Distribution, social organization, and management of Semnopithecus johnii: An umbrella species of fragmented landscape of the Western Ghats

“…Earlier, the occurrence of Nilgiri langur was not clear from the Wayanad plateau, Palghat Hills, Nelliyampathi Hills, Cardamom Hills, High Wavy Mountains to Varushanad. However, recent studies confirm their occurrence in those hills (Kavana et al, 2014;Kumara et al, 2014;Kumara & Singh, 2004a;Ram, 2007;Singh et al, 2016) except for the Palghat gap where they are absent. This gap of 41 km in the Western Ghats appears to be a major biogeographic barrier Hunting in many of these regions also further affected the remnant populations of Nilgiri langur (Kumara & Singh, 2004b;Oates, 1979;Pillay et al, 2011).…”

Demography and Birth Seasonality in the Nicobar Long-Tailed Macaque (<i>Macaca fascicularis Umbrosus</i>)

“…Keywords: Birth rate, demography, group size, population dynamics. DEMOGRAPHIC characteristics are the evolutionary consequences of life history traits which fix in a population as they maximize individual reproductive output [1][2][3] . Demographic characteristics including group size, age and sex composition of the group, birth rate, mortality, migration frequency of individuals, and growth rate, change over time due to ecological constraints 4 .…”