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Vidya, T. N. C.

Publications and source records attributed to Vidya, T. N. C..

9 recordsLinked to original sources
bioRxiv2025

Female Asian elephant clans have age-based order but weak dominance resolution

The variation in dominance relationships in group-living species is often interpreted through socioecological frameworks that link social structures to resource-risk distributions. However, in elephants, such inferences are hindered by a lack of comparable assessments of within-group dominance in different species. To advance our understanding of elephant socioecology, we present here, the first study on agonistic and dominance relationships within female Asian elephant clans (most inclusive social groups), and compare our results with those from African savannah elephants. By analysing agonistic interactions, and dominance and association networks based on over four years of observations of five clans, we show that Asian elephants have a resolved but weakly structured within-clan dominance order. Female dyads showed unidirectionality, but triad motif structures of dominance networks suggested resolved dominance only in some clans. Older females were more dominant although there were moderate levels of reversals against age-based order and age difference did not dampen dyadic conflict. Neither older age nor dominant status conferred more central status in the female association network. Weak dominance resolution and the effects of age contrast with the stronger dominance and age-based order found in African savannah elephants. We identify potential socioecological and demographic explanations of female dominance in elephants.

animal behavior and cognition↗
bioRxiv2025

Young Asian elephant calves show differentiated social relationships with conspecifics

Social relationships may increase longevity and reproductive success of individuals, thereby providing crucial benefits in social species. Adults of many social species have differentiated social relationships; however, when and how these relationships form and are maintained are often not understood. We studied spatial and behavioural interactions between young calves ([≤]6 months old) and conspecific females ([≥]5 years old) to understand social ontogeny in a wild Asian elephant (Elephas maximus) population in Nagarahole and Bandipur National Parks, southern India. We found that elephant groups with calves comprised females - mother and escort, who provided active care, and females who did not provide overt, active care - other females. Escorts, apart from coordinating their movement with the calf, provided allomaternal care by initiating positive and helpful interactions with the calf. Other females rarely initiated interactions, which were usually negative, towards calves. Primarily calves, rather than conspecific females, initiated and terminated proximity contacts and behavioural interactions. Calves were near and interacted similarly with their mothers and escorts, under feeding, resting, and social contexts, and almost never interacted with other females. Similarly, we found remarkable similarities between mothers and escorts in their behaviours towards calves, with the primary difference being that escorts did not provide milk. Our results suggest that calves begin to form differentiated social relationships from a young age. The presence of calves and their interactions with escorts might result from existing close social relationship between mothers and escorts or may establish new relationships. Allomaternal care may also reinforce relationship differentiation in such social species. As calf-escort interactions involved behaviours that may potentially be helpful in protection and feeding skill acquisition, the development and survival of calves may be affected by the presence of, and interactions, with allomothers. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=197 HEIGHT=200 SRC="FIGDIR/small/650831v2_ufig1.gif" ALT="Figure 1"> View larger version (83K): org.highwire.dtl.DTLVardef@1564ccdorg.highwire.dtl.DTLVardef@cc276aorg.highwire.dtl.DTLVardef@12fc57corg.highwire.dtl.DTLVardef@14e7a8e_HPS_FORMAT_FIGEXP M_FIG C_FIG We studied spatial and behavioural interactions between young calves ([≤]6 months old) and conspecific females to understand social ontogeny in a wild Asian elephant population. We found differentiated relationships between calves and conspecifics even at a young age. Escorts, who showed coordinated movement with calves, engaged in other positive interactions with calves, with remarkable similarity to the mothers, whereas other females rarely initiated such interactions. Escorts are thus allomothers in the Kabini elephant population. Calves, rather than conspecifics, initiated and terminated most of the proximity and behavioural interactions and were thus precocial in forming new relationships.

animal behavior and cognition↗
bioRxiv2019

A test of the socioecological model in female Asian elephants: the effects of food abundance, food distribution, and competitor density on within-clan and between-clan contests

O_LISocioecological theory attributes variation in social organization of female-bonded species to differences in within- and between-group competition, shaped by food distribution. Strong between-group contests are expected over large, monopolisable resources, and are not generally expected in species that feed on low quality resources distributed across large, undefended home ranges. Within groups, frequent contests are expected over discrete feeding sites but not over low-quality, dispersed resources. C_LIO_LIWe report on the first tests of socioecological theory, largely unexplored in non-primate species, in female Asian elephants. Asian elephants show graminivory, overlapping home ranges, and high fission-fusion dynamics, traits that are thought to be associated with infrequent contests. C_LIO_LIWe studied agonistic interactions within and between female elephant clans with respect to food distribution, food abundance, and competitor density effects of group size and clan density, in a grassland habitat around the Kabini backwaters, southern India. C_LIO_LIWe found that the Kabini grassland had three times the grass biomass as adjacent forests, and between-clan encounters were considerably higher than that known from a neighbouring forest. Individual-level agonism was also more frequent between clans than within clans. Thus, the food-rich habitat patch probably enabled strong between-clan contest competition under graminivory. Moreover, the rate of between-clan encounters increased when more clans were present, and the duration of encounters was positively related to grass biomass at the contested sites. Despite fission-fusion dynamics, within-clan agonism was also somewhat frequent, but not influenced by food distribution, in contradiction to classic socioecological predictions, possibly because of intensified competition due to high density. Interestingly, within-clan agonism increased with female group size until intermediate group sizes, suggesting that the tension between within-group and between-group competition might govern group size, since larger groups are advantageous in this strong between-clan contest regime. C_LIO_LIOur findings refine the current understanding of female elephant socioecology. Despite predominant graminivory and fission-fusion dynamics, within-group agonism can be frequent, especially when large groups face ecological constraints at high density. Further, frequent between-group contests may arise despite graminivory and non-territoriality when food becomes patchy and density is high. These changes may be effected by anthropogenic alteration of habitats. C_LI

ecology↗
bioRxiv2018

Effects of male age and female presence on male associations in a large, polygynous mammal in southern India

We present a detailed study of male associations in a roving species, the Asian elephant, using six years of data on identified, nonmusth males. Adult males spent greater proportions of their time solitarily than in mixed-sex or in all-male groups. Old (over 30 years) males were sighted more frequently with their age-peers and less frequently with young (15-30 years) males than expected at random in all-male groups. Young males were not sighted more frequently with old males than with young males, and did not disproportionately initiate associations with old males. These results suggest that male associations, in the absence of females, primarily allow for old nonmusth males to test strengths against age-peers. Social learning from older individuals did not seem to be important in male associations, unlike that observed in African savannah elephants. We also found a constraint on the sizes of all-male groups, similar to that seen in female groups in our study population, and with male group sizes being smaller than that of African savannah elephants. However, most males had a significant top associate in female absence. In mixed-sex groups, male associations occurred at random, suggesting that males were tracking female groups independently. Thus, we find some differences in male social organisation compared to the phylogenetically related African savannah elephant that occupies a similar niche, and suggest that ecological factors might have shaped the differences in these male societies.Competing Interest StatementThe authors have declared no competing interest.View Full Text

animal behavior and cognition↗
bioRxiv2018

Overwhelming presence of non-food vegetation undermines the reliability of NDVI as a surrogate of forage abundance for a large herbivore in a tropical forest habitat

The use of remotely-sensed vegetation indices has increased in wildlife studies but field-based support for their utility as a measure of forage availability largely comes from open-canopy habitats. In this paper, we assessed whether the popular vegetation index, NDVI, actually represents forage availability for Asian elephants in a southern Indian tropical forest. We found that the number of food species was a small percentage of all plant species, and the abundance of food species compared to total species abundance varied across different vegetation categories. NDVI was not a good measure of food abundance in any vegetation category partly because of a) small to moderate proportional abundances of food species relative to the total abundance of all species in that category (herb and shrub categories), b) abundant overstorey vegetation resulting in low correlations between NDVI and food abundance despite a high proportional abundance of food species and a concordance between total abundance and food species abundance (graminoid category), and c) the relevant variables measured and important as food at the ground level (count and GBH) not being related to primary productivity (trees and recruits). NDVI had a negative relationship with the total abundance of graminoids, which represent a bulk of elephant and other herbivore diet, because of the presence of other vegetation types and canopy cover that positively explained NDVI. We also found that spatially interpolated total graminoid abundance modelled from field data outperformed NDVI in predicting total graminoid abundance, although interpolation models of food graminoid species abundance were not satisfactory. Our results reject the utility of NDVI as a surrogate of elephant forage abundance in tropical forests with multistorey vegetation, a finding that has implications for studies of other herbivores in such habitats.

ecology↗
bioRxiv2017

Effects of Social Organization, Trap Arrangement and Density, Sampling Scale, and Population Density on Bias in Population Size Estimation Using Some Common Mark-Recapture Estimators

Mark-recapture estimators are commonly used for population size estimation, and typically yield unbiased estimates for most solitary species with low to moderate home range sizes. However, these methods assume independence of captures among individuals, an assumption that is clearly violated in social species that show fission-fusion dynamics, such as the Asian elephant. In the specific case of Asian elephants, doubts have been raised about the accuracy of population size estimates. More importantly, the potential problem for the use of mark-recapture methods posed by social organization in general has not been systematically addressed. We developed an individual-based simulation framework to systematically examine the potential effects of type of social organization, as well as other factors such as trap density and arrangement, spatial scale of sampling, and population density, on bias in population sizes estimated by POPAN, Robust Design, and Robust Design with detection heterogeneity. In the present study, we ran simulations with biological, demographic and ecological parameters relevant to Asian elephant populations, but the simulation framework is easily extended to address questions relevant to other social species. We collected capture history data from the simulations, and used those data to test for bias in population size estimation. Social organization significantly affected bias in most analyses, but the effect sizes were variable, depending on other factors. Social organization tended to introduce large bias when trap arrangement was uniform and sampling effort was low. POPAN clearly outperformed the two Robust Design models we tested, yielding close to zero bias if traps were arranged at random in the study area, and when population density and trap density were not too low. Social organization did not have a major effect on bias for these parameter combinations at which POPAN gave more or less unbiased population size estimates. Therefore, the effect of social organization on bias in population estimation could be removed by using POPAN with specific parameter combinations, to obtain population size estimates in a social species.

ecology↗
bioRxiv2017

Niche construction in evolutionary theory: the construction of an academic niche?

In recent years, fairly far-reaching claims have been repeatedly made about how niche construction, the modification by organisms of their environment, and that of other organisms, represents a vastly neglected phenomenon in ecological and evolutionary thought. The proponents of this view claim that the niche construction perspective greatly expands the scope of standard evolutionary theory and that niche construction deserves to be treated as a significant evolutionary process in its own right, almost at par with natural selection. Claims have also been advanced about how niche construction theory represents a substantial extension to, and re-orientation of, standard evolutionary theory, which is criticized as being narrowly gene-centric and ignoring the rich complexity and reciprocity of organism-environment interactions. We examine these claims in some detail and show that they do not stand up to scrutiny. We suggest that the manner in which niche construction theory is sought to be pushed in the literature is better viewed as an exercise in academic niche construction whereby, through incessant repetition of largely untenable claims, and the deployment of rhetorically appealing but logically dubious analogies, a receptive climate for a certain sub-discipline is sought to be manufactured within the scientific community. We see this as an unfortunate, but perhaps inevitable, nascent post-truth tendency within science.

evolutionary biology↗
bioRxiv2017

Group size constraints may mask underlying similarities in social structure: a comparison of female elephant societies

We report on female Asian elephant social structure in Nagarahole and Bandipur National Parks (Kabini population), southern India, and examine the role of group size in affecting the outcome of social structure analysis in female elephants, which show high fission-fusion dynamics. Based on five years of data, we found the Kabini association network structured into highly modular communities that we call clans. We then modified the dataset (to obtain the Kabini 500-m dataset) to match sampling methods previously used in a study each of Asian (Uda Walawe) and African savannah (Samburu) elephants, so that network and association statistics could be compared across populations. Measures of association and network structure previously used were more similar amongst the Asian elephant populations compared to Samburu. The Samburu population formed a hierarchically-nested multilevel society whereas the Asian populations did not. However, we found hierarchical clustering levels in all three populations using Louvain community detection. Moreover, the average community sizes obtained through the Louvain method were not significantly different across populations, indicating basic similarities in social structure. Since fission-fusion dynamics allow for community members to form groups of different sizes, we examined the effect of average group size on association and network statistics. Higher average association index and degree, and lower average path length in Samburu compared to the Kabini 500-m dataset were explained by the larger average group size in Samburu. Thus, underlying similarities in the social networks of species showing fission-fusion dynamics may be obscured by differences in average group size.\n\nSignificance StatementVarious measures of associations and social network analyses have been used to compare social structures of different populations. We studied the social structure of female Asian elephants in a southern Indian population and compared it with those of a Sri Lankan Asian elephant population and an African savannah elephant population. We showed that, while there were social differences between the Asian and African savannah elephant populations using previous methods, there were basic similarities across all three populations using a method of network community detection. This discrepancy across analyses partly stemmed from differences in average group size between populations. Average group size in fission-fusion societies variously affected different association and network statistics, which has implications for inferences about social structure.

animal behavior and cognition↗