Ashoka Ranjeewa

University of Colombo · Department of Zoology

Electric fences are widely used in human–elephant conflict mitigation. However, elephants constantly challenge and overcome fences, which is a growing concern. We studied how elephants crossed the perimeter electric fence around the Udawalawe National Park (UWNP), Sri Lanka. Using camera traps, we monitored 18 fence posts and an open gate in the fe...

Collective movements feature multiple consecutive processes involving different types of initiative behavior. It remains unclear whether, and to what extent, the same individual consecutively performs different initiative behaviors in a single collective-movement event. We conducted behavioral observations of wild Asian elephants (Elephas maximus)...

Population structure provides important information for managing and conserving free ranging Asian elephant populations. A variety of size-age classes, based on estimating height or age and measuring captive animals of known age, have been used previously. Here we propose a simple scale, using the individual’s height relative to an adult female. We...

Population health and habitat quality are intimately related and seasonal changes in habitat quality are likely to be reflected in the body condition of animals. We studied seasonal variation of body condition in free ranging Asian elephants (Elephas maximus) in Udawalawe National Park, Sri Lanka based on visual scoring of individually identified e...

Tourism-induced disturbance is a growing concern in wildlife conservation worldwide. This case study in a key protected area in Sri Lanka, examined the behavioral changes of Asian elephants in the context of elephant watching tourism activities. Observations of different age–sex-group classes of elephants were conducted focusing on the feeding acti...

Figure_S1.pdf. Association index matrices and matrices of uncertainty by season. SRI matrices (left column) and the matrices of uncertainty measure based on expression [S1] in the supplementary text (right column). See additional File 7 for supplementary text. x- and y- axes represent individuals, ordered by the total number of sightings across the...

Figure_S2.pdf. Temporal SRI trajectories of type A. Type A trajectories are relationships that are maintained at SRI values above 0.3 in all seasons, and hence exemplify stable associations.

Figure_S3.pdf. Determining the optimal number of clusters for clustering temporal SRI trajectories. Bayesian Information Criterion (BIC) as a function of the number of clusters, K, into which the temporal SRI trajectories are partitioned by the K-means algorithm. Light gray curves represent 100 K-means clustering runs with random initial conditions...

Figure_S6.pdf. Social network for randomized T1 data. An example of a social network generated by the randomization procedure described in the methods. The network is relatively homogenous, without distinct clusters.

Supplementary_Text.doc. Description of the procedure to estimate uncertainty in the estimate of an association index.

Figure_S7.pdf. Maximum modularity Qmax as a function of the SRI threshold. Data for each of the seasonal data sets correspond to the network structure curves shown in Figure 8 in the main text (see Methods in the main text for details).

Figure_S4.pdf. Trade-off between the number of associates and the strength of association by season. Each point shows the number of associates of a core individual (abscissa) and the average non-zero SRI value for that individual (ordinate). Data is displayed for each season separately (averages across seasons are shown in Figure 4 in the main text...

Figure_S5.pdf. Girvan-Newman clusters for season T1 at various SRI thresholds. This figure is analogous to the schematic shown in Figure 7 in the main text. Corresponding network structure curves are shown in Figure 8 of the main text. Individuals that do not have ties at or above the threshold value are removed for the sake of clarity. Arrows indi...

Figure_S8.pdf. Detecting differences in the shape of network structure curves. P-value for the Mann-Whitney test of the comparison between the distribution of the network structure curve increments within window w before each SRI threshold with the corresponding distribution within the window w after that threshold are shown. Different colors corre...

Patterns in the association of individuals can shed light on the underlying conditions and processes that shape societies. Here we characterize patterns of association in a population of wild Asian Elephants at Uda Walawe National Park in Sri Lanka. We observed 286 individually-identified adult female elephants over 20 months and examined their soc...

We provide estimates of population size and other demographic variables for individually-identified Asian elephants (Elephas maximus) in Uda Walawe National Park (UWNP), Sri Lanka based on systematic year-round observations. Two hundred and eighty-six adult females and 241 adult males were identified, of which four adults (2% of males) had tusks. S...