In the present study, we aim to assess the affiliative tendencies of Asian elephants ( Elephas maximus ) toward conspecifics in response to distress, using similar methodology to that used in the conflict resolution literature. To our knowledge, this is the first systematic investigation of distress-related affiliation in elephants based on a priori hypotheses (but see Bates et al. , 2008 and Hart, Hart & Pinter-Wollman, 2008 for other possible displays of empathy and stress-related emotional responses).

Materials and methods

(a) Study area and subjects This study was conducted at the Elephant Nature Park (the “Park”) in the Mae Tang district of Chiang Mai province, Thailand. Although the Park owns many of the elephants on-site, some are leased or contracted so that the general elephant population changed regularly during the study period. The data in this study refer to 26 elephants with approximate ages ranging from 3 to 60 years old, although due to unverifiable records, ageing elephants precisely was impossible. Although genetic tests on the relatedness of the elephants were never done, it is reasonable to conclude based on the relayed life histories of the individual elephants that all individuals, except for mother-juvenile pairs brought to the Park together, were unrelated. Each elephant was taken care of by one or two mahouts (elephant caretakers) every day. Adult male elephants (n = 4) were completely excluded from the study as they were regularly prevented, for safety and husbandry reasons, from participating in most of the natural, social interactions within groups. When a female was first brought to the Park, she was generally allowed to integrate with a smaller group of elephants. In this study, these smaller, social units (generally of n = 5–7 individuals) are labeled “managed groups” because they consisted of individuals that spent most of their social time together under the guidance of their mahouts. There was no single herd at the Park, but six individual managed groups that interacted at specific times during the day. These groups were delineated based on interviews with the Park mahouts during data collection but prior to data analysis. Each day, elephants followed a specific routine established by Park management. Mahouts moved their elephants to a specific location on the property, as a managed group, beginning at 0700 h. They ate at a central location at 1130 h – fed either by their mahouts or visiting tourists – bathed communally at 1300 h and 1630 h, and returned to their night shelters, in which they were tethered for the night, at 1700 h. Mahouts moved elephants with vocal commands or by grasping their ears or legs and walking them to different locations on the property. Throughout the day, elephants were left to graze or play in various parts of the property within their social groups. Although individual elephants were generally allowed to interact with members of other managed groups, the mahouts often intervened at unpredictable times to separate volatile pairings.

(c) General data collection We chose locations on the property from which to collect data to ensure both a full view of pre-selected managed groups and the observer’s safety. These locations included viewing platforms constructed specifically for observations, and in fields in close proximity to mahouts. Observation locations were chosen based on three factors in decreasing priority: (1) safety of observation vantage point at any given time, (2) view of a maximum number of managed groups at the beginning of the observation period, and (3) view of the managed groups from which there were the least amount of data. The property was approximately 55 acres in total size, but only 30 acres were observable for this study. The property was divided into four grids for observation purposes, and an observation location was chosen within a grid based on the aforementioned factors. On average, data were collected during 1–2 week periods each month from April, 2008–February, 2009. General observation periods ran for no less than 30 min and no more than 180 min per session from 0730 to 1030 and from 1400 to 1630, with scan samples taken every 10 min. Data on proximity distance only were collected for relationship quality within elephant groups. All observation periods began after 10 min of no mahout interference on elephant behavior, and individual scan samples were cancelled if such interference occurred within a given 10-min period. All-occurrence sampling was used for distress behaviors and the reactions of others to these behaviors (Altmann, 1974). In addition, if an interaction was clearly and completely observed outside these specific observation periods, the same data were collected ad-libitum (<20% of total cases), and a subsequent control observation period (see below) was scheduled.

(d) Post-distress data collection – PD and MC observations Although the human staff responsible for the elephants’ care artificially constructed the managed group over several years, we focused on spontaneous, affiliative behavior reflective of natural, social interactions (de Waal, 1982; Sukumar, 2003, 2006; de Silva, Ranjeewa & Kryazhimskiy, 2011). Post-distress data for this study were collected at the Park on 26 semi-free ranging individuals in six managed groups following the PC (post-conflict, or PD, post-distress)/MC (matched-control) methodology developed for reconciliation and consolation behavior in primates (de Waal & Yoshihara, 1983). The PD period was an observation period in which all approach and affiliative behavior was recorded (as were all data on potential stimuli for distress, individuals present within 50 m, and date, time and weather), for a 10-min block following the first distress display. We chose a 10-min duration because it (a) follows the methodology employed with many other non-human species (see Aureli & de Waal, 2000, for a review), and (b) far exceeded the average time of first bystander response to another’s distress in a baseline observation period conducted by the first author prior to the start of data collection. Because elephant interactions may involve multiple distressed individuals (Lee, 1987), the first individual to vocalize, or display a distress behavior was labeled the victim and thus the focal individual in each PD period. If more than one individual responded simultaneously, the rarest case (if known, the least-often distressed individual) was chosen for observation. Each PD period was compared to an MC (matched control) period, or another 10-min block of observation taken of the victim and bystanders on the next possible day following the PD. An MC period was selected when as many variables from the PD – in prioritized order: high percentage of original individuals present, location, time of day and weather – could be maintained, and, most importantly, no new distress event occurred in the 30 min prior to (or during) the period of observation. An MC was collected within seven days of its corresponding PD (in 80% of PD/MC cases, the MC was collected within 48 h). If an MC was conducted when an elephant that had made contact with the distressed individual in the corresponding PD was absent or more than 25 m away, that PD/MC dyad was excluded from the analysis to avoid biasing the data in favor of our predictions.

(e) Scan-sampling for proximity – “friends” and “non-friends” We attempted to differentiate between contact directed toward “friends” (closely-bonded individuals) and “non-friends” (those outside managed groups) by collecting 68 h of scan-sampling proximity data (for procedure, see Romero & de Waal, 2010). Although mahouts did not interfere with most day-to-day social interactions within established, managed groups (and thus we were able to specify controlled parameters for the PD/MC data), they often discriminately prevented outsider elephants from coming too close to avoid potential conflict. Such conflict between elephants at the Park was also not representative of natural, wild elephant groups (in which conflict is relatively rare), probably due to a high level of unrelatedness within and between managed groups at the Park. Unfortunately, we were forced to exclude the scan-sampling data from our analysis due to circumstances beyond our control. Thus, we were unable to measure relationship quality and its effect on levels of affiliative behavior in this study.