Short Communication
Movements of Semi-captive Elephants during Skidding Season in Myanmar
2023 Volume 29 Pages 11-15
Details
2023 Volume 29 Pages 11-15
Semi-captive Asian elephants (Elephas maximus) engaged in forestry activities in Myanmar account for 20% of all captive and semi-captive Asian elephants in the world, and are important for both forestry and the conservation of Asian elephant populations. Understanding moving behavior of the semi-captive elephants is required to sustain them. Our specific goals are 1) to determine the moving range during free time, and 2) to determine the hourly moving distance during skidding and when off duty. Three elephants were fitted with handheld global navigation satellite systems with the signals of global positioning system to collect data on their movements. The elephants were generally located between 0.534 and 0.875 km from the camp with temporary housing of the elephant handler when not skidding (i.e., free time) and between 1.365 and 1.372 km when skidding (i.e., work time). The hourly moving distance during free time (0.622–0.655 km) and work time (1.522 and 1.629 km) did not differ greatly from the hourly moving distance of wild Asian elephants (0.010–1.500 km). The elephants remained within 0.875 km of the camp of the elephant handler, and some variation in movements among individuals was observed during free time. Thus, the conservation of forest in areas near the camp is important for the well-being of these elephants.
Selective logging is a common logging practice, especially in tropical natural forests (Bicknell et al., 2014). Well-planned and carefully controlled selective logging has a small negative impact on biodiversity (Gibson et al., 2011; Burivalova et al., 2015), while selective logging without careful planning can result in forest degradation or intensive ground disturbance (Pereira et al., 2002). Myanmar Selection System (MSS) is the system of selective logging conducted in Myanmar. Selective logging under the MSS results in considerably lower ground disturbance compared with selective logging in other countries (Khai et al., 2020), because MSS use Asian elephants (Elephas maximus) instead of machines for skidding (Khai et al., 2020).
The elephants used for skidding for the MSS are semi-captive, which means that they are partially free-ranging when off duty. Because the semi-captive elephants for MSS rest and get forage by themselves in forests when off duty, conservation of forest areas where the semi-captive Asian elephants spend their time is critically important for the MSS. In order to determine the forests that should be conserved for the semi-captive elephants for MSS, it is first necessary to understand the moving range of the elephants when off duty.
Recently, an increasing number of studies have focused on the semi-captive elephants. However, the behavior of elephants when off duty has not yet been examined. Most studies of semi-captive elephants have focused on topics related to elephant populations, such as mortality rate (Mar et al., 2012), reproduction (Robinson et al., 2012), and population dynamics (Jackson et al., 2019). Other studies have focused on the personality of elephants (Seltmann et al., 2018, 2019) and their diet (Campos-Arceiz et al., 2008). Crawley et al. (2019) investigated the attitude and experience of elephant handlers and their relationships to recent political and economic changes in Myanmar. No studies to date have investigated the behavior of the semi-captive elephants used in the MSS.
An understanding of the behavior of semi-captive elephants used in the MSS is also important for the conservation of Asian elephants. The Asian elephant is listed as an endangered species in the International Union for Conservation of Nature (IUCN) Red List (Choudhury et al., 2008). The estimated total population of the Asian elephant is approximately 63,000–67,000 in the world (Menon and Tiwari, 2019) and captive and semi-captive Asian elephants account for approximately 15,000 (23%) of the total estimated population of Asian elephants. While captive elephants in zoos around the world only number approximately 1,000 and rarely breed (Sukumar, 2006), the number of semi-captive elephants used in the MSS is nearly 3,000 (Ministry of Natural Resources and Environmental Conservation, 2018). The value is equivalent to 20% of the captive and semi-captive Asian elephants in the world, despite the ban on routine capturing elephants used in the MSS over 25 years ago (Mar et al., 2012). Therefore, appropriate management of semi-captive elephants used in the MSS is important for the conservation of Asian elephants. Moving distance per unit of time is one of the criteria used in describing animal behavior patterns (e.g. Mills et al., 2018; Crawley et al., 2019). By showing the moving distance per unit of time when semi-captive elephants used in the MSS are used for skidding and when off-duty, information can be provided about the workload that the semi-captive elephants are exposed to.
Here, we studied the behavior of semi-captive elephants used in the MSS when they were being used for skidding and when off-duty. Our specific goals are 1) to determine the moving range during free time, and 2) to determine the hourly moving distance during skidding and when off duty. We tracked the movements of three semi-captive elephants using a handleld global navigation satellite system (GNSS) with the signals of global positioning system and determined the moving speed and moving distance of the elephants. We expect that this quantitative information on their movements will facilitate the management and conservation of semi-captive elephants.
CONTEXT: Ordinary daily schedule of semi-captive elephants in the skidding seasonDuring the skidding season, which is generally between June and February, elephant handlers stay at a camp with temporary housing near the skidding site and a stream. The camp and the area surrounding the camp are also where the semi-captive elephants spend much of their time when off duty.
Before skidding, the elephant handler locates the semi-captive elephants that were released the previous night and escorts them to the camp. The elephants are then washed in a stream and fed a light meal, which composed of 0.16 kg of tamarind and 0.08 kg of salt. This helps the elephants' health as an appetizer and as a digestive catalyst. The health status of the elephants is also examined by the handler when they are being washed. The leader of the camp also checks the health status of elephants. Health conditions are checked from a variety of perspectives, including injury and degree of tiredness. After that, semi-captive elephants and the handlers leave the camp for skidding. After skidding, the semi-captive elephants and handlers return to the camp, the health status of the elephants is assessed, and elephants are fed a light meal. Semi-captive elephants are generally released to forests to rest and forage. Sometimes, the elephants are not free to roam but instead tied to a place where food is ample near the camp depending on their health. This is a procedure that is occasionally employed when necessary. When elephants are at the camp, they are provided with food, bathed, and subjected to health assessments.
The study site was located in compartment 18 of Pyinde Reserved Forest in Katha and Kawlin, Myanmar (23°57′–58′N, 95°55′–57′E). The site is mountainous with an altitudinal range from 196 to 350 m above sea level. The forests are dominated by hardwood species such as teak (Tectona grandis), tauk-kyant (Terminalia tomentosa), and bamboo (Thyrsostachys oliveri). Monthly average temperature is ranging from 21°C to 31°C and monthly average rainfall is ranging from 4.8mm to 489.8mm. The camp is situated near a stream where the shade, water food is ample.
Three semi-captive elephants were fitted with handheld GNSSs (GPSmap 62SJ, Garmin Ltd., Schaffhausen, Switzerland) by hitching a collar around their necks and were tracked from 11:15 a.m. on December 23th to 4:30 p.m. on December 27th in 2019 (Fig. 1). The three elephants were 19–35 years old (Table 1). Two elephants were male, and the other was female.
An example of semi-captive elephants with a GNSS.
| Elephant | Sex | Age (years) |
MTE (Myanmar Timber Enterprise) classification |
| 1 | Male | 19 | Full growth |
| 2 | Male | 29 | Full growth |
| 3 | Female | 35 | Full growth |
Because our study focused on the behavior of semi-captive elephants during their free time and work time, we defined both free time and work time at first. Work time was defined as the period between the time when the elephants left the camp for skidding and the time when the elephants returned to the camp. Free time was defined as the period between the time when the elephants were released from the camp and the time when the elephants returned to the camp. The elephants were equipped with the handheld GNSS just before their work time and free time, and it was removed when they returned to the camp. The start and end time of the work time and free time for each elephant was also recorded. The GNSS data were acquired approximately every 30 s during the tracking period.
The GNSS fell off an elephant during free time one time. We found this GNSS in the field and could estimate the time when the GNSS fell off the elephant because the GNSS tracking data showed the time when the GNSS arrived at the point where it fell off. We thus removed data acquired after the GNSS fell off the elephant in our analysis.
Data AnalysisBefore analyzing the data, we categorized the GNSS data into two classes: free time and work time. We then removed outlier points based on the moving speed and turning angle following previous studies of animal movement using GNSS data (Bjørneraas et al., 2010). Points exceeding the pre-defined moving speed were defined as outliers. Points were also classified as outliers when the turning angle was smaller than the pre-defined threshold. Because the appropriate thresholds for the semi-captive Asian elephant was not determined, we used a data-driven threshold (Gupte et al., 2022). We assumed that outliers corresponded to the 1 percentile of all data points and defined the pre-defined moving speed threshold and the turning angle threshold as 5.18 km/hour and 1.72 degrees, respectively. If a given point (outlier) was removed, the moving speed and turning angle were updated using the new data set without the outlier. Because the updated moving speed and turning angle may still exceed the pre-defined threshold, we recursively removed the outliers until the updated moving speed and turning angle satisfied the criteria.
After filtering the GNSS data, we calculated the distance from the camp and the moving distance. The distance from the camp was defined as the horizontal distance between the center of the camp and each GNSS data point. The center location of the camp was recorded using a handheld GNSS (GPS map 62SJ). The distances were summarized for every elephant by discriminating free time and work time (i.e., the time for skidding).
The moving distance was also calculated horizontally. Based on the GNSS data classified into work time and free time, we calculated the total moving distance and hourly moving distance of each elephant by dividing the total moving distance by the free time and work time.
The analysis was conducted in R ver. 4.0.3 (R Core Team, 2021).
All three elephants spent approximately the same amount of time for skidding (13% of the study period) regardless of both their age and sex. However, the amount of free time varied (ranging from 63% to 80%) (Fig. 2). The free times of each elephant were between 3739 and 4925 minutes. The reason for the variation in the amount of free time is that elephant handlers judged two elephants, one male and one female, were tired. The two elephants were tied down for long periods as described in context section.
Free and work time ratio of each elephant.
Figure 3 showed movement trajectories of elephants. The trajectories varied among elephants during free time but were concentrated around the camp (Fig. 3). The mean distances from the camp for each elephant were between 0.172 and 0.364 km for free time (Fig. 4) and significantly varied among elephants (P < 0.05, Games-Howell test). The maximum distance that elephants moved from the camp was 0.875 km. The results suggested that the elephants were located near the camp where elephant handlers could find them.
Movement trajectories of elephants and the location of the camp of elephant handlers. The background image is the true-color image derived from Landsat 8 (acquired 18 November 2019).
Distance from the camp of elephant handlers.
Different letters in each plot indicate significant differences (Games-Howell test, p <0.05).
The trajectories of the three elephants during work time were similar (Fig. 3). The mean distances from the camp for each were between 1.365 and 1.396 km (Fig. 4) and did not significantly differ among elephants (P > 0.05, Games-Howell test). This is because all three elephants went to the same logging sites and worked as a group during the study period.
The total moving distances of elephants during free time were more than twice as long as the total moving distances during work time (Fig. 5). This was because free time was much longer than work time (Fig. 2). The hourly moving distance was between 0.622 and 0.655 km and between 1.522 and 1.629 km for free time and work time, respectively (Fig. 5). The hourly distance traveled by wild Asian elephants ranged from 0.010 to 1.500 km (Leighty et al., 2009). Thus, the hourly distance of semi-captive Asian elephants in both free time and work time was similar to that of wild Asian elephants, but the time in work time was close to the upper limit of wild Asian elephants.
Total moving distance and hourly moving distance of elephant.
Semi-captive elephants spent their free time within 0.875 km of the camp. Because the semi-captive elephants forage (especially bamboo) and rest during free time, sufficient supplies of food near the camp are needed. Therefore, the conservation of forest in areas used for camp is important for the MSS as well as the conservation of Asian elephants.
The semi-captive elephants mainly spent their time within 0.875 km of the camp of the elephant handler, but there was some variation among individuals when semi-captive elephants were off duty. During work time, the elephants needed to go more than 1 km away from the camp. No significant differences in the movements between elephants were observed during work time because the elephants worked as a group. The hourly moving distance of the semi-captive elephants during free time and work time in this study was similar to that of wild elephants. Additional studies are needed to explore the movement behavior of semi-captive elephants under other seasonal schedules, in resting camps, in tourism camps, and in other skidding sites.
We thank Edanz (https://jp.edanz.com/ac) for editing the English text of a draft of this manuscript.
