Night-day speed ratio of elephants as indicator of poaching levels

Abstract

Poaching has escalated in recent years and is becoming the greatest immediate threat to elephants' survival. There is an urgent need to develop innovative and cost-effective methods for monitoring changes in elephant poaching levels remotely to complement the existing traditional field-based ground surveys. Since elephants are known to respond to anthropogenic risks by alterations in their speed of travel, we quantified this alteration as a ratio of night time speed to the day time speed (night-day speed ratio) and examined its relationship with poaching levels. Our hypothesis here is that poaching is a clear daytime risk, and thus an increase in night time movement rates over those seen during the day will support this hypothesis. Using elephant GPS tracking and mortality data collected in the Laikipia-Samburu ecosystem of northern Kenya between 2002 and 2012, we calculated the mean night-day speed ratio for collared elephants that utilised any of 13 contiguous land units, each under different ownership and management status, and related this ratio to the corresponding poaching levels before and during a poaching surge. Our study shows that the mean night-day speed ratio of both male and female elephants did not vary significantly by month, ruling out possible seasonal effect. However, both male and female elephants moved more at night than during the day where and when poaching levels were high. The relationship between poaching levels and night-day speed ratios was stronger for females than for males. We concluded that the variation in the night-day speed ratio of elephants might be used as an effective indicator for changes poaching levels on a near real-time basis. We recommend its adoption as a complimentary anti-poaching tool, where GPS tracking data is already available, because it would increase the geographical range for monitoring of poaching levels. The significant alteration in movement behaviour by elephants in response to poaching also has potential implications for their foraging strategy, reproduction and ultimate survival, all of which are not yet fully understood.

Differing physiological and behavioral responses to anthropogenic factors between resident and non-resident African elephants at Mpala Ranch, Laikipia County, Kenya

“…Based on other studies, we hypothesized that resident elephants with small home ranges would exhibit lower adrenal GC activity than long-distance migrants (Wilcove & Wikelski, 2008;Pontzer & Kamilar, 2009;Wittemyer et al, 2017). With the Laikipia-Samburu ecosystem experiencing high levels of poaching between 2007 and 2012, elephants have been observed to alter their circadian rest patterns in response to human activities (Wittemyer et al, 2017), increase their speed while traversing through risky landscapes (Douglas-Hamilton, Krink & Vollrath, 2005), and shift movement patterns to be more active at night (Ihwagi et al, 2018). So we expected to observe higher FGM concentrations among the non-resident elephants.…”

Zoo elephant research: contributions to conservation of captive and free‐ranging species

“…Both African elephants -Savanna elephants Loxodonta africana and Forest elephants Loxodonta cyclotisand Asian elephants Elephas maximus are threatened because of habitat loss and fragmentation (Evans et al, 2018), and poaching for ivory (Breuer et al, 2016;Ihwagi et al, 2018) and, more recently, skins (Sampson et al, 2018). These activities disrupt social hierarchies (Jones et al, 2018) and increase stress, which may decrease resilience (Vijayakrishnan et al, 2018).…”

Timely poacher detection and localization using sentinel animal movement

“…It thus proved to be important to explicitly consider the spatial-temporal context of the movementenvironment interplay when using sentinel movement metrics as early warning indicators. Solely using movement speed as indicator 14 without incorporating environmental conditions is therefore not very informative (Fig 1).…”