Hiding in The Darkness: Nocturnal Behavior in Response to Human Disturbance

Shimon Shuchat
Jan 21, 2019 · 4 min read
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Two forest elephants in Dzanga Bai (Central African Republic) at dawn © Anahita Verahrami

Poaching has become widespread in forest elephants’ Central African home and poses a major threat to their survival¹. The stress presented by poachers has become so pronounced that the elephants have begun to significantly alter their behavior in response to it. One such change is a propensity towards increased nocturnal activity since poachers tend to be more active during the day². Monitoring these behavior modifications can allow for more efficient tracking of poachers’ movements which would help law enforcement focus attention on locations in the direst state.

A recent study² from Kenya’s Laikipia-Samburu Ecosystem found that savannah elephants become more active at night when poaching levels are high. In this study, Dr. Festus Ihwagi and his colleagues analyzed the relationship between poaching activity and the distance elephants travel at night. The researchers used previously collected satellite data from multiple sources and data on elephant mortality obtained by the Convention on International Trade in Endangered Species. The data showed that elephants’ nighttime travel rate significantly increased as poaching levels increased and following a poaching surge that took place between 2010–2012. These changes also occurred in the reverse². For example, at the Sera Conservancy (a portion of the ecosystem) nighttime travel decreased when poaching was reduced² due to improved human-wildlife conflict management³.

Dr. Ihwagi suggests that these movement pattern alterations could be used as an indicator of poaching levels². Utilizing this indicator can allow for poaching activity to be tracked more efficiently by comparison to the on the ground monitoring system primarily being used now. Since elephants are already being monitored with a GPS system in many protected areas, no new monetary investment would be necessary. It would only involve deeper analysis of existing data². If such analysis reveals that elephants in specific locations are becoming more nocturnal it can be assumed that poaching activity is on the rise there. Law enforcement resources can then be directed towards the affected areas.

Nocturnal behavior in response to human activity is also exhibited in forest elephants and Elephant Listening Project (ELP) researchers have documented this phenomenon on multiple occasions. For example, in 2010 ELP published a study⁴, in conjunction with Ithaca College’s physics department, that analyzed the impact of oil drilling on elephants from Loango National Park, Gabon. Researchers found that the elephants steadily increased their nighttime activity as human activity became more pronounced in their range. Elephants did not distinguish between preparatory teams that weren’t engaged in drilling and workers who were. This shows that they were primarily responding to the presence of humans, not noise from the drilling⁴. According to Dr. Peter Wrege, ELP’s director, the elephants’ fear of humans was likely stimulated by previous experience with poachers. ELP researchers have also found that elephants visit forest clearings mostly during the night while forested land is used during both day and night (almost equally)⁵ ⁶. This is most likely because elephants are more vulnerable to poaching activity at exposed clearings⁷.

Elephants aren’t the only animals that become more nocturnal in response to human disturbance. Such behavioral changes are actually found in a wide range of mammals ranging from tigers and coyotes to deer and wild boar⁸. However, large mammals, like elephants, are a little more prone to develop this behavior modification since they require a lot of space which could potentially make their range more likely to overlap with human inhabited land⁸. Increased nocturnal activity can have both positive and negative consequences. On the positive side it reduces animals’ chances of interacting with humans, thereby reducing the likelihood of violent conflicts occurring. As a result, animals may be better able to share space with humans and will therefore have access to more habitat. On the negative side, animals may not be adapted to nocturnal activity which can make foraging more difficult and costly⁸.

Poaching is imposing a large amount of stress on elephant populations and is causing them to significantly modify their behavior patterns. Understanding these behavioral alterations is integral to elephant conservation since tracking changes in nocturnal activity can allow wildlife managers to more efficiently monitor and respond to poaching activity. This new strategy may reduce the number of elephants who get killed thereby hastening their populations’ recovery.

References:

¹Poulsen, John R., Sally E. Koerner, Sarah Moore, Vincent P. Medjibe, Stephen Blake, Connie J. Clark, Mark Ella Akou et al. “Poaching empties critical Central African wilderness of forest elephants.” Current Biology 27, no. 4 (2017): R134-R135.

http://www.sciencedirect.com/science/article/pii/S0960982217300246

²Ihwagi, Festus W., Chris Thouless, Tiejun Wang, Andrew K. Skidmore, Patrick Omondi, and Iain Douglas-Hamilton. “Night-day speed ratio of elephants as indicator of poaching levels.” Ecological indicators 84 (2018): 38–44.

https://www.sciencedirect.com/science/article/pii/S1470160X17305290#bib0125

³Ihwagi, Festus W., Tiejun Wang, George Wittemyer, Andrew K. Skidmore, Albertus G. Toxopeus, Shadrack Ngene, Juliet King, Jeffrey Worden, Patrick Omondi, and Iain Douglas-Hamilton. “Using poaching levels and elephant distribution to assess the conservation efficacy of private, communal and government land in northern Kenya.” PloS One 10, no. 9 (2015): e0139079.

https://journals.plos.org/plosone/articleid=10.1371/journal.pone.0139079

⁴Wrege, Peter H., Elizabeth D. Rowland, Bruce G. Thompson, and Nikolas Batruch. “Use of acoustic tools to reveal otherwise cryptic responses of forest elephants to oil exploration.” Conservation Biology 24, no. 6 (2010): 1578–1585.

https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1523-1739.2010.01559.x

⁵Wrege, Peter H., Elizabeth D. Rowland, Nicolas Bout, and Modeste Doukaga. “Opening a larger window onto forest elephant ecology.” African Journal of Ecology 50, no. 2 (2012): 176–183.

https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2028.2011.01310.x

⁶Wrege, Peter H., Elizabeth D. Rowland, Sara Keen, and Yu Shiu. “Acoustic monitoring for conservation in tropical forests: examples from forest elephants.” Methods in Ecology and Evolution 8, no. 10 (2017): 1292–1301.

https://onlinelibrary.wiley.com/doi/abs/10.1111/2041-210X.12730

⁷Fishlock, Vicki, and Thomas Breuer. Studying Forest Elephants. Stuttgart: Neuer Sportverlag, 2015. Print.

⁸Gaynor, Kaitlyn M., Cheryl E. Hojnowski, Neil H. Carter, and Justin S. Brashares. “The influence of human disturbance on wildlife nocturnality.” Science 360, no. 6394 (2018): 1232–1235.

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