Just as humans possess a fight or flight mode in times of danger, prey animals exhibit antipredator behavior such as alertness, aggression, flight, or vocalization. A recent study focused for the first time on the different night time antipredator behavior of Asian elephants when threatened by leopard and tiger growls.
In crop fields around the Bandipur Tiger Reserve and Wayanad Wildlife Refuge in southern India, tigers are known to prey on elephant calves in nighttime crop-raiding family groups. Leopards, on the other hand, pose no predation threat.
Researchers Vivek Thuppil and Richard G. Coss from the Animal Behavior Graduate Group and Department of Psychology at UC Davis studied the nighttime antipredator behavior of Asian elephants. They found the antipredator behavior differed significantly in response to tiger and leopard growls.
Previously, only antipredator behavior of African elephants had been studied. Identified and studied threats include male lions, which pose greater danger than female lions, and African bees.
Researchers found that family groups were able to discern the sounds of a male versus a female lion roar and to identify the sound of threatening African bees. Particularly, older matriarchs were quick to retreat and alarm call in response to the sounds of potential threats.
Thuppil and Coss shed light on the antipredator behavior of Asian elephants who like their African cousins “may possess a broad, low-frequency acoustical-assessment ability” (3).
First, the researchers recorded agitated tiger and leopard-growl playbacks using AUDACITY software at the Bannerghatta Zoological Park, Bangalore. The growls were then digitized and amplified in waterproof speaker systems.
The speaker systems were positioned approximately 50 m ahead of infrared beams that triggered the feline playbacks. In concordance with nighttime crop-raiding behavior, the playback systems were close to crop fields.
A total of 26 playback activations occurred at three study sites from August 2010 to February 2011. For analysis, the researchers only considered incidents of elephants encountering the playback system for the first time.
Behaviors were therefore analyzed from seven tiger-growl playback encounters and eight leopard-growl playback encounters.
In the morning, footprints were tracked using a Garmin eTrex device. Movements were categorized using compass bearing positioning on the speakers into toward, lateral, and away movements.
Using variance analysis tests, the researchers determined there was no significant difference in elephant triggered movement between a tiger and leopard-growl playback. In both cases, the elephants eventually moved away from the growls.
Variance did occur, however, in immediate behavioral responses as collected with high-definition infrared video cameras equipped with microphones.
The cameras allowed for categorization of elephants based on morphological attributes. The authenticity of the playbacks was confirmed by the presence of tigers and leopards in the study areas as captured by the cameras.
After leopard-growl playbacks, elephants exhibited alert and investigative behaviors and vocalizations in the form of grunts, growls, and trumpets. After tiger-growl playbacks, no vigilant or vocal behaviors were recorded.
Thuppil and Cross discovered that the more dangerous tiger-growls resulted in silent retreat. Whereas the leopard-growls triggered aggressive vocalizations in all but one encounter.
The differing antipredator behavior indicates that Asian elephants can discriminate between tiger and leopard growls. Asian elephants can also associate these growls with different levels of threat.
The researchers claim that further antipredator behavior research can have beneficial implications on conservation. For example, African elephants are deterred from crop raiding by dangerous African bee hives on fences.
Perhaps the incorporation of tiger-growl playbacks can reduce the disruption of crops by Asian elephants and thereby eliminate the threat of conflict with local farmers.
Thuppil V, Coss RG. (2013) Wild Asian elephants distinguish aggressive tiger and leopard growls according to perceived danger. Biology Letters 9: 20130518.