Quantifying Ant Activity Using Vibration Measurements

Abstract

Ant behaviour is of great interest due to their sociality. Ant behaviour is typically observed visually, however there are many circumstances where visual observation is not possible. It may be possible to assess ant behaviour using vibration signals produced by their physical movement. We demonstrate through a series of bioassays with different stimuli that the level of activity of meat ants (Iridomyrmex purpureus) can be quantified using vibrations, corresponding to observations with video. We found that ants exposed to physical shaking produced the highest average vibration amplitudes followed by ants with stones to drag, then ants with neighbours, illuminated ants and ants in darkness. In addition, we devised a novel method based on wavelet decomposition to separate the vibration signal owing to the initial ant behaviour from the substrate response, which will allow signals recorded from different substrates to be compared directly. Our results indicate the potential to use vibration signals to classify some ant behaviours in situations where visual observation could be difficult.

An Innovative Signal Processing Method to Extract Ants’ Walking Signals

“…We applied two thin layers of Fluon (polytetrafluoroethylene based) to the walls of the PVC tube in order to avoid insects climbing the PVC tube and dropping thus creating 'unnatural behaviour' (cf. Oberst et al [17]). The measurements were performed using a single point laser vibrometer Polytec PVD-100 with a data acquisition system Polytec VIB-E-220, connected to a Toshiba notebook with Vibsoft 8.8 analysis software.…”

“…Temperature measurements, humidity measurements and video recordings were triggered using an Arduino UNO microcontroller with temperature and humidity sensor (Freetronic, DHT22) and a switch connected to a LED which indicated the recording status in the recorded videos. The setup (lid only of the insect box used in Oberst et al [17], foam, wood on two bricks) as depicted schematically in Fig. 1 was supported by foam on a steel frame placed in the middle of the anechoic room.…”

“…A veneer disc was placed inside the cylindrical container and then pushed down by a PVC tube (cf. [17,18] for more details on the insect box). Veneer discs were cut from Pinus radiata veneer sheets of unknown origin for the production of plywood panels.…”

“…Recently vibrations have been shown to be able to quantify the different activity levels of the ant species Iridomyrmex purpureus responding to different stimuli such as light, darkness, stones and neighbouring nest-mates [17]. A classification of vibration excitations according to their response in a wavelet-filtered, blind deconvolution inverse process using an accelerometer setup in an anechoic room has been limited to only detecting three activities: the falling and impacting of an ant on the substrate, scratching/biting and the dragging/carrying and subsequent dropping of stones as a combination of the previous two signals [17,18]. The walking response was buried in noise and the veneer disc as the substrate was modelled as a generalised parametric isotropic linear model, which allowed deconvolution to retrieve the excitation signal.…”

“…This is a preliminary study aimed at quantifying the excitation signal extracted from the vibration response of a substrate over which an ant walks. For this purpose a more sensitive and better environmental vibrations isolated experiment than that used by Oberst et al [17] has been designed using an air cushion damped laser vibrometer setup in an anechoic room. In order to overcome the problem of inverse blind deconvolution of the recorded response, the system's transfer function has been measured first.…”