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Research Highlights

Development for Novel Approaches to Detect Invasion of Sika Deer Using Their Howls

Associate Professor Hiroto Enari, Ph.D. (Ecology/Environment)

Sika deer (Cervus nippon) often cause damage to agriculture. Among the damage to agriculture caused by wild mammals, the one by sika deer is most serious and damage cost has reached 6 to 7 billion yen (=$60 million) per year. Sika deer are also known as ecosystem engineer because their high feeding presser sometimes leads to the loss of biodiversity in native forests. In recent years, the expansion of sika deer distributions has begun to be confirmed also in heavy snow regions. Since the increase of deer population is really striking, it is difficult to regulate the population after the population enters the increasing phase of their population dynamics. Now, precautionary measures are urgently required during the initial stage of invasion, however, there was no effective approach to detect sika deer during the stage because there is a problem that deer in low density are not detected effectively with existing methods using the spotlight and camera-trap surveys. In this context, Enari developed 2 new approaches—Passive Acoustic Monitoring (PAM) and Active Acoustic Monitoring (AAM)—to detect male deer using their loud calls during the rut (i.e., fall).

  • Passive Acoustic Monitoring (PAM)
    Recording spontaneous howls of males using with high-sensitive sound recorders to evaluate the time and variation in howl frequency. Had a detection zone of around 6 ha in defoliated forest, which was over 200 times greater than that of camera traps.
  • Active Acoustic Monitoring (AAM)
    In 10 categorized loud calls, Enari discovered that there is howl-back of other sika deer males against howls during the rut. The howl-back methods of sika deer were devised to record responses from other males by playback of their howls with the loudspeakers.

These bio-acoustic population monitoring approaches are considered to enhance the future sika deer management by predicting the population expansion and the impacts on native vegetation and social industry.

High-sensitive sound recorder (Song Meter SM2+)

Sika deer invading the Iide Mountain Range

Published Paper

Ecological Indicators
Volume 79, August 2017, Pages 155-162
Hiroto Enari, Haruka Enari, Kei Okuda, Miho Yoshida, Takuya Kuno, Kana Okuda
Feasibility assessment of active and passive acoustic monitoring of sika deer populations.

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