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Chapter 4: Introduction to acoustic SCR

Lecture: Introduction to acoustic SCR

For acoustic SCR, we use calls as the detection unit and estimate call density. In order to convert call density to animal density we need to estimate the call rate which is the number of calls made by an individual animal during a sampling occasion (call density = animal density x call rate).

  • We again use an example with 16 detectors in a square configuration and five animals. Each animal makes between 1 and 3 calls during the sampling occasion. These calls form the basis for the capture history which is analysed in the acoustic SCR model.

  • Using the capture history, the acoustic SCR model estimates call density as the number of calls per hectare per duration of the sampling occasion.

  • Parameters of the acoustic SCR model that require estimation include (at minimum):

    1. Density

    2. g0

    3. sigma

  • Call rate of animals can be estimated by following multiple animals individually and recording each call for the same duration as the sampling occasion. For example, if the sampling occasion is from 7am-9am, call rate data should be collected form 7am-9am on a day close to the sampling occasion.

Demo: Acoustic SCR - frog example

In this demo we use real data to fit an acoustic SCR model using the R package ascr. The data are the detections extracted from 25 seconds of acoustic recordings taken by six microphones in the habitat of the frog Arthroleptella lightfooti occurring in South Africa.

  • We explain how to access the data provided with the package including the capture history, detector locations and the mask.

  • We fit the model and interpret the resulting density estimate.

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Continue with Chapter 5

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