Table 1 Abbreviations and descriptions of the physiological, behavioural and vocal parameters measured

Physiology

RR (ms)

Inter-heart-beat interval

A

RespRate (breaths/s)

Respiration rate

A

SkinT (°C)

Skin temperature

V + A

Behaviour

Locomotion

Proportion of time spent moving (walk, trot or canter)

A

HeadMov (min-1)

Number of rapid head movements per minute

V + A

HeadHigh

Proportion of time spent with the eye line above the tip of the shoulder

V

Chewing

Proportion of time spent chewing (i.e. moving the lower jaw up and down in a chewing motion). This behaviour is performed without the presence of food in the mouth

V + A

VocRate (min-1)

Number of vocalisations (whinnies or nickers) per minute

V (nickers)

LatenceRes

Latency from the onset of the call played back to the first behavioural response (including all the above described behaviours)

-

Vocalisations

Dur (s)

Duration of the whinny

V + A

G0Start (Hz)

Frequency value of G0 at the start of the whinny

V + A

G0Max (Hz)

Maximum G0 frequency value across the whinny

V + A

G0Mean (Hz)

Mean G0 frequency value across the whinny

V + A

F0Start (Hz)

Frequency value of F0 at the start of the whinny

A

F0Max (Hz)

Maximum F0 frequency value across the whinny

V + A

F0Mean (Hz)

Mean F0 frequency value across the whinny

A

AMVar (dB/s)

Cumulative variation in amplitude divided by the total whinny duration

V + A

AMExtent (dB)

Mean peak-to-peak variation of each amplitude modulation

V + A

Q25% (Hz)

Frequency value at the upper limit of the first quartiles of energy

V + A

Q50% (Hz)

Frequency value at the upper limit of the second quartiles of energy

V + A

Q75% (Hz)

Frequency value at the upper limit of the third quartiles of energy

V + A