This invention relates to a birthing sensor (1 ) for mounting on the tail of a pregnant animal. The birthing sensor comprises a casing (3) and an adjustable strap (5) for securing the casing to the tail of the pregnant animal. The casing houses monitoring equipment communication equipment and a power supply. There is provided a padding insert (7, 37, 47) for location between the casing the strap and the animal s tail. The padding insert comprises a sheet of resiliently deformable material such as rubber having a plurality of ventilation passageways formed therein. The ventilation passageways allow passage of air over the cow s tail underneath the sensor and further allow escape of urine and faeces from under the sensor. The passageways may be formed by having a plurality of upstanding bosses (9) on the surface of the padding insert and the passageways are the spaces between these upstanding bosses (9).
