An ethological perspective on defecation as an integral part of anti-predatory behaviour in the grey partridge (Perdix perdix L.) at night

Night-time flight behaviour of the grey partridge (Perdix perdix) was studied in three agricultural landscapes in Germany during the winter of 2005/2006. Thermography was used to detect roosting coveys and record flight behaviour. The main focus of the study was an analysis of defecation behaviour during the escape flight. A total of 640 partridges in 102 coveys were detected and approached during 85 scanning hours. Flight initiation distance averaged 22.8 m. In at least 75% of the coveys, defecation occurred upon being flushed. A covey of 15 partridges can produce 60 droppings that appear as a shower on the thermal record distributed over an estimated area of 200 mA(2). It can be hypothesised that defecation in the context of escape behaviour has various selective advantages in addition to the reduction of body weight. Predators may be irritated or deterred by the excretion of faeces of the partridges taking off. As defecation also appears in flushed partridges not in an immediate life-threatening situation, this behaviour seems to be uncoupled from the parasympathetic reaction of fear. Permanent predator pressure may have selected for a strategic integration of defecation in the escape behaviour of partridges at night.