Spotlight counts, site fidelity and migration of European rabbits (Oryctolagus cuniculus)

Abstract

Regardless of their sex and age, the persistence of 76 rabbits (Oryctolagus cuniculus) translocated onto 5 different sites with relatively low rabbit densities was identical to that of resident rabbits. Emigration and exploratory movements by rabbits from 12 discrete populations were positively correlated with rabbit density and mainly undertaken by adult rabbits. Adult males moved significantly more often and further than adult females. Two peaks in immigration were observed; a large peak (usually in January) immediately following the breeding season, and a second but smaller peak in March which preceded the start of the next breeding season. Again, significantly more adult males than females immigrated. The proportion of rabbits seen in spotlight counts was positively correlated with rabbit density, which suggests that biases in population estimates could result in some situations. No clear patterns on the effects of a variety of weather variables on spotlight counts could be established, but increasing rainfall, wind speed and moonlight may have reduced rabbit activity.

Towards a standardized index of European rabbit abundance in Iberian Mediterranean habitats

“…This may be related to a rabbit avoidance of dusk-time hours to prevent higher predation risk (hunting and diurnal raptors, Fernández de Simón et al 2009) or to an avoidance of dirt tracks during the day to prevent human disturbance (similarly as the roe deer Capreolus capreolus; Ward et al 2004). Driving transect counts may be affected by environmental factors such as visibility, wind speed, and rainfall, which may affect rabbit activity (Villafuerte et al 1993;Twigg et al 1998;Martins et al 2003). Similarly, numbers of predators and hunting pressure should be considered when conducting these surveys as rabbits may shift their activity to reduce the predation risk (Fernández de Simón et al 2009).…”

“…Caution must be taken with KAIs because they do not control for habitat variation in rabbit detectability (Marchandeau et al 2006). Furthermore, sight counts may underestimate rabbit abundance (Twigg et al 1998;Poole et al 2003) since the proportion of rabbits seen in a population are inversely related to rabbit density due to social interactions (Twigg et al 1998). However, at rabbit densities found in the Iberian Peninsula, much lower than those found in Australia (Barrio 2010), the proportion of active rabbits is relatively high during the night and therefore spotlight counts are less affected by inactive rabbits (Twigg et al 1998).…”

“…One alternative to the Distance Sampling method is the kilometric abundance index (sightings per kilometer; Beltrán 1991; Moreno et al 2007;Williams et al 2007), which is correlated with population density Barrio et al 2010a) and provide data for a range of abundances. Rabbit counts also have several drawbacks, such as environment variables affecting the rabbit activity patterns (see e.g., Villafuerte et al 1993;Twigg et al 1998;Martins et al 2003). Other direct methods used to estimate densities are based on live trapping, mostly by means of capturerecapture (e.g., Ballinger and Morgan 2002;Marchandeau et al 2006) and the minimum number of individuals known to be alive (MNA, King and Wheeler 1985;Wood 1988).…”

Introduced mammals in Australian rangelands: Future threats and the role of monitoring programmes in management strategies

“…below ground or obscured) at any one time. A complicating factor is that the proportion of the population seen during spotlight counts tends to be negatively correlated to density (Twigg et al . 1998).…”

“…1998). This suggests that at least some rabbits might undergo a temporal behavioural shift at high densities (Twigg et al . 1998).…”