Four possible causes are identified for stable low rabbit population densities: 1) bottom-up control of density due to food quality, 2) disease outbreaks that impact low density populations, 3) lack of protective burrow systems at low densities, and 4) increased predation by generalist predators at low densities. The document also discusses how rabbit populations at low densities cannot facilitate population growth to exceed the low density threshold due to lack of vegetation diversity and protective cover. Rabbits are shown to enhance vegetation diversity and limit scrub encroachment at high population densities.

1. Four possible causes of a stable ‘low population density’
• A bottom-up control of rabbit density at highly productive sites, the “food quality threshold hypothesis”(Van De Koppel
et al., 1996).
• Disease: The epidemics of myxomatosis (1953) and RHD (1990) affect populations at low density where the diseases
come and go, so the population does not acquire immunity (Henning et al., 2006).
• Lack of cover against predation or weather: After a period of low population density, the old, elaborate, safe burrow
system is destroyed (Lockley, 1954); Drees et al., 2007; Weijers, unpublished, 2013).
• Predation: Prey populations at low density in an ecosystem with generalist predators like the red fox can get in a
‘predator dip’ (Pech et al., 1991; Drees en Dekker, 2008).
Alternative stable states of rabbit populations
Marijke Drees 1 & Jasja Dekker 2
Dunes with rabbits at low population density Dunes with rabbits at high density
Rabbits can enhance vegetation diversity and push back scrub encroachment (Provoost et al., 2001)
For these reasons, a rabbit population that is in a state of low density,
cannot facilitate itself and stays under the threshold of low density.
2 Jasja Dekker1 Marijke Drees.
dreesmarijke@gmail.com
Dick Klees Dick Klees
Trend on mainland with foxes (--) and Wadden islands without (--) foxes
NEM: Zoogdiervereniging,CBS
High grasses mean low food quality
Palatable vegetation, but unsuitable landscape
without burrows. Meeuwenduinen, Westerschouwen,
after RHD epidemics
Dramatic decline since RHD epidemic in 1990
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Wadden islands
Mainland dunes