alternative stable states of rabbit populations
TRANSCRIPT
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system is destroyed (Lockley, 1954); Drees et al., 2007; Weijers, unpublished, 2013).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 Dekker 1 Marijke Drees. [email protected]
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
0
100
200
300
400
500
19
84
19
87
19
90
19
93
19
96
19
99
20
02
20
05
20
08
20
11
Wadden islands
Mainland dunes