Many species of carnivores, such as the Iberian lynx (Lynx pardinus), depend on the rabbit (Oryctolagus cuniculus) for their survival. Now Spanish and Argentinean researchers have evaluated how certain carnivores in Spain's Doñana National Park responded to the sudden collapse of the rabbit population in the 1980s. The results show that this decline primarily affected the lynx, which was unable to hunt other prey.
The population of rabbits (Oryctolagus cuniculus), the main prey animal in Mediterranean ecosystems, collapsed when viral haemorrhagic disease (VHD) arrived in the late 1980s.
In order to find out what impact this population plunge had on the rabbits' predators, the researchers analysed the diet of the badger (Meles meles), fox (Vulpes vulpes), Egyptian mongoose (Herpestes ichneumon), genet (Genetta genetta) and Iberian lynx (Lynx pardinus).
"All the carnivores reduced their consumption of rabbits following the arrival of VHD, although this reduction varied from one species to another," Pablo Ferreras, lead author of the study and a researcher at the Research Institute on Cynegetic Resources (IREC), a joint centre of the University of Castilla-La Mancha, the CSIC and the regional government of Castilla-La Mancha, said.
According to the study, which has been published in Basic and Applied Ecology, the greatest reduction in rabbit consumption was seen among the badger (falling from 71.8 to 26.2%) and the fox (from 20.2 to 9.8%).
The fox altered its diet more significantly than any other carnivore in response to this decline, primarily substituting rabbits for ungulates (in the form of carrion), birds and small mammals.
"The fox displayed a numerical response to the reduction in rabbits, declining in abundance during the five years following the arrival of VHD," Ferreras points out. However, the Egyptian mongoose and the genet did not reduce their consumption of rabbits to such a great extent, and their population numbers did not fall.
The Iberian lynx, unable to change its prey
Even though the rabbit number density was the lowest ever recorded in this area, the Iberian lynx "hardly reduced its consumption of rabbits, which continued to form the basis of 75% of its diet," explains Ferreras, saying that this shows the lynx is "by necessity a rabbit specialist."
The lynx's social system altered too following the arrival of this rabbit disease -- the animals became less territorial and the size of the females' home ranges increased, while the sub-adults remained in the areas they had been born in.
The critical situation of the Iberian lynx, considered to be one of the most highly endangered felines in the world, "was made even worse, if this is possible, by its inability to hunt non-rabbit prey." The researchers also point out that the lynx's social system was disturbed in the first year of the rabbit population collapse, as the juvenile animals did not disperse, which increased local density.
The majority of rabbit populations in the Iberian Peninsula have not recovered from the collapse caused by this illness. Predation may be impacting on recovery, with rabbits having entered a low-density population balance regulated by predation. The scientists say that the scarcity of rabbits could "seriously" threaten specialist predators such as the lynx.
The researchers are calling for management measures that would increase rabbit number density, through restocking programmes or habitat improvement, for example.
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