Over several decades, the growth in deer, roe deer and wild boar populations has spread to all of France. Cemagref researchers have shown that in spite of the damage caused, notably to bushes and young trees in forests and to crops, these animals also help in increasing plant diversity.
They studied the floristic surveys carried out from 1976 to 2006 at Arc-en-Barrois (Haute-Marne department), a unique observation site in France due to its long-term monitoring data. A plant, the gypsy flower (Cynoglossum officinale), was not found during the first survey, but then appeared in 1981 and has since spread widely. It is now present in the zones where large, forest mammals are most frequently found.
How did this plant, though threatened by predators, make such great strides? By hanging on tight! Its seeds can latch on to the fur of animals thus ensuring dissemination (epizoochory) and it is also a plant with a circular arrangement of leaves (rosette) that is not consumed by fauna because it contains toxic substances. These characteristics provide significant advantages enabling the plant to settle far and wide.
A brush with the boars
Wild boars are an excellent dispersal agent. Their fur comprises two strata, an undercoat of often curly hair and stiff bristles, that can easily lock in and transport seeds over many kilometres, contrary to deer and roe deer with their shorter hair.
Their behaviour is also a decisive factor in seed dispersal. When wallowing, their fur picks up seeds in the mud that are then transported to dryer ground when the boars scratch themselves, rub against trees or dig up the topsoil looking for food.
After brushing boars killed by hunters, scientists counted a total of almost 40 different seed species. Thanks to its morphology and behaviour, the wild boar is a champion seed disperser.
Cemagref is the coordinator of the Diplo project to quantify the role of common low-land ungulates (deer, roe deer and wild boar) as long-distance seed-dispersal agents. The researchers evaluate the impact of animal movements on the success of seeds from the time they are picked up to their release to the soil.
The project is funded by the Water and biodiversity department at the Ecology ministry for the period 2009 to 2011. Partners include the National veterinary school in Maisons-Alfort, INRA in Toulouse, the National agency for hunting and wildlife (ONCFS) and Animal contact (Loiret department).
Further information: http://cemadoc.cemagref.fr/cemoa/PUB00029836
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