I've lifted and translated this article on Acorns and rats in Castile straight from 'Vida', by Miguel Delibes del Castro, 2001. an entertaining collection of essays on biodiversity and its threats, with a Spanish slant on things. Delibes, son of the famous writer (and hunter) the also-Miguel Delibes, is one of Spain's leading zoologists, and was director of the 'Doñana Biological Station' from 1988-96.

holm oak wood

"The holm oak and savine woods which dot the cereal fields of the two Castillas are magnificent examples of forest fragments. In winter, when long-cycle wheat is beginning to grow, and short-cycle wheat has yet to be planted, these woods emerge like veritable forested islands in a bleak and barren sea. At this time of year, almost all small rodents make for these refuges, from where they re-colonise the fields, and breed as spring comes on and slips into summer. If it's been a good year, after the harvest, immense hordes of field mice, born and raised in the wheat fields, invade these forested enclaves. Tomás Santos and José Luis Tellería, professors from the Universidad Complutense, have studied what happens in these forested fragments.

When the forest-island is large, most of the mice stay on the edges. Here they feast on the harvest of acorns, and probably cut back the growth of new plants. However, in the heart of the enclave, there are still acorns, and some manage to geminate. In a good year's production, there are just not enough mice to finish off the acorns of an extensive holm oak wood. However, when it's a copse, the whole wood functions like an 'edge'. In this situation, the invading field mice are capable of nibbling off the entire harvest without leaving a single acorn to germinate. The only new plants which appear are shoots from roots. Here, the very survival of the wood is threatened by its small size, as no regeneration takes place.

Some studies have warned that the tropical forests of Indonesia could be already condemned by a similar process as that detected in the forested hills of Castilla. Like the holm oak, the balaus and keruings, giant trees of the dipterocarpaceas family, are veceros*. The strategy of vecero* trees is to produce lots of fruit in one burst, although not every year, so that the vast majority of them are consumed by fruit-eating animals, enough survive to produce new plants. It's as if they have saturated the market, and at these moments, supply greatly exceeds demand, and so there is always enough to germinate. Now, however, there are so few large trees, and in such small and localised patches that when they do bear fruit, and attract fruit-eaters, the production is not enough for all, and not one seed survives to ensure reproduction. Here once again, although not all the habitat has disappeared, and forest remains, the fragments are too small to ensure in the medium term the conservation of biodiversity. "

* means they produce a lot of fruit in one year and none the next. Can't remember the translation for this, though I've read it somewhere. Any ideas?

Key words: spanish acorns, rats and acorns, Miiguel Delibes, rat ecology, acorn ecology, acorn forests, castilla acorns, bellotas Spain, spanish bellota