Removal of mesquite seeds by small rodents in the Monte desert, Argentina

Abstract

We examined the removal of Prosopis flexuosa pods by small rodents, and addressed four specific questions: (1) do Monte Desert small rodents remove mesquite pods? (2) if they do, do they store them above-ground? (3) how far are pods carried? and (4) what condition are removed pods and seeds in? We carried out the experiments in March 2000 and June 2003, at two sand-dune sites in the Ñacuñán Reserve, Mendoza plain (Argentina), where Eligmodontia typus, Graomys griseoflavus, Akodon molinae, and Calomys musculinus (Sigmodontidae) are present. On each site we established 32 feeding stations. We recorded the weight of pods and the number of seeds left on the dishes, number of seeds and weight of pods removed, number of caches and their distances from trays, and the condition of pods and seeds in the caches. We found that rodents did remove and scatterhoard Prosopis pods; in many cases rodents only removed the exocarp and mesocarp. Over a 48-h period rodents removed 42% and 18% of the seeds provided in 2000 and 2003, respectively. In 2000, we only recovered 13% of the removed seeds in the 58 caches detected; in 2003, we found 20.4% of the removed seeds in the 55 caches detected. The fates of remaining removed seeds (87-79.6%) is uncertain. Pods in caches exhibited a different degree of damage caused by rodents: seeds outside pods amounted to 25%, endocarps with no seeds represented only 0-1.4%, and 51-61% of the seeds were inside pods or pod segments.