Mammalian herbivores can play a role in the endozoochorous dispersal of Prosopis seeds in the arid zones of Argentina, and the introduction of exotic mammals can change relevant parameters of the plant's reproductive ecology. Our specific goals were to quantify the seeds of Prosopis flexuosa, P. chilensis and P. torquata contained in the faeces of native [mara (Dolichotis patagonum), guanaco (Lama guanicoe)] and exotic [donkey (Equus asinus) and hare (Lepus europaeus)] mammals, and to determine the mortality, germination percentage and germination speed of seeds borne in faeces, compared with those collected from trees. In 2006, seeds were collected directly from trees or removed from mammal faeces. Seeds were counted and classified as apparently healthy or damaged. P. torquata and P. flexuosa seeds were found in the dung of guanaco, hare and mara, whereas only P. flexuosa seeds appeared in donkey faeces. P. chilensis seeds were only found in guanaco faeces. There was a notable relative abundance of seeds contained in small herbivore faeces in comparison to the large herbivores. The passage through the digestive tract of animals modified seed germination capacity and speed, with great variability between animal species. Guanacos had greater effects than donkeys on mortality, germination percentage and germination speed. Differences between the effects of both smaller-sized herbivores on seeds were much smaller.

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Hoarding food is an important strategy of rodents in desert environments characterized by unpredictable and poor food resource availability. In the Monte Desert, Prosopis produces abundant food, unevenly in time and space, in the form of pods and seeds. Sigmodontine rodents (Graomys griseoflavus,Akodon molinae, Eligmodontia typus and Calomys musculinus) use Prosopis propagules extensively, and they could be predators or dispersers depending on how they handle and where they leave the propagules. The objectives of this study were: (1) to know what rodent species transported propagules; (2) to evaluate what hoarding pattern was used by species that transport propagules (larder and scatterhoarding); and (3) to analyse in which condition were propagules left by the rodent species, both at the food source and in caches. Our results showed that all four species transported propagules, with G. griseoflavus and E. typus being the species that carried more seeds. Our study supported the evidence that food caching is common among species and that many species both larderhoard and scatterhoard food. Graomys griseoflavus and A. molinae, the largest species, larderhoarded more than did the smaller E. typus. These results uphold the hypothesis that larger species will show greater propensity to larderhoard than smaller species. Considering the interaction between seed-hoarding patterns and plants, E. typus was the species that could most improve germination because it scatterhoarded propagules and left seeds out of pods. In contrast, G. griseoflavus could have a negative impact on plant populations because this was the species that predated more seeds and larderhoarded a high percentage of them. The smallest C. musculinus was the species that transported propagules least, and left them as seeds inside pods or pod segments mainly at the food source, which makes seeds more vulnerable to predation.