Plant-ungulate interaction: goat gut passage effect on survival and germination of Mediterranean shrub seeds

Questions: (i) How do large proportions of seeds pass through the guts of goats without damage? (ii) What is the temporal pattern of seed defecation? (iii) Does ingestion by goats enhance or depress seed germination? Location: Donana Natural Park, SW Spain. Methods: Six female goats of similar size and age were fed with 1000 seeds of four common Mediterranean shrub species (Cistus salvifolius, Halimium halimifolium, Myrtus communis, Pistacia lentiscus), which were retrieved from the goat's dung 96 h after ingestion. The seeds retrieved were tested for germination and viability, along with seeds not eaten by the goats. Results: Less than 30% of the seeds eaten were retrieved from the dung, with significant differences between species. No seeds of P. lentiscus were retrieved. The major part of the seeds was retrieved between 48 and 72 h after ingestion in all other species. The passage through the goat gut significantly increased seed germination in C. salvifolius and H. halimifolium, and depressed it in M. communis. Viability was significantly lower in the eaten seeds of M. communis than in the uneaten ones, while there were no differences in C. salvifolius and H. halimifolium. Conclusions: Goats can potentially disperse seeds of the plants that they eat. This should be taken into account when designing management plans in order to prevent shrub invasion in undesired areas. It could also be used as a management tool for spreading populations of desireable shrub species.