The pollination success of Agave palmeri is strongly dependent on nectar—feeding bats. In areas with very low or nonexistent bat populations, Agave seed set is<5% of its maximum potential. A 30 yr trend of declining seed set parallels a decline in bat numbers during that period. We speculate that habitat destruction and an increase in human use of Agave are causal factors. Over half of the measurable energy in the plant biomass is allocated to advertising and reproduction. We discuss the costs and risks involved in the semelparous strategy when pollinators decline. Where bats remain, agaves in dense patches show higher seed set than do outlying plants, suggesting that the pollinators favor grouped plants. This behavior may reinforce the plants' colonial tendencies.