Observations on diet and seed digestion in a Sand Dune Lizard, Meroles anchietae

Abstract

Shovel‐snouted sand dune lizards, Meroles anchietae, are reported to include much seed from grasses and fig marigolds in their diets year‐round. This diet is quite unusual for a reptile, and invites investigation. We had an opportunity to examine the diet and to measure seed digestibility for M. anchietae living on dunes near Gobabeb, Namibia. Stomach contents taken harmlessly via esophageal cannulation in the field revealed that the average diet included 37% (dry mass basis) immature seeds, 61% arthropods and 2% green plant leaves and flowers. Captive lizards fed measured amounts of whole mature (dehisced) grass seeds, both with and without hulls, were unable to digest and assimilate any significant dry matter from them. Microscopic examination of seeds recovered from stomachs along with seed remains found in fresh fecal pellets from free‐living M. anchietae indicated that most of the “seeds” apparently were soft, moist, somewhat green and immature when eaten, and may be better termed “ovules”. This food, perhaps eaten directly from the flowers of the plant, would be much more digestible and nutritious than mature, dry, shed (dehisced) seeds. We suggest that the seed‐eating behavior of M. anchietae might be better described as herbivory than as granivory.