Snakes as ecosystem engineers: secondary seed rescue, germination success, seedling viability, and implications for dispersal in nature

Schuett, Gordon W.

gwschuett@yahoo.com

Department of Biology ǀ Neuroscience Institute

Georgia State University

Atlanta, Georgia USA

Chiricahua Desert Museum

Rodeo, New Mexico USA

Reiserer, Randall S.

Chiricahua Desert Museum

Rodeo, New Mexico USA

Salywon, Andrew M.

Blackwell, Steven

Hodgson, Wendy C.

Desert Botanical Garden,

Phoenix, Arizona USA

Foster, C. Drew

Hall, James

Zach, Ryan*

Arizona Center for Nature Conservation ǀ Phoenix Zoo

Phoenix, Arizona USA

Davis, Mark A.

Prairie Research Institute, University of Illinois Urbana Champaign

Champaign, Illinois USA

Greene, Harry W.

Department of Integrative Biology

University of Texas at Austin

Austin, Texas USA

* Zoo Miami

Miami, Florida USA

The importance of vertebrates as seed dispersers (zoochory) has received increasing attention from researchers over the past 20 years yet one speciose group—snakes—remains understudied. Although snakes are among the most abundant predators of granivorous vertebrates, our knowledge of seed rescue and secondary dispersal is almost nil. The phenomenon of diploendozoochory refers to a two-phase seed dispersal system whereby a secondary seed predator (carnivorous vertebrate) consumes a primary seed predator or granivore (rodents, birds) with seeds in its digestive tract (mouth, cheek pouch, crop, stomach, or other organ), which are subsequently eliminated with feces. In our first report using museum-preserved specimens, we showed that three desert-dwelling rattlesnake species consumed heteromyid rodents with seeds in their cheek pouches, and that secondarily ingested seeds occasionally germinated in snakes’ colons. More recently, we reported on a study of live snake subjects of the Sonoran Desert (one viperid and two colubrine species) and seeds of the Foothill Palo Verde (Parkinsonia microphylla), a dominant tree of the same region. We experimentally tested germination frequency and rate, and seedling viability. Our study provides support for the role of snakes as important agents of seed rescue and dispersal in nature, their potential as ecosystem engineers, and crucial evidence for the investment of field-based studies on diploendozoochorous systems in deserts and other ecosystems. We hope that by highlighting their potential new role as agents of seed rescue and secondary dispersal will encourage both academic and public involvement (e.g., citizen scientists) in generating interest and legislature for their protection and long-term conservation.