Fossil pollen grains in the digesta of mice and mastodonts

McAndrews, J. H.,
Departments of Botany and Geology, University of Toronto, 25 Wilcocks St., Toronto ON M5S 3B2 Canada

Two contrasting sites with fossil digesta (gut contents and dung) illustrate herbivore diets. January Cave, Alberta (50o 11' N, ll4o 31' W, 2040 m asl), is a rockshelter surrounded by Rocky Mountain subalpine forest of Pinus contorta; it lies 400 m below alpine tundra. The landscape was not glaciated. Unlike the modern pollen rain, the dry cave earth of weathered limestone had <7% tree pollen and most pollen was of entomophilous alpine tundra plants such as Claytonia, Phlox, Polemonium, Polygonum viviparum and Saussurea. Contemporaneous bones, dominated by the rodents Peromyscus and Spermophilus but also including small carnivores, date 33,000 to 23,000 yr B. P. Most pollen was transported to the cave in rodent digesta by birds of prey (mostly owls) and small carnivores.

The Hiscock Site, New York (43 05' N, 78 05' W, 189 m asl), in the St. Lawrence Lowland is a 0.8 ha Typha-dominated terrigenous peatland surrounded by farm fields. Following deglaciation 12,500 yrs B. P., a salt-water pond attracted vertebrates and a mastodon bone-rich Fibrous Gravelly Clay layer dating 11,450 to 10,200 yr B. P. was deposited. It contains a Picea glauca-dominated tree pollen assemblage that indicates spruce woodland. There is also super-abundant pollen of non-arboreal upland plants - Gramineae, Cyperaceae, Compositae and Rosaceae (probably Potentilla fruticosa), together with occasional pollen of entomophilous Lonicera, Cornus, Ericaceae, Elaeagnus, Salix, Shepherdia canadensis, Ranunculus, Epilobium, Galium, Campanula, Sanguisorba and Polygonum bistorta and anemophilous Thalictrum, Chenopodiineae, Artemisia, Plantago major type, Selaginella selaginoides, Botrychium, Lycopodium annotinum and fungal spores. This palynomorph assemblage, together with barkless spruce twigs, spruce needle fragments and clay testifies that the layer is digesta from mastodon, who browsed on spruce trees and shrubs, grazed on herbs and ate soil.