Document Type

Thesis - University Access Only

Award Date

2003

Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

First Advisor

E. Larson

Abstract

Leafy spurge infestations are serious threats to the biodiversity and economics of a region, especially within the Northern Great Plains. Knowing possible dispersal vectors is essential to understand the ecology and methods of infestation by leafy spurge. This project analyzes the potential of wildlife to consume and disperse viable leafy spurge and other forage seeds within their feces. Controlled feeding trials were used to determine the effect that gastrointestinal tract passage through deer, grouse and turkey had on the recovery and viability of leafy spurge seed. I used 4 deer (2 white-tailed and 2 mule deer), 4 sharp-tailed grouse and 4 wild turkeys during 5-day trials. Recovery of leafy spurge seeds from grouse, deer and turkeys varied within and between species. Turkeys only passed 0.14% of seeds fed with total viability of 26% compared to 94% for controls. Grouse had the highest seed recovery rate of 10% of seeds fed with seeds passing up to three days after ingestion. Viable seeds from grouse were only recovered one day after ingestion with an average viability of 36%. Deer passed about 4% of the seeds fed over the 5-day trial, but were still passing seeds through the last day. Viable seeds were recovered up to 4 days after ingestion. Viability of seeds recovered from deer was reduced to about 42% one day after ingestion and to 1 % four days after ingestion. Fecal samples from free-ranging deer, grouse and turkeys were collected from Theodore Roosevelt National Park (TRNP), North Dakota, and only deer samples from Medicine Lake National Wildlife Refuge (MLNWR), Montana. Recovery of leafy spurge seeds from free-ranging wildlife was minimal. No evidence of leafy spurge seeds was found from the 206 wild turkey fecal samples analyzed. One intact, nonviable leafy spurge seed was recovered from 201 sharp-tailed grouse fecal samples. Of the 134 TRNP deer samples analyzed, one sample contained two Euphorbia serpyllifolia and another contained two unidentified and nonviable Euphorbia sp. seeds, which were possibly immature E. esula. Forty-two MLNWR deer samples were analyzed where one E. esula seed was found in each of four samples. Also, two unidentified Euphorbia sp. seeds, possibly immature E. esula, were recovered from another sample. One of the E. esula seeds from a MLNWR sample germinated, whereas the other seeds were not viable. Evidence of utilization of leafy spurge by wildlife was documented in TRNP and MLNWR. Ungulates within TRNP and MLNWR grazed parts of leafy spurge plants in several locations within each study area. I recovered 26,274 seeds that were other than Euphorbia species within free-ranging turkey, grouse and deer fecal samples. Turkey samples contained 14,931 (24 seeds/g dry feces) total seeds from 48 identified taxa. The most frequently occurring seed taxa in turkey samples were currant, Kentucky bluegrass, green needlegrass, panicgrass and sedges. Grouse feces had 7,575 (20 seeds/g dry feces) total seeds from 42 identified taxa. The most frequent taxa in grouse feces were chokecherry, currant, buffaloberry, tansy mustard and wild rose. TRNP deer samples had 2,683 (1 seed/ g dry feces) total seeds from 44 identified taxa. Currant, lambsquarters, bluegrass species, Kentucky bluegrass, and serviceberry were the most frequent taxa recovered from TRNP deer feces. MLNWR deer samples had 1,096 total seeds from 22 taxa, where Kentucky bluegrass, pellitory, scurfpea, lambsquarters and stinging nettle were the most frequent seed taxa recovered. This study suggests that wildlife in general are probably not major endozoochorous vectors of leafy spurge since my results show that survival of ingested seed through the gastrointestinal tract is very low. If endozoochoric dispersal of leafy spurge was common, then long distance dispersal of leafy spurge in TRNP would likely be even more pronounced since wildlife and leafy spurge have interacted there for decades. My results indicate that grouse and deer could possibly disperse very low numbers of viable leafy spurge seeds in the wild, whereas turkeys are not likely to serve as vectors. Admittedly, only one viable leafy spurge seed is required to initiate an infestation, but endozoochoric dispersal of viable seed by deer, grouse and turkeys is shown to be a low probability event.

Library of Congress Subject Headings

Leafy spurge -- Seeds -- Dispersal.
Seeds -- Dispersal.
Animal-plant relationships.
Wildlife -- Manure.

Publisher

South Dakota State University

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Rights Statement

In Copyright