The gopher tortoise (Gopherus polyphemus) is critical to upland communities and considered a keystone species. A recent threat to gopher tortoise habitat is the invasive cogongrass (Imperata cylindrica), which spreads rapidly, eliminating native vegetation. This study consisted of three experiments to investigate the effects of the cogongrass on a population of gopher tortoises. A feeding experiment revealed that individuals readily ate native vegetation, but would not eat cogongrass. A tracking experiment showed that there was a significantly different mean angle of movement between individuals whose home ranges were outside cogongrass compared to those that overlapped cogongrass, indicating that the presence of cogongrass disrupts normal movement patterns. An orientation experiment showed that individuals outside cogongrass oriented in a direction that would take them to their home burrow, while individuals inside cogongrass showed no preferred directional orientation. Cogongrass effectively eliminates the gopher tortoises' food source and habitat, and disrupts orientation. The experiments indicate that a cogongrass infestation has the capacity to eliminate populations of gopher tortoises if its spread is not checked.

Due to the significant threats posed by nonnative fish species worldwide, it is important to understand how life-history strategies of individual species interact with environmental conditions to explain the success or failure of nonnative fish invasions. Brown trout are prolific invaders, but often exhibit upstream distributional limits in Intermountain West streams, potentially due to a maladaptive reproductive life-history strategy influenced by hydrologic conditions in high-elevation areas. We used redd counts, egg survival experiments, and temperature modeling to investigate the reproductive life-history strategy of brown trout and its potential for success along an elevational stream gradient. We documented brown trout spawning in stream reaches at elevations higher than where we typically encounter brown trout during summer electrofishing surveys, indicating the potential for upstream invasion. We observed a decline in egg survival at higher elevation, cooler water sites, but did not document complete recruitment failure at these sites, again indicating the potential for successful invasion at this life-stage. Temperature data indicate that during most years, incubating brown trout eggs would likely fail to emerge from the gravel prior to peak spring flows in these high-elevation stream reaches, suggesting that damaging spring floods may cause significant egg and sac-fry mortality at high elevations, and may determine invasion success in these areas. Our results highlight the importance of identifying specific mechanisms of recruitment failure in order to better predict nonnative fish invasions in the future.

The non-game wildlife trade poses a risk to our natural landscape, natural heritage, economy, and security. Specifically, the trade in non-game reptiles and amphibians exploits native populations, and is likely not sustainable for many species. Exotic amphibian and reptile species pose risk of invasion and directly or indirectly alter the native landscape. The extent of non-game amphibian and reptile trade is not fully understood and is poorly documented. To quantitatively describe the trade in Texas, I solicited data from the United States Fish and Wildlife Service's (USFWS) Law Enforcement Management Information System (LEMIS) and Texas Parks and Wildlife Department's (TPWD) non-game dealer permits. I surveyed amphibian and reptile pet owners, breeders, Internet sites, pet shops, and meat and seafood establishments by visits, electronic surveys, and observations. The trade in exotic species of amphibians and reptiles in the state of Texas was found to be popular in two ways; the importation of wildlife products and sale of live specimens for pets. Persisting in the pet trade were species known to be exotic, a problem made worse by lack of regulations governing the import, export, and keeping of exotic species. Trade in wild collected native species was primarily for export to foreign countries. Collection of turtles from the wild in Texas was heavy until 2008, when TPWD restricted collection to private waters. Collection of other species from the wild was minimal, with the exception of the Western Diamond-backed Rattlsnake (Crotalus atrox) for rattlesnake roundups. Native species were found to exist in the pet trade, but primarily as genetic color variants that do not occur in the wild, an indication that captive breeding may be relieving pressures on wild caught specimens. Minor changes in reporting requirements and permitting systems at the state and federal level would improve the management of exotic and native amphibians and reptiles that persist in the trade. Changes that include standardized taxonomic reporting requirements at state and federal level, streamlined permitting system for individuals wishing to collect from the wild in Texas, bag limits and seasons for wild collection, increased reporting requirements for owners of exotics, and enforcement of reporting errors would aid in management of exotic and native amphibians and reptiles in the trade.

Habitat fragmentation and destruction caused by linear infrastructure, including roads, railways, and power line corridors, are recognized as major threats to biodiversity around the world. Roads can act as barriers by impeding animal movement and restricting animal space use. An understanding of factors that influence barrier effects is important to discern the impacts of habitat fragmentation and to develop appropriate mitigation. The barrier effects of roads are driven by several distinct but not mutually exclusive mechanisms that include traffic, edge, and gap avoidance. We used an endangered forest obligate, the Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis), as our study organism to assess effects of traffic noise on animal occurrence and demonstrated that traffic noise had spatially extensive and negative effects on site occupancy after accounting for effects of distance from roads and the environment. We investigated barrier effects of forest roads and assessed effects of traffic, road edges, and canopy gaps on space use of Mt. Graham red squirrels and compared to the response of introduced, edge-tolerant Abert's squirrels (Sciurus aberti). Forest roads acted as partial barriers for red squirrels regardless of traffic volume likely due to avoidance of canopy gap created by roads, whereas Abert's squirrels showed no avoidance of roads. Therefore, roads restricted movement and space use of a native forest-dependent species while creating habitat preferred by an introduced, edge-tolerated species. Through a meta-analysis of studies that quantified road crossing behavior by mammals, we found that all types of roads, from major highways to narrow forest roads, can impede movement for certain species of mammals. Magnitude of barrier effects of roads decreased as species body mass increased, and was affected positively by increasing road width. We suggest that the species-specific magnitude of barrier effects of roads may be anticipated with basic information from life history traits and road characteristics that are readily accessed through open resources or easily measured.

The responses of invasive exotic plant species (IES) to silvicultural treatments one growing season after timber harvesting were examined in the Cumberland Plateau region of Southeastern Kentucky. Treatments included a commercial deferment harvest and unharvested control applied to five watersheds within University of Kentucky’s Robinson Forest. The effects of harvesting were compared between treatments and between preharvest and postharvest samplings. The spatial distribution and abundance of targeted IES throughout forest sites and trail systems were calculated from several sampling schemes. Additional analyses were performed to quantify forest disturbances derived from harvest activities to determine the relationships between soil, light levels, and other environmental characteristics and IES cover. Logistic and multivariate analysis techniques were used to analyze differences in IES distribution between pre-harvest and post-harvest units to relate post-harvest IES to microsite conditions. Microsite conditions within the forest and along the trail system proved important for explaining the presence and distribution of IES. Timber harvesting caused a significant increase in both Ailanthus altissima and Microstegium vimineum within harvested areas. However, many other identified IES did not initially respond to disturbances. Throughout the treatment units, species were influenced by disturbance type and intensity, as well as proximity to reclaimed surface mined land.

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Boston University. University Professors Program Senior theses. / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / 2031-01-02