Invasive Species

Contributed Paper
ROOM: CC, Room 19

1:10PM Spatial Optimization of Invasive Species Management Using Structured Decision Making
Jennifer L. Price Tack; Angela K. Fuller; Carrie Brown-Lima; Jennifer Dean; Qinru Shi; Carla P. Gomes
Managing invasive species across large areas often requires multiple objective decisions involving numerous species with a wide range of biological characteristics, impacts to valued goods and services, and many treatment options. Although there have been advancements in models informing the management of invasive species to reduce their impacts, few approaches are available that address the issue of spatially optimizing the allocation of treatments for multiple species that explicitly considers difficult tradeoffs. Structured decision making provides a framework for informing such complex decisions that is robust, transparent, and values-focused. We demonstrate how structured decision making can be used to aid invasive species management decisions, and present a novel decision tool that mangers can use to identify where and which treatments to apply for multiple invasive species that accounts for species-specific impacts, invasive pathways, and treatment feasibility. We apply our approach to the management of invasive species in New York, considering alternatives for prevention, surveillance, control, and education. We discuss the utility of our decision tool to inform invasive species management beyond New York, and highlight areas where additional research or monitoring can improve model performance.
1:30PM Life History Traits Determine Resilience of Native Mammals to an Invasive Predator, the Burmese Python, in the Greater Everglades Ecosystem
Jose R. Soto-Shoender; Robert A. McCleery; Daniel C. Gwinn
Invasive Burmese pythons (Python molurus bivittatus) are causing declines in native mammal populations and diversity in the Greater Everglades Ecosystem (GEE). However, empirical evidence suggests that some species (e.g., rodents) may be resilient to python presence. This differential response may be the result of life-history traits (e.g., fecundity, body mass) that alter a species’ vulnerability or resilience to pythons. Our objectives were to evaluate the response of native mammals to Burmese pythons and identify life-history traits that influence vulnerability or resilience to this invasive snake in the GEE. We collected presence/absence data for mammals at 113 randomly selected sites across the GEE with camera traps, faecal pellet surveys, and baited buckets designed for rodent sampling. We then used a multi-species hierarchical occupancy model to evaluate the influence of pythons on the species detected and examine the association between python influence on species occupancy and species life-history traits. Occupancy patterns of nine of 18 species showed significant negative effects and two (both rodents), a significant positive response to pythons. Three of the seven species traits examined were positively and significantly associated with the python effect on mammal occupancy (mass, fecundity, and habitat breadth), indicating these traits increased resilience to pythons. Thus, larger species, along with those that present high reproductive output, and are habitat generalists are more resilient to python occurrence. Our model also confirms an indirect effect of pythons: increased presence of rodents in sites with more pythons, likely due to high fecundity rates and habitat breadths, and a reduction of predator occurrence in high python density sites.
1:50PM Soil Microbial Fauna Associated with Hawaiian Feral Pigs
Nathaniel H. Wehr; Kealohanuiopuna M. Kinney
Nonnative feral pigs (Sus scrofa) are recognized throughout the New World as ecosystem engineers that modify habitats, alter biogeochemical processes, and serve as vectors of disease. However, little published data exists examining changes to the soil microbial community in ecosystems that they inhabit. As such, the goal of this study was to explore and characterize the soil microbial community associated with soils being transported by feral pigs. These microbial communities were assessed by collecting samples from the hooves and snouts of feral pigs harvested by recreational sportsmen on the Island of Hawai‘i. Assessment of the samples’ individual microbial communities included the fungi, bacteria, archae, and viruses. eDNA was extracted using MP Biomedicals’s FastDNA SPIN Kit for Soil. Molecular sequencing utilized Illumina chromatin immunoprecipitation sequencing (ChIP-Seq), and the results were corroborated using Oxford Nanopore Sequencing. Completed sequences were compared against the GenBank online database to identify individual taxa. These sequences were then used to associate specific soil microorganisms with feral pigs allowing for the characterization of a previously unstudied community. The results of this examination indicate that feral pigs are likely distributing soil microorganisms throughout habitats associated with their normal movements. This information, coupled with our collection of taxa associated with feral pigs, provides important information to scientists and land managers alike toward facilitating adequate and improved monitoring of potential disease transmission by feral pigs, as well as other nonnative ungulates, across ecosystems. This information will assist in the protection of humans, livestock, and wildlife from diseases spread by feral pigs and allow for improved conservation of native ecosystems in the presence of feral pigs.
2:10PM Examining Sexual Dimorphism and Ontogenetic Head Size Changes of Invasive Red-Tailed Boa in Puerto Rico
Aura Y. Muñiz Torres
Sexual dimorphism, phenotypic differences between sexes of the same species, in snakes may result in diet divergence. One snake that shows sexual dimorphism is the Boa constrictor, with females being larger than males. The B. constrictor has been reported since 1992 as an invasive species in Puerto Rico, with the largest population on the west side of the island. The objective of this study was to determine if sexual dimorphism is present within populations of the invasive boa in Puerto Rico, since it has been reported that species in island populations become smaller when compared to mainland populations. In addition we wanted to test possible ontogenic diet shifts between adults and juveniles. We measured 266 adults and 105 juvenile individuals of B. constrictor. The head width, height, length; snout to vent length and total length were recorded for each individual during necropsies. The Total Length of female Boa constrictor (n=157) averaged (1881.041±.20.064mm) and males (n=109) average size was (1808.528±23.933mm) which demonstrate sexual dimorphism. The average head measurements for females (n=157) were: head length (59.271±0.585mm); head width (43.045±0.515mm) and head height (16.510±0.243mm). For males (n=109) head length (55.568±0.554mm); head width (39.017±0.495mm) and head height (15.455±0.301mm). Our results suggest this invasive species is still maintaining certain allometrical characteristics outside of their native range. The relationship of the head measurements when compared to the total length best explained the ontogenetic shift. Our results also demonstrate that head height varies significantly from juveniles to adults in both sexes, suggesting a change in diet. In conclusion, our results support that the Boa constrictor is still maintaining their sexual dimorphism in Puerto Rico. In addition, this invasive specie has modified their mouth gap size from juveniles to adults in order to adapt to the prey size of the island.
2:30PM Refreshment Break
3:20PM Mapping the Expansion of Coyotes Across the Continent and Towards South America.
Roland Kays; Ricardo Moreno; Ninon F. V. Meyer; James Hody
The geographic distribution of coyotes (Canis latrans) has dramatically expanded since 1900, spreading across much of North America in a period when most other carnivores have been declining. However, existing descriptions of coyote spread have been coarse, anecdotal, and give conflicting results regarding their original geographic distribution. We mapped the historic range of coyotes using archaeological and fossil records, and then plotted their expansion across North America from 1900 to 2016 using museum specimens, peer-reviewed reports, and game department records. We also conducted new surveys in Panama to document the southernmost edge of their expansion. Museum specimens confirm that coyotes have been present in the arid west and California throughout the Holocene, well before European colonization of the continent. Coyote range in the late 1800s was undistinguishable from earlier periods, and matches the distribution of non-forest habitat. Coyote expansion began around 1900 as they moved north into taiga forests, east into deciduous forests, northwest into costal temperate rain forests, and south into tropical rainforests. Forest fragmentation and the extirpation of larger predators probably enabled these expansions. In addition, hybridization with wolves and/or dogs has been documented in the east, and suspected in the south, where our camera traps documented likely hybrids. We found that their expansion in Panama is bringing them close to South America, although the heavily forested Darien Gap could block their intercontinental movement. Furthermore, we found that coyotes are now in direct contact, for the first time ever, with the crab-eating fox (Cerdocyon thous), a South America canid that has recently expanded its range into Panama. Our detailed account of the original range of coyotes and their subsequent expansion represents a large scale ecological experiment that can help us better understand the ecology of predation, as well as evolution through hybridization.
3:40PM Environmental Impacts of a Low-Density Wild Pig Population in Central Michigan, Usa
Steven M. Gray; Gary J. Roloff; Robert A. Montgomery; Daniel B. Kramer; Dwayne R. Etter; Kurt C. VerCauteren
Invasive wild pigs (Sus scrofa) are purported to be one of the most destructive species occurring in the United States. Through their rooting, wild pigs are capable of overturning large expanses of soil in search of subterranean forage. Given the extensiveness and severity of rooting, this species can have profound effects on local biotic and abiotic environments. Further, disturbances caused by wild pig rooting may facilitate the colonization and establishment of invasive plant species, a phenomenon referred to as the invasion complex. In this way, wild pigs can potentially function as invasive engineers. As wild pigs spread into northern latitudes of the United States, there is a need to understand the risks this species poses to native ecosystems. In this study, we: i) compared ground-layer plant community composition and soil chemistry between rooted and unrooted sites, ii) assessed the influence of wild pig rooting on non-native plant cover, and iii) evaluated wild pig rooting impacts on tree species in the central Lower Peninsula of Michigan. We used non-metric multidimensional scaling, Manly’s selectivity measure, and generalized linear mixed models to compare impacts to natural resources at disturbed and undisturbed locations. Rooting had the most profound impact on herbaceous plant community composition, where proportion of rooting within a plot explained 71.5% of the deviance. Overall, soil nutrients, ammonium, and nitrate did not significantly differ between disturbed and undisturbed sites, however, these patterns varied by soil type. Wild pigs did not select for particular tree species when rooting, suggesting that other below ground forage (such as fungi or rodent caches) was influencing this behavior. Models revealed that rooting depth and days since rooting significantly and negatively influenced non-native plant cover. Our findings suggest that at low-densities, wild pig impacts to soil and flora are mixed and may be negligible in certain respects.
4:00PM The Role of Ruffed and Spruce Grouse in Recent Localized Range Expansion of Blacklegged Ticks in New Brunswick, Canada
Douglas T. Munn
Ixodid ticks parasitize grouse in the western US and Europe but there is little evidence of their interactions with Ruffed Grouse (Bonasa umbellus) and Spruce Grouse (Falcipennis canadensis). Range expansion of blacklegged ticks (Ixodes scapularis) in northern latitudes has largely been attributed to changing climate conditions, and long-distance dispersal by migratory bird hosts. Comparatively little is known about localized range expansion and intermediary hosts. We examine the role of two non-migratory ground-dwelling birds, Ruffed and Spruce Grouse, as potential hosts of blacklegged ticks in New Brunswick, Canada. Blacklegged ticks are the primary vector of several infectious diseases in eastern North America, including Lyme Disease, Human Granulocytic Anaplasmosis, and Babesiosis. We determine the rate at which grouse are exposed to blacklegged ticks by assaying for these three pathogens in hearts of grouse harvested during the 2017 hunting season. These test results are the first assessment of Ruffed and Spruce grouse as carriers of pathogenic ticks. This study is timely as climate change is predicted to redistribute favored landscape characteristics, increase the probability of parasitism, alter seasonal movements, and increase predation. Shifting forest composition away from conifer-dominant will likely retract the Spruce Grouse’s range northward, while expanding the preferred habitat and distribution of Ruffed Grouse. These changes, and increased parasite loads, may negatively impact seasonal movements. Predation rates are also expected to respond positively to increased parasite loads. Future research objectives include targeting the pathogen reservoir competency of these grouse as they may provide an underestimated pathway by which vector inoculation occurs.
4:20PM Assessment of Density Dependence in Breeding Productivity of an Invasive Waterbird
Randall T. Knapik; David R. Luukkonen; Scott R. Winterstein
A fundamental underpinning of many wildlife population models is that vital rates vary in relation to some measure of density for the species. This relationship must be accounted for when conserving species in peril or controlling those which are overabundant. The need for long-term datasets to capture natural population fluctuations has resulted in few definitive derivations of density-dependent vital rates in wildlife populations. Ongoing control efforts for an invasive waterbird, the mute swan (Cygnus olor), have provided a unique opportunity to measure reproductive rates, under high and low breeding densities in the core of their North American distribution. Number of breeding pairs, clutch size, number of hatched young, and number of fledged young were documented in 3 breeding seasons (2016-2018) across 6 sites throughout Michigan’s Lower Peninsula. Mean breeding productivity (i.e., number of fledged young per pair) pooled across sites and years was low (1.3 fledged young/pair) despite high clutch sizes (mean 7.2 eggs/clutch, range 1 – 10), but productivity varied among the 6 study sites (range 0.6 fledged young/pair – 2.3 fledged young/pair). Mean breeding productivity per pair decreased as the number of breeding pairs increased across sites; however, there was an exception as breeders at the site with the fewest pairs also fledged the lowest number of young (3 fledged young/5 pair [0.6 per pair]). Decreased breeding productivity in areas of high breeding pair density likely results from density-dependent effects on reproduction for mute swans in Michigan. Our study contributes to understanding factors that result in variation of mute swan demographic parameters and will improve population models that simulate alternative control strategies for mute swans in the Great Lakes region.
4:40PM Hard Mast and Feral Hogs: Seed Predator Satiation, Or Regeneration Devastation?
Richard G. Vaerewyck; William L. Headlee
Feral hogs (Sus scrofa) are a costly nuisance throughout the entire Southeastern United States. They cause over a billion dollars of damage nationwide to agriculture, but the damage done to forest lands is harder to quantify. The relationships between feral hogs, hard mast production, and bottomland hardwood regeneration are not clearly understood – importantly, is seed predator satiation a viable regeneration strategy with an abundant population of invasive feral hogs? The first portion of the study examines feral hog stomach contents to determine seasonal reliance on hard mast. This is compared to visual mast surveys to determine forage availability. In years of high mast production, acorns comprise a major part of the feral hog diet well into summer, whereas in years of low mast production, feral hogs will switch over to a diet heavy in plant matter in early winter. The other portion of the study seeks to quantify the relationships growth and germination rates of willow oaks (Quercus phellos) in bottomland hardwood forests have with feral hog visitation rates, acorn production and viability, and several seed tree characteristics. Data collection will conclude in June 2018, with final results being presented at the conference.
12:50PM Rethinking Nonlethal Management of “Problem” Wildlife Species: the European Starling as a Case Example
Bradley F. Blackwell; Thomas W. Seamans; Morgan B. Pfeiffer
Urban adaptor and invasive wildlife species generally show less-conservative antipredator responses to perceived risk, relative to indigenous populations exposed to natural predation. For instance, the success of the European starling (Sturnus vulgaris), a secondary cavity nester and competitor with indigenous cavity nesters in North America, is thought to be due, in part, to enhanced assessment of predation risk. We hypothesized that predator scent from the raccoon (Procyon lotor), an evolutionarily-novel predator, placed inside nest boxes would enhance perceived risk to European starlings, thus reducing use of treated sites and reproduction. Indirect predator cues near nests have been shown to enhance perceived predation risk and associated antipredator behaviors in breeding animals across taxa, and particularly with birds. During early spring, starlings selected from nest boxes treated with equal volumes of predator scent, a novel odor, or water (n = 40 boxes per treatment). We evaluated effects of treatment on nest establishment and reproductive traits via generalized linear models. Starlings established nest bowls in 61% of nest boxes (predator scent, n = 27 boxes; novel odor, n = 24 boxes; control (water), n = 22 boxes); clutches were laid in 68 boxes. We observed no effects of treatment on the likelihood of a clutch (≥1 egg) or nest failure. Further, we found no treatment effects on date of first egg, clutch size, or hatchling number. We conclude that starling antipredator response to enhanced, indirect risk of nest predation is contingent upon a combination of predator cues, as well as direct or indirect experience with nest predation.


Contributed Paper
Location: Cleveland CC Date: October 10, 2018 Time: 12:50 pm - 5:00 pm