Geology topics

Samantha N. Smith

Publications and source records attributed to Samantha N. Smith.

3 recordsLinked to original sources

USGS2025

The American black bear (Ursus americanus) as an apex predator: Investigating the ecological role of the world’s most abundant large carnivore

Introduction American black bears ( Ursus americanus ) have been documented to have top-down effects, both consumptive (through predation) and nonconsumptive (through fear effects). However, their behavioural and dietary adaptability has led to uncertainty about the conditions under which these may occur. Objectives We aimed to (1) investigate when, where, and how often black bears influence lower trophic levels, and (2) critically assess the experimental design of such studies to determine trends and biases. Methods We conducted a systematic literature search and used linear mixed-effects models to assess the relationships among prey age class, the presence of other large carnivores, and the percentage of ungulate mortality due to black bears. We also summarised the measured effects of black bears on other carnivores and the results of any experimental studies. Results We found a strong negative relationship between puma presence and the percentage of ungulate mortality due to black bears, but only in areas with at least one other large carnivore (e.g., wolves). Among 16 studies of black bears' impacts on other carnivores, most documented negative behavioural effects. While only 5% of studies had strong experimental design, bear removal consistently increased juvenile ungulate survival. Discussion and Synthesis Our findings highlight black bears' strong top-down effects, resembling or exceeding those of other large carnivores. These effects were greatest when no other large carnivores were present, but as highly effective kleptoparasites, black bears can alter the feeding habits of other large carnivores. Thus, we argue that ‘apex’ is a conditional state, not a species-wide status.

Mammal Review↗

USGS2025

Invasive hitchhiking organisms on aquarium plants: An emerging pathway of introduction

The aquarium trade is a global industry responsible for the movement of live plants and animals, but it also serves as a major pathway for the introduction and spread of aquatic invasive species. Invasive species contribute to biodiversity loss, disrupt ecosystems, and can have widespread economic and societal impacts. A significant but poorly understood invasion risk in the plant aquarium trade is the transport of hitchhiking species, which are organisms unintentionally transported along with a species of primary interest in trade. Aquatic hitchhikers can persist in aquaria and later be released into the wild, potentially establishing invasive populations. While some studies have identified hitchhiking as a pathway for aquatic species spread, it remains largely unrecognized in international regulations. Increased awareness, triggered by incidents such as zebra mussels found in aquarium plants, highlights the need for further investigation into this emerging pathway of concern. As a response, we reviewed the current state of knowledge regarding aquatic plants in the aquarium trade as vectors for transporting invasive hitchhiking species, with a particular focus on how morphological complexity of plants influences associated hitchhikers. We found that although awareness of hitchhiking species in the aquarium trade is increasing, few studies have empirically examined aquarium plants as vectors for invasive species. Understanding this pathway can help to inform invasive species management around the plant aquarium trade and to keep aquarium organisms in a sustainable manner.

Management of Biological Invasions↗

USGS2024

Using camera traps to estimate site occupancy of invasive Argentine Black and White Tegus (Salvator merianae) in South Florida

The introduction of nonnative species is a leading cause of biodiversity loss. Many invasive species are cryptic or elusive in nature and therefore often evade detection, complicating their management. Occupancy modeling can reveal the presence and spread of invasive species over time and therefore has important management implications. Camera traps can be used to estimate occupancy, or the proportion of sites that are occupied by a target species. During a 4-year study (2016–2020), we used camera traps both with and without lures to detect the presence of invasive Salvator merianae (Argentine Black and White Tegu) at sites in Miami-Dade County, FL. Our results from a multi-season occupancy model revealed that a quadratic effect of ordinal day was the best predictor of detection, with a peak in June, while occupancy was correlated with distance to landscape features that may facilitate tegu movement. We did not detect any large-scale changes in occupancy over the course of our study. We also discovered that the use of lures with camera traps did not impact detection, indicating fewer resources would be required from invasive species managers for effective monitoring. Understanding the factors that impact occupancy and detection probabilities can inform surveillance and removal efforts, leading to more efficient management strategies.

Florida↗