Geology topics

E. Gurarie

Publications and source records attributed to E. Gurarie.

3 recordsLinked to original sources

USGS2021

Mapping out a future for ungulate migrations

Migration of ungulates (hooved mammals) is a fundamental ecological process that promotes abundant herds, whose effects cascade up and down terrestrial food webs. Migratory ungulates provide the prey base that maintains large carnivore and scavenger populations and underpins terrestrial biodiversity (fig. S1). When ungulates move in large aggregations, their hooves, feces, and urine create conditions that facilitate distinct biotic communities. The migrations of ungulates have sustained humans for thousands of years, forming tight cultural links among Indigenous people and local communities. Yet ungulate migrations are disappearing at an alarming rate ( 1 ). Efforts by wildlife managers and conservationists are thwarted by a singular challenge: Most ungulate migrations have never been mapped in sufficient detail to guide effective conservation. Without a strategic and collaborative effort, many of the world's great migrations will continue to be truncated, severed, or lost in the coming decades. Fortunately, a combination of animal tracking datasets, historical records, and local and Indigenous knowledge can form the basis for a global atlas of migrations, designed to support conservation action and policy at local, national, and international levels.

Science↗

USGS2018

Integrating encounter theory with decision analysis to evaluate collision risk and determine optimal protection zones for wildlife

1.Better understanding human‐wildlife interactions and their links with management can help improve the design of wildlife protection zones. One example is the problem of wildlife collisions with vehicles or human‐built structures (e.g. power lines, wind farms). In fact, collisions between marine wildlife and watercraft are among the major threats faced by several endangered species of marine mammals. Natural resource managers are therefore interested in finding cost‐effective solutions to mitigate these threats. 2.We combined abundance estimators with encounter rate theory to estimate relative lethal collision risk of the Florida manatee ( Trichechus manatus latirostris ) from watercraft. We first modeled seasonal abundance of watercraft and manatees using a Bayesian analysis of aerial survey count data. We then modeled relative lethal collision risk in space and across seasons. Finally, we applied decision analysis and Linear Integer Programming to determine the optimal design of speed zones in terms of relative risk to manatees and costs to waterway users. We used a Pareto efficient frontier approach to evaluate the performance of alternative zones, which included additional practical considerations (e.g. spatial aggregation of speed zones) in relation to the optimal zone configurations. 3.Under the various relationships for probability of death given strike speed that we considered, the current speed zones reduced the relative lethal collision risk by an average of 51.5% to 70% compared to the scenario in which all speed regulations were removed (i.e. the no‐protection scenario). We identified optimal zones and near‐optimal zones with additional management considerations that improved upon the current zones in terms of cost or relative risk. 4.Policy Implications : Our analytical framework combines encounter rate theory and decision analysis to quantify the effectiveness of speed zones protecting manatees while accounting for uncertainty. Our approach can be used to optimize the design of protection zones intended to reduce conflicts between human waterborne activity and marine mammals. This framework could be extended to address many other problems of human‐wildlife interactions, such as the optimal placement of wind farms to minimize collisions with wildlife or the optimal allocation of ranger effort to mitigate poaching threats.

Journal of Applied Ecology↗

USGS2009

Spatial habitat use patterns of sea otters in coastal washington

Sea otter (Enhydra lutris kenyoni) movements, home range, and activity budgets were described from data collected during very-high-frequency radiotelemetry studies of 75 individuals on the outer coast of Washington State between 1992 and 1999. Sea otters were located at least once per week from 22 accessible sites along the coast. Over the 7-year study period, range expansion occurred from the core range north and east into the Strait of Juan de Fuca (SJF) as well as southward on the outer coast. Forty-three percent of the sea otters moved into the SJF at least once, most often in winter, using habitat that had not been occupied by sea otters since their extirpation 100 years ago. All sea otters spent portions of their time in the vicinity of Cape Alava, and many animals demonstrated consistent periodic seasonal shifts between specific portions of the coastline over several years. Ninety-five percent annual linear home ranges differed between sex and age classes. Adult males used the largest amount of coastline (50 km ?? 9 5D) and subadult females used the least (24 ?? 9 km). Both adult males and females demonstrated high seasonal periodicity in range use in summer and winter. Twenty-four-hour time budgets in the core portion of the range revealed on average sea otters spent 41% ?? 14% SD of the time foraging and 45% ?? 13% of the time resting (age and sex classes pooled). Adult and subadult female sea otters were most frequently found resting and foraging close to shore (< 1,000 m) and in shallow water (0-10 m), whereas adult and subadult males rested and foraged > 1,000 m offshore and at depths between 10 and 30 m. Given current rates of population growth and observed mobility, sea otters in Washington have high potential for range expansion into unoccupied habitat such as Grays Harbor, Willapa Bay, the SJF, or along Vancouver Island. ?? 2009 American Society of Mammalogists.

Journal of Mammalogy↗