The U.S. Fish and Wildlife Service is soliciting public input on ways to modify the rules involving the accidental killing or injuring of endangered and threatened species as well as regulations involving measures private landowners take to conserve these imperiled creatures.
Section 10(a) of the U.S. Endangered Species Act (ESA) deals with what happens to federally listed and at-risk species management on private and nonfederal lands. Subsections authorize the Service (USFWS) to issue permits that allow for “take”— the killing, injuring or removal—of listed species under specific circumstances. These include the take of organisms for scientific purposes or to enhance the propagation or survival of an affected species.
Section 10(a) tools play an important role in engaging private landowners in species recovery and proactive conservation. For example, Safe Harbor Agreements—a tool designed to help private landowners work with the USFWS for conservation—have helped landowners plant longleaf pine, conduct prescribed burns to maintain open forest structure in the U.S. Southeast; and install artificial nesting cavities that boost habitat for red-cockaded woodpeckers (Leuconotopicus borealis). These agreements ensure that landowners do not face additional restrictions on management activities if their conservation efforts boost woodpecker populations on their land.
The Service has specifically requested information on barriers preventing applicants from pursuing these methods, aiming to streamline permit implementation processes and the funding and resources to enhance voluntary conservation incentives. They are also interested in Service-user relations and have requested input on ways to enhance communications on 10(a) programs, specifically how to clarify the roles and responsibilities of the Service and applicants during conservation planning and permit issuance.
Interested parties, including wildlife professionals and private land conservation partners, have until July 9 to provide feedback to the USFWS.
The Wildlife Society is excited to introduce you to the Class of 2025 of the Leadership Institute, TWS’ flagship leadership development program. Members of this year’s class were selected from a competitive pool of applicants. Throughout the six-month program, participants will engage in a variety of distance learning and hands-on projects and develop a greater understanding of how to apply leadership skills in their professional careers. The Leadership Institute will culminate at TWS’ 32nd Annual Conference in Edmonton, Alberta, Canada, this October.
A committee of TWS members and staff selects Leadership Institute participants based on factors such as demonstrated leadership capability or potential, commitment to and involvement in TWS and the wildlife profession, and potential to contribute to the growth and development of the group as a whole.
Meet the Leadership Institute Class of 2025:
Nicole Bealer, Montana Fish, Wildlife & Parks – Bealer works in the Research Unit for Montana Fish, Wildlife & Parks, where she implements applied research projects focused on elk spatial ecology and population dynamics.
Jessica Brown, The Connecticut Agricultural Experiment Station – Brown is a postdoctoral scientist at The Connecticut Agricultural Experiment Station, where she studies integrated tick management, focusing mostly on reducing populations by treating wildlife hosts.
Grace Campbell, Lykes Bros. Inc. – Campbell is a wildlife biologist for Lykes Bros. Inc., one of the largest landowners in Florida, with operations including cattle, forestry, hunting and land and water resource management. She manages the gopher tortoise recipient site program, which includes client relations, coordination of tortoise intake, extensive data management and prescribed burning to maintain tortoise habitat.
Hannah Clipp, USDA Forest Service Northern Research Station – Clipp is an Oak Ridge Institute for Science and Education (ORISE) postdoctoral research fellow with the USDA Forest Service Northern Research Station, working with scientists in the Landscape Change Research Group to model climate change effects on birds, trees and forest pests.
Mallory Gyovai White, Virginia Department of Wildlife Resources – Gyovai White is the human dimensions program manager at the Virginia Department of Wildlife Resources, where she provides social science research and information for the various divisions within the agency.
Jane Kunberger, Texas A&M University – Kunberger is a senior research associate at Texas A&M University, where she researches how land management practices affect wildlife distributions and behaviors. She is also interested in testing the effectiveness of wildlife monitoring technologies and creating tools to assist with conservation decision-making.
Amanda O’Brien, University of Florida – O’Brien is a recently graduated wildlife ecologist from the University of Florida, passionate about field biology, travel, cultural exchange, scientific research and conservation storytelling and journalism. She is currently working in a seasonal position in California.
Elizabeth Painter-Flores, University of Montana – Painter-Flores recently completed her PhD at the University of Montana, modeling interactions between white-tailed deer populations and their predators. Last year, she cofounded the Latin American and Caribbean Working Group within TWS to build connections between Latin American and Caribbean researchers and U.S.-based scientists working internationally.
Sarah Pesi, South Carolina Department of Natural Resources – Pesi is a wildlife biologist in the small game program with the South Carolina Department of Natural Resources, where she coordinates research and monitoring efforts in the state for mourning doves, bobwhite quail and other small game species.
Emma Schultz, Mississippi State University Geosystems Research Institute – Schultz recently completed her doctoral program in the Department of Wildlife, Fisheries and Aquaculture at Mississippi State University. She has a varied research background ranging from sea turtle ecology to agent-based modeling informing effective drone use for wildlife surveys.
Over the course of their Leadership Institute experience, these participants will have the opportunity to learn from TWS Council and staff, take part in discussions on a variety of leadership topics and engage in mentorship activities with Leadership Institute alumni.
Congratulations again to the Leadership Institute Class of 2025!
The Wildlife Society is grateful for the Dallas Safari Club Foundation‘s ongoing support for the Leadership Institute program. Their dedication to ensuring the conservation of wildlife through public engagement, education and advocacy is evident through their dedication to helping the Leadership Institute thrive.
A population of grouse in Wyoming and Colorado that is considered Columbian sharp-tailed grouse may actually be a distinct subspecies. The Columbian sharp-tailed grouse (Tympanuchus phasianellus columbianus) is a subspecies that can be found in far western Wyoming, northern Utah and parts of the Pacific Northwest. Another population in south-central Wyoming and northwest Colorado is also designated as Columbian sharp-tailed grouse, and researchers wondered if that was accurate. Examining habitat characteristics, the birds’ appearance and genetic data, a research team determined the sharp-tailed grouse could potentially represent its own distinct subspecies. “Our results may potentially change the current understanding of sharp-tailed grouse subspecies in western North America, which can impact how to manage them,” wrote the researchers in a study published in Ecology and Evolution. These findings have several implications for grouse management. For example, the potentially new isolated subpopulation may need to be managed differently, and individuals from the isolated population should not be translocated to Columbian sharp-tailed grouse populations.
Wildlife professionals are ringing the alarm bell on the prospect of a screwworm infestation that could impact wildlife in the southern United States and create a massive impact on hunting and cattle industries.
To prepare for the infestation some believe is imminent, experts are calling for interagency collaboration, funding and international cooperation to prepare a strategy for dealing with a problem most have not experienced in their lifetime.
“It poses a threat to populations of warm-blooded mammals and birds,” said Neal Wilkins, CEO and president of the East Foundation, a private ranch focused on land stewardship, cattle-raising and wildlife conservation. “The penalty for overpreparation is nowhere near the penalty for underpreparation.”
What is screwworm?
The New World screwworm fly (Cochliomyia hominivorax) has a particularly macabre life cycle. Adult flies lay their eggs on the open wounds of animals—usually mammals. The eggs hatch into maggots—the screwworms—which proceed to gorge themselves on the healthy flesh of the unfortunate creature.
Screwworm flies often target the areas around the antlers of deer. Credit: Val Preziosi
Cattle are particularly susceptible to screwworms, especially around the wounds caused by dehorning or castration. Calves can also get infected around their navels. Occasionally, otherwise healthy soft tissue areas, such as the corners of eyes, can become infected. Humans can also contract screwworms, although doctors usually treat infections in the early stages.
Wildlife and cattle aren’t so lucky. Female flies can lay 200-300 eggs on a wound. The maggots screw themselves into the wound—hence their name—opening it up more and more. If untreated—which is typical with animals—they can die directly from the wound or from secondary infections by bacteria or other parasites.
Screwworms, being endemic to North America, were a persistent problem in the U.S. from at least the 19th century until their official eradication in the 1960s. If they do come back, the impact on wildlife, cattle and the hunting industry would be huge.
“This is a food security issue; it’s a border security issue; it’s a national security issue,” said Andrew Earl, director of conservation at the Texas Wildlife Association. “We think it’s a tremendous threat to native wildlife,” he continued, adding that even pets can be infected by screwworms. “Fido and Spike are at risk, too.”
How were screwworms eliminated from the U.S.?
The fly is native to the Americas. Its natural range encompasses much of the tropics of Latin America, historically stretching into southern U.S. states. But a massive, decades-long effort starting in the U.S. in the 1950s began to push the insect’s range down into Mexico. The screwworm was considered eradicated in the U.S. by 1966 and then from Mexico and most of Central America in succeeding decades. By the 1990s, the screwworm was basically blocked from entering South America due to ongoing control efforts at the Darien Gap in Panama, where the isthmus meets Colombia.
The novel eradication strategy at the time involved a technique of releasing sterilized male flies. In this method, breeders produce hundreds of millions of flies in facilities. They sterilize these by exposing them to radiation at specialized facilities. Technicians then release these sterilized males into the wild. The sterile males will still mate with females, but they produce no offspring. Over generations, the population of fertile screwworms is whittled down to nothing.
“You breed it out of existence locally,” said Earl.
In the heyday of screwworm eradication, the U.S. maintained various facilities, each producing hundreds of millions of sterile flies every week—one in Texas, one in Florida, one in Tuxtla Gutierrez in southern Mexico and one in Panama.
Unfortunately, only the facility in Panama remains. The facilities in Florida and Texas stopped producing sterilized flies, while the Tuxtla Gutierrez facility closed in 2012. “It was a big loss when the USDA gave the existing facility in Chiapas to the Mexican government in 2012,” Wilkins said. “The Mexican government shut it down, and we lost all of our investment as a nation.”
The screwworm story was ripe for a sequel.
How did we stop the screwworm in Florida?
Usually, when you take your foot off the gas, the car eventually stops moving. Dating back more than a half century, the vehicle was speeding full throttle as U.S. authorities worked with scientists, wildlife managers and foreign governments to drop sterilized flies all across Mexico and Central America.
In the summer of 2016, screwworms first made their way to the Florida Keys. In July, a few cases popped up in Key deer (Odocoileus virginianus clavium), a subspecies of white-tailed deer (O. virginianus) endemic to the Keys and considered endangered by the U.S. Fish and Wildlife Service (USFWS). Nobody is entirely sure how it arrived, but cases occur in parts of the Caribbean. “A hurricane could have blown it in, [or] it could have come in via some trade or animal movement,” said Roel Lopez, director of the Texas A&M Natural Resources Institute. By the fall rutting seasons, cases shot up into the dozens per month.
A Key deer succumbed to injuries caused by screwworm maggots in the 2016 infestation in Florida. Credit: Val Preziosi
Lopez, who has worked on Key deer for three decades since his PhD thesis on the topic, and his colleagues set out to collect carcasses and euthanize any infected deer captured. Out of 127 cases of deer killed by the fly, they found 92% of them were male, and most were adults. Lopez said that rutting-related fights provided open wounds for the flies to lay their eggs during this season, resulting in a wave of deaths. “The story would have been different, we suspect, if it were in the spring when the does were fawning,” he said, adding that pregnancy-related exposure some deer experienced at the time may have resulted in more infections for mothers and their young rather than just adult males.
By October, technicians mobilized a larger response, dropping hundreds of millions of sterile flies produced at the Panama facility onto the Keys. The work produced immediate results. “It’s amazing to me how effective the sterilized fly program was in disease control,” he said. The last two known deer deaths from screwworm occurred in January 2017. After a quick seven months, screwworms were basically eradicated in the Keys once more.
How close are screwworms to the U.S.-Mexican border?
Unfortunately, the Florida situation may have just been a preview of an upcoming feature on the mainland. Screwworms first began appearing past the containment area in Panama’s Darien Gap in 2022. By late 2024, reports began to surface in Guatemala and Honduras of screwworm infections. It’s difficult to say how they made it past the Darien Gap, but there are several possibilities, Earl said. Monitoring and surveillance for screwworm was relaxed due to the COVID-19 pandemic several years ago, and an increase in illegal cattle trafficking in the region might also be helping to spread animals infected with maggots. The increase in human migration northward may also be playing a role, Earl said.
In November 2024, Mexican authorities announced a case in the country’s south. The U.S. shut down the Mexican border to live animal trade but then opened it back up in February after the Mexican government and the U.S. Animal & Plant Health Inspection Service (APHIS) put a new pre-clearance inspection and treatment protocol into place.
APHIS began releasing sterilized flies in southern Mexico and other parts of Central America. When screwworms were detected in Oaxaca and Veracruz in an area only 700 miles from the U.S. border, U.S. Secretary of Agriculture Brooke Rollins closed the border to live cattle, horse and bison (Bison bison) imports again in May.
How would the screwworm affect U.S. wildlife?
A female screwworm fly can lay up to 3,000 eggs during its 10-day lifespan. The impact on cattle in southern states like Texas would be huge. But other mammals like javelina (Pecari tajacu) and even ocelots (Leopardus pardalis), considered endangered by the USFWS, could be affected.
The Key deer situation shows just what a problem screwworm can be for an endangered species. The subspecies numbered about 600-700 before the infestation began. Some 127 deer were known to have died from the worms—about 20% of the population. Then surviving deer were further decimated by Hurricane Irma, which swept through Florida in August 2017. “It was an unfortunate episode for Key deer,” Lopez said.
Wilkins said that some estimates project a localized loss of a quarter of the population of some mammals due to screwworms. With less than 100 ocelots living in the U.S.—all just north of the border in southern Texas—wildlife managers could see a huge loss in numbers for a species that millions of conservation dollars have been invested in. “I don’t think an endangered species can withstand a loss of 25%,” he said. “It’s a problem with a lot of dimensions,” he said.
Meanwhile, a substantial loss in deer numbers will hit the hunting industry hard. The white-tailed deer hunting industry in Texas alone contributes $2.3 billion to the state’s gross domestic product, according to Texas A&M University.
Solutions aren’t clear-cut
Screwworms were successfully eradicated from the U.S. and Central America in the past thanks in part to international cooperation. But the recent outbreak in Central America and Mexico is happening against the backdrop of increased international tension due in part to tariffs instituted by the Trump administration.
“Success in the years ahead will require cooperation at all levels of government, on both sides of our southern border,” Earl said, adding that the U.S. shouldn’t be relying solely on other countries to ensure protection from screwworms. While Rollins recently announced a partnership with Mexico and a $21 million investment to upgrade an existing fruit fly facility in Metapa into a screwworm fly sterilization facility, it’s unclear when the plan will be finalized.
“Having several production facilities creates some redundancy and helps with risk management,” said Wilkins in response to the announcement. “Reducing our capacity from three major facilities in the 1970s to only one now definitely contributed to the problem that we are facing at present.”
In the meantime, Earl said that the U.S. needs a facility on home soil for additional security. “We need to have the capacity to produce and distribute these flies within the United States.”
Wilkins worries about the current location of the screwworm, as weeks have passed without reports.
“Mexico is now blaming the United States for the entirety of the problem,” he said. “They are now not monitoring or not reporting,” he said.
If they were 700 miles from the border several weeks ago, in theory, flies could have already made it near the border. “These flies can travel 12 miles a day when not on livestock,” Wilkins said. “There is a real possibility that they are closer than they were two weeks ago.”
He also worries that the flies are approaching the U.S. at the beginning of the summer, when the insects thrive. “If you are a screwworm, this is the perfect time to hit the U.S. border,” he said.
At this point, even if the U.S. takes all the flies produced at the Panama facility and releases them near the border, it will only be about a third of the total amount used to boot them southwards in the 1960s, when there were three facilities operating.
“We have no opportunities for a legitimate containment barrier until they hit the United States,” Wilkins said.
In the meantime, Wilkins and Earl said the U.S. needs a well-developed plan that involves collaboration among agencies, cattle ranchers, wildlife organizations and hunters.
Some strategies could involve adding an antiparasitic drug like Ivermectin to deer feed, but secondary ecological impacts and secondary physiological impacts on deer need to be considered.
Wilkins said that other regulatory hurdles also need to be straightened out. For example, if a deer with signs of screwworm infection appears on private land, are managers there permitted to control and remove the deer, even outside of hunting season? And what should be done with the carcass?
He also said that landowners and other wildlife interests—whether they be private, government agencies or nonprofits—will also need more veterinarians on the ground.
An additional challenge is that federal agencies that would be involved in the screwworm effort are being affected by reductions in force (RIFs), travel freezes and hiring freezes—at a time when travel and interagency collaboration are necessary for this issue. The U.S. Department of Agriculture’s Knipling-Bushland U.S. Livestock Insects Research Laboratory in Kerrville, Texas, has been working on methods to fight screwworms since World War II, Wilkins said. “They’ve done a lot of work, but they haven’t been able yet to put it into operation due to funding cuts and hiring freezes,” he said.
He suspects the Trump administration will get on board with efforts to support USDA’s labs like Knipling-Bushland, but these efforts need to happen sooner rather than later. For most experts working on the issue, it’s a matter of when, not if, screwworms will cross the Mexican border, with some saying it may happen within weeks and others saying months.
TWS welcomes its summer 2025 policy and communications intern, Kaylyn Zipp.
Zipp grew up in Broad Channel, Queens, in the heart of New York City, admiring the sights and sounds of her backyard, the Jamaica Bay Wildlife Refuge. Zipp completed her bachelor’s in environmental science with a concentration in watershed science at the State University of New York College of Environmental Science and Forestry (SUNY ESF), where she worked on a variety of research projects including the Chittenango ovate amber snail (Novisuccinea chittenangoensis), common terns (Sterna hirundo), blueback herring (Alosa aestivalis) and trout perch (Percopsis omiscomaycus). It was through her U.S. National Science Foundation Research Experiences for Undergraduates (NSF-REU) and undergraduate thesis work on trace elemental analysis of trout perch otoliths at the Cornell Biological Field Station that she found her passion for research.
Zipp has traveled extensively across the country pursuing that passion and addressing fisheries-related issues. She earned her master’s degree in wildlife and fisheries resources at West Virginia University, where her research focused on microplastic ingestion in black bass. During this time, she also contributed to long-term monitoring programs for brook trout (Salvelinus fontinalis) and conducted environmental regulatory assessments related to coal-fired power plants, examining larval fish, crayfish and zooplankton. Her travels have now taken her to the University of Maine Pelagic Fisheries Lab, where she is currently pursuing a PhD in marine biology. Zipp’s research focuses on international fisheries management and movement of highly migratory species, specifically Atlantic bluefin tuna (Thunnus thynnus).
Zipp is passionate about science communication, community advocacy and sustainable socioecological systems. Her favorite activities include public education and outreach events where she can relay science to varied audiences from children to fishermen to policy makers. In the future, Zipp hopes to continue breaking down barriers in science communication while contributing to decision-support science that informs natural resource management. She is particularly committed to bridging the gap between science and policy, ensuring that research findings are accessible, actionable and integrated into effective resource management and conservation decisions.
Kaylyn Zipp and her advisor discuss the physiology of Atlantic bluefin tuna with fishermen at a local fishing tournament. Credit: Makenzie O’Donnell
In her spare time, Zipp can be found scouting out a new eatery, engaging in community service or hiking the coastlines and mountains of Maine.
During her internship, Zipp is excited to help track U.S. federal policies, engage in coalition meetings, legislative hearings and agency briefings that impact wildlife and wildlife professionals. She looks forward to communicating these findings with TWS members and aiding in communicating their work with the broader community. She is excited to support and engage with the TWS community and learn more about policy engagement.
The most interesting field experience I’ve ever had involves a slender brown bug that I found while studying in Malaysia. This tiny insect that probably wouldn’t get a second glance from most shifted my perspective toward conservation and my goals toward ecology.
In 2017, I moved from Jamaica to Malaysia to pursue my bachelor’s degree in ecology. For my honors project, I sampled the diversity of Heteroptera, a group of true bugs, in the Ulu Gombak Forest Reserve northeast of Kuala Lumpur. Every weekend I would go out and sweep a net along two transects. I grew increasingly tired of catching the same, dull brown bug that made up most of my samples. There were hundreds of them—they were like ants.
Credit: Steffani Singh
I became even more frustrated when I tried to identify the species, which proved impossible. I spent weeks behind a microscope, looking at museum collections, contacting entomologists and referencing any insect identification book I could find—to no avail. How could it be this hard to identify such a common species? Eventually, I pinned down the genus from a black and white photo in a book published in the 1950s. After searching through the known species of that genus, I still didn’t find any bug that looked the same as mine. I was shocked to find that a species so ubiquitous in one of the most famous research forests in Malaysia was probably undescribed.
This experience was the first time I really thought about what we know, or rather, how little we know, about tropical biodiversity. Specifically, I realized how this lack of information is a huge challenge to conservation, including in my home country. In Jamaica, there are over 1,000 endemic species of flora and fauna. In fact, there are so many endemic species in Jamaica that you can’t go a day without seeing one. Even common backyard lizards are endemic species. Despite this, we know almost nothing about the populations of most of these animals and plants. Jamaican boas (Epicrates subflavus), Jamaican owls (Asio grammicus), Jamaican coneys (Geocapromys brownii), and black-billed Amazon parrots (Amazona agilis) are among the most iconic animals in the country but are also understudied and extremely threatened.
Singh moves through rough terrain while searching for a Steller’s jay (Cyanocitta stelleri) nest in Darke Lake Provincial Park, British Columbia. Credit: Marcus Cosentino
As I reflect on Caribbean Heritage Month, I find myself thinking about how these endemic species are an irreplaceable part of Jamaican culture and that losing them means losing a part of our heritage. The success of the Jamaican iguana (Cyclura collei) conservation program has been a huge inspiration for me to learn how we can protect the rest of our wildlife. From sampling insect diversity in Malaysia to researching owl habitat use in Canada, I have spent my academic career gaining skills that I hope to bring back to Jamaica to uncover more about our irreplaceable endemic populations. I believe that by protecting wildlife, we protect our heritage.
Wildlife Vocalizations is a collection of short personal perspectives from people in the field of wildlife sciences. Learn more aboutWildlife Vocalizations, and read other contributions.
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After years of targeted bullfrog removal, juvenile pond turtles returned to two ponds in Yosemite National Park.
“We didn’t expect to see those first turtles pop up so fast,” said Sidney Woodruff, a doctoral student at the University of California, Davis. “It was really exciting.”
American bullfrogs (Lithobates catesbianus) are native to the eastern U.S., but people brought them around the world to farm. In the mid-1970s, people deliberately introduced them to the Hetch Hetchy Reservoir region of the park, although the reason remains unclear.
An adult American bullfrog. Credit: National Park Service
The frogs are voracious eaters, swallowing everything from small birds to other amphibians. They also eat hatchling northwestern pond turtles (Actinemys marmorata)—the slow-growing species takes about three years to get larger than a bullfrog’s mouth. These turtles, which are found from central California up to Washington with isolated populations in Nevada, are declining in numbers due to bullfrog predation, habitat loss, drought and pollution. They are currently under proposal for listing under the U.S. Endangered Species Act.
Remote frog removal
In order to restore the ecosystem and study the link between bullfrogs and pond turtles, wildlife managers began removing frogs from two sites in Yosemite’s Hetch Hetchy Reservoir region. They examined each frog’s stomach and continually monitored the pond turtle populations, publishing their results in a new study in Biological Conservation.
The bullfrog crew hikes out from the field site. Credit: Sidney Woodruff
From 2015 to 2022, Woodruff and their teams hiked seven miles out to the remote ponds with their food and gear, staying in the backcountry for about a week at a time. They captured, euthanized and collected data on bullfrogs from around 9 p.m. to 4 a.m., when the frogs were most active, focusing their efforts on the shore and within about a foot of water. Sometimes, they took small rafts out to the middle of the ponds to access hard-to-reach areas or small islands where the frogs would hide. “I’m from Georgia, where bullfrogs are native to, and I love hearing that call,” Woodruff said. “Ultimately, it’s not the bullfrogs’ fault [that they’re here]; it’s ours.”
The team removed over 12,000 bullfrogs, larvae and egg masses from one pond and around 4,000 from another.
They also monitored the turtle population using a mark-recapture survey and modified foldable crab traps baited with mackerel at the two ponds where they removed bullfrogs, as well as another two that had no bullfrogs.
Quick results
Before eradication, the armies of invasive American bullfrogs at these two sites ate juvenile pond turtles. Although an aging population of adult turtles remained, the only evidence of juvenile northwestern pond turtles that researchers could find in the early days of their project was in the bellies of the frogs. At one of the ponds, the adult pond turtle population was as low as 30 individuals. The sites without bullfrogs, which were either ponds of the same size or even smaller, had around 300 turtles.
Sidney Woodruff holds an adult northwestern pond turtle in Yosemite National Park. Courtesy of Sidney Woodruff
At the bullfrog ponds, turtles were 26-36% larger and 76-97% heavier than at the bullfrog-free ponds. Turtle abundance and densities were also two to 100 times higher at bullfrog-free ponds compared to bullfrog ponds.
In the nick of time
It wasn’t until 2019—four years into their study, when researchers had nearly eradicated the amphibians—that the researchers first found a juvenile pond turtle that wasn’t a frog meal. More juveniles began to turn up in their traps.
“We fully believe those would have been turtles that would have been gobbled up by a bullfrog,” Woodruff said.
Baby pond turtles face a host of challenges beyond bullfrogs. From land, raccoons (Prycon lotor), foxes, and skunks dig up nests and feast on their nests. Then, as hatchlings make their way to the water, birds like ravens (Corvus corax) will attack from the air. Largemouth bass (Micropterus nigricans), another introduced species, waits for them under the water. But if they are lucky enough to survive all these challenges and outgrow the mouth of a bullfrog, which takes about three years, Woodruff said their survival is high—around 97%.
A juvenile northwestern pond turtle caught in a trap. Credit: Sidney Woodruff
Although turtles can live for decades, they take about eight to 12 years to reach reproductive age and only lay around six to 10 eggs per year. So, the adults that survived the bullfrog invasion were unable to produce any young that could grow to reproductive age to sustain the population. Woodruff believes this population was on the brink of disaster before researchers intervened.
Preserving California’s turtle diversity
The northwestern pond turtle is one of California’s two native freshwater turtles, the other being the southwestern pond turtle (A. pallida), which was recently separated as a distinct species. Northwestern pond turtles have been lost in around 80% of their range because of climate change, pollution, habitat loss, invasive species and drought, but places like national parks can offer safe havens.
Woodruff emphasized that inconsistent and haphazard invasive species removal efforts can cause population rebounds and make things even worse than before and that prevention is a more cost-effective and efficient method than eradication. But this intervention worked because of consistent funding from both nonprofit and federal partners—the latter of which was recently terminated—and a “unique set of circumstances that came together.” Those circumstances include ponds being isolated from visitors, the bullfrogs being intentionally introduced and isolated from other bullfrog populations, and researchers being able to dedicate lots of time and funding to total eradication.
Extreme weather due to climate change is amplifying the ongoing conservation crisis that amphibians are experiencing across the world. Researchers examined climate data for the past 40 years throughout the globe. Focusing on areas that had experienced a jump in droughts, cold spells or heat waves, the team looked at the ranges of more than 7,000 amphibian species. In the study published recently in Conservation Biology, they found that areas with increased heat waves and droughts have more amphibians that are doing poorly, as measured by threat status on the International Union for Conservation of Nature’s Red List. “Amphibians’ dependence on temporary wetlands for breeding makes them particularly vulnerable to droughts and temperature shifts that cause their breeding grounds to dry prematurely,” said Evan Twomey, the lead author of the study and a biologist at Goethe University Frankfurt, Frankfurt am Main, in a press release. Areas that have been particularly hit hard are Europe, the Amazon region and Madagascar.
Changes in the appearance of loggerhead shrikes captive-bred for release in southern Ontario had wildlife professionals concerned that their program was accidentally prompting evolution that may not suit them in the wild.
But research reveals that conditions in zoos may not be driving changes in bird mass and leg sizes.
“The changes seem to line up more closely with genetic drift,” said Drew Sauve, an adjunct assistant professor at Queen’s University and manager of research and conservation at the African Lion Safari—a drive-through wildlife park in southern Ontario. Genetic drift is a term that refers to the random shifts in genes that occur within a population, which isn’t considered part of natural selection.
The loggerhead shrike (Lanius ludovicianus) is a songbird found widely across North America. The range stretches into southern Ontario, with a unique subspecies considered endangered in that province. Their numbers are likely dropping there due to landscape use changes away from cattle production. Shrikes prefer to hunt insects and other small creatures in the open habitats that agriculture offers, impaling food they catch on hawthorn tree spikes, sharp branches or even barbed wire. Drops in their numbers may also be related to problems the shrikes are experiencing during their migration, though researchers don’t know as much about these challenges. To help conserve the declining subspecies, the nonprofit Wildlife Preservation Canada coordinates a captive breeding program currently involving six facilities in Canada and the United States. The program contributes birds that scientists release into two rural areas near Toronto.
A captive breeding program is working to reintroduce loggerhead shrikes into the wild in parts of Ontario. Credit: Helmi Hess/Wildlife Preservation Canada
But breeders had noticed that the birds they had been keeping had begun to look a little different from usual. They were larger in mass and often had shorter but thicker legs—so much so that the workers had to move up a leg band size in tagging some of the shrikes.
Researchers became concerned that the breeding program may be somehow causing evolutionary changes in the birds—a potential problem for those slated for reintroduction, as any changes the species developed to be more suited to their captive ecosystems may not be favorable in the wild.
“We don’t want to be driving the change ourselves through some sort of selection,” Sauve said.
Loggerhead shrikes sometimes store their food by impaling prey on spikes or sharp tree branches. Credit: Helmi Hess/Wildlife Preservation Canada
In a study published recently in Animal Conservation, Sauve and his colleagues gathered breeding data from the African Lion Safari and seven other zoos and facilities that were part of the captive breeding program that contributed to releases in southern Ontario to try to determine the causes of these changes.
They homed in on several characteristics, like bird mass and wing and leg bone length. Statistical analysis of the recorded characteristics of the birds’ bodies, as well as genetic analysis, revealed that gene flow in shrikes had changed compared to wild birds about halfway through the program.
They found that the changes were mostly driven by genetic drift. This essentially means that it was likely coincidence—that birds with certain characteristics showed up more commonly for a few years by chance before those characteristics became less common again.
While the researchers didn’t take environmental factors that might be causing any changes in bird bodies into account, Sauve said the discovery that it was likely genetic drift is a “relief” for people managing the program. The results seem to show that accidental breeding selection in the program isn’t likely driving these changes. While the size and shape shifts they saw changed back to normal in more recent years, the next steps will be to analyze environmental factors that might be driving some change, Sauve said.
Some of the changes that researchers noticed in shrikes over time may have also been due to a change in process. “Over time in the study, we noticed that the age that we measured the birds was a little later in time,” Sauve said.
There are more than 6,500 invasive species in the United States that have caused immeasurable damage to native ecosystems. Mechanical control, like weeding; chemical control, like applying pesticides; or biological control, like introducing specialized insects, are all strategies scientists use to combat invasive species. However, public perceptions of invasive species management aren’t always clear and can impact the long-term success of projects.
In a new paper in People and Nature, Wade Simmons, a PhD candidate at Cornell University, studied public perceptions of introduced species management. Simmons mainly works on biological control of water chestnut (Trapa natans), an invasive species in New York.
Credit: Liz Kreitinger
To complete the study, Simmons and his collaborators presented a representative sample of the American public with a set of scenarios around invasive species management. The team structured the stories using four basic building blocks of introduced species management: a target species, a proposed method of control and the level and type of associated risks. In order to avoid bias, they didn’t specifically name the three methods of control—chemical, mechanical or biological—but rather described the mode of action in the scenario. The stories were general and didn’t provide many specifics with the goal of getting to the heart of Americans’ attitudes toward each management intervention.
We spoke with Simmons to learn more about Americans’ attitudes towards invasive species management and how scientists may be able to build public trust.
What made you want to complete this study and how did you design it?
If you tell someone you do biocontrol science, they’ve got all kinds of questions and assumptions. You can see a lot of suspicion and alarm bells going off in people’s minds. But perceptions of modern biocontrol, especially of plants as being unpredictable or risky, do not match the overwhelming positive track record. I had this nagging question—is biocontrol really more controversial with the American public than other forms of control, like mechanical or chemical? If you asked people in a standardized way, how much do these ideas really diverge?
To get away from some of that ambiguity, we standardized our experiment just for control of plants and insects. Insects and plants were a good place to start because there were comparable biological, chemical and physical control methods across species. We also recognized that people’s emotions, attitudes and values seem to stand apart across taxa. We were really careful in choosing descriptive words and avoiding emotional ones. For that reason, we didn’t label species as invasive but used descriptors like “a plant species has arrived in a place where it didn’t previously exist and is causing negative effects on the environment.”
As researchers, we want to use the most evidence-based and effective management strategies, but those aren’t always the most socially acceptable. This study was a first step in mapping out public feelings towards shared, fundamental components of management.
What did you find?
Overall, our findings suggest that many standard practices for managing introduced species are not broadly accepted by the U.S. public. Unsurprisingly, we found greater support for management considered low-risk relative to high-risk scenarios and that mechanical control is generally more acceptable than both chemical and biological control. These two methods often had similar levels of low support.
We didn’t specifically test why mechanical control was more acceptable, but it likely relates to its familiarity: people understand cutting down a tree or pulling weeds. What happens as chemicals break down, or biocontrol insects spread more widely in the environment is less clear to most people.
The problem is we just don’t have very good evidence that mechanical control is an effective way to reduce the impacts of nonnative species, at least at scale. It’s problematic that the method with the most social acceptability is perhaps the least effective, and the method with the best supporting evidence—biocontrol—has the lowest acceptability.
We also found that acceptability for managing plants and insects did not differ, nor did the acceptability for management with risks to human well-being compared to risks to native species. We didn’t define risks in a granular way, so it’s likely that we’d see a separation in attitudes when risks became more specific to respondents’ personal situations. Still, it was heartening to see the concern for native species. This leaves really inviting follow-up directions for future research.
What are your big takeaways from this project?
Our work shows that managing introduced species continues to be controversial, and public support for management should not be assumed for projects. We also find a disconnect between what can work, at least at scale, and what is popular. So what can we do to try to increase public support for management, or at least better communicate and defend the important management work that is being done?
We know from plenty of other work that simply giving people more information is not an effective strategy for changing minds on its own, but we do see a clear need for more evidence here. Many management projects are motivated and justified by the desire to protect native species or ecosystems, yet we often lack the appropriate evidence to judge the impacts of nonnative species or evaluate whether management actions are making a difference toward these goals. Removing so many acres of an aquatic plant may be a success if the goal is opening up space for human recreation, but it doesn’t tell us anything about whether water quality improves or if native species recover. Without better outcome monitoring, accountability for management actions can break down, and these management actions may be more susceptible to controversy if claims of benefits can’t be corroborated.
Controversies surrounding nonnative species will likely never go away, but the intensity of the disagreements may be inflamed if controversial actions are not well supported by evidence. And the need for evidence can change over time. In early stages of invasion, when threats and harms are unclear and chances of eradication are high, taking actions without clear evidence may be well justified. But for species that are well established and have been targeted with management for years, the evidence justifying their management should also grow and deepen, and that is commonly not the case.
The burden of building a culture of greater outcome monitoring should be a shared responsibility, and it is on funders to require it in grants and on scientists and managers to test, develop and implement it together. Showing that action “X” can lead to species “Y” recovering may meaningfully change people’s attitudes, or it may not, but it seems extremely important in terms of accountability for actions being taken with public money, on public lands and for public benefits. While the controversies may never go away, our understanding of risks and outcomes of management should grow over time so we can better determine which species should be managed, and how, with our limited conservation resources.
