Q&A: Regulating invasive terminology 

December 9, 2024 by Joshua Rapp Learn

Non-native species occur nearly everywhere in the world. They travel in ship cargo, escape from aquariums into nearby waterways and occasionally even float to new islands on top of hurricane debris.  

Many of these species don’t last long in their new home—the conditions usually aren’t right for them. Others thrive, filling ecological niches that native species don’t occupy, or outcompeting them in others. A subset of the latter species can cause serious issues to native species, human health and infrastructure, and native ecosystems as a whole.  

But how do scientists define these terms? When does a non-native species become invasive? And what constitutes an alien species?  

To delve more into these questions, The Wildlife Society connected with Ismael Soto, a PhD student at the University of South Bohemia in České Budějovice, who recently published a paper on the subject in Biological Reviews titled “Taming the terminological tempest in invasion science.” The Wildlife Society caught up Budějovice to find out how to tackle these questions.  

Why is it important to agree on terms “alien species,” “invasive species” or “non-native species?” 

In science—and everywhere—it is crucial to define terms clearly and understand their meanings. The use of polysemous—words with multiple meanings—and/or redundant terms in our field can hinder progress. I will start with “invasive.” This term is by far the most problematic, with an increasing number of definitions emerging each year. We have reached a point where we don’t truly understand what “invasive” means. For example, at a conference, if someone mentions they are working with the invasive species “X,” it is unclear whether they are referring to the species spreading, having a significant impact, both or neither, thus creating confusion. This ambiguity dilutes the useful potential of the word, which was initially intended to describe a subset of non-native species of particular concern. Furthermore, it appears that the terms “invasive” and “non-native” are now used synonymously, which they should not be. Probably the root of the problem lies in the three main ways of defining these terms—impact, spread, and impact and spread—each having its deficiencies.  

Regarding “alien/non-native,” the issue is simpler and of less concern. These terms are interchangeable as they share the same meaning. The problem with “alien” is that for some audiences, it might convey images of extraterrestrial beings like the classic green silhouette or subjects from the movie Alien vs. Predator. The main reason I avoid using “alien” is due to its strong negative connotations with things like immigration policies. Indeed, the term has been used for a long time, but as language evolves, we have to adapt to new contexts. “Non-native” is currently my preferred term, as it is not politically charged. 

Although I have my definitions and reasons for considering them the best, I do not claim they are the absolute truth. However, I believe in the necessity of clearly defining and limiting these terms. While a global consensus may seem naïve or impossible, there have been successful cases in related fields such as the Venice System, which is used to classify different types of water according to their salinity.  

When does a non-native species become an invasive species?  

The answer depends on who you ask, and this is because there are over 25 different definitions of “invasive.” While not all of these definitions are currently in use, they certainly contribute to confusion in the field. In my personal opinion, although it’s far from perfect, the term “invasive species” should be linked to the concept of “spread.” Therefore, I believe that an invasive species is a non-native species that spreads beyond its point of introduction and establishes new populations. However, I also acknowledge that some people have chosen to stop using the term due to the vagueness of the definitions we currently have. 

When does a non-native species become a native species? 

By definition, this should never happen. Even in cases of old invasions—whether dating back to colonialism or even ancient Australasian migrations—the effects of these invasions are still visible today. However, it is true that some non-native species have become part of the culture in certain region, such as with crayfish festivals, and as a result, little or no management is applied to them. Some people also refer to certain species as “naturalized,” meaning that the species can survive and reproduce. However, this is another controversial term with multiple definitions. 

Are there regulatory repercussions for not having a standardized set of definitions for these terms? 

Definitively, how can we manage these populations if we are unclear about the terms we are using? The concurrent definitions of several terms complicate our understanding and actions. Moreover, how should we prioritize these populations—based on impact, spread or both? A recent example from a colleague highlighted that in Australia, there is no unified list of non-native or invasive species, and the definitions—and therefore the terms—vary by state, leading to a lack of communication in the same country. Imagine this at a global scale. Another consideration, just as food for thought, is that our classifications of native, non-native or invasive species are often based on political borders, which are meaningless to the species themselves. This discrepancy can lead to curious anomalies. 

The IUCN has defined terms that many other countries also use—categories like “critically endangered” or “vulnerable.” Should the IUCN or a similar international regulatory body set guidelines for the meaning of invasive species terminology? 

All efforts to harmonize terminology are greatly welcomed, as I consider inconsistent definitions a critical issue. However, such efforts must be implemented on a global scale and take into account diverse perspectives and points of view, from early-career researchers to professors. Without this inclusive approach, the effort may prove fruitless or, even worse, lead to greater confusion. Or it may become just another failure to harmonize the terminology. 

What can be gained by improving the agreement on the definition of these terms? 

As we say in Spanish, “everything to win, nothing to lose.” A field that progresses in consensus will undoubtedly accelerate the rate of innovation, not merely by focusing on new ideas but by fostering a shared understanding. While these definitions should remain open to debate and not become dogmatic, we need solid arguments to support or challenge these discussions. Biological invasion is a global issue with complex solutions, if any. Thus, any effort we make to mitigate impacts and prevent future expansions is already an advancement. 

The state of lions, leopards and hyenas in Uganda 

December 9, 2024 by The Wildlife Society

The first comprehensive population estimate of Uganda’s lions, leopards and spotted hyenas in almost two decades has revealed that lion numbers in the country are extremely low. Leopards (Panthera pardus) are holding on across the country, and hyenas are faring well. In a collaboration involving more than 100 conservation stakeholders, researchers used spatial capture-recapture methods to look at the three species in six major protected areas in Uganda. The researchers uncovered that lions (Panthera leo) are declining, with fewer than 40 individuals in Queen Elizabeth National Park and 20 in Kidepo Valley National Park. Spotted hyenas (Crocuta crocuta), on the other hand, are doing well throughout the country, particularly in Murchison Falls National Park. The researchers said these high numbers could potentially indicate a trophic imbalance. Uganda officials are already using the findings from this study in its new Strategic Action Plan for Large Carnivore Conservation.  

Read the study in Global Ecology and Conservation.  

Grassland conservation benefits American burying beetle 

December 6, 2024 by The Wildlife Society

Large-scale grassland conservation efforts have helped increase the threatened American burying beetle population.  

In a Working Lands for Wildlife-affiliated project, Caleb Roberts, a U.S. Geological Survey research ecologist and unit leader at the Arkansas Cooperative Fish and Wildlife Research Unit, studied population counts of the species taken by the Nebraska Game and Parks Department. He and his colleagues specifically looked at populations in the state’s Loess Canyons Experimental Landscape from 2007 to 2019.  

The research showed that maintaining intact, highly connected grasslands is the most effective way to conserve the American burying beetle (Nicrophorus americanus). Scale and spatially explicit conservation tactics were also important for managing for small species like the beetle, the team found. 

The American burying beetle’s range once included 25 U.S. states and even Canada. Today, most remaining populations live on privately owned grasslands in Nebraska, Kansas, Texas, Oklahoma, Arkansas and South Dakota.  

First listed as federally endangered in 1989, the beetle’s status was changed to threatened in 2020. These nocturnal carrion beetles play an important role in ecology by helping recycle nutrients. Its presence or absence can also help land managers gauge the overall health of an ecosystem.  

Read more from Working Lands for Wildlife.  

Hawaiian crow released in Maui 

December 6, 2024 by The Wildlife Society

The U.S. Fish and Wildlife Service and partners released five Hawaiian crows on Maui recently in an effort to return the species to its historical range. After years of preparation by the USFWS, Hawaii’s department of land and natural resources division of forestry and wildlife and the University of Hawaii, experts released two females and three males that had been in conservation centers for months. Also known as “alala,” Hawaiian crows (Corvus hawaiiensis) went extinct in the wild in 2002 due to habitat loss, predation and disease. “The translocation of alala to Maui is a monumental step forward in conserving the species and a testament to the importance of partnership in reversing biodiversity loss,” Megan Owen, vice president of conservation science at the San Diego Zoo Wildlife Alliance, told The Guardian.  

Read more in The Guardian.  

Invasive spotted lanternflies thrive in cities

December 5, 2024 by The Wildlife Society

Warm cities may provide the best conditions for the spread of invasive lanternflies. Spotted lanternflies (Lycorma delicatula), native to Asia, first arrived in the U.S. in 2014 in Pennsylvania. They have since spread across the Northeast and into the Midwest and Southeast. Scientists tapped into the citizen science platform iNaturalist to learn more about why the insects are doing so well in New York City. “Cities tend to have milder winters, creating favorable conditions for species that otherwise would only be able to live in hot, tropical climates,” said Kristin Winchell, an assistant professor of biology at New York University who studies ecology and evolution in urban environments, in a press release. “Cities are also highly connected places where trade happens, and organisms may end up on shipments in planes or boats traveling between cities.” After looking at nearly 20,000 photos of lanternflies taken between 2014 and 2022, the team found that nymph and adult lanternflies were showing up earlier each year and remaining active later. This longer active time means more time to reproduce and spread, Winchell said. Winchell and her colleagues hope this information can help with monitoring and mitigation of spotted lanternflies and other invasive species. 

Read the study in the Biological Journal of Linnean Society.

Wildlife Vocalizations: Kirstin Palumbo 

December 5, 2024 by Kristin Palumbo

Growing up, I was always outdoors. Whether it was going on hikes, hunting and fishing with my dad, or just watching the critters in my backyard, I was always entertained by what surrounded me.  

But the moment I knew I wanted to become a wildlife biologist was during my junior year of high school.  

I always loved my general science classes. Unfortunately, my high school did not offer any environmental courses. Back then, the only environmental-related jobs I heard of were game wardens and park rangers. While those options were always in the back of my mind, I knew it wasn’t quite what I was looking for. 

I had a lot going on at the time for a high schooler: Advanced Placement classes, working five days a week and attending daily after-school activities. While I enjoyed all of this, the routine and busyness of it all drove me into a rut. 

Kirstin Palumbo helps her professor, Carol Bocetti, capture and PIT tag Delmarva fox squirrels (Sciurus niger) to monitor their population at Maryland’s Blackwater National Wildlife Refuge in May 2018. Credit: Courtesy Kirstin Palumbo

That fall, I went hunting with my dad. I remember sitting in the tree stand, watching the sunrise early in the morning, when the feeling of both relief and excitement came over me. The feeling that I had made me realize that my happiness and my passion were rooted in the outdoors.  

I knew that I wanted to be the one to investigate the impacts that actions had on the environment. I wanted to be the one who knew the science behind how different species interacted. I wanted to be the one that was able to better educate people about the wildlife around them.  

Kirstin Palumbo attended the joint AFS-TWS Conference in Reno, Nevada in October 2019, as a member of the California University of Pennsylvania Student Chapter. Credit: Kirstin Palumbo

That beautiful, serene morning, I realized that whatever path I chose for my future, I had to help the environment that helped pull me out of that rut. 

Wildlife Vocalizations  is a collection of short personal perspectives from people in the field of wildlife sciences.   

Learn more about Wildlife Vocalizations, and read other contributions.  

Submit your story for Wildlife Vocalizations or nominate your peers and colleagues to encourage them to share their story. For questions, please contact tws@wildlife.org.  

Lessons from the past may improve the future for manatees 

December 4, 2024 by Megan Radke

While current manatee populations in Florida are threatened, their populations are higher than they ever historically were. 

Records show that manatee (Trichechus manatus) populations grew and began expanding across the Florida Peninsula during the same documented periods of human population increases, anthropogenic landscape changes, and social and policy changes. But with an increase in humans, they face new problems like pollution and algal blooms. The U.S. Fish and Wildlife Service initially listed them as endangered in the 1970s, and they were recently downlisted to threatened in the 2017.

“What we can say for sure is that manatees are sparsely represented in the archeological and historical records until the 1700s and 1800s,” said Thomas Pluckhahn, a professor in the Department of Anthropology at the University of South Florida. 

Pluckhahn, a co-author of a new study  on manatees published in PLOS One, pored over records of manatee remains at archeology sites, as well as historical accounts of manatee sightings from newspapers and journals ranging from 12,000 BC through the mid-20th century. He attributes manatee population growth to a few factors, including warming ocean waters.  

Florida manatees increased with human presence in Florida. Credit: Carol Grant, USFWS

Temperature fluctuations  

Pluckhahn said there was a centuries-long cold spell called the “Little Ice Age” that began in the 1200s and lasted into the 1800s. He said that the effects of this are often debated, but studies of corals in the Caribbean suggest that water surface temperatures during that time were lower in the winter.  

“Manatees are subject to cold stress even today, but you can imagine with the water temperature even a couple of degrees colder in the winter that would have been a limiting factor in their populations,” he said.  

Though the impacts of anthropogenic climate change on manatees are a mixed bag, warmer waters surrounding Florida have helped the species.  

“It’s made things more hospitable for manatees,” Pluckhahn said. “Manatees need warm water. After going through newspaper accounts of when they started to be spotted more often in South Florida, they were being seen in yacht basins, canals and shallow water.” 

Residents in the Miami area even noticed that manatees were populating industrial outflows—such as those surrounding power plants—because of the warmer water, he said. 

“We started building more and more power plants, and now those areas are critical refuges for manatees,” Pluckhahn said. 

As power plants go offline, the U.S. Fish and Wildlife Service, the Florida Fish and Wildlife Conservation commission and other partners are also working to implement a warmwater habitat action plan.

New neighbors 

Despite an increasingly complicated relationship between manatees and Florida’s growing population, the influx of power plants to support infrastructure isn’t the only human action that has helped the aquatic mammals.  

Pluckhahn said that another reason for manatees’ growing populations can be attributed to Florida enacting legal protections for the species. Additionally, the creation of protected areas like Everglades National Park allowed manatees to expand their range.  

“Manatees and humans are thoroughly entangled, and people love them,” he said. 

It’s that love for manatees that has also benefited Florida in the way of tourism dollars—though there’s always the possibility that it could be too much of a good thing.  

“Manatees benefited from the increasing population of Florida, and the Anthropocene was good for them up to a point,” Pluckhahn said. “Today, they aren’t benefiting as much, especially with the increase of algal blooms, the loss of seagrass and pollution.”  Boat strikes also continue to be a major problem for manatees.

Pluckhahn said that on the east coast of Florida, due to the loss of seagrass meadows, resource managers have had to resort to supplementing manatee diets with lettuce.  

A better future 

Even though manatees may be better off in the modern era according to historical accounts, Pluckhahn said that he does not suggest the species shouldn’t be protected.  

In fact, some people argue the species should be uplisted from threatened to endangered. “We don’t want this research to argue that manatees shouldn’t be listed as endangered,” he said. “They were downlisted, and that hasn’t worked out very well. Our point with this research was that it’s important to protect them, especially because we, as humans, value them.”  

Pluckhahn added that examining historical evidence of the species could further improve their health and numbers. 

“Even if we can’t get back to a historical baseline, there’s a value in understanding how manatee populations have developed and how we want to plan for the future,” he said. 

Rodenticides found in turkey vultures despite bans 

December 4, 2024 by The Wildlife Society

Although California recently banned the use of anticoagulant rodenticides, turkey vultures in the state still have evidence of exposure to the chemicals in their bodies. Researchers studied the vultures’ exposure to eight different types of rodenticide in southern California from 2016 to 2021. The team found 11% of the birds they studied were exposed to anticoagulant rodenticides. “The presence of rodenticides in the blood of a few individuals is just the tip of the iceberg and demonstrates that these compounds are still out there,” said Miguel Saggese, a faculty member at the College of Veterinary Medicine at Western University of Health Sciences and an author of a recent study on the turkey vultures (Cathartes aura). Saggese and his colleagues said that these findings may mean that other more vulnerable raptor species like burrowing owls (Athene cunicularia), white-tailed kites (Elanus leucurus) and California condors (Gymnogyps californianus) could potentially be exposed. 

Read the study in the Journal of Raptor Research. 

Doctoral candidates recognized for presentations during #TWS2024 

December 3, 2024 by The Wildlife Society

The Wildlife Society granted Gilia Patterson and Sadie Roth the Best Oral Presentation and Best Poster Presentation awards, respectively, during the TWS Annual Conference in Baltimore. The Society will provide each winner with a complimentary registration for the 2025 TWS Annual Conference in Edmonton.  

Gilia Patterson (left) was awarded Best Oral Presentation for her research on estimating population size from genetic data.

Analyzing population sizes with genetics 

Patterson, a PhD candidate in the University of Oregon’s Institute of Ecology and Evolution, earned Best Oral Presentation for her work entitled, “A Spatially Explicit Close Kin Mark-Recapture Method for Estimating Population Size from Genetic Data.”  

“We developed a new method of looking at population size from genetic data,” Patterson said.  

Often, scientists use genetic samples taken from hair or scat at multiple time points to decipher what animal is passing through and to extrapolate population size.  

But these samples can provide genetic information about relatives, too, Patterson said. “It can tell you if you captured the same individual or its parent or sibling.” 

Patterson said that scientists haven’t broadly used these so-called “close kin mark-recapture methods” up to this point, primarily because they don’t often account for spatial information.  

“Most often, relatives are located close together, and when you’re sampling some parts of the landscape more than others, the estimate can be biased,” she said. “But we developed a spatial version of close kin mark-recapture that gives unbiased estimates, even when you sample some areas more intensely than others.” 

Patterson said biologists can use this method when they are conducting capture-recapture work but aren’t getting many recaptures. Genetic information from relatives can fill in some of the gaps. She also said agencies can use this method to manage harvested populations—they can input hunter harvest data from individuals and relatives into their model to learn more about population sizes.  

Patterson said this was her second TWS Annual Conference, and she appreciates the chance it provided to talk to so many different people, which in turn can help make her research better.  

“I really want the methods I’m working on to be useful, and I want them to advance conservation, which means it’s important for me to learn what type of data people have and what issues they’re running into,” she said.  

Patterson felt surprised upon learning that her presentation was recognized as Best Oral Presentation. 

“I went to a lot of good talks,” she said. “I spend a lot of time on my computer writing code, and to have my research be so well received felt amazing.”  

Sadie Roth was awarded Best Poster Presentation for her research on amphibian pathogens in the Sonoran Desert. Courtesy Sadie Roth

Tackling an amphibian pathogen 

Roth, a PhD candidate at Texas Tech University, was presented with Best Poster Presentation for her work entitled, “Dynamics of the Amphibian Pathogen Batrachochytrium dendrobatidis (Bd) in the Sonoran Desert.” 

The poster presentation covered Roth’s research on the dynamics of Bd in the Sonoran Desert. “This pathogen can devastate amphibian populations, and understanding the conditions under which it most threatens species in this system can help us better predict the timing and location of outbreaks in the future,” she said. 

Roth found that Bd occupancy probability and prevalence were highest in years with lower rainfall, which indicates that the threats of Bd and drought could work synergistically to threaten amphibians in this system. 

This was also Roth’s second TWS Annual Conference. 

“I really enjoyed the presentations I attended, and I feel like I learned a lot that I can use to improve my own research,” Roth said. “On top of that, it is always great to meet other researchers and hear about their work.” 

Roth said she was honored to be recognized for her poster presentation and greatly enjoys the visual storytelling that goes into a poster. 

“I’m glad that others appreciated the way I chose to present this work,” she said. “I saw so many great posters at TWS, and I am very proud to be a part of this year’s excellent poster session.” 

USFWS proposes new rules for recovery of Canada lynx 

December 3, 2024 by The Wildlife Society

The U.S. Fish and Wildlife Service is moving forward with Canada lynx conservation by taking two steps. The Service is proposing to revise the current habitat designation for the species. The new habitat designation would cover more than 19,000 square miles in Colorado, Idaho, Montana, New Mexico, Washington and Wyoming. In addition, collaboration between the Service and state, Tribal and federal partners resulted in a newly proposed Canada lynx (Lynx canadensis) recovery plan addressing threats like climate change. The proposed rule will be published in the Federal Register on Nov. 29. The Service will review public comments by Jan. 28. 

Read the full recovery plan at the U.S. Fish and Wildlife Service.