TWS2024: Invasive cedar impedes Galapagos tortoise migration

April 18, 2025 by Joshua Rapp Learn

Invasive Spanish cedar on the Galapagos Islands could be impeding the seasonal migration of the islands’ biggest herbivores.

If Galapagos tortoises can’t access the most nutritious vegetation available in a given season, there could be impacts on the critically endangered species.

“If you take an energy hit, you just have less energy to live and to reproduce,” said Stephen Blake, an assistant professor in biology at Saint Louis University.

People brought Spanish cedar (Cedrela odorata) from mainland Latin America to Santa Cruz—the most populous island on the Galapagos Archipelago—in the 1940s to provide a source of timber. “It’s relatively fast-growing—it’s nice, easy-to-work wood,” Blake said.

An invasive Spanish cedar forest. Credit: Stephen Blake

Farmers still have plantations where they grow and harvest the trees today. But because its seeds are wind-dispersed, the plant also took off in humid and semi-humid areas on the island. The problem is the cedar has toxic compounds, which it uses to poison competitor plants around it—this resistance to pests in part makes it popular for products like cigar boxes. “It’s quite toxic, and it’s relatively insect-proof,” Blake said. “Native and endemic species tend not to do well in Cedrela forest.”

Tortoise migration

Western Santa Cruz tortoises (Chelonoidis porteri), a species of Galapagos tortoise considered critically endangered by the International Union for Conservation of Nature, are partial seasonal migrants. They spend the rainy season in lowland areas, when a burst of precipitation stimulates fast-growing, nutritious vegetation. Once the dry season begins, many adult tortoises migrate up to the highlands, where year-round rain offers reliable food that is less nutritious than the lowlands during the rainy season but better than the sparse pickings of the now arid lowlands. Tortoises travel an average of about 20 kilometers to complete these annual treks, Blake said.

Anecdotally, researchers noticed that tortoises tended to avoid forests made up of Spanish cedars. In research presented at the 2024 TWS Conference in Baltimore, Maryland, Blake and his colleagues tracked tortoises on Santa Cruz to see how they were reacting to cedar forests during migration. The study was published in Ecology and Evolution in 2024.

Stephen Blake fixes a GPS tracking device on a western Santa Cruz tortoise in the island’s highlands. Credit: Stephen Blake

The team used plumber’s epoxy to glue GPS tracking devices onto the shells of 25 tortoises since 2009, when Blake initiated the Galapagos Tortoise Movement Ecology Programme. In previous work, Blake and his colleagues combined this with maps of cedar forests made by Gonzalo Rivas Torres—a coauthor of Blake’s on the recent work—and his collaborators. Most of the cedar forests that sit in the migration path of the tortoises straddle the border of Galapagos National Park and the agricultural zone in the highlands of Santa Cruz.

Toxic obstacles

The analysis revealed that when the tortoises moved between the lowlands and the highlands on their migration, they chose to navigate through small areas of native forest and vegetation that sit between large expanses of Spanish cedar forest in all but a few cases. “A few tortoises bludgeon their way through it,” Blake said. But they typically prefer to move through the native forest. “They almost invariably migrate through these little gaps through the Cedrela—these little corridors.”

A patch of Spanish cedar abuts an agricultural zone in Santa Cruz. Credit: Stephen Blake

Blake isn’t sure why tortoises avoid these areas—whether it’s the understory of invasive blackberry sometimes associated with cedar, the shading effect of dense canopy or the toxicity of the plants that they shy away from.

Researchers also aren’t sure why the Spanish cedar hasn’t colonized certain areas—more research is needed to better understand this. But wildlife managers interested in conserving tortoises should pay attention to maintaining currently uninvaded habitat that offers passage for migrating tortoises and to the expansion dynamics of cedar forests, Blake said.

A tortoise moves through a patch of Spanish cedar forest. Credit: Stephen Blake

Tricky solutions

Effective ways to remove Spanish cedar have not yet been found. Removal can create ideal conditions for invasive blackberry, which can grow in extensive, dense stands, taking over and providing an effective barrier against tortoise migration.  

“Some methods of harvesting Cedrela can make the situation even worse,” Blake said.

However, if the cedars are not controlled, western Santa Cruz tortoises could stand to lose their migration routes. Large reptiles with low metabolic rates may be better able to adapt to changes in their nutrition compared to mammals, Blake said. But long-term loss of the migration route tortoises have adapted to find the most nutritious food could negatively impact their energy budgets, with species-level impacts.

“If you live in a suboptimal environment, you’re going to get suboptimal reproduction,” Blake said. While the problem isn’t as bad on other Galapagos Islands as it is in Santa Cruz, it could also become a bigger problem in these areas if cedar invasion takes off.

“Tortoises are but one biodiversity problem that Cedrela creates,” Blake said.

Tortoises can barrel their way through vegetation, but they choose to avoid Spanish cedar areas. Credit: Stephen Blake

Watch: Elephants huddle protectively as earthquake rumbles

April 18, 2025 by The Wildlife Society

As soon as a 5.2-magnitude earthquake began to rumble in Southern California, elephants in the zoo rallied together into a protective huddle. A video capture of an enclosure at the San Diego Zoo Safari Park showed five African savanna elephants (Loxodonta africana) before, during and after the quake that shook the ground April 14. At first, the elephants were somewhat dispersed in the enclosure, then they ran toward a more open area just as the ground began to rock, forming a circle with the younger animals in the middle. “This video demonstrates the strong social family structure in elephant herds,” a spokesperson from the zoo said in a statement. “The herd, consisting of Ndlula, Umngani, Khosi and youngsters Zuli and Mkhaya, went back to normal after about four minutes, though they did stay close to one another.”

Read more at AP News.

Alaska predator control deemed unconstitutional

April 17, 2025 by The Wildlife Society

An Anchorage Superior Court judge recently ruled that the Alaska Department of Fish and Game’s program to kill nearly 200 brown and black bears to boost a caribou herd was unconstitutional. The agency originally developed the program to kill wolves (Canis lupus) and increase their prey species. The department expanded the program in 2022 to include brown bears (Ursus arctos), which prey on the Mulchatna caribou (Rangifer tarandus) herd, which has been struggling and sits at about 13,000 individuals. Judge Andrew Guidi’s recent ruling, citing a lack of due process and adequate public notice of the program, means, at least temporarily, the Alaska Department of Fish and Game must end the brown bear control program.

Read more in the Alaska Beacon.

Utah remains rich in bee diversity

April 16, 2025 by The Wildlife Society

Utah is living up to its nickname as the “Beehive State,” after researchers found high bee diversity there. Researchers set out to document Utah’s bee species to determine the best way to conserve them. To do so, the team used online records from the Symbiota Collection of Arthropods Network as well as specimen records from the USDA-ARS Pollinating Insect Research Unit. In total, the researchers documented 1,167 bee species in the state. “Our checklist helps scientists and managers understand bee distributions, which are essential to protecting these vital pollinators,” said Anthony Hunsaker, an undergraduate researcher and author of the study. “The information can help managers limit adverse impacts if a new invasive species is introduced.”

Read the study in Diversity.

WSB: Tracking down North Carolina weasels

April 15, 2025 by The Wildlife Society

The best way to attract weasels to understand more about their populations may be to use red meat as bait. Weasels in North Carolina, particularly the least weasel (Mustela nivalis), often evade camera traps, making it hard for scientists to monitor their populations. “We’re a little worried about the weasels,” said TWS member Roland Kays, a research professor at North Carolina State University and scientist at the North Carolina Museum of Natural Sciences, in a press release. “We don’t see them very often, but it’s difficult to tell if they’re actually gone or if they’re just so sneaky that we can’t find them. We decided that we needed to better understand the best method to detect them. There wasn’t a great consensus on that.” In a recent study, Kays and his colleagues baited 486 camera traps across the central and eastern U.S. where weasels live. Using seven types of lures, they found that red meat worked the best, particularly when supplemented with salmon oil. The challenge is that red meat also attracts other predators, so researchers may have to take extra precautions to make it harder for larger animals to reach the bait. “Now that we have an understanding of the best ways to lure the weasels, we can be more confident in the findings of our surveys,” Kays said. “When we have sites where we don’t detect them, we can be much more assured that they aren’t just in hiding, they’re really just not there at all.”

Read the study in the Wildlife Society Bulletin.

DOGE may threaten sustainability of FWS waterfowl limits

April 14, 2025 by The Wildlife Society

Cuts to U.S. Fish and Wildlife Service employees could threaten waterfowl surveys that help wildlife managers to maintain sustainable harvest limits for hunting seasons across the country. Retired bird bosses and lawmakers have expressed concern that the ongoing cuts made by Elon Musk’s Department of Government Efficiency may impact the annual waterfowl survey that helps agencies determine appropriate bag limits and quotas. “If there’s a decrease somewhere in the Fish and Wildlife Service, particularly at refuges and the Division of Migratory Bird Management, it will affect the staffing for the surveys,” Brad Bortner, a retired biologist who served as the Chief of Migratory Bird Management, told Field & Stream.

Read more at Field & Stream.

Jaguar parts widely sold online in Mexico

April 11, 2025 by Joshua Rapp Learn

Jaguar claws, tooth talisman necklaces, throw rugs and full skulls are just some of the illegal jaguar parts from Mexico that people are advertising and selling on platforms like Facebook and Etsy.

“The sales of jaguars and other wild felines on online platforms were more common than we thought,” said Antonio de la Torre, a postdoctoral researcher at the Autonomous Metropolitan University, located just west of Mexico City.

The International Union for Conservation of Nature lists jaguars (Panthera onca) as near threatened. The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) has prohibited the trade of jaguar parts since 1975, but a 2022 CITES study found that poaching and the illegal trade are a “growing threat” to the large cats.

De la Torre, who also works for Bioconciencia, a biological and cultural civic association, became interested in the topic of the online sale of jaguar parts after seeing a study that Wildlife Conservation Society (WCS) researchers conducted, tracking the online sale of jaguar parts across the world in various languages and platforms. In that study, the team found people were selling more parts from Mexico than from other countries.

Jaguar paws were among the most commonly offered items. Credit: WCS Mesoamerica

De la Torre was a little skeptical at first and began to do his own online search. The more he looked, the more examples he found of jaguar and other felid parts being sold in Mexico.

As a result, he and his colleagues conducted a study, published recently in Animal Conservation, delving more deeply into the Mexican market for these parts. They used the same standardized search protocol as the WCS study. For example, they used search terms like “jaguar claw” in both Spanish and English, using the word combinations in searches on various platforms like eBay, Etsy, Facebook, Google and Yahoo!

Open jaguar market

The team recorded all of the posts they found that used these terms, including photos and videos. They tried to infer the location of the users posting using the videos, photos and the publicly available profiles. They also read the comments on these posts between sellers and potential buyers to help determine where the buyers were located.

Jaguar teeth were sold in the form of amulets or sometimes as necklaces. Credit: WCS Mesoamerica

Their search, which examined posts in the 10 years preceding the end of May 2022, revealed 713 posts involving wild felid parts from Mexico. These posts—and responding comments—were made by 157 users from 60 locations, everything from small towns to Mexico City. About half of these posts explicitly mentioned the parts were for sale.

While jaguars were featured often, sellers in Mexico were also offering parts from other large felids, such as pumas (Puma concolor). But the team found posts featuring parts from species not native to Mexico, like African lions (Panthera leo) and tigers (Panther tigris), as well. De la Torre said that these parts likely come from breeding facilities located in Mexico, both legal and illegal.

Most of the posts selling jaguar parts were on Facebook, where de la Torre said it’s easier for users to offer these kinds of materials.

“Analysis of the buyers revealed that most were in Mexico, but there was also plenty of international interest,” de la Torre said. “When we talk about the illegal trade of parts, people mostly think the demand is in Asia, but we found that people are interested in Europe and the U.S.”

A live jaguar kitten for offer. Credit: WCS Mesoamerica

What jaguar parts are sold?

The team also analyzed what people were doing with the parts they were purchasing. They found a diverse range of uses, from decorative ornamentation to jewelry and clothing. Most of the posters were selling jaguar claws, which is apparently the most desired part, de la Torre said. Other popular items included skins, necklaces made of jaguar teeth or claws, or jaguar tooth pendants. Users were also selling full jaguar skulls.

De la Torre said that researchers need to better understand the sources of all felid parts, whether they come from poached jaguars or animals in breeding centers.

Skulls were sometimes also offered. Credit: WCS Mesoamerica

But it would also be beneficial, he said, for Facebook and other online platforms to censor these types of posts trafficking in illegal wildlife parts. The nature of the social platform makes it easy for traffickers to find buyers all around the world, he said.

Conversely, de la Torre said that authorities could monitor social media and other online posts, identifying potential trafficking and poaching networks.

Authorities could also do a better job of using social media to inform users that the sale of jaguar and other felid parts is illegal, he said.

Wild birds like pelicans, falcons help spread avian flu

April 10, 2025 by The Wildlife Society

For years, wildlife managers controlled new outbreaks of avian flu by culling infected domestic birds. But new research suggests these efforts may not be working to stymie the recent spread of highly pathogenic avian influenza because wild birds have now become carriers of the virus, spreading it to Europe, Africa and the Americas. In a study published recently in GeoHealth, researchers combined wildlife GIS tracking with epidemiology to better understand why the patterns of avian flu have shifted west from its southeast Asia hot spot since the 1990s. Analysis revealed where wild birds and poultry operations mixed, showing potential vectors for the spread of the disease. Whereas migrations of ducks, geese and swans may have caused earlier waves of avian flu, now other types of birds like cormorants, pelicans, buzzards, vultures, hawks and peregrine falcons (Falco peregrinus) are carrying it to new populations.

Read more at the AGU newsroom.

JWM: Busy trails repel California wildlife

April 9, 2025 by Olivia Milloway

Social fitness apps are a great way to track trail use in and around cities. But researchers are now using them to determine the wildlife activity that isn’t happening when humans are out recreating.

“[Wildlife] were using trails for travel,” said TWS member Erin Lacour, a restoration project manager at John Heinz National Wldlife Refuge at Tinicum in Philadelphia, Pennsylvania. “But they’re still avoiding people because they’re using them more frequently at nighttime.”

In a recent study published in The Journal of Wildlife Management, lead author Lacour and her colleagues found that several species changed their behavior around high-use trails on Mount Tamalpais in California’s Bay Area. The shift could affect the way that predators and prey interact in these areas.

The new finding adds to a growing body of research revealing how even low-impact human activity might affect wildlife populations in protected areas.

Lacour was a master’s student at San José State University during the coronavirus pandemic when fieldwork was challenging. She began to search for pre-existing datasets and thought of the Marin Wildlife Watch project run by One Tam, a partnership between state, federal and private organizations that works to protect, restore and care for Mount Tam, where she had interned during her studies. However, the trail cameras in One Tam’s project were positioned in a way that they weren’t capturing human activity on the trails, so she needed to look for another method to estimate human activity.

One of the camera traps used in the study attached to a Douglas fir. Credit: Erin Lacour

To fill in the blanks, she turned to Strava, a popular social media app where users track and share their running, cycling, hiking and even swimming activities using GPS. Strava makes recreation data available for free to researchers typically studying urban planning and commuting via Strava Metro.

She decided to combine the Strava data with trail camera photos from One Tam from 2016 and 2017 to see how wildlife changed their behavior in response to human presence. “All of these parks are protected against development, but there are still people there doing people things: walking their dogs, riding their bikes, blasting music on speakers,” she said. “I was interested to see if we are still causing disturbances on wildlife in these conserved spaces.”

Lacour compared cameras that were close (within 30 meters) to trails with cameras far away from trails (100 meters to 1 kilometer away). Mule deer (Odocoileus hemionus), gray fox (Urocyon cinereoargentus) and black-tailed jackrabbit (Lepus californicus) were more frequently detected on cameras closer to trails compared to cameras farther away, but in trail areas, many of these species were more active at night.

Erin Lacour on top of Bolinas Ridge on Mount Tamalpais, removing invasive Euphorbia oblongata during her internship with One Tam. Photo courtesy of Erin Lacour

Meanwhile, western gray squirrels (Sciurus griseus), which are considered a sensitive species in California and are endangered in Washington, were detected more frequently at cameras farther from trails.

Wildlife also responded differently to different recreation types. When accounting for both hiking and biking, both mule deer and brush rabbits (Sylvilagus bachmani) were less frequent near trails with high levels of mountain biking.

Lacour’s findings correlate with those of another recent study from Santa Monica National Recreation Area using Strava data. That research found that mountain lions (Puma concolor) changed their activity in response to recreation, becoming more active at night to avoid people.

These types of shifts can change the way that an ecosystem works in a larger sense.

“When you see these temporal shifts, you can get changes in predator-prey dynamics,” Lacour said. In other words, if a prey species becomes more active at night to avoid humans, it may overlap more with potential predator species—or vice versa.

While Lacour doesn’t know how many visitors to Mount Tam use Strava to track their outdoor activity, other studies have shown the app accurately estimates average daily trends in recreation. She said this is still a fairly novel and untapped data source for wildlife studies and thinks future studies in areas with lots of recreation should use apps like this to better incorporate human use of trails. “My study was a good stepping stone using already existing data,” she said.

Lacour thinks that trails are one important way that people can create connections with nature, but they still need to be managed with safety zones for wildlife in mind. By learning more about the extent of human disturbance in wild places, scientists can direct management actions and create buffer zones between high-use trails and more sensitive species. “When you use data from Strava, you can see which areas have the most disturbance and manage from there.”

This article features research that was published in a TWS peer-reviewed journal. Individual online access to all TWS journal articles is a benefit of membership.  Join TWS now  to read the latest in wildlife research. 

Saw-whet owls make stopovers to refuel on migration

April 8, 2025 by The Wildlife Society

Tracking devices are revealing previously unknown routes and stopover behavior of one of the smallest owls in North America during their migration. Researchers don’t know exactly where northern saw-whet owls (Aegolius acadicus) migrate—the human hand-sized raptors are fairly cryptic. But a new study published in the Journal of Raptor Research using VHF tracking devices has revealed that populations in western Montana pause to rest and refuel during their seasonal movements. Most tracked owls moved three to five miles per night, though one took a 40-mile trip during a single night. “Stopover behavior is really difficult to tease out from banding data, so it’s been largely unexplored until now,” said lead author Kate Stone from MPG Ranch in a press release. “This behavior shows that saw-whets really are reliant on ground conditions to support their migratory journeys.” Learning more about these migration routes could help conservation planning and habitat connectivity action.

Read more at the Journal of Raptor Research.